Add SkTypeface::getVariationDesignParameters

This adds a way for users to query the axis parameters for a typeface.

Change-Id: Idc2ac0d84bc7ae2ca484ae410cba5b01883418e5
Reviewed-on: https://skia-review.googlesource.com/137706
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Reed <reed@google.com>

5 files changed, 141 insertions, 11 deletions

diff --git a/src/ports/SkFontHost_FreeType.cpp b/src/ports/SkFontHost_FreeType.cpp
index b8ce2033b1..03f499fcf6 100644
--- a/src/ports/SkFontHost_FreeType.cpp
+++ b/src/ports/SkFontHost_FreeType.cpp
@@ -72,6 +72,12 @@
 #    define FT_LOAD_BITMAP_METRICS_ONLY ( 1L << 22 )
 #endif
 
+// FT_VAR_AXIS_FLAG_HIDDEN was introduced in FreeType 2.8.1
+// The variation axis should not be exposed to user interfaces.
+#ifndef FT_VAR_AXIS_FLAG_HIDDEN
+#    define FT_VAR_AXIS_FLAG_HIDDEN 1
+#endif
+
 //#define ENABLE_GLYPH_SPEW     // for tracing calls
 //#define DUMP_STRIKE_CREATION
 //#define SK_FONTHOST_FREETYPE_RUNTIME_VERSION
@@ -104,6 +110,7 @@ class FreeTypeLibrary : SkNoncopyable {
 public:
     FreeTypeLibrary()
         : fGetVarDesignCoordinates(nullptr)
+        , fGetVarAxisFlags(nullptr)
         , fLibrary(nullptr)
         , fIsLCDSupported(false)
         , fLCDExtra(0)
@@ -153,6 +160,19 @@ public:
         }
 #endif
 
+#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02080100
+        fGetVarAxisFlags = FT_Get_Var_Axis_Flags;
+#elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN
+        if (major > 2 || ((major == 2 && minor > 7) || (major == 2 && minor == 7 && patch >= 0))) {
+            //The FreeType library is already loaded, so symbols are available in process.
+            void* self = dlopen(nullptr, RTLD_LAZY);
+            if (self) {
+                *(void**)(&fGetVarAxisFlags) = dlsym(self, "FT_Get_Var_Axis_Flags");
+                dlclose(self);
+            }
+        }
+#endif
+
         // Setup LCD filtering. This reduces color fringes for LCD smoothed glyphs.
         // The default has changed over time, so this doesn't mean the same thing to all users.
         if (FT_Library_SetLcdFilter(fLibrary, FT_LCD_FILTER_DEFAULT) == 0) {
@@ -177,6 +197,12 @@ public:
     using FT_Get_Var_Blend_CoordinatesProc = FT_Error (*)(FT_Face, FT_UInt, FT_Fixed*);
     FT_Get_Var_Blend_CoordinatesProc fGetVarDesignCoordinates;
 
+    // FT_Get_Var_Axis_Flags was introduced in FreeType 2.8.1
+    // Get the ‘flags’ field of an OpenType Variation Axis Record.
+    // Not meaningful for Adobe MM fonts (‘*flags’ is always zero).
+    using FT_Get_Var_Axis_FlagsProc = FT_Error (*)(FT_MM_Var*, FT_UInt, FT_UInt*);
+    FT_Get_Var_Axis_FlagsProc fGetVarAxisFlags;
+
 private:
     FT_Library fLibrary;
     bool fIsLCDSupported;
@@ -1546,18 +1572,21 @@ SkTypeface::LocalizedStrings* SkTypeface_FreeType::onCreateFamilyNameIterator()
 }
 
 int SkTypeface_FreeType::onGetVariationDesignPosition(
-        SkFontArguments::VariationPosition::Coordinate coordinates[], int coordinateCount) const
+    SkFontArguments::VariationPosition::Coordinate coordinates[], int coordinateCount) const
 {
     AutoFTAccess fta(this);
     FT_Face face = fta.face();
+    if (!face) {
+        return -1;
+    }
 
