/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! # Overlay profiler
//!
//! ## Profiler UI string syntax
//!
//! Comma-separated list of of tokens with trailing and leading spaces trimmed.
//! Each tokens can be:
//! - A counter name with an optional prefix. The name corresponds to the displayed name (see the
//!   counters vector below.
//!   - By default (no prefix) the counter is shown as average + max over half a second.
//!   - With a '#' prefix the counter is shown as a graph.
//!   - With a '*' prefix the counter is shown as a change indicator.
//!   - Some special counters such as GPU time queries have specific visualizations ignoring prefixes.
//! - A preset name to append the preset to the UI (see PROFILER_PRESETS).
//! - An empty token to insert a bit of vertical space.
//! - A '|' token to start a new column.
//! - A '_' token to start a new row.

use api::{ColorF, ColorU};
#[cfg(feature = "debugger")]
use api::debugger::{ProfileCounterUpdate, ProfileCounterId};
use glyph_rasterizer::profiler::GlyphRasterizeProfiler;
use crate::renderer::DebugRenderer;
use crate::device::query::GpuTimer;
use euclid::{Point2D, Rect, Size2D, vec2, default};
use crate::internal_types::FastHashMap;
use crate::renderer::{FullFrameStats, MAX_VERTEX_TEXTURE_WIDTH, init::wr_has_been_initialized};
use api::units::DeviceIntSize;
use std::collections::vec_deque::VecDeque;
use std::fmt::{Write, Debug};
use std::f32;
use std::ops::Range;
use std::time::Duration;

macro_rules! set_text {
    ($dst:expr, $($arg:tt)*) => {
        $dst.clear();
        write!($dst, $($arg)*).unwrap();
    };
}

const GRAPH_WIDTH: f32 = 1024.0;
const GRAPH_HEIGHT: f32 = 320.0;
const GRAPH_PADDING: f32 = 8.0;
const GRAPH_FRAME_HEIGHT: f32 = 16.0;
const PROFILE_SPACING: f32 = 15.0;
const PROFILE_PADDING: f32 = 10.0;
const BACKGROUND_COLOR: ColorU = ColorU { r: 20, g: 20, b: 20, a: 220 };

const ONE_SECOND_NS: u64 = 1_000_000_000;

/// Profiler UI string presets. Defined in the profiler UI string syntax, can contain other presets.
static PROFILER_PRESETS: &'static[(&'static str, &'static str)] = &[
    // Default view, doesn't show everything, but still shows quite a bit.
    (&"Default", &"FPS,|,Slow indicators,_,Time graphs,|,Frame times, ,Transaction times, ,Frame stats, ,Memory, ,Interners,_,GPU time queries,_,Paint phase graph"),
    // Smaller, less intrusive overview
    (&"Compact", &"FPS, ,Frame times, ,Frame stats"),
    // Even less intrusive, only slow transactions and frame indicators.
    (&"Slow indicators", &"*Slow transaction,*Slow frame"),

    // Counters:

    // Timing information for per layout transaction stages.
    (&"Transaction times", &"DisplayList,Scene building,Content send,API send"),
    // Timing information for per-frame stages.
    (&"Frame times", &"Frame CPU total,Frame building,Visibility,Prepare,Batching,Glyph resolve,Texture cache update,Shader build time,Renderer,GPU"),
    // Stats about the content of the frame.
    (&"Frame stats", &"Primitives,Visible primitives,Draw calls,Vertices,Color passes,Alpha passes,Rendered picture tiles,Rasterized glyphs"),
    // Texture cache allocation stats.
    (&"Texture cache stats", &"Atlas textures mem, Standalone textures mem, Picture tiles mem, Render targets mem, Depth targets mem, Atlas items mem,
        Texture cache standalone pressure, Texture cache eviction count, Texture cache youngest evicted, ,
        Atlas RGBA8 linear pixels, Atlas RGBA8 glyphs pixels, Atlas A8 glyphs pixels, Atlas A8 pixels, Atlas A16 pixels, Atlas RGBA8 nearest pixels,
        Atlas RGBA8 linear textures, Atlas RGBA8 glyphs textures, Atlas A8 glyphs textures, Atlas A8 textures, Atlas A16 textures, Atlas RGBA8 nearest textures,
        Atlas RGBA8 linear pressure, Atlas RGBA8 glyphs pressure, Atlas A8 glyphs pressure, Atlas A8 pressure, Atlas A16 pressure, Atlas RGBA8 nearest pressure,"
    ),
    // Graphs to investigate driver overhead of texture cache updates.
    (&"Texture upload perf", &"#Texture cache update,#Texture cache upload, ,#Staging CPU allocation,#Staging GPU allocation,#Staging CPU copy,#Staging GPU copy,#Upload time, ,#Upload copy batches,#Rasterized glyphs, ,#Cache texture creation,#Cache texture deletion"),

    // Graphs:

    // Graph overview of time spent in WebRender's main stages.
    (&"Time graphs", &"#DisplayList,#Scene building,#Blob rasterization, ,#Frame CPU total,#Frame building,#Renderer,#Texture cache update, ,#GPU,"),
    // Useful when investigating render backend bottlenecks.
    (&"Backend graphs", &"#Frame building, #Visibility, #Prepare, #Batching, #Glyph resolve"),
    // Useful when investigating renderer bottlenecks.
    (&"Renderer graphs", &"#Rendered picture tiles,#Draw calls,#Rasterized glyphs,#Texture uploads,#Texture uploads mem, ,#Texture cache update,#Renderer,"),

    // Misc:

    (&"GPU Memory", &"External image mem, Atlas textures mem, Standalone textures mem, Picture tiles mem, Render targets mem, Depth targets mem, Atlas items mem, GPU cache mem, GPU buffer mem, GPU total mem"),
    (&"CPU Memory", &"Image templates, Image templates mem, Font templates,Font templates mem, DisplayList mem"),
    (&"Memory", &"$CPU,CPU Memory, ,$GPU,GPU Memory"),
    (&"Interners", "Interned primitives,Interned clips,Interned pictures,Interned text runs,Interned normal borders,Interned image borders,Interned images,Interned YUV images,Interned line decorations,Interned linear gradients,Interned radial gradients,Interned conic gradients,Interned filter data,Interned backdrop renders, Interned backdrop captures"),
    // Gpu sampler queries (need the pref gfx.webrender.debug.gpu-sampler-queries).
    (&"GPU samplers", &"Alpha targets samplers,Transparent pass samplers,Opaque pass samplers,Total samplers"),

    (&"Render reasons", &"Reason scene, Reason animated property, Reason resource update, Reason async image, Reason clear resources, Reason APZ, Reason resize, Reason widget, Reason cache flush, Reason snapshot, Reason resource hook, Reason config change, Reason content sync, Reason flush, On vsync, Reason testing, Reason other"),

    (&"Slow frame breakdown", &"Total slow frames CPU, Total slow frames GPU, Slow: frame build, Slow: upload, Slow: render, Slow: draw calls, Slow: targets, Slow: blobs, Slow: after scene, Slow scroll frames"),

    (&"Compositor", &"Compositor surface underlays,Compositor surface overlays,Compositor surface blits"),
    (&"Video", &"FPS,_,#Rendered picture tiles,_,Compositor"),
];

fn find_preset(name: &str) -> Option<&'static str> {
    for preset in PROFILER_PRESETS {
        if preset.0 == name {
            return Some(preset.1);
        }
    }

    None
}

// The indices here must match the PROFILE_COUNTERS array (checked at runtime).
pub const FRAME_BUILDING_TIME: usize = 0;
pub const FRAME_VISIBILITY_TIME: usize = 1;
pub const FRAME_PREPARE_TIME: usize = 2;
pub const FRAME_BATCHING_TIME: usize = 3;

pub const RENDERER_TIME: usize = 4;
pub const TOTAL_FRAME_CPU_TIME: usize = 5;
pub const GPU_TIME: usize = 6;

pub const CONTENT_SEND_TIME: usize = 7;
pub const API_SEND_TIME: usize = 8;

pub const DISPLAY_LIST_BUILD_TIME: usize = 9;
pub const DISPLAY_LIST_MEM: usize = 10;

pub const SCENE_BUILD_TIME: usize = 11;

pub const SLOW_FRAME: usize = 12;
pub const SLOW_TXN: usize = 13;

pub const FRAME_TIME: usize = 14;

pub const TEXTURE_UPLOADS: usize = 15;
pub const TEXTURE_UPLOADS_MEM: usize = 16;
pub const TEXTURE_CACHE_UPDATE_TIME: usize = 17;
pub const CPU_TEXTURE_ALLOCATION_TIME: usize = 18;
pub const STAGING_TEXTURE_ALLOCATION_TIME: usize = 19;
pub const UPLOAD_CPU_COPY_TIME: usize = 20;
pub const UPLOAD_GPU_COPY_TIME: usize = 21;
pub const UPLOAD_TIME: usize = 22;
pub const UPLOAD_NUM_COPY_BATCHES: usize = 23;
pub const TOTAL_UPLOAD_TIME: usize = 24;
pub const CREATE_CACHE_TEXTURE_TIME: usize = 25;
pub const DELETE_CACHE_TEXTURE_TIME: usize = 26;
pub const GPU_CACHE_UPLOAD_TIME: usize = 27;

pub const RASTERIZED_BLOBS: usize = 28;
pub const RASTERIZED_BLOB_TILES: usize = 29;
pub const RASTERIZED_BLOBS_PX: usize = 30;
pub const BLOB_RASTERIZATION_TIME: usize = 31;

pub const RASTERIZED_GLYPHS: usize = 32;
pub const GLYPH_RESOLVE_TIME: usize = 33;

pub const DRAW_CALLS: usize = 34;
pub const VERTICES: usize = 35;
pub const PRIMITIVES: usize = 36;
pub const VISIBLE_PRIMITIVES: usize = 37;

pub const USED_TARGETS: usize = 38;
pub const CREATED_TARGETS: usize = 39;
pub const PICTURE_CACHE_SLICES: usize = 40;

pub const COLOR_PASSES: usize = 41;
pub const ALPHA_PASSES: usize = 42;
pub const PICTURE_TILES: usize = 43;
pub const RENDERED_PICTURE_TILES: usize = 44;

pub const FONT_TEMPLATES: usize = 45;
pub const FONT_TEMPLATES_MEM: usize = 46;
pub const IMAGE_TEMPLATES: usize = 47;
pub const IMAGE_TEMPLATES_MEM: usize = 48;

pub const GPU_CACHE_ROWS_TOTAL: usize = 49;
pub const GPU_CACHE_ROWS_UPDATED: usize = 50;
pub const GPU_CACHE_BLOCKS_TOTAL: usize = 51;
pub const GPU_CACHE_BLOCKS_UPDATED: usize = 52;
pub const GPU_CACHE_BLOCKS_SAVED: usize = 53;

