Bug 1349417 - Part 2: stylo: Add basic system font support, use for font-size and font-family; r=xidorn

MozReview-Commit-ID: 4ZMR83GkAZN

layout/style/ServoBindings.cpp

@@ -904,6 +904,12 @@ Gecko_Atomize(const char* aString, uint32_t aLength)
   return NS_Atomize(nsDependentCSubstring(aString, aLength)).take();
 }
 
+nsIAtom*
+Gecko_Atomize16(const nsAString* aString)
+{
+  return NS_Atomize(*aString).take();
+}
+
 void
 Gecko_AddRefAtom(nsIAtom* aAtom)
 {
@@ -977,6 +983,33 @@ Gecko_CopyFontFamilyFrom(nsFont* dst, const nsFont* src)
   dst->fontlist = src->fontlist;
 }
 
+void
+Gecko_nsFont_InitSystem(nsFont* aDest, int32_t aFontId,
+                        const nsStyleFont* aFont, RawGeckoPresContextBorrowed aPresContext)
+{
+
+  const nsFont* defaultVariableFont =
+    aPresContext->GetDefaultFont(kPresContext_DefaultVariableFont_ID,
+                                 aFont->mLanguage);
+
+  // We have passed uninitialized memory to this function,
+  // initialize it. We can't simply return an nsFont because then
+  // we need to know its size beforehand. Servo cannot initialize nsFont
+  // itself, so this will do.
+  nsFont* system = new (aDest) nsFont(*defaultVariableFont);
+
+  *system = *defaultVariableFont;
+  LookAndFeel::FontID fontID = static_cast<LookAndFeel::FontID>(aFontId);
+  nsRuleNode::ComputeSystemFont(system, fontID, aPresContext);
+}
+
+void
+Gecko_nsFont_Destroy(nsFont* aDest)
+{
+  aDest->~nsFont();
+}
+
+
 void
 Gecko_SetImageOrientation(nsStyleVisibility* aVisibility,
                           double aRadians, bool aFlip)

layout/style/ServoBindings.h

@@ -232,6 +232,7 @@ RawServoAnimationValueBorrowedOrNull Gecko_AnimationGetBaseStyle(
 
 // Atoms.
 nsIAtom* Gecko_Atomize(const char* aString, uint32_t aLength);
+nsIAtom* Gecko_Atomize16(const nsAString* aString);
 void Gecko_AddRefAtom(nsIAtom* aAtom);
 void Gecko_ReleaseAtom(nsIAtom* aAtom);
 const uint16_t* Gecko_GetAtomAsUTF16(nsIAtom* aAtom, uint32_t* aLength);
@@ -243,6 +244,11 @@ void Gecko_FontFamilyList_Clear(FontFamilyList* aList);
 void Gecko_FontFamilyList_AppendNamed(FontFamilyList* aList, nsIAtom* aName, bool aQuoted);
 void Gecko_FontFamilyList_AppendGeneric(FontFamilyList* list, FontFamilyType familyType);
 void Gecko_CopyFontFamilyFrom(nsFont* dst, const nsFont* src);
+// will not run destructors on dst, give it uninitialized memory
+// font_id is LookAndFeel::FontID
+void Gecko_nsFont_InitSystem(nsFont* dst, int32_t font_id,
+                             const nsStyleFont* font, RawGeckoPresContextBorrowed pres_context);
+void Gecko_nsFont_Destroy(nsFont* dst);
 
 // Visibility style
 void Gecko_SetImageOrientation(nsStyleVisibility* aVisibility,

layout/style/nsRuleNode.h

@@ -1087,6 +1087,10 @@ public:
   static void FillAllMaskLists(nsStyleImageLayers& aLayers,
                                uint32_t aMaxItemCount);
 
+  static void ComputeSystemFont(nsFont* aSystemFont,
+                                mozilla::LookAndFeel::FontID aFontID,
+                                const nsPresContext* aPresContext);
+
 private:
 #ifdef DEBUG
   // non-inline helper function to allow assertions without incomplete
@@ -1099,9 +1103,6 @@ private:
   static void StoreStyleOnContext(nsStyleContext* aContext,
                                   nsStyleStructID aSID,
                                   void* aStruct);
-  static void ComputeSystemFont(nsFont* aSystemFont,
-                                mozilla::LookAndFeel::FontID aFontID,
-                                const nsPresContext* aPresContext);
 };
 
 /**