-    if (!face || !(face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS)) {
+    if (!(face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS)) {
         return 0;
     }
 
     FT_MM_Var* variations = nullptr;
     if (FT_Get_MM_Var(face, &variations)) {
-        return 0;
+        return -1;
     }
     SkAutoFree autoFreeVariations(variations);
 
@@ -1590,6 +1619,44 @@ int SkTypeface_FreeType::onGetVariationDesignPosition(
     return variations->num_axis;
 }
 
+int SkTypeface_FreeType::onGetVariationDesignParameters(
+    SkFontParameters::Variation::Axis parameters[], int parameterCount) const
+{
+    AutoFTAccess fta(this);
+    FT_Face face = fta.face();
+    if (!face) {
+        return -1;
+    }
+
+    if (!(face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS)) {
+        return 0;
+    }
+
+    FT_MM_Var* variations = nullptr;
+    if (FT_Get_MM_Var(face, &variations)) {
+        return -1;
+    }
+    SkAutoFree autoFreeVariations(variations);
+
+    if (!parameters || parameterCount < SkToInt(variations->num_axis)) {
+        return variations->num_axis;
+    }
+
+    for (FT_UInt i = 0; i < variations->num_axis; ++i) {
+        parameters[i].tag = variations->axis[i].tag;
+        parameters[i].min = SkFixedToScalar(variations->axis[i].minimum);
+        parameters[i].def = SkFixedToScalar(variations->axis[i].def);
+        parameters[i].max = SkFixedToScalar(variations->axis[i].maximum);
+        FT_UInt flags = 0;
+        bool hidden = gFTLibrary->fGetVarAxisFlags &&
+            !gFTLibrary->fGetVarAxisFlags(variations, i, &flags) &&
+            (flags & FT_VAR_AXIS_FLAG_HIDDEN);
+        parameters[i].setHidden(hidden);
+    }
+
+    return variations->num_axis;
+}
+
 int SkTypeface_FreeType::onGetTableTags(SkFontTableTag tags[]) const {
     AutoFTAccess fta(this);
     FT_Face face = fta.face();
diff --git a/src/ports/SkFontHost_FreeType_common.h b/src/ports/SkFontHost_FreeType_common.h
index 1386775bb8..939aa4b643 100644
--- a/src/ports/SkFontHost_FreeType_common.h
+++ b/src/ports/SkFontHost_FreeType_common.h
@@ -107,6 +107,8 @@ protected:
 
     int onGetVariationDesignPosition(SkFontArguments::VariationPosition::Coordinate coordinates[],
                                      int coordinateCount) const override;
+    int onGetVariationDesignParameters(SkFontParameters::Variation::Axis parameters[],
+                                       int parameterCount) const override;
     int onGetTableTags(SkFontTableTag tags[]) const override;
     size_t onGetTableData(SkFontTableTag, size_t offset,
                           size_t length, void* data) const override;
diff --git a/src/ports/SkFontHost_win.cpp b/src/ports/SkFontHost_win.cpp
index 264ae9226d..07d37aedfe 100644
--- a/src/ports/SkFontHost_win.cpp
+++ b/src/ports/SkFontHost_win.cpp
@@ -277,6 +277,11 @@ protected:
     {
         return -1;
     }
+    int onGetVariationDesignParameters(SkFontParameters::Variation::Axis parameters[],
+                                       int parameterCount) const override
+    {
+        return -1;
+    }
     int onGetTableTags(SkFontTableTag tags[]) const override;
     size_t onGetTableData(SkFontTableTag, size_t offset, size_t length, void* data) const override;
 };
diff --git a/src/ports/SkTypeface_win_dw.cpp b/src/ports/SkTypeface_win_dw.cpp
index a7bad0d24e..3bf61347df 100644
--- a/src/ports/SkTypeface_win_dw.cpp
+++ b/src/ports/SkTypeface_win_dw.cpp
@@ -185,8 +185,9 @@ SkTypeface::LocalizedStrings* DWriteFontTypeface::onCreateFamilyNameIterator() c
     return nameIter;
 }
 
