Bug 1759686 - patch 3 - Ensure prefs that may be accessed by canvas2d text code are atomic. r=lsalzman

These need to be atomic so that they can be accessed by canvas code when running on a worker thread
without calling main-thread-only Preferences APIs.

Depends on D144185

Differential Revision: https://phabricator.services.mozilla.com/D144186

dom/canvas/CanvasRenderingContext2D.cpp

@@ -3696,7 +3696,7 @@ struct MOZ_STACK_CLASS CanvasBidiProcessor
         mOp(CanvasRenderingContext2D::TextDrawOperation::FILL),
         mTextRunFlags(),
         mDoMeasureBoundingBox(false) {
-    if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+    if (StaticPrefs::gfx_missing_fonts_notify()) {
       mMissingFonts = MakeUnique<gfxMissingFontRecorder>();
     }
   }

layout/base/nsPresContext.cpp

@@ -304,7 +304,7 @@ nsPresContext::nsPresContext(dom::Document* aDocument, nsPresContextType aType)
     mTextPerf = MakeUnique<gfxTextPerfMetrics>();
   }
 
-  if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+  if (StaticPrefs::gfx_missing_fonts_notify()) {
     mMissingFonts = MakeUnique<gfxMissingFontRecorder>();
   }
 
@@ -580,7 +580,7 @@ void nsPresContext::PreferenceChanged(const char* aPrefName) {
                               MediaFeatureChangePropagation::JustThisDocument);
   }
   if (prefName.EqualsLiteral(GFX_MISSING_FONTS_NOTIFY_PREF)) {
-    if (Preferences::GetBool(GFX_MISSING_FONTS_NOTIFY_PREF)) {
+    if (StaticPrefs::gfx_missing_fonts_notify()) {
       if (!mMissingFonts) {
         mMissingFonts = MakeUnique<gfxMissingFontRecorder>();
         // trigger reflow to detect missing fonts on the current page

modules/libpref/init/StaticPrefList.yaml

@@ -3696,22 +3696,22 @@
   mirror: always
 
 - name: dom.textMetrics.actualBoundingBox.enabled
-  type: bool
+  type: RelaxedAtomicBool
   value: true
   mirror: always
 
 - name: dom.textMetrics.baselines.enabled
-  type: bool
+  type: RelaxedAtomicBool
   value: false
   mirror: always
 
 - name: dom.textMetrics.emHeight.enabled
-  type: bool
+  type: RelaxedAtomicBool
   value: false
   mirror: always
 
 - name: dom.textMetrics.fontBoundingBox.enabled
-  type: bool
+  type: RelaxedAtomicBool
   value: false
   mirror: always
 
@@ -5412,6 +5412,13 @@
   value: true
   mirror: once
 
+# Do we fire a notification about missing fonts, so the front-end can decide
+# whether to try and do something about it (e.g. download additional fonts)?
+- name: gfx.missing_fonts.notify
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 #if !defined(MOZ_WIDGET_ANDROID)
 - name: gfx.egl.prefer-gles.enabled
   type: bool

modules/libpref/init/all.js

@@ -592,10 +592,6 @@ pref("gfx.downloadable_fonts.fallback_delay_short", 100);
 // the uncached load behavior across pages (useful for testing reflow problems)
 pref("gfx.downloadable_fonts.disable_cache", false);
 
-// Do we fire a notification about missing fonts, so the front-end can decide
-// whether to try and do something about it (e.g. download additional fonts)?
-pref("gfx.missing_fonts.notify", false);
-
 // whether to always search all font cmaps during system font fallback
 pref("gfx.font_rendering.fallback.always_use_cmaps", false);