Bug 1432552 - patch 2 - Linux font back-end implementation of getVariationInstances. r=dholbert

gfx/thebes/gfxFcPlatformFontList.cpp

@@ -360,8 +360,37 @@ gfxFontconfigFontEntry::gfxFontconfigFontEntry(const nsAString& aFaceName,
     mIgnoreFcCharmap = true;
 }
 
+typedef FT_Error (*GetVarFunc)(FT_Face, FT_MM_Var**);
+typedef FT_Error (*DoneVarFunc)(FT_Library, FT_MM_Var*);
+static GetVarFunc sGetVar;
+static DoneVarFunc sDoneVar;
+static bool sInitializedVarFuncs = false;
+
+static void
+InitializeVarFuncs()
+{
+    if (sInitializedVarFuncs) {
+        return;
+    }
+    sInitializedVarFuncs = true;
+    sGetVar = (GetVarFunc)dlsym(RTLD_DEFAULT, "FT_Get_MM_Var");
+    sDoneVar = (DoneVarFunc)dlsym(RTLD_DEFAULT, "FT_Done_MM_Var");
+}
+
 gfxFontconfigFontEntry::~gfxFontconfigFontEntry()
 {
+    if (mMMVar) {
+        // Prior to freetype 2.9, there was no specific function to free the
+        // FT_MM_Var record, and the docs just said to use free().
+        // InitializeVarFuncs must have been called in order for mMMVar to be
+        // non-null here, so we don't need to do it again.
+        if (sDoneVar) {
+            MOZ_ASSERT(mFTFace, "How did mMMVar get set without a face?");
+            (*sDoneVar)(mFTFace->glyph->library, mMMVar);
+        } else {
+            free(mMMVar);
+        }
+    }
 }
 
 nsresult
@@ -469,6 +498,14 @@ gfxFontconfigFontEntry::MaybeReleaseFTFace()
     // only close out FT_Face for system fonts, not for data fonts
     if (!mIsDataUserFont) {
         if (mFTFace) {
+            if (mMMVar) {
+                if (sDoneVar) {
+                    (*sDoneVar)(mFTFace->glyph->library, mMMVar);
+                } else {
+                    free(mMMVar);
+                }
+                mMMVar = nullptr;
+            }
             Factory::ReleaseFTFace(mFTFace);
             mFTFace = nullptr;
         }
@@ -1017,31 +1054,36 @@ gfxFontconfigFontEntry::HasVariations()
     return false;
 }
 
+FT_MM_Var*
+gfxFontconfigFontEntry::GetMMVar()
+{
+    if (mMMVarInitialized) {
+        return mMMVar;
+    }
+    mMMVarInitialized = true;
+    InitializeVarFuncs();
+    if (!sGetVar) {
+        return nullptr;
+    }
+    FT_Face face = GetFTFace();
+    if (!face) {
+        return nullptr;
+    }
+    if (FT_Err_Ok != (*sGetVar)(face, &mMMVar)) {
+        mMMVar = nullptr;
+    }
+    return mMMVar;
+}
+
 void
 gfxFontconfigFontEntry::GetVariationAxes(nsTArray<gfxFontVariationAxis>& aAxes)
 {
     MOZ_ASSERT(aAxes.IsEmpty());
-    FT_Face face = GetFTFace();
-    if (!face) {
-        return;
-    }
-    typedef FT_Error (*GetVarFunc)(FT_Face, FT_MM_Var**);
-    static GetVarFunc getVar;
-    typedef FT_Error (*DoneVarFunc)(FT_Library, FT_MM_Var*);
-    static DoneVarFunc doneVar;
-    static bool firstTime = true;
-    if (firstTime) {
-        firstTime = false;
-        getVar = (GetVarFunc)dlsym(RTLD_DEFAULT, "FT_Get_MM_Var");
-        doneVar = (DoneVarFunc)dlsym(RTLD_DEFAULT, "FT_Done_MM_Var");
-    }
-    if (!getVar) {
-        return;
-    }
-    FT_MM_Var* mmVar;
-    if (FT_Err_Ok != (*getVar)(face, &mmVar)) {
+    FT_MM_Var* mmVar = GetMMVar();
+    if (!mmVar) {
         return;
     }
+    aAxes.SetCapacity(mmVar->num_axis);
     for (unsigned i = 0; i < mmVar->num_axis; i++) {
         const auto& a = mmVar->axis[i];
         gfxFontVariationAxis axis;
@@ -1052,13 +1094,40 @@ gfxFontconfigFontEntry::GetVariationAxes(nsTArray<gfxFontVariationAxis>& aAxes)
         axis.mName.Assign(NS_ConvertUTF8toUTF16(a.name));
         aAxes.AppendElement(axis);
     }
-    // Prior to freetype 2.9, there was no specific function to free the FT_MM_Var,
-    // and the docs just said to use free().
-    if (doneVar) {
-        (*doneVar)(face->glyph->library, mmVar);
-    } else {
-        free(mmVar);
+}
+
+void
+gfxFontconfigFontEntry::GetVariationInstances(
+    nsTArray<gfxFontVariationInstance>& aInstances)
+{
+    MOZ_ASSERT(aInstances.IsEmpty());
+    FT_MM_Var* mmVar = GetMMVar();
+    if (!mmVar) {
+        return;
     }
+    hb_blob_t* nameTable = GetFontTable(TRUETYPE_TAG('n','a','m','e'));
+    if (!nameTable) {
+        return;
+    }
+    aInstances.SetCapacity(mmVar->num_namedstyles);
+    for (unsigned i = 0; i < mmVar->num_namedstyles; i++) {
+        const auto& ns = mmVar->namedstyle[i];
+        gfxFontVariationInstance inst;
+        nsresult rv =
+            gfxFontUtils::ReadCanonicalName(nameTable, ns.strid, inst.mName);
+        if (NS_FAILED(rv)) {
+            continue;
+        }
+        inst.mValues.SetCapacity(mmVar->num_axis);
+        for (unsigned j = 0; j < mmVar->num_axis; j++) {
+            gfxFontVariationValue value;
+            value.mAxis = mmVar->axis[j].tag;
+            value.mValue = ns.coords[j] / 65536.0;
+            inst.mValues.AppendElement(value);
+        }
+        aInstances.AppendElement(inst);
+    }
+    hb_blob_destroy(nameTable);
 }
 
 nsresult

gfx/thebes/gfxFcPlatformFontList.h

@@ -18,6 +18,7 @@
 #include "ft2build.h"
 #include FT_FREETYPE_H
 #include FT_TRUETYPE_TABLES_H
+#include FT_MULTIPLE_MASTERS_H
 #include <cairo.h>
 #include <cairo-ft.h>
 
@@ -115,8 +116,11 @@ public:
 
     FT_Face GetFTFace();
 
+    FT_MM_Var* GetMMVar();
+
     bool HasVariations() override;
     void GetVariationAxes(nsTArray<gfxFontVariationAxis>& aAxes) override;
+    void GetVariationInstances(nsTArray<gfxFontVariationInstance>& aInstances) override;
 
     hb_blob_t* GetFontTable(uint32_t aTableTag) override;
 
@@ -188,6 +192,11 @@ protected:
     };
 
     UnscaledFontCache mUnscaledFontCache;
+
+    // Because of FreeType bug 52955, we keep the FT_MM_Var struct when it is
+    // first loaded, rather than releasing it and re-fetching it as needed.
+    FT_MM_Var* mMMVar = nullptr;
+    bool mMMVarInitialized = false;
 };
 
 class gfxFontconfigFontFamily : public gfxFontFamily {