Bug 1457103 - patch 3 - Make gfxFontEntry::GetVariationAxes and GetVariationInstances pure virtual, and provide missing subclass implementations. r=jwatt

gfx/thebes/gfxFT2FontList.cpp

@@ -635,6 +635,43 @@ FT2FontEntry::HasVariations()
     return mHasVariations;
 }
 
+void
+FT2FontEntry::GetVariationAxes(nsTArray<gfxFontVariationAxis>& aAxes)
+{
+    if (!HasVariations()) {
+        return;
+    }
+    AutoFTFace face(this);
+    if (!face) {
+        return;
+    }
+    FT_MM_Var* mmVar;
+    if (FT_Err_Ok != (FT_Get_MM_Var(face, &mmVar))) {
+        return;
+    }
+    gfxFT2Utils::GetVariationAxes(mmVar, aAxes);
+    FT_Done_MM_Var(FT_Face(face)->glyph->library, mmVar);
+}
+
+void
+FT2FontEntry::GetVariationInstances(
+    nsTArray<gfxFontVariationInstance>& aInstances)
+{
+    if (!HasVariations()) {
+        return;
+    }
+    AutoFTFace face(this);
+    if (!face) {
+        return;
+    }
+    FT_MM_Var* mmVar;
+    if (FT_Err_Ok != (FT_Get_MM_Var(face, &mmVar))) {
+        return;
+    }
+    gfxFT2Utils::GetVariationInstances(this, mmVar, aInstances);
+    FT_Done_MM_Var(FT_Face(face)->glyph->library, mmVar);
+}
+
 void
 FT2FontEntry::AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
                                      FontListSizes* aSizes) const

gfx/thebes/gfxFT2FontList.h

@@ -88,6 +88,8 @@ public:
                                    nsTArray<uint8_t>& aBuffer) override;
 
     bool HasVariations() override;
+    void GetVariationAxes(nsTArray<gfxFontVariationAxis>& aVariationAxes) override;
+    void GetVariationInstances(nsTArray<gfxFontVariationInstance>& aInstances) override;
 
     // Check for various kinds of brokenness, and set flags on the entry
     // accordingly so that we avoid using bad font tables

gfx/thebes/gfxFontEntry.h

@@ -365,14 +365,19 @@ public:
 
     bool SupportsScriptInGSUB(const hb_tag_t* aScriptTags);
 
-    // For variation font support; default implementations assume it is not present.
+    /**
+     * Font-variation query methods.
+     *
+     * Font backends that don't support variations should provide empty
+     * implementations.
+     */
     virtual bool HasVariations() = 0;
-    virtual void GetVariationAxes(nsTArray<gfxFontVariationAxis>& aVariationAxes)
-    {
-    }
-    virtual void GetVariationInstances(nsTArray<gfxFontVariationInstance>& aInstances)
-    {
-    }
+
+    virtual void
+    GetVariationAxes(nsTArray<gfxFontVariationAxis>& aVariationAxes) = 0;
+
+    virtual void
+    GetVariationInstances(nsTArray<gfxFontVariationInstance>& aInstances) = 0;
 
     // Set up the entry's weight/stretch/style ranges according to axes found
     // by GetVariationAxes (for installed fonts; do NOT call this for user

gfx/thebes/gfxGDIFontList.h

@@ -163,7 +163,10 @@ public:
 
     gfxFontEntry* Clone() const override;
 
+    // GDI backend doesn't support font variations:
     bool HasVariations() override { return false; }
+    void GetVariationAxes(nsTArray<gfxFontVariationAxis>&) override {}
+    void GetVariationInstances(nsTArray<gfxFontVariationInstance>&) override {}
 
     // create a font entry for a font with a given name
     static GDIFontEntry* CreateFontEntry(const nsAString& aName,

gfx/thebes/gfxUserFontSet.h

@@ -639,7 +639,17 @@ public:
       return mSrcList;
     }
 
-    bool HasVariations() override { return false; }
+    // The variation-query APIs should not be called on placeholders.
+    bool HasVariations() override {
+      MOZ_ASSERT_UNREACHABLE("not meaningful for a userfont placeholder");
+      return false;
+    }
+    void GetVariationAxes(nsTArray<gfxFontVariationAxis>&) override {
+      MOZ_ASSERT_UNREACHABLE("not meaningful for a userfont placeholder");
+    }
+    void GetVariationInstances(nsTArray<gfxFontVariationInstance>&) override {
+      MOZ_ASSERT_UNREACHABLE("not meaningful for a userfont placeholder");
+    }
 
 protected:
     const uint8_t* SanitizeOpenTypeData(const uint8_t* aData,