// Atlas items represents the area occupied by items in the cache textures.
// The actual texture memory allocated is ATLAS_TEXTURES_MEM.
pub const ATLAS_ITEMS_MEM: usize = 54;
pub const ATLAS_A8_PIXELS: usize = 55;
pub const ATLAS_A8_TEXTURES: usize = 56;
pub const ATLAS_A16_PIXELS: usize = 57;
pub const ATLAS_A16_TEXTURES: usize = 58;
pub const ATLAS_RGBA8_LINEAR_PIXELS: usize = 59;
pub const ATLAS_RGBA8_LINEAR_TEXTURES: usize = 60;
pub const ATLAS_RGBA8_NEAREST_PIXELS: usize = 61;
pub const ATLAS_RGBA8_NEAREST_TEXTURES: usize = 62;
pub const ATLAS_RGBA8_GLYPHS_PIXELS: usize = 63;
pub const ATLAS_RGBA8_GLYPHS_TEXTURES: usize = 64;
pub const ATLAS_A8_GLYPHS_PIXELS: usize = 65;
pub const ATLAS_A8_GLYPHS_TEXTURES: usize = 66;
pub const ATLAS_COLOR8_LINEAR_PRESSURE: usize = 67;
pub const ATLAS_COLOR8_NEAREST_PRESSURE: usize = 68;
pub const ATLAS_COLOR8_GLYPHS_PRESSURE: usize = 69;
pub const ATLAS_ALPHA8_PRESSURE: usize = 70;
pub const ATLAS_ALPHA8_GLYPHS_PRESSURE: usize = 71;
pub const ATLAS_ALPHA16_PRESSURE: usize = 72;
pub const ATLAS_STANDALONE_PRESSURE: usize = 73;

pub const TEXTURE_CACHE_EVICTION_COUNT: usize = 74;
pub const TEXTURE_CACHE_YOUNGEST_EVICTION: usize = 75;
pub const EXTERNAL_IMAGE_BYTES: usize = 76;
pub const ATLAS_TEXTURES_MEM: usize = 77;
pub const STANDALONE_TEXTURES_MEM: usize = 78;
pub const PICTURE_TILES_MEM: usize = 79;
pub const RENDER_TARGET_MEM: usize = 80;

pub const ALPHA_TARGETS_SAMPLERS: usize = 81;
pub const TRANSPARENT_PASS_SAMPLERS: usize = 82;
pub const OPAQUE_PASS_SAMPLERS: usize = 83;
pub const TOTAL_SAMPLERS: usize = 84;

pub const INTERNED_PRIMITIVES: usize = 85;
pub const INTERNED_CLIPS: usize = 86;
pub const INTERNED_TEXT_RUNS: usize = 87;
pub const INTERNED_NORMAL_BORDERS: usize = 88;
pub const INTERNED_IMAGE_BORDERS: usize = 89;
pub const INTERNED_IMAGES: usize = 90;
pub const INTERNED_YUV_IMAGES: usize = 91;
pub const INTERNED_LINE_DECORATIONS: usize = 92;
pub const INTERNED_LINEAR_GRADIENTS: usize = 93;
pub const INTERNED_RADIAL_GRADIENTS: usize = 94;
pub const INTERNED_CONIC_GRADIENTS: usize = 95;
pub const INTERNED_PICTURES: usize = 96;
pub const INTERNED_FILTER_DATA: usize = 97;
pub const INTERNED_BACKDROP_CAPTURES: usize = 98;
pub const INTERNED_BACKDROP_RENDERS: usize = 99;
pub const INTERNED_POLYGONS: usize = 100;
pub const INTERNED_BOX_SHADOWS: usize = 101;
pub const DEPTH_TARGETS_MEM: usize = 102;

pub const SHADER_BUILD_TIME: usize = 103;

pub const RENDER_REASON_FIRST: usize = 104;
pub const RENDER_REASON_SCENE: usize = 104;
pub const RENDER_REASON_ANIMATED_PROPERTY: usize = 105;
pub const RENDER_REASON_RESOURCE_UPDATE: usize = 106;
pub const RENDER_REASON_ASYNC_IMAGE: usize = 107;
pub const RENDER_REASON_CLEAR_RESOURCES: usize = 108;
pub const RENDER_REASON_APZ: usize = 109;
pub const RENDER_REASON_RESIZE: usize = 110;
pub const RENDER_REASON_WIDGET: usize = 111;
pub const RENDER_REASON_TEXTURE_CACHE_FLUSH: usize = 112;
pub const RENDER_REASON_SNAPSHOT: usize = 113;
pub const RENDER_REASON_POST_RESOURCE_UPDATE_HOOKS: usize = 114;
pub const RENDER_REASON_CONFIG_CHANGE: usize = 115;
pub const RENDER_REASON_CONTENT_SYNC: usize = 116;
pub const RENDER_REASON_FLUSH: usize = 117;
pub const RENDER_REASON_TESTING: usize = 118;
pub const RENDER_REASON_OTHER: usize = 119;
pub const RENDER_REASON_VSYNC: usize = 120;

pub const TEXTURES_CREATED: usize = 121;
pub const TEXTURES_DELETED: usize = 122;

pub const SLOW_FRAME_CPU_COUNT: usize = 123;
pub const SLOW_FRAME_GPU_COUNT: usize = 124;
pub const SLOW_FRAME_BUILD_COUNT: usize = 125;
pub const SLOW_UPLOAD_COUNT: usize = 126;
pub const SLOW_RENDER_COUNT: usize = 127;
pub const SLOW_DRAW_CALLS_COUNT: usize = 128;
pub const SLOW_TARGETS_COUNT: usize = 129;
pub const SLOW_BLOB_COUNT: usize = 130;
pub const SLOW_SCROLL_AFTER_SCENE_COUNT: usize = 131;

pub const GPU_CACHE_MEM: usize = 132;
pub const GPU_BUFFER_MEM: usize = 133;
pub const GPU_TOTAL_MEM: usize = 134;

pub const GPU_CACHE_PREPARE_TIME: usize = 135;

pub const FRAME_SEND_TIME: usize = 136;
pub const UPDATE_DOCUMENT_TIME: usize = 137;

pub const COMPOSITOR_SURFACE_UNDERLAYS: usize = 138;
pub const COMPOSITOR_SURFACE_OVERLAYS: usize = 139;
pub const COMPOSITOR_SURFACE_BLITS: usize = 140;

pub const NUM_PROFILER_EVENTS: usize = 141;

pub struct Profiler {
    counters: Vec<Counter>,
    gpu_frames: ProfilerFrameCollection,
    frame_stats: ProfilerFrameCollection,
    slow_scroll_frames: ProfilerFrameCollection,

    start: u64,
    avg_over_period: u64,
    num_graph_samples: usize,
    slow_cpu_frame_threshold: f32,

    // For FPS computation. Updated in update().
    frame_timestamps_within_last_second: Vec<u64>,

    /// Total number of slow frames on the CPU.
    slow_frame_cpu_count: u64,
    /// Total number of slow frames on the GPU.
    slow_frame_gpu_count: u64,
    /// Slow frames dominated by frame building.
    slow_frame_build_count: u64,
    /// Slow frames dominated by draw call submission.
    slow_render_count: u64,
    /// Slow frames dominated by texture uploads.
    slow_upload_count: u64,
    /// Slow renders with a high number of draw calls.
    slow_draw_calls_count: u64,
    /// Slow renders with a high number of render targets.
    slow_targets_count: u64,
    /// Slow uploads with a high number of blob tiles.
    slow_blob_count: u64,
    /// Slow scrolling or animation frame after a scene build.
    slow_scroll_after_scene_count: u64,

    ui: Vec<Item>,
}

impl Profiler {
    pub fn new() -> Self {

        fn float(name: &'static str, unit: &'static str, index: usize, expected: Expected<f64>) -> CounterDescriptor {
            CounterDescriptor { name, unit, show_as: ShowAs::Float, index, expected }
        }

        fn int(name: &'static str, unit: &'static str, index: usize, expected: Expected<i64>) -> CounterDescriptor {
            CounterDescriptor { name, unit, show_as: ShowAs::Int, index, expected: expected.into_float() }
        }

        // Not in the list below:
        // - "GPU time queries" shows the details of the GPU time queries if selected as a graph.
        // - "GPU cache bars" shows some info about the GPU cache.

        // TODO: This should be a global variable but to keep things readable we need to be able to
        // use match in const fn which isn't supported by the current rustc version in gecko's build
        // system.
        let profile_counters = &[
            float("Frame building", "ms", FRAME_BUILDING_TIME, expected(0.0..6.0).avg(0.0..3.0)),
            float("Visibility", "ms", FRAME_VISIBILITY_TIME, expected(0.0..3.0).avg(0.0..2.0)),
            float("Prepare", "ms", FRAME_PREPARE_TIME, expected(0.0..3.0).avg(0.0..2.0)),
            float("Batching", "ms", FRAME_BATCHING_TIME, expected(0.0..3.0).avg(0.0..2.0)),

            float("Renderer", "ms", RENDERER_TIME, expected(0.0..8.0).avg(0.0..5.0)),
            float("Frame CPU total", "ms", TOTAL_FRAME_CPU_TIME, expected(0.0..15.0).avg(0.0..6.0)),
            float("GPU", "ms", GPU_TIME, expected(0.0..15.0).avg(0.0..8.0)),

            float("Content send", "ms", CONTENT_SEND_TIME, expected(0.0..1.0).avg(0.0..1.0)),
            float("API send", "ms", API_SEND_TIME, expected(0.0..1.0).avg(0.0..0.4)),
            float("DisplayList", "ms", DISPLAY_LIST_BUILD_TIME, expected(0.0..5.0).avg(0.0..3.0)),
            float("DisplayList mem", "MB", DISPLAY_LIST_MEM, expected(0.0..20.0)),
            float("Scene building", "ms", SCENE_BUILD_TIME, expected(0.0..4.0).avg(0.0..3.0)),

            float("Slow frame", "", SLOW_FRAME, expected(0.0..0.0)),
            float("Slow transaction", "", SLOW_TXN, expected(0.0..0.0)),

