Bug 1435984 - patch 5 - Apply variation settings from the font entry when instantiating fonts on macOS. r=lsalzman

--HG--
extra : source : ec70fb9a28ac4952b15f1acd4890d727067788ca

gfx/thebes/gfxFontUtils.cpp

@@ -1944,6 +1944,24 @@ gfxFontUtils::GetVariationInstances(gfxFontEntry* aFontEntry,
     }
 }
 
+void
+gfxFontUtils::MergeVariations(const nsTArray<gfxFontVariation>& aEntrySettings,
+                              const nsTArray<gfxFontVariation>& aStyleSettings,
+                              nsTArray<gfxFontVariation>* aMerged)
+{
+    MOZ_ASSERT(!aEntrySettings.IsEmpty() &&
+               !aStyleSettings.IsEmpty() &&
+               aMerged->IsEmpty());
+    // Settings from the CSS style will take precedence over those from the
+    // font entry (i.e. from the @font-face descriptor).
+    aMerged->AppendElements(aStyleSettings);
+    for (auto& setting : aEntrySettings) {
+        if (!aMerged->Contains(setting.mTag, VariationTagComparator())) {
+            aMerged->AppendElement(setting);
+        }
+    }
+}
+
 #ifdef XP_WIN
 
 /* static */

gfx/thebes/gfxFontUtils.h

@@ -6,6 +6,7 @@
 #ifndef GFX_FONT_UTILS_H
 #define GFX_FONT_UTILS_H
 
+#include "gfxFontVariations.h"
 #include "gfxPlatform.h"
 #include "nsComponentManagerUtils.h"
 #include "nsTArray.h"
@@ -26,8 +27,6 @@
 
 typedef struct hb_blob_t hb_blob_t;
 
-struct gfxFontVariationInstance;
-
 class gfxSparseBitSet {
 private:
     enum { BLOCK_SIZE = 32 };   // ==> 256 codepoints per block
@@ -1011,6 +1010,22 @@ public:
     GetVariationInstances(gfxFontEntry* aFontEntry,
                           nsTArray<gfxFontVariationInstance>& aInstances);
 
+    // Merge a list of font-variation-settings from a font entry and a list
+    // from a gfxFontStyle, to get a combined collection of settings that can
+    // be used to instantiate a font.
+    static void
+    MergeVariations(const nsTArray<gfxFontVariation>& aEntrySettings,
+                    const nsTArray<gfxFontVariation>& aStyleSettings,
+                    nsTArray<gfxFontVariation>* aMerged);
+
+    // Helper used by MergeVariations, and other code that wants to check
+    // whether an array of variation settings includes a particular tag.
+    struct VariationTagComparator {
+        bool Equals(const gfxFontVariation& aVariation, uint32_t aTag) const {
+            return aVariation.mTag == aTag;
+        }
+    };
+
 protected:
     friend struct MacCharsetMappingComparator;
 

gfx/thebes/gfxFontVariations.h

@@ -8,6 +8,8 @@
 #define GFX_FONT_VARIATIONS_H
 
 #include "mozilla/gfx/FontVariation.h"
+#include "nsString.h"
+#include "nsTArray.h"
 
 typedef mozilla::gfx::FontVariation gfxFontVariation;
 

gfx/thebes/gfxMacFont.cpp

@@ -36,17 +36,34 @@ gfxMacFont::gfxMacFont(const RefPtr<UnscaledFontMac>& aUnscaledFont,
 {
     mApplySyntheticBold = aNeedsBold;
 
-    if (mVariationFont && aFontStyle->variationSettings.Length() > 0) {
+    if (mVariationFont && (!aFontStyle->variationSettings.IsEmpty() ||
+                           !aFontEntry->mVariationSettings.IsEmpty())) {
         CGFontRef baseFont = aUnscaledFont->GetFont();
         if (!baseFont) {
             mIsValid = false;
             return;
         }
+
+        // Probably one of the lists of variations, either from the @font-face
+        // descriptor or from the property, will be empty. So skip merging them
+        // unless really necessary.
+        const nsTArray<gfxFontVariation>* vars;
+        AutoTArray<gfxFontVariation,4> mergedSettings;
+        if (aFontStyle->variationSettings.IsEmpty()) {
+            vars = &aFontEntry->mVariationSettings;
+        } else if (aFontEntry->mVariationSettings.IsEmpty()) {
+            vars = &aFontStyle->variationSettings;
+        } else {
+            gfxFontUtils::MergeVariations(aFontEntry->mVariationSettings,
+                                          aFontStyle->variationSettings,
+                                          &mergedSettings);
+            vars = &mergedSettings;
+        }
+
         mCGFont =
-            UnscaledFontMac::CreateCGFontWithVariations(
-                baseFont,
-                aFontStyle->variationSettings.Length(),
-                aFontStyle->variationSettings.Elements());
+            UnscaledFontMac::CreateCGFontWithVariations(baseFont,
+                                                        vars->Length(),
+                                                        vars->Elements());
         if (!mCGFont) {
           ::CFRetain(baseFont);
           mCGFont = baseFont;