Bug 1722487 - Avoid some work for font list updates. r=jfkthame

Differential Revision: https://phabricator.services.mozilla.com/D123363

dom/ipc/ContentChild.cpp

@@ -2392,6 +2392,14 @@ mozilla::ipc::IPCResult ContentChild::RecvFontListChanged() {
   return IPC_OK();
 }
 
+mozilla::ipc::IPCResult ContentChild::RecvForceGlobalReflow(
+    bool aNeedsReframe) {
+  gfxPlatform::ForceGlobalReflow(aNeedsReframe ? gfxPlatform::NeedsReframe::Yes
+                                               : gfxPlatform::NeedsReframe::No);
+
+  return IPC_OK();
+}
+
 mozilla::ipc::IPCResult ContentChild::RecvGeolocationUpdate(
     nsIDOMGeoPosition* aPosition) {
   RefPtr<nsGeolocationService> gs =

dom/ipc/ContentChild.h

@@ -339,6 +339,7 @@ class ContentChild final : public PContentChild,
       nsTArray<IPCBlob>&& aBlobs, nsTArray<nsCString>&& aChangedKeys);
 
   mozilla::ipc::IPCResult RecvFontListChanged();
+  mozilla::ipc::IPCResult RecvForceGlobalReflow(bool aNeedsReframe);
 
   mozilla::ipc::IPCResult RecvGeolocationUpdate(nsIDOMGeoPosition* aPosition);
 

dom/ipc/PContent.ipdl

@@ -645,7 +645,7 @@ child:
      * This message has raised priority so that it will take precedence over
      * vsync messages to the child.
      */
-    [Priority=mediumhigh] async RebuildFontList(bool aFulLRebuild);
+    [Priority=mediumhigh] async RebuildFontList(bool aFullRebuild);
 
     /**
      * The shared font list has been modified, potentially adding matches
@@ -654,6 +654,12 @@ child:
      */
     async FontListChanged();
 
+    /**
+     * The font list or prefs have been updated in such a way that we might need
+     * to do a reflow and maybe reframe.
+     */
+    async ForceGlobalReflow(bool aNeedsReframe);
+
     /**
      * A new shmem block has been added to the font list; the child process
      * should map the new block and add to its index.

gfx/thebes/gfxDWriteFonts.cpp

@@ -132,7 +132,7 @@ void gfxDWriteFont::SystemTextQualityChanged() {
   // flush cached stuff that depended on the old setting, and force
   // reflow everywhere to ensure we are using correct glyph metrics.
   gfxPlatform::FlushFontAndWordCaches();
-  gfxPlatform::ForceGlobalReflow();
+  gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::No);
 }
 
 mozilla::Atomic<bool> gfxDWriteFont::sForceGDIClassicEnabled{true};

gfx/thebes/gfxFcPlatformFontList.cpp

@@ -2429,8 +2429,8 @@ void gfxFcPlatformFontList::CheckFontUpdates(nsITimer* aTimer, void* aThis) {
   FcConfig* current = FcConfigGetCurrent();
   if (current != pfl->GetLastConfig()) {
     pfl->UpdateFontList();
-    pfl->ForceGlobalReflow();
 
+    gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::Yes);
     mozilla::dom::ContentParent::NotifyUpdatedFonts(true);
   }
 }

gfx/thebes/gfxMacPlatformFontList.mm

@@ -1313,9 +1313,7 @@ void gfxMacPlatformFontList::RegisteredFontsChangedNotificationCallback(
   // xxx - should be carefully pruning the list of fonts, not rebuilding it from scratch
   fl->UpdateFontList();
 
-  // modify a preference that will trigger reflow everywhere
-  fl->ForceGlobalReflow();
-
+  gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::Yes);
   dom::ContentParent::NotifyUpdatedFonts(true);
 }
 

gfx/thebes/gfxPlatform.cpp

@@ -141,6 +141,7 @@ static const uint32_t kDefaultGlyphCacheSize = -1;
 #include "SoftwareVsyncSource.h"
 #include "nscore.h"  // for NS_FREE_PERMANENT_DATA
 #include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/TouchEvent.h"
 #include "gfxVR.h"
 #include "VRManager.h"
@@ -2260,20 +2261,20 @@ void gfxPlatform::FlushFontAndWordCaches() {
 }
 
