Bug 1714282 - Handle bitmap font sizes in the shared font list on Linux. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D116874

gfx/thebes/SharedFontList.cpp

@@ -11,6 +11,7 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/Logging.h"
+#include "mozilla/Unused.h"
 
 #define LOG_FONTLIST(args) \
   MOZ_LOG(gfxPlatform::GetLog(eGfxLog_fontlist), LogLevel::Debug, args)
@@ -231,34 +232,46 @@ void Family::AddFaces(FontList* aList, const nsTArray<Face::InitData>& aFaces) {
   }
 }
 
-void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
-                                  nsTArray<Face*>& aFaceList,
-                                  bool aIgnoreSizeTolerance) const {
+bool Family::FindAllFacesForStyleInternal(FontList* aList,
+                                          const gfxFontStyle& aStyle,
+                                          nsTArray<Face*>& aFaceList) const {
   MOZ_ASSERT(aFaceList.IsEmpty());
   if (!IsInitialized()) {
-    return;
+    return false;
   }
 
   Pointer* facePtrs = Faces(aList);
   if (!facePtrs) {
-    return;
+    return false;
   }
 
-  // If the family has only one face, we simply return it; no further
-  // checking needed.
+  // Depending on the kind of family, we have to do varying amounts of work
+  // to figure out what face(s) to use for the requested style properties.
+
+  // If the family has only one face, we simply use it; no further style
+  // checking needed. (However, for bitmap fonts we may still need to check
+  // whether the size is acceptable.)
   if (NumFaces() == 1) {
     MOZ_ASSERT(!facePtrs[0].IsNull());
-    aFaceList.AppendElement(static_cast<Face*>(facePtrs[0].ToPtr(aList)));
-    return;
+    Face* face = static_cast<Face*>(facePtrs[0].ToPtr(aList));
+    if (face && face->HasValidDescriptor()) {
+      aFaceList.AppendElement(face);
+#ifdef MOZ_WIDGET_GTK
+      if (face->mSize) {
+        return true;
+      }
+#endif
+    }
+    return false;
   }
 
   // Most families are "simple", having just Regular/Bold/Italic/BoldItalic,
   // or some subset of these. In this case, we have exactly 4 entries in
   // mAvailableFonts, stored in the above order; note that some of the entries
   // may be nullptr. We can then pick the required entry based on whether the
-  // request is for bold or non-bold, italic or non-italic, without running the
-  // more complex matching algorithm used for larger families with many weights
-  // and/or widths.
+  // request is for bold or non-bold, italic or non-italic, without running
+  // the more complex matching algorithm used for larger families with many
+  // weights and/or widths.
 
   if (mIsSimple) {
     // Family has no more than the "standard" 4 faces, at fixed indexes;
@@ -270,15 +283,20 @@ void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
     uint8_t faceIndex =
         (wantItalic ? kItalicMask : 0) | (wantBold ? kBoldMask : 0);
 
-    // if the desired style is available, return it directly
+    // If the desired style is available, use it directly.
     Face* face = static_cast<Face*>(facePtrs[faceIndex].ToPtr(aList));
     if (face && face->HasValidDescriptor()) {
       aFaceList.AppendElement(face);
-      return;
+#ifdef MOZ_WIDGET_GTK
+      if (face->mSize) {
+        return true;
+      }
+#endif
+      return false;
     }
 
-    // order to check fallback faces in a simple family, depending on requested
-    // style
+    // Order to check fallback faces in a simple family, depending on the
+    // requested style.
     static const uint8_t simpleFallbacks[4][3] = {
         {kBoldFaceIndex, kItalicFaceIndex,
          kBoldItalicFaceIndex},  // fallback sequence for Regular
@@ -294,7 +312,12 @@ void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
       face = static_cast<Face*>(facePtrs[order[trial]].ToPtr(aList));
       if (face && face->HasValidDescriptor()) {
         aFaceList.AppendElement(face);
-        return;
+#ifdef MOZ_WIDGET_GTK
+        if (face->mSize) {
+          return true;
+        }
+#endif
+        return false;
       }
     }
 
@@ -302,7 +325,7 @@ void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
     // can happen if we're on a stylo thread and caught the font list being
     // updated; in that case we just fail quietly and let font fallback do
     // something for the time being.
-    return;
+    return false;
   }
 