            float("Frame", "ms", FRAME_TIME, Expected::none()),

            int("Texture uploads", "", TEXTURE_UPLOADS, expected(0..10)),
            float("Texture uploads mem", "MB", TEXTURE_UPLOADS_MEM, expected(0.0..10.0)),
            float("Texture cache update", "ms", TEXTURE_CACHE_UPDATE_TIME, expected(0.0..3.0)),
            float("Staging CPU allocation", "ms", CPU_TEXTURE_ALLOCATION_TIME, Expected::none()),
            float("Staging GPU allocation", "ms", STAGING_TEXTURE_ALLOCATION_TIME, Expected::none()),
            float("Staging CPU copy", "ms", UPLOAD_CPU_COPY_TIME, Expected::none()),
            float("Staging GPU copy", "ms", UPLOAD_GPU_COPY_TIME, Expected::none()),
            float("Upload time", "ms", UPLOAD_TIME, Expected::none()),
            int("Upload copy batches", "", UPLOAD_NUM_COPY_BATCHES, Expected::none()),
            float("Texture cache upload", "ms", TOTAL_UPLOAD_TIME, expected(0.0..5.0)),
            float("Cache texture creation", "ms", CREATE_CACHE_TEXTURE_TIME, expected(0.0..2.0)),
            float("Cache texture deletion", "ms", DELETE_CACHE_TEXTURE_TIME, expected(0.0..1.0)),
            float("GPU cache upload", "ms", GPU_CACHE_UPLOAD_TIME, expected(0.0..2.0)),

            int("Rasterized blobs", "", RASTERIZED_BLOBS, expected(0..15)),
            int("Rasterized blob tiles", "", RASTERIZED_BLOB_TILES, expected(0..15)),
            int("Rasterized blob pixels", "px", RASTERIZED_BLOBS_PX, expected(0..300_000)),
            float("Blob rasterization", "ms", BLOB_RASTERIZATION_TIME, expected(0.0..8.0)),

            int("Rasterized glyphs", "", RASTERIZED_GLYPHS, expected(0..15)),
            float("Glyph resolve", "ms", GLYPH_RESOLVE_TIME, expected(0.0..4.0)),

            int("Draw calls", "", DRAW_CALLS, expected(1..120).avg(1..90)),
            int("Vertices", "", VERTICES, expected(10..5000)),
            int("Primitives", "", PRIMITIVES, expected(10..5000)),
            int("Visible primitives", "", VISIBLE_PRIMITIVES, expected(1..5000)),

            int("Used targets", "", USED_TARGETS, expected(1..4)),
            int("Created targets", "", CREATED_TARGETS, expected(0..3)),
            int("Picture cache slices", "", PICTURE_CACHE_SLICES, expected(0..5)),

            int("Color passes", "", COLOR_PASSES, expected(1..4)),
            int("Alpha passes", "", ALPHA_PASSES, expected(0..3)),
            int("Picture tiles", "", PICTURE_TILES, expected(0..15)),
            int("Rendered picture tiles", "", RENDERED_PICTURE_TILES, expected(0..5)),

            int("Font templates", "", FONT_TEMPLATES, expected(0..40)),
            float("Font templates mem", "MB", FONT_TEMPLATES_MEM, expected(0.0..20.0)),
            int("Image templates", "", IMAGE_TEMPLATES, expected(0..100)),
            float("Image templates mem", "MB", IMAGE_TEMPLATES_MEM, expected(0.0..50.0)),

            int("GPU cache rows total", "", GPU_CACHE_ROWS_TOTAL, expected(1..50)),
            int("GPU cache rows updated", "", GPU_CACHE_ROWS_UPDATED, expected(0..25)),
            int("GPU blocks total", "", GPU_CACHE_BLOCKS_TOTAL, expected(1..65_000)),
            int("GPU blocks updated", "", GPU_CACHE_BLOCKS_UPDATED, expected(0..1000)),
            int("GPU blocks saved", "", GPU_CACHE_BLOCKS_SAVED, expected(0..50_000)),

            float("Atlas items mem", "MB", ATLAS_ITEMS_MEM, expected(0.0..100.0)),
            int("Atlas A8 pixels", "px", ATLAS_A8_PIXELS, expected(0..1_000_000)),
            int("Atlas A8 textures", "", ATLAS_A8_TEXTURES, expected(0..2)),
            int("Atlas A16 pixels", "px", ATLAS_A16_PIXELS, expected(0..260_000)),
            int("Atlas A16 textures", "", ATLAS_A16_TEXTURES, expected(0..2)),
            int("Atlas RGBA8 linear pixels", "px", ATLAS_RGBA8_LINEAR_PIXELS, expected(0..8_000_000)),
            int("Atlas RGBA8 linear textures", "", ATLAS_RGBA8_LINEAR_TEXTURES, expected(0..3)),
            int("Atlas RGBA8 nearest pixels", "px", ATLAS_RGBA8_NEAREST_PIXELS, expected(0..260_000)),
            int("Atlas RGBA8 nearest textures", "", ATLAS_RGBA8_NEAREST_TEXTURES, expected(0..2)),
            int("Atlas RGBA8 glyphs pixels", "px", ATLAS_RGBA8_GLYPHS_PIXELS, expected(0..4_000_000)),
            int("Atlas RGBA8 glyphs textures", "", ATLAS_RGBA8_GLYPHS_TEXTURES, expected(0..2)),
            int("Atlas A8 glyphs pixels", "px", ATLAS_A8_GLYPHS_PIXELS, expected(0..4_000_000)),
            int("Atlas A8 glyphs textures", "", ATLAS_A8_GLYPHS_TEXTURES, expected(0..2)),
            float("Atlas RGBA8 linear pressure", "", ATLAS_COLOR8_LINEAR_PRESSURE, expected(0.0..1.0)),
            float("Atlas RGBA8 nearest pressure", "", ATLAS_COLOR8_NEAREST_PRESSURE, expected(0.0..1.0)),
            float("Atlas RGBA8 glyphs pressure", "", ATLAS_COLOR8_GLYPHS_PRESSURE, expected(0.0..1.0)),
            float("Atlas A8 pressure", "", ATLAS_ALPHA8_PRESSURE, expected(0.0..1.0)),
            float("Atlas A8 glyphs pressure", "", ATLAS_ALPHA8_GLYPHS_PRESSURE, expected(0.0..1.0)),
            float("Atlas A16 pressure", "", ATLAS_ALPHA16_PRESSURE, expected(0.0..1.0)),
            float("Texture cache standalone pressure", "", ATLAS_STANDALONE_PRESSURE, expected(0.0..1.0)),

            int("Texture cache eviction count", "items", TEXTURE_CACHE_EVICTION_COUNT, Expected::none()),
            int("Texture cache youngest evicted", "frames", TEXTURE_CACHE_YOUNGEST_EVICTION, Expected::none()),
            float("External image mem", "MB", EXTERNAL_IMAGE_BYTES, Expected::none()),
            float("Atlas textures mem", "MB", ATLAS_TEXTURES_MEM, Expected::none()),
            float("Standalone textures mem", "MB", STANDALONE_TEXTURES_MEM, Expected::none()),
            float("Picture tiles mem", "MB", PICTURE_TILES_MEM, expected(0.0..150.0)),
            float("Render targets mem", "MB", RENDER_TARGET_MEM, Expected::none()),

            float("Alpha targets samplers", "%", ALPHA_TARGETS_SAMPLERS, Expected::none()),
            float("Transparent pass samplers", "%", TRANSPARENT_PASS_SAMPLERS, Expected::none()),
            float("Opaque pass samplers", "%", OPAQUE_PASS_SAMPLERS, Expected::none()),
            float("Total samplers", "%", TOTAL_SAMPLERS, Expected::none()),

            int("Interned primitives", "", INTERNED_PRIMITIVES, Expected::none()),
            int("Interned clips", "", INTERNED_CLIPS, Expected::none()),
            int("Interned text runs", "", INTERNED_TEXT_RUNS, Expected::none()),
            int("Interned normal borders", "", INTERNED_NORMAL_BORDERS, Expected::none()),
            int("Interned image borders", "", INTERNED_IMAGE_BORDERS, Expected::none()),
            int("Interned images", "", INTERNED_IMAGES, Expected::none()),
            int("Interned YUV images", "", INTERNED_YUV_IMAGES, Expected::none()),
            int("Interned line decorations", "", INTERNED_LINE_DECORATIONS, Expected::none()),
            int("Interned linear gradients", "", INTERNED_LINEAR_GRADIENTS, Expected::none()),
            int("Interned radial gradients", "", INTERNED_RADIAL_GRADIENTS, Expected::none()),
            int("Interned conic gradients", "", INTERNED_CONIC_GRADIENTS, Expected::none()),
            int("Interned pictures", "", INTERNED_PICTURES, Expected::none()),
            int("Interned filter data", "", INTERNED_FILTER_DATA, Expected::none()),
            int("Interned backdrop captures", "", INTERNED_BACKDROP_CAPTURES, Expected::none()),
            int("Interned backdrop renders", "", INTERNED_BACKDROP_RENDERS, Expected::none()),
            int("Interned polygons", "", INTERNED_POLYGONS, Expected::none()),
            int("Interned box-shadows", "", INTERNED_BOX_SHADOWS, Expected::none()),

            float("Depth targets mem", "MB", DEPTH_TARGETS_MEM, Expected::none()),
            float("Shader build time", "ms", SHADER_BUILD_TIME, Expected::none()),
            // We use the expected range to highlight render reasons that are happening.
            float("Reason scene", "", RENDER_REASON_SCENE, expected(0.0..0.01)),
            float("Reason animated property", "", RENDER_REASON_ANIMATED_PROPERTY, expected(0.0..0.01)),
            float("Reason resource update", "", RENDER_REASON_RESOURCE_UPDATE, expected(0.0..0.01)),
            float("Reason async image", "", RENDER_REASON_ASYNC_IMAGE, expected(0.0..0.01)),
            float("Reason clear resources", "", RENDER_REASON_CLEAR_RESOURCES, expected(0.0..0.01)),
            float("Reason APZ", "", RENDER_REASON_APZ, expected(0.0..0.01)),
            float("Reason resize", "", RENDER_REASON_RESIZE, expected(0.0..0.01)),
            float("Reason widget", "", RENDER_REASON_WIDGET, expected(0.0..0.01)),
            float("Reason cache flush", "", RENDER_REASON_TEXTURE_CACHE_FLUSH, expected(0.0..0.01)),
            float("Reason snapshot", "", RENDER_REASON_SNAPSHOT, expected(0.0..0.01)),
            float("Reason resource hook", "", RENDER_REASON_POST_RESOURCE_UPDATE_HOOKS, expected(0.0..0.01)),
            float("Reason config change", "", RENDER_REASON_CONFIG_CHANGE, expected(0.0..0.01)),
            float("Reason content sync", "", RENDER_REASON_CONTENT_SYNC, expected(0.0..0.01)),
            float("Reason flush", "", RENDER_REASON_FLUSH, expected(0.0..0.01)),
            float("Reason testing", "", RENDER_REASON_TESTING, expected(0.0..0.01)),
            float("Reason other", "", RENDER_REASON_OTHER, expected(0.0..0.01)),
            float("On vsync", "", RENDER_REASON_VSYNC, expected(0.0..0.01)),