 /* static */
-void gfxPlatform::ForceGlobalReflow() {
+void gfxPlatform::ForceGlobalReflow(NeedsReframe aNeedsReframe) {
   MOZ_ASSERT(NS_IsMainThread());
+  const bool reframe = aNeedsReframe == NeedsReframe::Yes;
+  // Send a notification that will be observed by PresShells in this process
+  // only.
+  if (nsCOMPtr<nsIObserverService> obs = services::GetObserverService()) {
+    char16_t needsReframe[] = {char16_t(reframe), 0};
+    obs->NotifyObservers(nullptr, "font-info-updated", needsReframe);
+  }
   if (XRE_IsParentProcess()) {
-    // Modify a preference that will trigger reflow everywhere (in all
-    // content processes, as well as the parent).
-    static const char kPrefName[] = "font.internaluseonly.changed";
-    bool fontInternalChange = Preferences::GetBool(kPrefName, false);
-    Preferences::SetBool(kPrefName, !fontInternalChange);
-  } else {
-    // Send a notification that will be observed by PresShells in this
-    // process only.
-    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
-    if (obs) {
-      obs->NotifyObservers(nullptr, "font-info-updated", nullptr);
+    // Propagate the change to child processes.
+    for (auto* process :
+         dom::ContentParent::AllProcesses(dom::ContentParent::eLive)) {
+      Unused << process->SendForceGlobalReflow(reframe);
     }
   }
 }

gfx/thebes/gfxPlatform.h

@@ -626,7 +626,8 @@ class gfxPlatform : public mozilla::layers::MemoryPressureListener {
    * something about platform settings changes that might have an effect
    * on layout, such as font rendering settings that influence metrics.
    */
-  static void ForceGlobalReflow();
+  enum class NeedsReframe : bool { No, Yes };
+  static void ForceGlobalReflow(NeedsReframe);
 
   static void FlushFontAndWordCaches();
 

gfx/thebes/gfxPlatformFontList.cpp

@@ -170,7 +170,7 @@ static void FontListPrefChanged(const char* aPref, void* aData = nullptr) {
                 !strcmp(aPref, "privacy.resistFingerprinting"))) {
     gfxPlatformFontList::PlatformFontList()->SetVisibilityLevel();
     if (XRE_IsParentProcess()) {
-      gfxPlatform::ForceGlobalReflow();
+      gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::No);
     }
   }
 }
@@ -188,7 +188,7 @@ gfxFontListPrefObserver::Observe(nsISupports* aSubject, const char* aTopic,
   FontListPrefChanged(nullptr);
 
   if (XRE_IsParentProcess()) {
-    gfxPlatform::ForceGlobalReflow();
+    gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::No);
   }
   return NS_OK;
 }
@@ -336,9 +336,6 @@ void gfxPlatformFontList::FontWhitelistPrefChanged(const char* aPref,
   dom::ContentParent::NotifyUpdatedFonts(true);
 }
 
-// number of CSS generic font families
-const uint32_t kNumGenerics = 5;
-
 void gfxPlatformFontList::ApplyWhitelist() {
   uint32_t numFonts = mEnabledFontsList.Length();
   mFontFamilyWhitelistActive = (numFonts > 0);
@@ -637,7 +634,7 @@ void gfxPlatformFontList::FontListChanged() {
     // safe to use: ensure they all get flushed.
     RebuildLocalFonts(/*aForgetLocalFaces*/ true);
   }
-  ForceGlobalReflow();
+  gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::Yes);
 }
 
 void gfxPlatformFontList::GenerateFontListKey(const nsACString& aKeyName,
@@ -857,7 +854,7 @@ void gfxPlatformFontList::UpdateFontList(bool aFullRebuild) {
     if (mStartedLoadingCmapsFrom != 0xffffffffu) {
       InitializeCodepointsWithNoFonts();
       mStartedLoadingCmapsFrom = 0xffffffffu;
-      gfxPlatform::ForceGlobalReflow();
+      gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::No);
     }
   }
 }
@@ -2491,7 +2488,7 @@ void gfxPlatformFontList::CleanupLoader() {
                     FindFamiliesFlags::eNoAddToNamesMissedWhenSearching));
         });
     if (forceReflow) {
-      ForceGlobalReflow();
+      gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::No);
     }
 
     mOtherNamesMissed = nullptr;
@@ -2523,10 +2520,6 @@ void gfxPlatformFontList::GetPrefsAndStartLoader() {
   }
 }
 
-void gfxPlatformFontList::ForceGlobalReflow() {
-  gfxPlatform::ForceGlobalReflow();
-}
-
 void gfxPlatformFontList::RebuildLocalFonts(bool aForgetLocalFaces) {
   for (auto* fontset : mUserFontSetList) {
     if (aForgetLocalFaces) {

gfx/thebes/gfxPlatformFontList.h

@@ -760,9 +760,6 @@ class gfxPlatformFontList : public gfxFontInfoLoader {
   // read the loader initialization prefs, and start it
   void GetPrefsAndStartLoader();
 
