Revert:

       https://bugs.webkit.org/show_bug.cgi?id=306148

This change was introduced in 2.50.5; it adversely affects system font
selection under GTK3.


diff --git a/Source/WebKit/UIProcess/glib/WebProcessPoolGLib.cpp b/Source/WebKit/UIProcess/glib/WebProcessPoolGLib.cpp
index 1821d55a9d32..044ddc0c3e95 100644
--- a/Source/WebKit/UIProcess/glib/WebProcessPoolGLib.cpp
+++ b/Source/WebKit/UIProcess/glib/WebProcessPoolGLib.cpp
@@ -366,6 +366,14 @@ const String& WebProcessPool::accessibilityBusAddress() const
         return m_accessibilityBusAddress.value();
     }
 
+#if PLATFORM(GTK)
+    auto address = Display::singleton().accessibilityBusAddress();
+    if (!address.isEmpty()) {
+        m_accessibilityBusAddress = WTF::move(address);
+        return m_accessibilityBusAddress.value();
+    }
+#endif
+
     m_accessibilityBusAddress = queryAccessibilityBusAddress();
     return m_accessibilityBusAddress.value();
 }
diff --git a/Source/WebKit/UIProcess/gtk/Display.cpp b/Source/WebKit/UIProcess/gtk/Display.cpp
index e650d414e64d..7a829a0b5b1b 100644
--- a/Source/WebKit/UIProcess/gtk/Display.cpp
+++ b/Source/WebKit/UIProcess/gtk/Display.cpp
@@ -96,6 +96,24 @@ GLDisplay* Display::glDisplay() const
     return nullptr;
 }
 
+String Display::accessibilityBusAddress() const
+{
+    if (!m_gdkDisplay)
+        return { };
+
+#if USE(GTK4)
+    if (const char* atspiBusAddress = static_cast<const char*>(g_object_get_data(G_OBJECT(m_gdkDisplay.get()), "-gtk-atspi-bus-address")))
+        return String::fromUTF8(atspiBusAddress);
+#endif
+
+#if PLATFORM(X11)
+    if (isX11())
+        return accessibilityBusAddressX11();
+#endif
+
+    return { };
+}
+
 #if !PLATFORM(X11)
 bool Display::isX11() const
 {
diff --git a/Source/WebKit/UIProcess/gtk/Display.h b/Source/WebKit/UIProcess/gtk/Display.h
index 660d0a7869ae..f8243a9c65a2 100644
--- a/Source/WebKit/UIProcess/gtk/Display.h
+++ b/Source/WebKit/UIProcess/gtk/Display.h
@@ -51,10 +51,13 @@ public:
     bool isX11() const;
     bool isWayland() const;
 
+    String accessibilityBusAddress() const;
+
 private:
     Display();
 #if PLATFORM(X11)
     bool initializeGLDisplayX11() const;
+    String accessibilityBusAddressX11() const;
 #endif
 #if PLATFORM(WAYLAND)
     bool initializeGLDisplayWayland() const;
diff --git a/Source/WebKit/UIProcess/gtk/DisplayX11.cpp b/Source/WebKit/UIProcess/gtk/DisplayX11.cpp
index 64cc213251a1..b59cdd684fcc 100644
--- a/Source/WebKit/UIProcess/gtk/DisplayX11.cpp
+++ b/Source/WebKit/UIProcess/gtk/DisplayX11.cpp
@@ -77,6 +77,26 @@ bool Display::initializeGLDisplayX11() const
     return false;
 }
 
+String Display::accessibilityBusAddressX11() const
+{
+    auto* xDisplay = GDK_DISPLAY_XDISPLAY(m_gdkDisplay.get());
+    Atom atspiBusAtom = XInternAtom(xDisplay, "AT_SPI_BUS", False);
+    Atom type;
+    int format;
+    unsigned long itemCount, bytesAfter;
+    unsigned char* data = nullptr;
+    XErrorTrapper trapper(xDisplay, XErrorTrapper::Policy::Ignore);
+    WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN // GTK port.
+    XGetWindowProperty(xDisplay, RootWindowOfScreen(DefaultScreenOfDisplay(xDisplay)), atspiBusAtom, 0L, 8192, False, XA_STRING, &type, &format, &itemCount, &bytesAfter, &data);
+    WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
+
+    auto atspiBusAddress = String::fromUTF8(reinterpret_cast<char*>(data));
+    if (data)
+        XFree(data);
+
+    return atspiBusAddress;
+}
+
 } // namespace WebKit
 
 #endif // PLATFORM(X11)