            int("Textures created", "", TEXTURES_CREATED, expected(0..5)),
            int("Textures deleted", "", TEXTURES_DELETED, Expected::none()),

            int("Total slow frames CPU", "", SLOW_FRAME_CPU_COUNT, Expected::none()),
            int("Total slow frames GPU", "", SLOW_FRAME_GPU_COUNT, Expected::none()),
            int("Slow: frame build", "%", SLOW_FRAME_BUILD_COUNT, Expected::none()),
            int("Slow: upload", "%", SLOW_UPLOAD_COUNT, Expected::none()),
            int("Slow: render", "%", SLOW_RENDER_COUNT, Expected::none()),
            int("Slow: draw calls", "%", SLOW_DRAW_CALLS_COUNT, Expected::none()),
            int("Slow: targets", "%", SLOW_TARGETS_COUNT, Expected::none()),
            int("Slow: blobs", "%", SLOW_BLOB_COUNT, Expected::none()),
            int("Slow: after scene", "%", SLOW_SCROLL_AFTER_SCENE_COUNT, Expected::none()),

            float("GPU cache mem", "MB", GPU_CACHE_MEM, Expected::none()),
            float("GPU buffer mem", "MB", GPU_BUFFER_MEM, Expected::none()),
            float("GPU total mem", "MB", GPU_TOTAL_MEM, Expected::none()),

            float("GPU cache preapre", "ms", GPU_CACHE_PREPARE_TIME, Expected::none()),
            float("Frame send", "ms", FRAME_SEND_TIME, Expected::none()),
            float("Update document", "ms", UPDATE_DOCUMENT_TIME, Expected::none()),

            int("Compositor surface underlays", "", COMPOSITOR_SURFACE_UNDERLAYS, Expected::none()),
            int("Compositor surface overlays", "", COMPOSITOR_SURFACE_OVERLAYS, Expected::none()),
            int("Compositor surface blits", "", COMPOSITOR_SURFACE_BLITS, Expected::none()),
        ];

        let mut counters = Vec::with_capacity(profile_counters.len());

        for (idx, descriptor) in profile_counters.iter().enumerate() {
            debug_assert_eq!(descriptor.index, idx);
            counters.push(Counter::new(descriptor));
        }

        Profiler {
            gpu_frames: ProfilerFrameCollection::new(),
            frame_stats: ProfilerFrameCollection::new(),
            slow_scroll_frames: ProfilerFrameCollection::new(),

            counters,
            start: zeitstempel::now(),
            avg_over_period: ONE_SECOND_NS / 2,
            slow_cpu_frame_threshold: 10.0,

            num_graph_samples: 500, // Would it be useful to control this via a pref?
            frame_timestamps_within_last_second: Vec::new(),

            slow_frame_cpu_count: 0,
            slow_frame_gpu_count: 0,
            slow_frame_build_count: 0,
            slow_render_count: 0,
            slow_upload_count: 0,
            slow_draw_calls_count: 0,
            slow_targets_count: 0,
            slow_blob_count: 0,
            slow_scroll_after_scene_count: 0,

            ui: Vec::new(),
        }
    }

    pub fn set_parameter(&mut self, param: &api::Parameter) {
        match param {
            api::Parameter::Float(api::FloatParameter::SlowCpuFrameThreshold, threshold) => {
                self.slow_cpu_frame_threshold = *threshold;
            }
            _ => {}
        }
    }

    /// Sum a few counters and if the total amount is larger than a threshold, update
    /// a specific counter.
    ///
    /// This is useful to monitor slow frame and slow transactions.
    fn update_slow_event(&mut self, dst_counter: usize, counters: &[usize], threshold: f64) -> bool {
        let mut total = 0.0;
        for &counter in counters {
            if self.counters[counter].value.is_finite() {
                total += self.counters[counter].value;
            }
        }

        if total > threshold {
            self.counters[dst_counter].set(total);
            return true;
        }

        false
    }

    fn classify_slow_cpu_frame(&mut self) {
        let is_apz = self.counters[RENDER_REASON_ANIMATED_PROPERTY].value > 0.5
            || self.counters[RENDER_REASON_APZ].value > 0.5;
        if !is_apz {
            // Only consider slow frames affecting scrolling for now.
            return;
        }

        let frame = CpuFrameTimings::new(&self.counters);
        self.slow_scroll_frames.push(frame.to_profiler_frame());

        if self.counters[RENDER_REASON_SCENE].value > 0.5 {
            self.slow_scroll_after_scene_count += 1;
        }

        let frame_build = self.counters[FRAME_BUILDING_TIME].value;
        let uploads = self.counters[TEXTURE_CACHE_UPDATE_TIME].value;
        let renderer = self.counters[RENDERER_TIME].value - uploads;
        let mut reasons = [
            (frame_build, &mut self.slow_frame_build_count, SLOW_FRAME_BUILD_COUNT,),
            (renderer, &mut self.slow_render_count, SLOW_RENDER_COUNT,),
            (uploads, &mut self.slow_upload_count, SLOW_UPLOAD_COUNT,),
        ];

        reasons.sort_by(|a, b| b.0.partial_cmp(&a.0).unwrap());

        *reasons[0].1 += 1;
        let reason = reasons[0].2;
        std::mem::drop(reasons);

        self.slow_frame_cpu_count += 1;

        if reason == SLOW_RENDER_COUNT {
            let draw_calls = self.counters[DRAW_CALLS].value;
            if draw_calls > 200.0 {
                self.slow_draw_calls_count += 1;
            }

            let render_passes = self.counters[COLOR_PASSES].value + self.counters[ALPHA_PASSES].value;
            if render_passes > 20.0 {
                self.slow_targets_count += 1;
            }
        }

        if reason == SLOW_UPLOAD_COUNT {
            let count = self.counters[TEXTURE_UPLOADS].value;
            let blob_tiles = self.counters[RASTERIZED_BLOB_TILES].value;
            // This is an approximation: we rasterize blobs for the whole displayport and
            // only upload blob tiles for the current viewport. That said, the presence of
            // a high number of blob tiles compared to the total number of uploads is still
            // a good indication that blob images are the likely cause of the slow upload
            // time, or at least contributing to it to a large extent.
            if blob_tiles > count * 0.5 {
                self.slow_blob_count += 1;
            }
        }
    }

    #[cfg(feature = "debugger")]
    pub fn collect_updates_for_debugger(&self) -> Vec<ProfileCounterUpdate> {
        let mut updates = Vec::new();

        for (i, counter) in self.counters.iter().enumerate() {
            if let Some(value) = counter.get() {
                updates.push(ProfileCounterUpdate {
                    id: ProfileCounterId(i),
                    value,
                });
            }
        }

        updates
    }

    // Call at the end of every frame, after setting the counter values and before drawing the counters.
    pub fn update(&mut self) {
        let now = zeitstempel::now();
        let update_avg = (now - self.start) > self.avg_over_period;
        if update_avg {
            self.start = now;
        }
        let one_second_ago = now;
        self.frame_timestamps_within_last_second.retain(|t| *t > one_second_ago);
        self.frame_timestamps_within_last_second.push(now);

        let slow_cpu = self.update_slow_event(
            SLOW_FRAME,
            &[TOTAL_FRAME_CPU_TIME],
            self.slow_cpu_frame_threshold as f64,
        );
        self.update_slow_event(
            SLOW_TXN,
            &[DISPLAY_LIST_BUILD_TIME, CONTENT_SEND_TIME, SCENE_BUILD_TIME],
            80.0
        );

        if slow_cpu {
            self.classify_slow_cpu_frame();
        }

        let div = 100.0 / self.slow_frame_cpu_count as f64;
        self.counters[SLOW_FRAME_CPU_COUNT].set(self.slow_frame_cpu_count as f64);
        self.counters[SLOW_FRAME_GPU_COUNT].set(self.slow_frame_gpu_count as f64);
        self.counters[SLOW_FRAME_BUILD_COUNT].set(self.slow_frame_build_count as f64 * div);
        self.counters[SLOW_RENDER_COUNT].set(self.slow_render_count as f64 * div);
        self.counters[SLOW_UPLOAD_COUNT].set(self.slow_upload_count as f64 * div);
        self.counters[SLOW_DRAW_CALLS_COUNT].set(self.slow_draw_calls_count as f64 * div);
        self.counters[SLOW_TARGETS_COUNT].set(self.slow_targets_count as f64 * div);
        self.counters[SLOW_BLOB_COUNT].set(self.slow_blob_count as f64 * div);
        self.counters[SLOW_SCROLL_AFTER_SCENE_COUNT].set(self.slow_scroll_after_scene_count as f64 * div);

        self.update_total_gpu_mem();

        for counter in &mut self.counters {
            counter.update(update_avg);
        }
    }

    pub fn update_frame_stats(&mut self, stats: FullFrameStats) {
        if stats.gecko_display_list_time != 0.0 {
          self.frame_stats.push(stats.into());
        }
    }

    pub fn update_total_gpu_mem(&mut self) {
        let mut total = 0.0;
        for counter in [
            EXTERNAL_IMAGE_BYTES,
            ATLAS_TEXTURES_MEM,
            STANDALONE_TEXTURES_MEM,
            PICTURE_TILES_MEM,
            RENDER_TARGET_MEM,
            DEPTH_TARGETS_MEM,
            ATLAS_ITEMS_MEM,
            GPU_CACHE_MEM,
            GPU_BUFFER_MEM,
        ] {
            if let Some(val) = self.counters[counter].get() {
                total += val;
            }
        }
        self.counters[GPU_TOTAL_MEM].set(total);
    }

    pub fn set_gpu_time_queries(&mut self, gpu_queries: Vec<GpuTimer>) {
        let mut gpu_time_ns = 0;
        for sample in &gpu_queries {
            gpu_time_ns += sample.time_ns;
        }

        self.gpu_frames.push(ProfilerFrame {
          total_time: gpu_time_ns,
          samples: gpu_queries
        });

        let gpu_time = ns_to_ms(gpu_time_ns);
        self.counters[GPU_TIME].set_f64(gpu_time);
        if gpu_time > 12.0 {
            self.slow_frame_gpu_count += 1;
        }
    }