-  // for font list changes that affect all documents
-  void ForceGlobalReflow();
-
   // If aForgetLocalFaces is true, all gfxFontEntries for src:local fonts must
   // be discarded (not potentially reused to satisfy the rebuilt rules),
   // because they may no longer be valid.

layout/base/PresShell.cpp

@@ -9932,7 +9932,9 @@ PresShell::Observe(nsISupports* aSubject, const char* aTopic,
   }
 
   if (!nsCRT::strcmp(aTopic, "font-info-updated")) {
-    mPresContext->ForceReflowForFontInfoUpdate();
+    // See how gfxPlatform::ForceGlobalReflow encodes this.
+    bool needsReframe = aData && !!aData[0];
+    mPresContext->ForceReflowForFontInfoUpdate(needsReframe);
     return NS_OK;
   }
 

layout/base/nsPresContext.cpp

@@ -138,11 +138,42 @@ bool nsPresContext::IsDOMPaintEventPending() {
   return false;
 }
 
-void nsPresContext::ForceReflowForFontInfoUpdate() {
-  // We can trigger reflow by pretending a font.* preference has changed;
-  // this is the same mechanism as gfxPlatform::ForceGlobalReflow() uses
-  // if new fonts are installed during the session, for example.
-  PreferenceChanged("font.internaluseonly.changed");
+void nsPresContext::ForceReflowForFontInfoUpdate(bool aNeedsReframe) {
+  // In the case of a static-clone document used for printing or print-preview,
+  // this is undesirable because the nsPrintJob is holding weak refs to frames
+  // that will get blown away unexpectedly by this reconstruction. So the
+  // prescontext for a print/preview doc ignores the font-list update.
+  //
+  // This means the print document may still be using cached fonts that are no
+  // longer present in the font list, but that should be safe given that all the
+  // required font instances have already been created, so it won't be depending
+  // on access to the font-list entries.
+  //
+  // XXX Actually, I think it's probably a bad idea to do *any* restyling of
+  // print documents in response to pref changes. We could be in the middle
+  // of printing the document, and reflowing all the frames might cause some
+  // kind of unwanted mid-document discontinuity.
+  if (IsPrintingOrPrintPreview()) {
+    return;
+  }
+
+  // If there's a user font set, discard any src:local() faces it may have
+  // loaded because their font entries may no longer be valid.
+  if (auto* fonts = Document()->GetFonts()) {
+    fonts->GetUserFontSet()->ForgetLocalFaces();
+  }
+
+  FlushFontCache();
+
+  nsChangeHint changeHint =
+      aNeedsReframe ? nsChangeHint_ReconstructFrame : NS_STYLE_HINT_REFLOW;
+
+  // We also need to trigger restyling for ex/ch units changes to take effect,
+  // if needed.
+  auto restyleHint =
+      UsesExChUnits() ? RestyleHint::RecascadeSubtree() : RestyleHint{0};
+
+  RebuildAllStyleData(changeHint, restyleHint);
 }
 
 static bool IsVisualCharset(NotNull<const Encoding*> aCharset) {
@@ -567,46 +598,16 @@ void nsPresContext::PreferenceChanged(const char* aPrefName) {
       mMissingFonts = nullptr;
     }
   }
-  if (prefName.EqualsLiteral("font.internaluseonly.changed") &&
-      !IsPrintingOrPrintPreview()) {
-    // If there's a user font set, discard any src:local() faces it may have
-    // loaded because their font entries may no longer be valid.
-    if (auto* fonts = Document()->GetFonts()) {
-      fonts->GetUserFontSet()->ForgetLocalFaces();
-    }
 
