Bug 1715537 - Log a warning to the web console when a font request is blocked due to font-visibility restrictions. r=emilio

Depends on D124196

Differential Revision: https://phabricator.services.mozilla.com/D124345

gfx/thebes/gfxFontEntry.h

@@ -833,7 +833,7 @@ class gfxFontFamily {
         mCheckForFallbackFaces(false),
         mCheckedForLegacyFamilyNames(false) {}
 
-  const nsCString& Name() { return mName; }
+  const nsCString& Name() const { return mName; }
 
   virtual void LocalizedName(nsACString& aLocalizedName);
   virtual bool HasOtherFamilyNames();

gfx/thebes/gfxPlatformFontList.cpp

@@ -792,6 +792,9 @@ gfxFontEntry* gfxPlatformFontList::LookupInSharedFaceNameList(
   FontVisibility level =
       aPresContext ? aPresContext->GetFontVisibility() : FontVisibility::User;
   if (!IsVisibleToCSS(*family, level)) {
+    if (aPresContext) {
+      aPresContext->ReportBlockedFontFamily(*family);
+    }
     return nullptr;
   }
   gfxFontEntry* fe = CreateFontEntry(face, family);
@@ -1427,10 +1430,15 @@ bool gfxPlatformFontList::FindAndAddFamilies(
     }
     // Check whether the family we found is actually allowed to be looked up,
     // according to current font-visibility prefs.
-    if (family && (IsVisibleToCSS(*family, visibilityLevel) ||
-                   (allowHidden && family->IsHidden()))) {
-      aOutput->AppendElement(FamilyAndGeneric(family, aGeneric));
-      return true;
+    if (family) {
+      bool visible = IsVisibleToCSS(*family, visibilityLevel);
+      if (visible || (allowHidden && family->IsHidden())) {
+        aOutput->AppendElement(FamilyAndGeneric(family, aGeneric));
+        return true;
+      }
+      if (aPresContext) {
+        aPresContext->ReportBlockedFontFamily(*family);
+      }
     }
     return false;
   }
@@ -1438,20 +1446,33 @@ bool gfxPlatformFontList::FindAndAddFamilies(
   NS_ASSERTION(mFontFamilies.Count() != 0,
                "system font list was not initialized correctly");
 
+  auto isBlockedByVisibilityLevel = [=](gfxFontFamily* aFamily) -> bool {
+    bool visible = IsVisibleToCSS(*aFamily, visibilityLevel);
+    if (visible || (allowHidden && aFamily->IsHidden())) {
+      return false;
+    }
+    if (aPresContext) {
+      aPresContext->ReportBlockedFontFamily(*aFamily);
+    }
+    return true;
+  };
+
   // lookup in canonical (i.e. English) family name list
   gfxFontFamily* familyEntry = mFontFamilies.GetWeak(key);
-  if (familyEntry && !IsVisibleToCSS(*familyEntry, visibilityLevel) &&
-      !(allowHidden && familyEntry->IsHidden())) {
-    return false;
+  if (familyEntry) {
+    if (isBlockedByVisibilityLevel(familyEntry)) {
+      return false;
+    }
   }
 
   // if not found, lookup in other family names list (mostly localized names)
   if (!familyEntry) {
     familyEntry = mOtherFamilyNames.GetWeak(key);
   }
-  if (familyEntry && !IsVisibleToCSS(*familyEntry, visibilityLevel) &&
-      !(allowHidden && familyEntry->IsHidden())) {
-    return false;
+  if (familyEntry) {
+    if (isBlockedByVisibilityLevel(familyEntry)) {
+      return false;
+    }
   }
 
   // if still not found and other family names not yet fully initialized,
@@ -1472,9 +1493,10 @@ bool gfxPlatformFontList::FindAndAddFamilies(
       }
       mOtherNamesMissed->Insert(key);
     }
-    if (familyEntry && !IsVisibleToCSS(*familyEntry, visibilityLevel) &&
-        !(allowHidden && familyEntry->IsHidden())) {
-      return false;
+    if (familyEntry) {
+      if (isBlockedByVisibilityLevel(familyEntry)) {
+        return false;
+      }
     }
   }
 