    // Find the index of a counter by its name.
    pub fn index_of(&self, name: &str) -> Option<usize> {
        self.counters.iter().position(|counter| counter.name == name)
    }

    // Define the profiler UI, see comment about the syntax at the top of this file.
    pub fn set_ui(&mut self, names: &str) {
        let mut selection = Vec::new();

        self.append_to_ui(&mut selection, names);

        if selection == self.ui {
            return;
        }

        for counter in &mut self.counters {
            counter.disable_graph();
        }

        for item in &selection {
            if let Item::Graph(idx) = item {
                self.counters[*idx].enable_graph(self.num_graph_samples);
            }
        }

        self.ui = selection;
    }

    fn append_to_ui(&mut self, selection: &mut Vec<Item>, names: &str) {
        // Group successive counters together.
        fn flush_counters(counters: &mut Vec<usize>, selection: &mut Vec<Item>) {
            if !counters.is_empty() {
                selection.push(Item::Counters(std::mem::take(counters)))
            }
        }

        let mut counters = Vec::new();

        for name in names.split(",") {
            let name = name.trim();
            let is_graph = name.starts_with("#");
            let is_indicator = name.starts_with("*");
            let is_string = name.starts_with("$");
            let name = if is_graph || is_indicator {
                &name[1..]
            } else {
                name
            };
            // See comment about the ui string syntax at the top of this file.
            match name {
                "" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::Space);
                }
                "|" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::Column);
                }
                "_" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::Row);
                }
                "FPS" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::Fps);
                }
                "GPU time queries" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::GpuTimeQueries);
                }
                "GPU cache bars" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::GpuCacheBars);
                }
                "Paint phase graph" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::PaintPhaseGraph);
                }
                "Slow scroll frames" => {
                    flush_counters(&mut counters, selection);
                    selection.push(Item::SlowScrollFrames);
                }
                _ => {
                    if is_string {
                        selection.push(Item::Text(name[1..].into()));
                    } else if let Some(idx) = self.index_of(name) {
                        if is_graph {
                            flush_counters(&mut counters, selection);
                            selection.push(Item::Graph(idx));
                        } else if is_indicator {
                            flush_counters(&mut counters, selection);
                            selection.push(Item::ChangeIndicator(idx));
                        } else {
                            counters.push(idx);
                        }
                    } else if let Some(preset_str) = find_preset(name) {
                        flush_counters(&mut counters, selection);
                        self.append_to_ui(selection, preset_str);
                    } else {
                        selection.push(Item::Text(format!("Unknown counter: {}", name)));
                    }
                }
            }
        }

        flush_counters(&mut counters, selection);
    }

    pub fn set_counters(&mut self, counters: &mut TransactionProfile) {
        for (id, evt) in counters.events.iter_mut().enumerate() {
            if let Event::Value(val) = *evt {
                self.counters[id].set(val);
            }
            *evt = Event::None;
        }
    }

    #[cfg(feature = "debugger")]
    pub fn counters(&self) -> &[Counter] {
        &self.counters
    }

    pub fn get(&self, id: usize) -> Option<f64> {
        self.counters[id].get()
    }

    fn draw_counters(
        counters: &[Counter],
        selected: &[usize],
        mut x: f32, mut y: f32,
        text_buffer: &mut String,
        debug_renderer: &mut DebugRenderer,
    ) -> default::Rect<f32> {
        let line_height = debug_renderer.line_height();

        x += PROFILE_PADDING;
        y += PROFILE_PADDING;
        let origin = default::Point2D::new(x, y);
        y += line_height * 0.5;

        let mut total_rect = Rect::zero();

        let mut color_index = 0;
        let colors = [
            // Regular values,
            ColorU::new(255, 255, 255, 255),
            ColorU::new(255, 255, 0, 255),
            // Unexpected values,
            ColorU::new(255, 80, 0, 255),
            ColorU::new(255, 0, 0, 255),
        ];

        for idx in selected {
            // If The index is invalid, add some vertical space.
            let counter = &counters[*idx];

            let rect = debug_renderer.add_text(
                x, y,
                counter.name,
                colors[color_index],
                None,
            );
            color_index = (color_index + 1) % 2;

            total_rect = total_rect.union(&rect);
            y += line_height;
        }

        color_index = 0;
        x = total_rect.max_x() + 60.0;
        y = origin.y + line_height * 0.5;

        for idx in selected {
            let counter = &counters[*idx];
            let expected_offset = if counter.has_unexpected_avg_max() { 2 } else { 0 };

            counter.write_value(text_buffer);

            let rect = debug_renderer.add_text(
                x,
                y,
                &text_buffer,
                colors[color_index + expected_offset],
                None,
            );
            color_index = (color_index + 1) % 2;

            total_rect = total_rect.union(&rect);
            y += line_height;
        }

        total_rect = total_rect
            .union(&Rect { origin, size: Size2D::new(1.0, 1.0) })
            .inflate(PROFILE_PADDING, PROFILE_PADDING);

        debug_renderer.add_quad(
            total_rect.min_x(),
            total_rect.min_y(),
            total_rect.max_x(),
            total_rect.max_y(),
            BACKGROUND_COLOR,
            BACKGROUND_COLOR,
        );

        total_rect
    }

    fn draw_graph(
        counter: &Counter,
        x: f32,
        y: f32,
        text_buffer: &mut String,
        debug_renderer: &mut DebugRenderer,
    ) -> default::Rect<f32> {
        let graph = counter.graph.as_ref().unwrap();

        let max_samples = graph.values.capacity() as f32;

        let size = Size2D::new(max_samples, 100.0);
        let line_height = debug_renderer.line_height();
        let graph_rect = Rect::new(Point2D::new(x + PROFILE_PADDING, y + PROFILE_PADDING), size);
        let mut rect = graph_rect.inflate(PROFILE_PADDING, PROFILE_PADDING);

        let stats = graph.stats();

        let text_color = ColorU::new(255, 255, 0, 255);
        let text_origin = rect.origin + vec2(rect.size.width, 25.0);
        set_text!(text_buffer, "{} ({})", counter.name, counter.unit);
        debug_renderer.add_text(
            text_origin.x,
            text_origin.y,
            if counter.unit == "" { counter.name } else { text_buffer },
            ColorU::new(0, 255, 0, 255),
            None,
        );

        set_text!(text_buffer, "Samples: {}", stats.samples);

        debug_renderer.add_text(
            text_origin.x,
            text_origin.y + line_height,
            text_buffer,
            text_color,
            None,
        );

        if stats.samples > 0 {
            set_text!(text_buffer, "Min: {:.2} {}", stats.min, counter.unit);
            debug_renderer.add_text(
                text_origin.x,
                text_origin.y + line_height * 2.0,
                text_buffer,
                text_color,
                None,
            );

            set_text!(text_buffer, "Avg: {:.2} {}", stats.avg, counter.unit);
            debug_renderer.add_text(
                text_origin.x,
                text_origin.y + line_height * 3.0,
                text_buffer,
                text_color,
                None,
            );

            set_text!(text_buffer, "Max: {:.2} {}", stats.max, counter.unit);
            debug_renderer.add_text(
                text_origin.x,
                text_origin.y + line_height * 4.0,
                text_buffer,
                text_color,
                None,
            );
        }

        rect.size.width += 220.0;
        debug_renderer.add_quad(
            rect.min_x(),
            rect.min_y(),
            rect.max_x(),
            rect.max_y(),
            BACKGROUND_COLOR,
            BACKGROUND_COLOR,
        );

        let bx1 = graph_rect.max_x();
        let by1 = graph_rect.max_y();

        let w = graph_rect.size.width / max_samples;
        let h = graph_rect.size.height;

        let color_t0 = ColorU::new(0, 255, 0, 255);
        let color_b0 = ColorU::new(0, 180, 0, 255);

        let color_t2 = ColorU::new(255, 0, 0, 255);
        let color_b2 = ColorU::new(180, 0, 0, 255);

        if stats.max > 0.0 {
            for (index, sample) in graph.values.iter().enumerate() {
                if !sample.is_finite() {
                    // NAN means no sample this frame.
                    continue;
                }
                let sample = *sample as f32;
                let x1 = bx1 - index as f32 * w;
                let x0 = x1 - w;

                let y0 = by1 - (sample / stats.max as f32) as f32 * h;
                let y1 = by1;

                let (color_top, color_bottom) = if counter.is_unexpected_value(sample as f64) {
                    (color_t2, color_b2)
                } else {
                    (color_t0, color_b0)
                };

                debug_renderer.add_quad(x0, y0, x1, y1, color_top, color_bottom);
            }
        }

        rect
    }


    fn draw_change_indicator(
        counter: &Counter,
        x: f32, y: f32,
        debug_renderer: &mut DebugRenderer
    ) -> default::Rect<f32> {
        let height = 10.0;
        let width = 20.0;

        // Draw the indicator red instead of blue if is is not within expected ranges.
        let color = if counter.has_unexpected_value() || counter.has_unexpected_avg_max() {
            ColorU::new(255, 20, 20, 255)
        } else {
            ColorU::new(0, 100, 250, 255)
        };

        let tx = counter.change_indicator as f32 * width;
        debug_renderer.add_quad(
            x,
            y,
            x + 15.0 * width,
            y + height,
            ColorU::new(0, 0, 0, 150),
            ColorU::new(0, 0, 0, 150),
        );

        debug_renderer.add_quad(
            x + tx,
            y,
            x + tx + width,
            y + height,
            color,
            ColorU::new(25, 25, 25, 255),
        );

        Rect {
            origin: Point2D::new(x, y),
            size: Size2D::new(15.0 * width + 20.0, height),
        }
    }

    fn draw_bar(
        label: &str,
        label_color: ColorU,
        counters: &[(ColorU, usize)],
        x: f32, y: f32,
        debug_renderer: &mut DebugRenderer,
    ) -> default::Rect<f32> {
        let x = x + 8.0;
        let y = y + 24.0;
        let text_rect = debug_renderer.add_text(
            x, y,
            label,
            label_color,
            None,
        );

        let x_base = text_rect.max_x() + 10.0;
        let width = 300.0;
        let total_value = counters.last().unwrap().1;
        let scale = width / total_value as f32;
        let mut x_current = x_base;

        for &(color, counter) in counters {
            let x_stop = x_base + counter as f32 * scale;
            debug_renderer.add_quad(
                x_current,
                text_rect.origin.y,
                x_stop,
                text_rect.max_y(),
                color,
                color,
            );
            x_current = x_stop;