-    // If there's a change to the font list, we generally need to reconstruct
-    // frames, as the existing frames may be referring to fonts that are no
-    // longer available. But in the case of a static-clone document used for
-    // printing or print-preview, this is undesirable because the nsPrintJob
-    // is holding weak refs to frames that will get blown away unexpectedly by
-    // this reconstruction. So the prescontext for a print/preview doc ignores
-    // the font-list update.
-    //
-    // This means the print document may still be using cached fonts that are
-    // no longer present in the font list, but that should be safe given that
-    // all the required font instances have already been created, so it won't
-    // be depending on access to the font-list entries.
-    //
-    // XXX Actually, I think it's probably a bad idea to do *any* restyling of
-    // print documents in response to pref changes. We could be in the middle
-    // of printing the document, and reflowing all the frames might cause some
-    // kind of unwanted mid-document discontinuity.
-    changeHint |= nsChangeHint_ReconstructFrame;
-    // We also need to trigger restyling for ex/ch units changes to take effect,
-    // if needed.
-    if (UsesExChUnits()) {
-      restyleHint |= RestyleHint::RecascadeSubtree();
-    }
-  } else if (StringBeginsWith(prefName, "font."_ns) ||
-             // Changes to font family preferences don't change anything in the
-             // computed style data, so the style system won't generate a reflow
-             // hint for us.  We need to do that manually.
-             prefName.EqualsLiteral("intl.accept_languages") ||
-             // Changes to bidi prefs need to trigger a reflow (see bug 443629)
-             StringBeginsWith(prefName, "bidi."_ns) ||
-             // Changes to font_rendering prefs need to trigger a reflow
-             StringBeginsWith(prefName, "gfx.font_rendering."_ns)) {
+  if (StringBeginsWith(prefName, "font."_ns) ||
+      // Changes to font family preferences don't change anything in the
+      // computed style data, so the style system won't generate a reflow hint
+      // for us.  We need to do that manually.
+      prefName.EqualsLiteral("intl.accept_languages") ||
+      // Changes to bidi prefs need to trigger a reflow (see bug 443629)
+      StringBeginsWith(prefName, "bidi."_ns) ||
+      // Changes to font_rendering prefs need to trigger a reflow
+      StringBeginsWith(prefName, "gfx.font_rendering."_ns)) {
     changeHint |= NS_STYLE_HINT_REFLOW;
     if (UsesExChUnits()) {
       restyleHint |= RestyleHint::RecascadeSubtree();

layout/base/nsPresContext.h

@@ -1114,7 +1114,7 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
  public:
   // Used by the PresShell to force a reflow when some aspect of font info
   // has been updated, potentially affecting font selection and layout.
-  void ForceReflowForFontInfoUpdate();
+  void ForceReflowForFontInfoUpdate(bool aNeedsReframe);
 
   /**
    * Checks for MozAfterPaint listeners on the document

layout/style/PostTraversalTask.cpp

@@ -50,7 +50,7 @@ void PostTraversalTask::Run() {
       nsPresContext* pc =
           static_cast<ServoStyleSet*>(mTarget)->GetPresContext();
       if (pc) {
-        pc->ForceReflowForFontInfoUpdate();
+        pc->ForceReflowForFontInfoUpdate(/* aNeedsReframe = */ false);
       }
       break;
   }

security/sandbox/test/browser_bug1393259.js

@@ -97,22 +97,16 @@ add_task(async function() {
         }
       }
 
-      // Pref "font.internaluseonly.changed" is updated when system
-      // fonts change. We use it to wait for changes to be detected
-      // in the browser.
-      let prefBranch = Services.prefs.getBranch("font.internaluseonly.");
-
-      // Returns a promise that resolves when the pref is changed
+      // Returns a promise that resolves when font info is changed.
       let getFontNotificationPromise = () =>
         new Promise(resolve => {
-          let prefObserver = {
-            QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),
-            observe() {
-              prefBranch.removeObserver("changed", prefObserver);
-              resolve();
-            },
-          };
-          prefBranch.addObserver("changed", prefObserver);
+          const kTopic = "font-info-updated";
+          function observe() {
+            Services.obs.removeObserver(observe, kTopic);
+            resolve();
+          }
+
+          Services.obs.addObserver(observe, kTopic);
         });
 
       let homeDir = Services.dirsvc.get("Home", Ci.nsIFile);

widget/windows/nsWindow.cpp

@@ -5048,17 +5048,6 @@ const char16_t* GetQuitType() {
   return nullptr;
 }
 
-static void ForceFontUpdate() {
-  // update device context font cache
-  // Dirty but easiest way:
-  // Changing nsIPrefBranch entry which triggers callbacks
-  // and flows into calling mDeviceContext->FlushFontCache()
-  // to update the font cache in all the instance of Browsers
-  static const char kPrefName[] = "font.internaluseonly.changed";
-  bool fontInternalChange = Preferences::GetBool(kPrefName, false);
-  Preferences::SetBool(kPrefName, !fontInternalChange);
-}
-
 bool nsWindow::ExternalHandlerProcessMessage(UINT aMessage, WPARAM& aWParam,
                                              LPARAM& aLParam,
                                              MSGResult& aResult) {
@@ -5231,7 +5220,9 @@ bool nsWindow::ProcessMessage(UINT msg, WPARAM& wParam, LPARAM& lParam,
           do_GetService("@mozilla.org/gfx/fontenumerator;1", &rv);
       if (NS_SUCCEEDED(rv)) {
         fontEnum->UpdateFontList(&didChange);
-        ForceFontUpdate();
+        if (didChange) {
+          gfxPlatform::ForceGlobalReflow(gfxPlatform::NeedsReframe::Yes);
+        }
       }  // if (NS_SUCCEEDED(rv))
     } break;