   // Pick the font(s) that are closest to the desired weight, style, and
@@ -315,9 +338,11 @@ void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
   // normal platform fonts with a single font entry for each
   // weight/style/stretch combination, only the last matched font entry will
   // be added.
-
   double minDistance = INFINITY;
   Face* matched = nullptr;
+  // Keep track of whether we've included any non-scalable font resources in
+  // the selected set.
+  bool anyNonScalable = false;
   for (uint32_t i = 0; i < NumFaces(); i++) {
     Face* face = static_cast<Face*>(facePtrs[i].ToPtr(aList));
     if (face) {
@@ -332,6 +357,11 @@ void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
       } else if (distance == minDistance) {
         if (matched) {
           aFaceList.AppendElement(matched);
+#ifdef MOZ_WIDGET_GTK
+          if (matched->mSize) {
+            anyNonScalable = true;
+          }
+#endif
         }
         matched = face;
       }
@@ -341,7 +371,69 @@ void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
   MOZ_ASSERT(matched, "didn't match a font within a family");
   if (matched) {
     aFaceList.AppendElement(matched);
+#ifdef MOZ_WIDGET_GTK
+    if (matched->mSize) {
+      anyNonScalable = true;
     }
+#endif
+  }
+
+  return anyNonScalable;
+}
+
+void Family::FindAllFacesForStyle(FontList* aList, const gfxFontStyle& aStyle,
+                                  nsTArray<Face*>& aFaceList,
+                                  bool aIgnoreSizeTolerance) const {
+#ifdef MOZ_WIDGET_GTK
+  bool anyNonScalable =
+#else
+  Unused <<
+#endif
+      FindAllFacesForStyleInternal(aList, aStyle, aFaceList);
+
+#ifdef MOZ_WIDGET_GTK
+  // aFaceList now contains whatever faces are the best style match for
+  // the requested style. If specifically-sized bitmap faces are supported,
+  // we need to additionally filter the list to choose the appropriate size.
+  //
+  // It would be slightly more efficient to integrate this directly into the
+  // face-selection algorithm above, but it's a rare case that doesn't apply
+  // at all to most font families.
+  //
+  // Currently we only support pixel-sized bitmap font faces on Linux/Gtk (i.e.
+  // when using the gfxFcPlatformFontList implementation), so this filtering is
+  // not needed on other platforms.
+  //
+  // (Note that color-bitmap emoji fonts like Apple Color Emoji or Noto Color
+  // Emoji don't count here; they package multiple bitmap sizes into a single
+  // OpenType wrapper, so they appear as a single "scalable" face in our list.)
+  if (anyNonScalable) {
+    uint16_t best = 0;
+    gfxFloat dist = 0.0;
+    for (const auto& f : aFaceList) {
+      if (f->mSize == 0) {
+        // Scalable face; no size distance to compute.
+        continue;
+      }
+      gfxFloat d = fabs(gfxFloat(f->mSize) - aStyle.size);
+      if (!aIgnoreSizeTolerance && (d * 5.0 > f->mSize)) {
+        continue;  // Too far from the requested size, ignore.
+      }
+      // If we haven't found a "best" bitmap size yet, or if this is a better
+      // match, remember it.
+      if (!best || d < dist) {
+        best = f->mSize;
+        dist = d;
+      }
+    }
+    // Discard all faces except the chosen "best" size; or if no pixel size was
+    // chosen, all except scalable faces.
+    // This may eliminate *all* faces in the family, if all were bitmaps and
+    // none was a good enough size match, in which case we'll fall back to the
+    // next font-family name.
+    aFaceList.RemoveElementsBy([=](const auto& e) { return e->mSize != best; });
+  }
+#endif
 }
 