@@ -1505,9 +1527,10 @@ bool gfxPlatformFontList::FindAndAddFamilies(
       if (base && base->CheckForLegacyFamilyNames(this)) {
         familyEntry = mOtherFamilyNames.GetWeak(key);
       }
-      if (familyEntry && !IsVisibleToCSS(*familyEntry, visibilityLevel) &&
-          !(allowHidden && familyEntry->IsHidden())) {
-        return false;
+      if (familyEntry) {
+        if (isBlockedByVisibilityLevel(familyEntry)) {
+          return false;
+        }
       }
     }
   }

layout/base/nsPresContext.cpp

@@ -27,6 +27,7 @@
 #include "nsCOMPtr.h"
 #include "nsCSSFrameConstructor.h"
 #include "nsDocShell.h"
+#include "nsIConsoleService.h"
 #include "nsIContentViewer.h"
 #include "nsPIDOMWindow.h"
 #include "mozilla/ServoStyleSet.h"
@@ -835,6 +836,29 @@ bool nsPresContext::UpdateFontVisibility() {
   return mFontVisibility != oldValue;
 }
 
+void nsPresContext::ReportBlockedFontFamilyName(const nsCString& aFamily,
+                                                FontVisibility aVisibility) {
+  if (!mBlockedFonts.EnsureInserted(aFamily)) {
+    return;
+  }
+  nsAutoString msg;
+  msg.AppendPrintf(
+      "Request for font \"%s\" blocked at visibility level %d (requires %d)\n",
+      aFamily.get(), int(GetFontVisibility()), int(aVisibility));
+  nsContentUtils::ReportToConsoleNonLocalized(msg, nsIScriptError::warningFlag,
+                                              "Security"_ns, mDocument);
+}
+
+void nsPresContext::ReportBlockedFontFamily(const fontlist::Family& aFamily) {
+  auto* fontList = gfxPlatformFontList::PlatformFontList()->SharedFontList();
+  const nsCString& name = aFamily.DisplayName().AsString(fontList);
+  ReportBlockedFontFamilyName(name, aFamily.Visibility());
+}
+
+void nsPresContext::ReportBlockedFontFamily(const gfxFontFamily& aFamily) {
+  ReportBlockedFontFamilyName(aFamily.Name(), aFamily.Visibility());
+}
+
 void nsPresContext::InitFontCache() {
   if (!mFontCache) {
     mFontCache = new nsFontCache();

layout/base/nsPresContext.h

@@ -30,6 +30,7 @@
 #include "nsHashKeys.h"
 #include "nsRect.h"
 #include "nsStringFwd.h"
+#include "nsTHashSet.h"
 #include "nsTHashtable.h"
 #include "nsAtom.h"
 #include "nsIWidgetListener.h"  // for nsSizeMode
@@ -53,6 +54,7 @@ class nsIFrame;
 class nsFrameManager;
 class nsAtom;
 class nsIRunnable;
+class gfxFontFamily;
 class gfxFontFeatureValueSet;
 class gfxUserFontEntry;
 class gfxUserFontSet;
@@ -164,6 +166,8 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
   void UpdateFontCacheUserFonts(gfxUserFontSet* aUserFontSet);
 
   FontVisibility GetFontVisibility() const { return mFontVisibility; }
+  void ReportBlockedFontFamily(const mozilla::fontlist::Family& aFamily);
+  void ReportBlockedFontFamily(const gfxFontFamily& aFamily);
 
   /**
    * Get the nsFontMetrics that describe the properties of
@@ -1157,6 +1161,8 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
   // visibile to CSS. Returns whether the current visibility value actually
   // changed (in which case content should be reflowed).
   bool UpdateFontVisibility();
+  void ReportBlockedFontFamilyName(const nsCString& aFamily,
+                                   FontVisibility aVisibility);
 
   // IMPORTANT: The ownership implicit in the following member variables
   // has been explicitly checked.  If you add any members to this class,
@@ -1273,6 +1279,12 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
   nsTArray<RefPtr<mozilla::ManagedPostRefreshObserver>>
       mManagedPostRefreshObservers;
 
+  // If we block the use of a font-family that is explicitly requested,
+  // due to font visibility settings, we log a message to the web console;
+  // this hash-set keeps track of names we've logged for this context, so
+  // that we can avoid repeatedly reporting the same font.
+  nsTHashSet<nsCString> mBlockedFonts;
+
   ScrollStyles mViewportScrollStyles;
 
   uint16_t mImageAnimationMode;