        }

        let mut total_rect = text_rect;
        total_rect.size.width += width + 10.0;

        total_rect
    }

    fn draw_gpu_cache_bars(&self, x: f32, mut y: f32, text_buffer: &mut String, debug_renderer: &mut DebugRenderer) -> default::Rect<f32> {
        let color_updated = ColorU::new(0xFF, 0, 0, 0xFF);
        let color_free = ColorU::new(0, 0, 0xFF, 0xFF);
        let color_saved = ColorU::new(0, 0xFF, 0, 0xFF);

        let updated_blocks = self.get(GPU_CACHE_BLOCKS_UPDATED).unwrap_or(0.0) as usize;
        let saved_blocks = self.get(GPU_CACHE_BLOCKS_SAVED).unwrap_or(0.0) as usize;
        let allocated_blocks = self.get(GPU_CACHE_BLOCKS_TOTAL).unwrap_or(0.0) as usize;
        let allocated_rows = self.get(GPU_CACHE_ROWS_TOTAL).unwrap_or(0.0) as usize;
        let updated_rows = self.get(GPU_CACHE_ROWS_UPDATED).unwrap_or(0.0) as usize;
        let requested_blocks = updated_blocks + saved_blocks;
        let total_blocks = allocated_rows * MAX_VERTEX_TEXTURE_WIDTH;

        set_text!(text_buffer, "GPU cache rows ({}):", allocated_rows);

        let rect0 = Profiler::draw_bar(
            text_buffer,
            ColorU::new(0xFF, 0xFF, 0xFF, 0xFF),
            &[
                (color_updated, updated_rows),
                (color_free, allocated_rows),
            ],
            x, y,
            debug_renderer,
        );

        y = rect0.max_y();

        let rect1 = Profiler::draw_bar(
            "GPU cache blocks",
            ColorU::new(0xFF, 0xFF, 0, 0xFF),
            &[
                (color_updated, updated_blocks),
                (color_saved, requested_blocks),
                (color_free, allocated_blocks),
                (ColorU::new(0, 0, 0, 0xFF), total_blocks),
            ],
            x, y,
            debug_renderer,
        );

        let total_rect = rect0.union(&rect1).inflate(10.0, 10.0);
        debug_renderer.add_quad(
            total_rect.origin.x,
            total_rect.origin.y,
            total_rect.origin.x + total_rect.size.width,
            total_rect.origin.y + total_rect.size.height,
            ColorF::new(0.1, 0.1, 0.1, 0.8).into(),
            ColorF::new(0.2, 0.2, 0.2, 0.8).into(),
        );

        total_rect
    }

    // Draws a frame graph for a given frame collection.
    fn draw_frame_graph(
        frame_collection: &ProfilerFrameCollection,
        x: f32, y: f32,
        debug_renderer: &mut DebugRenderer,
    ) -> default::Rect<f32> {
        let mut has_data = false;
        for frame in &frame_collection.frames {
            if !frame.samples.is_empty() {
                has_data = true;
                break;
            }
        }

        if !has_data {
            return Rect::zero();
        }

        let graph_rect = Rect::new(
            Point2D::new(x + GRAPH_PADDING, y + GRAPH_PADDING),
            Size2D::new(GRAPH_WIDTH, GRAPH_HEIGHT),
        );
        let bounding_rect = graph_rect.inflate(GRAPH_PADDING, GRAPH_PADDING);

        debug_renderer.add_quad(
            bounding_rect.origin.x,
            bounding_rect.origin.y,
            bounding_rect.origin.x + bounding_rect.size.width,
            bounding_rect.origin.y + bounding_rect.size.height,
            BACKGROUND_COLOR,
            BACKGROUND_COLOR,
        );

        let w = graph_rect.size.width;
        let mut y0 = graph_rect.origin.y;

        let mut max_time = frame_collection.frames
            .iter()
            .max_by_key(|f| f.total_time)
            .unwrap()
            .total_time as f32;

        // If the max time is lower than 16ms, fix the scale
        // at 16ms so that the graph is easier to interpret.
        let baseline_ns = 16_000_000.0; // 16ms
        max_time = max_time.max(baseline_ns);

        let mut tags_present = FastHashMap::default();

        for frame in &frame_collection.frames {
            let y1 = y0 + GRAPH_FRAME_HEIGHT;

            let mut current_ns = 0;
            for sample in &frame.samples {
                let x0 = graph_rect.origin.x + w * current_ns as f32 / max_time;
                current_ns += sample.time_ns;
                let x1 = graph_rect.origin.x + w * current_ns as f32 / max_time;
                let mut bottom_color = sample.tag.color;
                bottom_color.a *= 0.5;

                debug_renderer.add_quad(
                    x0,
                    y0,
                    x1,
                    y1,
                    sample.tag.color.into(),
                    bottom_color.into(),
                );

                tags_present.insert(sample.tag.label, sample.tag.color);
            }

            y0 = y1;
        }

        let mut tags_present: Vec<_> = tags_present.iter().collect();
        tags_present.sort_by_key(|item| item.0);

        // If the max time is higher than 16ms, show a vertical line at the
        // 16ms mark.
        if max_time > baseline_ns {
            let x = graph_rect.origin.x + w * baseline_ns as f32 / max_time;
            let height = frame_collection.frames.len() as f32 * GRAPH_FRAME_HEIGHT;

            debug_renderer.add_quad(
                x,
                graph_rect.origin.y,
                x + 4.0,
                graph_rect.origin.y + height,
                ColorU::new(120, 00, 00, 150),
                ColorU::new(120, 00, 00, 100),
            );
        }


        // Add a legend to see which color correspond to what primitive.
        const LEGEND_SIZE: f32 = 20.0;
        const PADDED_LEGEND_SIZE: f32 = 25.0;
        if !tags_present.is_empty() {
            debug_renderer.add_quad(
                bounding_rect.max_x() + GRAPH_PADDING,
                bounding_rect.origin.y,
                bounding_rect.max_x() + GRAPH_PADDING + 200.0,
                bounding_rect.origin.y + tags_present.len() as f32 * PADDED_LEGEND_SIZE + GRAPH_PADDING,
                BACKGROUND_COLOR,
                BACKGROUND_COLOR,
            );
        }

        for (i, (label, &color)) in tags_present.iter().enumerate() {
            let x0 = bounding_rect.origin.x + bounding_rect.size.width + GRAPH_PADDING * 2.0;
            let y0 = bounding_rect.origin.y + GRAPH_PADDING + i as f32 * PADDED_LEGEND_SIZE;

            debug_renderer.add_quad(
                x0, y0, x0 + LEGEND_SIZE, y0 + LEGEND_SIZE,
                color.into(),
                color.into(),
            );

            debug_renderer.add_text(
                x0 + PADDED_LEGEND_SIZE,
                y0 + LEGEND_SIZE * 0.75,
                label,
                ColorU::new(255, 255, 0, 255),
                None,
            );
        }

        bounding_rect
    }

    pub fn draw_profile(
        &mut self,
        _frame_index: u64,
        debug_renderer: &mut DebugRenderer,
        device_size: DeviceIntSize,
    ) {
        let x_start = 20.0;
        let mut y_start = 150.0;
        let default_column_width = 400.0;

        // set_text!(..) into this string instead of using format!(..) to avoid
        // unnecessary allocations.
        let mut text_buffer = String::with_capacity(32);

        let mut column_width = default_column_width;
        let mut max_y = y_start;

        let mut x = x_start;
        let mut y = y_start;

        for elt in &self.ui {
            let rect = match elt {
                Item::Counters(indices) => {
                    Profiler::draw_counters(&self.counters, &indices, x, y, &mut text_buffer, debug_renderer)
                }
                Item::Graph(idx) => {
                    Profiler::draw_graph(&self.counters[*idx], x, y, &mut text_buffer, debug_renderer)
                }
                Item::ChangeIndicator(idx) => {
                    Profiler::draw_change_indicator(&self.counters[*idx], x, y, debug_renderer)
                }
                Item::GpuTimeQueries => {
                    Profiler::draw_frame_graph(&self.gpu_frames, x, y, debug_renderer)
                }
                Item::GpuCacheBars => {
                    self.draw_gpu_cache_bars(x, y, &mut text_buffer, debug_renderer)
                }
                Item::PaintPhaseGraph => {
                    Profiler::draw_frame_graph(&self.frame_stats, x, y, debug_renderer)
                }
                Item::SlowScrollFrames => {
                    Profiler::draw_frame_graph(&self.slow_scroll_frames, x, y, debug_renderer)
                }
                Item::Text(text) => {
                    let p = 10.0;
                    let mut rect = debug_renderer.add_text(
                        x + p,
                        y + p,
                        &text,
                        ColorU::new(255, 255, 255, 255),
                        None,
                    );
                    rect = rect.inflate(p, p);

                    debug_renderer.add_quad(
                        rect.origin.x,
                        rect.origin.y,
                        rect.max_x(),
                        rect.max_y(),
                        BACKGROUND_COLOR,
                        BACKGROUND_COLOR,
                    );

                    rect
                }
                Item::Fps => {
                    let fps = self.frame_timestamps_within_last_second.len();
                    set_text!(&mut text_buffer, "{} fps", fps);
                    let mut rect = debug_renderer.add_text(
                        x + PROFILE_PADDING,
                        y + PROFILE_PADDING + 5.0,
                        &text_buffer,
                        ColorU::new(255, 255, 255, 255),
                        None,
                    );
                    rect = rect.inflate(PROFILE_PADDING, PROFILE_PADDING);

                    debug_renderer.add_quad(
                        rect.min_x(),
                        rect.min_y(),
                        rect.max_x(),
                        rect.max_y(),
                        BACKGROUND_COLOR,
                        BACKGROUND_COLOR,
                    );

                    rect
                }
                Item::Space => {
                    Rect { origin: Point2D::new(x, y), size: Size2D::new(0.0, PROFILE_SPACING) }
                }
                Item::Column => {
                    max_y = max_y.max(y);
                    x += column_width + PROFILE_SPACING;
                    y = y_start;
                    column_width = default_column_width;

                    continue;
                }
                Item::Row => {
                    max_y = max_y.max(y);
                    y_start = max_y + PROFILE_SPACING;
                    y = y_start;
                    x = x_start;
                    column_width = default_column_width;

                    continue;
                }
            };

            column_width = column_width.max(rect.size.width);
            y = rect.max_y();

            if y > device_size.height as f32 - 100.0 {
                max_y = max_y.max(y);
                x += column_width + PROFILE_SPACING;
                y = y_start;
                column_width = default_column_width;
            }
        }
    }