 Face* Family::FindFaceForStyle(FontList* aList, const gfxFontStyle& aStyle,

gfx/thebes/SharedFontList.h

@@ -157,6 +157,9 @@ struct Face {
     nsCString mDescriptor;  // descriptor that can be used to instantiate a
                             // platform font reference
     uint16_t mIndex;        // an index used with descriptor (on some platforms)
+#ifdef MOZ_WIDGET_GTK
+    uint16_t mSize;  // pixel size if bitmap; zero indicates scalable
+#endif
     bool mFixedPitch;                  // is the face fixed-pitch (monospaced)?
     mozilla::WeightRange mWeight;      // CSS font-weight value
     mozilla::StretchRange mStretch;    // CSS font-stretch value
@@ -169,11 +172,15 @@ struct Face {
   Face(FontList* aList, const InitData& aData)
       : mDescriptor(aList, aData.mDescriptor),
         mIndex(aData.mIndex),
+#ifdef MOZ_WIDGET_GTK
+        mSize(aData.mSize),
+#endif
         mFixedPitch(aData.mFixedPitch),
         mWeight(aData.mWeight),
         mStretch(aData.mStretch),
         mStyle(aData.mStyle),
-        mCharacterMap(Pointer::Null()) {}
+        mCharacterMap(Pointer::Null()) {
+  }
 
   bool HasValidDescriptor() const {
     return !mDescriptor.IsNull() && mIndex != uint16_t(-1);
@@ -183,6 +190,9 @@ struct Face {
 
   String mDescriptor;
   uint16_t mIndex;
+#ifdef MOZ_WIDGET_GTK
+  uint16_t mSize;
+#endif
   bool mFixedPitch;
   mozilla::WeightRange mWeight;
   mozilla::StretchRange mStretch;
@@ -309,6 +319,11 @@ struct Family {
   void SetupFamilyCharMap(FontList* aList);
 
  private:
+  // Returns true if there are specifically-sized bitmap faces in the list,
+  // so size selection still needs to be done. (Currently only on Linux.)
+  bool FindAllFacesForStyleInternal(FontList* aList, const gfxFontStyle& aStyle,
+                                    nsTArray<Face*>& aFaceList) const;
+
   std::atomic<uint32_t> mFaceCount;
   String mKey;
   String mName;

gfx/thebes/gfxFcPlatformFontList.cpp

@@ -205,7 +205,8 @@ static FontStretch MapFcWidth(int aFcWidth) {
 
 static void GetFontProperties(FcPattern* aFontPattern, WeightRange* aWeight,
                               StretchRange* aStretch,
-                              SlantStyleRange* aSlantStyle) {
+                              SlantStyleRange* aSlantStyle,
+                              uint16_t* aSize = nullptr) {
   // weight
   int weight;
   if (FcPatternGetInteger(aFontPattern, FC_WEIGHT, 0, &weight) !=
@@ -231,6 +232,24 @@ static void GetFontProperties(FcPattern* aFontPattern, WeightRange* aWeight,
   } else if (slant > 0) {
     *aSlantStyle = SlantStyleRange(FontSlantStyle::Italic());
   }
+
+  if (aSize) {
+    // pixel size, or zero if scalable
+    FcBool scalable;
+    if (FcPatternGetBool(aFontPattern, FC_SCALABLE, 0, &scalable) ==
+            FcResultMatch &&
+        scalable) {
+      *aSize = 0;
+    } else {
+      double size;
+      if (FcPatternGetDouble(aFontPattern, FC_PIXEL_SIZE, 0, &size) ==
+          FcResultMatch) {
+        *aSize = uint16_t(NS_round(size));
+      } else {
+        *aSize = 0;
+      }
+    }
+  }
 }
 
 gfxFontconfigFontEntry::gfxFontconfigFontEntry(const nsACString& aFaceName,
@@ -1667,10 +1686,11 @@ void gfxFcPlatformFontList::InitSharedFontListForPlatform() {
     WeightRange weight(FontWeight::Normal());
     StretchRange stretch(FontStretch::Normal());
     SlantStyleRange style(FontSlantStyle::Normal());
-    GetFontProperties(aPattern, &weight, &stretch, &style);
+    uint16_t size;
+    GetFontProperties(aPattern, &weight, &stretch, &style, &size);
 
-    auto initData =
-        fontlist::Face::InitData{descriptor, 0, false, weight, stretch, style};
+    auto initData = fontlist::Face::InitData{descriptor, 0,       size, false,
+                                             weight,     stretch, style};
 
     // Add entries for any other localized family names. (Most fonts only have
     // a single family name, so the first call to GetString will usually fail).