Bug 1953907 - Avoid reading from uninitialized mHighContrastInfo.

MANUAL PUSH: UBSan fix CLOSED TREE

widget/ThemeColors.cpp

@@ -157,10 +157,10 @@ sRGBColor ThemeAccentColor::GetDarker() const {
   return sRGBColor::FromABGR(ColorPalette::GetDarker(*mAccentColor));
 }
 
-auto ThemeColors::ShouldBeHighContrast(const nsPresContext& aPc,
-                                       bool aCustomAccentColor)
+auto ThemeColors::ShouldBeHighContrast(const nsIFrame* aFrame)
     -> HighContrastInfo {
-  if (!aPc.GetBackgroundColorDraw()) {
+  auto* pc = aFrame->PresContext();
+  if (!pc->GetBackgroundColorDraw()) {
     // We make sure that we're drawing backgrounds, since otherwise layout
     // will darken our used text colors etc anyways, and that can cause
     // contrast issues with dark high-contrast themes.
@@ -177,18 +177,18 @@ auto ThemeColors::ShouldBeHighContrast(const nsPresContext& aPc,
     // or in "requested" mode (chrome-only) with no custom accent color.
     // Otherwise it causes issues when pages only override some of the system
     // colors, specially in dark themes.
-    switch (aPc.ForcedColors()) {
+    switch (pc->ForcedColors()) {
       case StyleForcedColors::None:
         break;
       case StyleForcedColors::Requested:
-        return !aCustomAccentColor;
+        return aFrame->StyleUI()->mAccentColor.IsAuto();
       case StyleForcedColors::Active:
         return true;
     }
     return false;
   }();
   const bool mustUseLight =
-      PreferenceSheet::PrefsFor(*aPc.Document()).mMustUseLightSystemColors;
+      PreferenceSheet::PrefsFor(*pc->Document()).mMustUseLightSystemColors;
   return {highContrast, mustUseLight};
 }
 

widget/ThemeColors.h

@@ -55,18 +55,17 @@ class ThemeColors {
   };
 
   const Document& mDoc;
+  const HighContrastInfo mHighContrastInfo;
   const ColorScheme mColorScheme;
   const AccentColor mAccentColor;
-  const HighContrastInfo mHighContrastInfo;
 
  public:
   explicit ThemeColors(const nsIFrame* aFrame, StyleAppearance aAppearance)
       : mDoc(*aFrame->PresContext()->Document()),
+        mHighContrastInfo(ShouldBeHighContrast(aFrame)),
         mColorScheme(
             ColorSchemeForWidget(aFrame, aAppearance, mHighContrastInfo)),
-        mAccentColor(*aFrame->Style(), mColorScheme),
-        mHighContrastInfo(ShouldBeHighContrast(*aFrame->PresContext(),
-                                               mAccentColor.IsCustom())) {}
+        mAccentColor(*aFrame->Style(), mColorScheme) {}
   virtual ~ThemeColors() = default;
 
   [[nodiscard]] static float ScaleLuminanceBy(float aLuminance, float aFactor) {
@@ -102,8 +101,8 @@ class ThemeColors {
   }
 
   // Whether we should use system colors (for high contrast mode).
-  static HighContrastInfo ShouldBeHighContrast(const nsPresContext&,
-                                               bool aCustomAccentColor);
+  static HighContrastInfo ShouldBeHighContrast(const nsIFrame*);
+
   static ColorScheme ColorSchemeForWidget(const nsIFrame*, StyleAppearance,
                                           const HighContrastInfo&);