    #[cfg(feature = "capture")]
    pub fn dump_stats(&self, sink: &mut dyn std::io::Write) -> std::io::Result<()> {
        for counter in &self.counters {
            if counter.value.is_finite() {
                writeln!(sink, "{} {:?}{}", counter.name, counter.value, counter.unit)?;
            }
        }

        Ok(())
    }
}

/// Defines the interface for hooking up an external profiler to WR.
pub trait ProfilerHooks : Send + Sync {
    /// Register a thread with the profiler.
    fn register_thread(&self, thread_name: &str);

    /// Unregister a thread with the profiler.
    fn unregister_thread(&self);

    /// Called at the beginning of a profile scope.
    fn begin_marker(&self, label: &str);

    /// Called at the end of a profile scope.
    fn end_marker(&self, label: &str);

    /// Called to mark an event happening.
    fn event_marker(&self, label: &str);

    /// Called with a duration to indicate a text marker that just ended. Text
    /// markers allow different types of entries to be recorded on the same row
    /// in the timeline, by adding labels to the entry.
    ///
    /// This variant is also useful when the caller only wants to record events
    /// longer than a certain threshold, and thus they don't know in advance
    /// whether the event will qualify.
    fn add_text_marker(&self, label: &str, text: &str, duration: Duration);

    /// Returns true if the current thread is being profiled.
    fn thread_is_being_profiled(&self) -> bool;
}

/// The current global profiler callbacks, if set by embedder.
pub static mut PROFILER_HOOKS: Option<&'static dyn ProfilerHooks> = None;

/// Set the profiler callbacks, or None to disable the profiler.
/// This function must only ever be called before any WR instances
/// have been created, or the hooks will not be set.
pub fn set_profiler_hooks(hooks: Option<&'static dyn ProfilerHooks>) {
    if !wr_has_been_initialized() {
        unsafe {
            PROFILER_HOOKS = hooks;
        }
    }
}

/// A simple RAII style struct to manage a profile scope.
pub struct ProfileScope {
    name: &'static str,
}


/// Register a thread with the Gecko Profiler.
pub fn register_thread(thread_name: &str) {
    unsafe {
        if let Some(ref hooks) = PROFILER_HOOKS {
            hooks.register_thread(thread_name);
        }
    }
}


/// Unregister a thread with the Gecko Profiler.
pub fn unregister_thread() {
    unsafe {
        if let Some(ref hooks) = PROFILER_HOOKS {
            hooks.unregister_thread();
        }
    }
}

/// Records a marker of the given duration that just ended.
pub fn add_text_marker(label: &str, text: &str, duration: Duration) {
    unsafe {
        if let Some(ref hooks) = PROFILER_HOOKS {
            hooks.add_text_marker(label, text, duration);
        }
    }
}

/// Records a marker of the given duration that just ended.
pub fn add_event_marker(label: &str) {
    unsafe {
        if let Some(ref hooks) = PROFILER_HOOKS {
            hooks.event_marker(label);
        }
    }
}

/// Returns true if the current thread is being profiled.
pub fn thread_is_being_profiled() -> bool {
    unsafe {
        PROFILER_HOOKS.map_or(false, |h| h.thread_is_being_profiled())
    }
}

impl ProfileScope {
    /// Begin a new profile scope
    pub fn new(name: &'static str) -> Self {
        unsafe {
            if let Some(ref hooks) = PROFILER_HOOKS {
                hooks.begin_marker(name);
            }
        }

        ProfileScope {
            name,
        }
    }
}

impl Drop for ProfileScope {
    fn drop(&mut self) {
        unsafe {
            if let Some(ref hooks) = PROFILER_HOOKS {
                hooks.end_marker(self.name);
            }
        }
    }
}

/// A helper macro to define profile scopes.
macro_rules! profile_marker {
    ($string:expr) => {
        let _scope = $crate::profiler::ProfileScope::new($string);
    };
}

#[derive(Debug, Clone)]
pub struct GpuProfileTag {
    pub label: &'static str,
    pub color: ColorF,
}

/// Ranges of expected value for a profile counter.
#[derive(Clone, Debug)]
pub struct Expected<T> {
    pub range: Option<Range<T>>,
    pub avg: Option<Range<T>>,
}

impl<T> Expected<T> {
     const fn none() -> Self {
        Expected {
            range: None,
            avg: None,
        }
    }
}

const fn expected<T>(range: Range<T>) -> Expected<T> {
    Expected {
        range: Some(range),
        avg: None,
    }
}

impl Expected<f64> {
    const fn avg(mut self, avg: Range<f64>) -> Self {
        self.avg = Some(avg);
        self
    }
}

impl Expected<i64> {
    const fn avg(mut self, avg: Range<i64>) -> Self {
        self.avg = Some(avg);
        self
    }

    fn into_float(self) -> Expected<f64> {
        Expected {
            range: match self.range {
                Some(r) => Some(r.start as f64 .. r.end as f64),
                None => None,
            },
            avg: match self.avg {
                Some(r) => Some(r.start as f64 .. r.end as f64),
                None => None,
            },
        }
    }
}

pub struct CounterDescriptor {
    pub name: &'static str,
    pub unit: &'static str,
    pub index: usize,
    pub show_as: ShowAs,
    pub expected: Expected<f64>,
}

#[derive(Debug)]
pub struct Counter {
    pub name: &'static str,
    pub unit: &'static str,
    pub show_as: ShowAs,
    pub expected: Expected<f64>,

    ///
    value: f64,
    /// Number of samples in the current time slice.
    num_samples: u64,
    /// Sum of the values recorded during the current time slice.
    sum: f64,
    /// The max value in in-progress time slice.
    next_max: f64,
    /// The max value of the previous time slice (displayed).
    max: f64,
    /// The average value of the previous time slice (displayed).
    avg: f64,
    /// Incremented when the counter changes.
    change_indicator: u8,

    graph: Option<Graph>,
}

impl Counter {
    pub fn new(descriptor: &CounterDescriptor) -> Self {
        Counter {
            name: descriptor.name,
            unit: descriptor.unit,
            show_as: descriptor.show_as,
            expected: descriptor.expected.clone(),
            value: std::f64::NAN,
            num_samples: 0,
            sum: 0.0,
            next_max: 0.0,
            max: 0.0,
            avg: 0.0,
            change_indicator: 0,
            graph: None,
        }
    }
    pub fn set_f64(&mut self, val: f64) {
        self.value = val;
    }

    pub fn set<T>(&mut self, val: T) where T: Into<f64> {
        self.set_f64(val.into());
    }

    pub fn get(&self) -> Option<f64> {
        if self.value.is_finite() {
            Some(self.value)
        } else {
            None
        }
    }

    pub fn write_value(&self, output: &mut String) {
        match self.show_as {
            ShowAs::Float => {
                set_text!(output, "{:.2} {} (max: {:.2})", self.avg, self.unit, self.max);
            }
            ShowAs::Int => {
                set_text!(output, "{:.0} {} (max: {:.0})", self.avg.round(), self.unit, self.max.round());
            }
        }
    }

    pub fn enable_graph(&mut self, max_samples: usize) {
        if self.graph.is_some() {
            return;
        }

        self.graph = Some(Graph::new(max_samples));
    }

    pub fn disable_graph(&mut self) {
        self.graph = None;
    }

    pub fn is_unexpected_value(&self, value: f64) -> bool {
        if let Some(range) = &self.expected.range {
            return value.is_finite() && value >= range.end;
        }

        false
    }

    pub fn has_unexpected_value(&self) -> bool {
        self.is_unexpected_value(self.value)
    }

    pub fn has_unexpected_avg_max(&self) -> bool {
        if let Some(range) = &self.expected.range {
            if self.max.is_finite() && self.max >= range.end {
                return true;
            }
        }

        if let Some(range) = &self.expected.avg {
            if self.avg < range.start || self.avg >= range.end {
                return true;
            }
        }

        false
    }

    fn update(&mut self, update_avg: bool) {
        let updated = self.value.is_finite();
        if updated {
            self.next_max = self.next_max.max(self.value);
            self.sum += self.value;
            self.num_samples += 1;
            self.change_indicator = (self.change_indicator + 1) % 15;
        }

        if let Some(graph) = &mut self.graph {
            graph.set(self.value);
        }

        self.value = std::f64::NAN;

        if update_avg {
            if self.num_samples > 0 {
                self.avg = self.sum / self.num_samples as f64;
                self.max = self.next_max;
            } else {
                // There has been no sample in the averaging window, just show zero.
                self.avg = 0.0;
                self.max = 0.0;
            }
            self.sum = 0.0;
            self.num_samples = 0;
            self.next_max = std::f64::MIN;
        }
    }
}

#[derive(Copy, Clone, Debug)]
pub enum Event {
    Start(u64),
    Value(f64),
    None,
}

// std::convert::From/TryFrom can't deal with integer to f64 so we roll our own...
pub trait EventValue {
    fn into_f64(self) -> f64;
}

impl EventValue for f64 { fn into_f64(self) -> f64 { self } }
impl EventValue for f32 { fn into_f64(self) -> f64 { self as f64 } }
impl EventValue for u32 { fn into_f64(self) -> f64 { self as f64 } }
impl EventValue for i32 { fn into_f64(self) -> f64 { self as f64 } }
impl EventValue for u64 { fn into_f64(self) -> f64 { self as f64 } }
impl EventValue for usize { fn into_f64(self) -> f64 { self as f64 } }

/// A container for profiling information that moves along the rendering pipeline
/// and is handed off to the profiler at the end.
pub struct TransactionProfile {
    pub events: Vec<Event>,
}

impl TransactionProfile {
    pub fn new() -> Self {
        TransactionProfile {
            events: vec![Event::None; NUM_PROFILER_EVENTS],
        }
    }

    pub fn start_time(&mut self, id: usize) {
        let ns = zeitstempel::now();
        self.events[id] = Event::Start(ns);
    }

    pub fn end_time(&mut self, id: usize) -> f64 {
        self.end_time_if_started(id).unwrap()
    }

    /// Similar to end_time, but doesn't panic if not matched with start_time.
    pub fn end_time_if_started(&mut self, id: usize) -> Option<f64> {
        if let Event::Start(start) = self.events[id] {
            let now = zeitstempel::now();
            let time_ns = now - start;

            let time_ms = ns_to_ms(time_ns);
            self.events[id] = Event::Value(time_ms);

            Some(time_ms)
        } else {
            None
        }
    }

    pub fn set<T>(&mut self, id: usize, value: T) where T: EventValue {
        self.set_f64(id, value.into_f64());
    }


    pub fn set_f64(&mut self, id: usize, value: f64) {
        self.events[id] = Event::Value(value);
    }

    pub fn get(&self, id: usize) -> Option<f64> {
        if let Event::Value(val) = self.events[id] {
            Some(val)
        } else {
            None
        }
    }

    pub fn get_or(&self, id: usize, or: f64) -> f64 {
        self.get(id).unwrap_or(or)
    }

    pub fn add<T>(&mut self, id: usize, n: T) where T: EventValue {
        let n = n.into_f64();

        let evt = &mut self.events[id];

        let val = match *evt {
            Event::Value(v) => v + n,
            Event::None => n,
            Event::Start(..) => { panic!(); }
        };

        *evt = Event::Value(val);
    }

    pub fn inc(&mut self, id: usize) {
        self.add(id, 1.0);
    }

    pub fn take(&mut self) -> Self {
        TransactionProfile {
            events: std::mem::take(&mut self.events),
        }
    }

    pub fn take_and_reset(&mut self) -> Self {
        let events = std::mem::take(&mut self.events);

        *self = TransactionProfile::new();

        TransactionProfile { events }
    }

    pub fn merge(&mut self, other: &mut Self) {
        for i in 0..self.events.len() {
            match (self.events[i], other.events[i]) {
                (Event::Value(v1), Event::Value(v2)) => {
                    self.events[i] = Event::Value(v1.max(v2));
                }
                (Event::Value(_), _) => {}
                (_, Event::Value(v2)) => {
                    self.events[i] = Event::Value(v2);
                }
                (Event::None, evt) => {
                    self.events[i] = evt;
                }
                (Event::Start(s1), Event::Start(s2)) => {
                    self.events[i] = Event::Start(s1.max(s2));
                }
                _=> {}
            }
            other.events[i] = Event::None;
        }
    }

    pub fn clear(&mut self) {
        for evt in &mut self.events {
            *evt = Event::None;
        }
    }
}

impl GlyphRasterizeProfiler for TransactionProfile {
    fn start_time(&mut self) {
        let id = GLYPH_RESOLVE_TIME;
        let ns = zeitstempel::now();
        self.events[id] = Event::Start(ns);
    }

    fn end_time(&mut self) -> f64 {
        let id = GLYPH_RESOLVE_TIME;
        self.end_time_if_started(id).unwrap()
    }

    fn set(&mut self, value: f64) {
        let id = RASTERIZED_GLYPHS;
        self.set_f64(id, value);
    }
}

#[derive(Debug)]
pub struct GraphStats {
    pub min: f64,
    pub avg: f64,
    pub max: f64,
    pub sum: f64,
    pub samples: usize,
}

#[derive(Debug)]
pub struct Graph {
    values: VecDeque<f64>,
}

impl Graph {
    fn new(max_samples: usize) -> Self {
        let mut values = VecDeque::new();
        values.reserve(max_samples);

        Graph { values }
    }

    fn set(&mut self, val: f64) {
        if self.values.len() == self.values.capacity() {
            self.values.pop_back();
        }
        self.values.push_front(val);
    }

    pub fn stats(&self) -> GraphStats {
        let mut stats = GraphStats {
            min: f64::MAX,
            avg: 0.0,
            max: -f64::MAX,
            sum: 0.0,
            samples: 0,
        };

        let mut samples = 0;
        for value in &self.values {
            if value.is_finite() {
                stats.min = stats.min.min(*value);
                stats.max = stats.max.max(*value);
                stats.sum += *value;
                samples += 1;
            }
        }

        if samples > 0 {
            stats.avg = stats.sum / samples as f64;
            stats.samples = samples;
        }

        stats
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum ShowAs {
    Float,
    Int,
}

struct ProfilerFrame {
    total_time: u64,
    samples: Vec<GpuTimer>,
}

struct ProfilerFrameCollection {
    frames: VecDeque<ProfilerFrame>,
}

impl ProfilerFrameCollection {
    fn new() -> Self {
        ProfilerFrameCollection {
            frames: VecDeque::new(),
        }
    }

    fn push(&mut self, frame: ProfilerFrame) {
        if self.frames.len() == 20 {
            self.frames.pop_back();
        }
        self.frames.push_front(frame);
    }
}

impl From<FullFrameStats> for ProfilerFrame {
  fn from(stats: FullFrameStats) -> ProfilerFrame {
    let new_sample = |time, label, color| -> GpuTimer {
      let tag = GpuProfileTag {
        label,
        color
      };

      let time_ns = ms_to_ns(time);

      GpuTimer {
        tag, time_ns
      }
    };

    let samples = vec![
      new_sample(stats.gecko_display_list_time, "Gecko DL", ColorF { r: 0.0, g: 1.0, b: 0.0, a: 1.0 }),
      new_sample(stats.wr_display_list_time, "WR DL", ColorF { r: 0.0, g: 1.0, b: 1.0, a: 1.0 }),
      new_sample(stats.scene_build_time, "Scene Build", ColorF { r: 1.0, g: 0.0, b: 1.0, a: 1.0 }),
      new_sample(stats.frame_build_time, "Frame Build", ColorF { r: 1.0, g: 0.0, b: 0.0, a: 1.0 }),
    ];

    ProfilerFrame {
      total_time: ms_to_ns(stats.total()),
      samples
    }
  }
}

pub struct CpuFrameTimings {
    pub total: f64,
    pub api_send: f64,
    pub update_document: f64,
    pub visibility: f64,
    pub prepare: f64,
    pub glyph_resolve: f64,
    pub batching: f64,
    pub frame_building_other: f64,
    pub frame_send: f64,
    pub uploads: f64,
    pub gpu_cache: f64,
    pub draw_calls: f64,
    pub unknown: f64,
}

impl CpuFrameTimings {
    pub fn new(counters: &[Counter]) -> Self {
        let total = counters[TOTAL_FRAME_CPU_TIME].get().unwrap_or(0.0);
        let api_send = counters[API_SEND_TIME].get().unwrap_or(0.0);
        let visibility = counters[FRAME_VISIBILITY_TIME].get().unwrap_or(0.0);
        let prepare = counters[FRAME_PREPARE_TIME].get().unwrap_or(0.0);
        let glyph_resolve = counters[GLYPH_RESOLVE_TIME].get().unwrap_or(0.0);
        let batching = counters[FRAME_BATCHING_TIME].get().unwrap_or(0.0);
        let frame_send = counters[FRAME_SEND_TIME].get().unwrap_or(0.0);
        let renderer = counters[RENDERER_TIME].get().unwrap_or(0.0);
        let uploads = counters[TEXTURE_CACHE_UPDATE_TIME].get().unwrap_or(0.0);
        let gpu_cache = counters[GPU_CACHE_PREPARE_TIME].get().unwrap_or(0.0);
        let frame_build = visibility + prepare + glyph_resolve + batching;
        let update_document = counters[UPDATE_DOCUMENT_TIME].get().unwrap_or(0.0) - frame_build;
        let draw_calls = renderer - uploads - gpu_cache;
        let unknown = (total - (api_send + update_document + frame_build + frame_send + renderer)).max(0.0);
        let frame_building_other = (counters[FRAME_BUILDING_TIME].get().unwrap_or(0.0) - frame_build).max(0.0);

        CpuFrameTimings {
            total,
            api_send,
            update_document,
            visibility,
            prepare,
            glyph_resolve,
            batching,
            frame_building_other,
            frame_send,
            uploads,
            gpu_cache,
            draw_calls,
            unknown,
        }
    }

    fn to_profiler_frame(&self) -> ProfilerFrame {
        fn sample(time_ms: f64, label: &'static str, color: ColorF) -> GpuTimer {
            let time_ns = ms_to_ns(time_ms);
            GpuTimer {
                time_ns,
                tag: GpuProfileTag { label, color },
            }
        }

        ProfilerFrame {
            total_time: ms_to_ns(self.total),
            // Number the label so that they are displayed in order.
            samples: vec![
                // Compositor -> frame building
                sample(self.api_send, "01. send", ColorF { r: 0.5, g: 0.5, b: 0.5, a: 1.0 }),
                // Frame building
                sample(self.update_document, "02. update document", ColorF { r: 0.2, g: 0.2, b: 0.7, a: 1.0 }),
                sample(self.visibility, "03. visibility", ColorF { r: 0.0, g: 0.5, b: 0.9, a: 1.0 }),
                sample(self.prepare, "04. prepare", ColorF { r: 0.0, g: 0.4, b: 0.3, a: 1.0 }),
                sample(self.glyph_resolve, "05. glyph resolve", ColorF { r: 0.0, g: 0.7, b: 0.4, a: 1.0 }),
                sample(self.batching, "06. batching", ColorF { r: 0.2, g: 0.3, b: 0.7, a: 1.0 }),
                sample(self.frame_building_other, "07. frame build (other)", ColorF { r: 0.1, g: 0.7, b: 0.7, a: 1.0 }),
                // Frame building -> renderer
                sample(self.frame_send, "08. frame send", ColorF { r: 1.0, g: 0.8, b: 0.8, a: 1.0 }),
                // Renderer
                sample(self.uploads, "09. texture uploads", ColorF { r: 0.8, g: 0.0, b: 0.3, a: 1.0 }),
                sample(self.gpu_cache, "10. gpu cache update", ColorF { r: 0.5, g: 0.0, b: 0.4, a: 1.0 }),
                sample(self.draw_calls, "11. draw calls", ColorF { r: 1.0, g: 0.5, b: 0.0, a: 1.0 }),
                // Unaccounted time
                sample(self.unknown, "12. unknown", ColorF { r: 0.3, g: 0.3, b: 0.3, a: 1.0 }),
            ],
        }
    }
}

pub fn ns_to_ms(ns: u64) -> f64 {
    ns as f64 / 1_000_000.0
}

pub fn ms_to_ns(ms: f64) -> u64 {
  (ms * 1_000_000.0) as u64
}

pub fn bytes_to_mb(bytes: usize) -> f64 {
    bytes as f64 / 1_000_000.0
}

#[derive(Debug, PartialEq)]
enum Item {
    Counters(Vec<usize>),
    Graph(usize),
    ChangeIndicator(usize),
    Fps,
    GpuTimeQueries,
    GpuCacheBars,
    PaintPhaseGraph,
    SlowScrollFrames,
    Text(String),
    Space,
    Column,
    Row,
}