-int DWriteFontTypeface::onGetVariationDesignPosition(SkFontArguments::VariationPosition::Coordinate coordinates[],
-    int coordinateCount) const {
+int DWriteFontTypeface::onGetVariationDesignPosition(
+    SkFontArguments::VariationPosition::Coordinate coordinates[], int coordinateCount) const
+{
 
 #if defined(NTDDI_WIN10_RS3) && NTDDI_VERSION >= NTDDI_WIN10_RS3
 
@@ -210,20 +211,73 @@ int DWriteFontTypeface::onGetVariationDesignPosition(SkFontArguments::VariationP
         }
     }
 
-    if (!coordinates || !coordinateCount || !variableAxisCount) {
+    if (!coordinates || coordinateCount < variableAxisCount) {
         return variableAxisCount;
     }
 
     SkAutoSTMalloc<8, DWRITE_FONT_AXIS_VALUE> fontAxisValue(fontAxisCount);
     HR_GENERAL(fontFace5->GetFontAxisValues(fontAxisValue.get(), fontAxisCount), nullptr, -1);
-    UINT32 minCount = SkMin32(variableAxisCount, SkTo<UINT32>(coordinateCount));
-    UINT32 coordinatesIndex = 0;
+    UINT32 coordIndex = 0;
+
+    for (UINT32 axisIndex = 0; axisIndex < fontAxisCount; ++axisIndex) {
+        if (fontResource->GetFontAxisAttributes(axisIndex) & DWRITE_FONT_AXIS_ATTRIBUTES_VARIABLE) {
+            coordinates[coordIndex].axis = SkEndian_SwapBE32(fontAxisValue[axisIndex].axisTag);
+            coordinates[coordIndex].value = fontAxisValue[axisIndex].value;
+        }
+    }
+
+    return variableAxisCount;
+
+#endif
+
+    return -1;
+}
+
+int DWriteFontTypeface::onGetVariationDesignParameters(
+    SkFontParameters::Variation::Axis parameters[], int parameterCount) const
+{
+
+#if defined(NTDDI_WIN10_RS3) && NTDDI_VERSION >= NTDDI_WIN10_RS3
+
+    SkTScopedComPtr<IDWriteFontFace5> fontFace5;
+    if (FAILED(fDWriteFontFace->QueryInterface(&fontFace5))) {
+        return -1;
+    }
+
+    // Return 0 if the font is not variable font.
+    if (!fontFace5->HasVariations()) {
+        return 0;
+    }
+
+    UINT32 fontAxisCount = fontFace5->GetFontAxisValueCount();
+    SkTScopedComPtr<IDWriteFontResource> fontResource;
+    HR_GENERAL(fontFace5->GetFontResource(&fontResource), nullptr, -1);
+    int variableAxisCount = 0;
+    for (UINT32 i = 0; i < fontAxisCount; ++i) {
+        if (fontResource->GetFontAxisAttributes(i) & DWRITE_FONT_AXIS_ATTRIBUTES_VARIABLE) {
+            variableAxisCount++;
+        }
+    }
+
+    if (!parameters || parameterCount < variableAxisCount) {
+        return variableAxisCount;
+    }
+
+    SkAutoSTMalloc<8, DWRITE_FONT_AXIS_RANGE> fontAxisRange(fontAxisCount);
+    HR_GENERAL(fontResource->GetFontAxisRanges(fontAxisRange.get(), fontAxisCount), nullptr, -1);
+    SkAutoSTMalloc<8, DWRITE_FONT_AXIS_VALUE> fontAxisDefaultValue(fontAxisCount);
+    HR_GENERAL(fontResource->GetDefaultFontAxisValues(fontAxisDefaultValue.get(), fontAxisCount),
+               nullptr, -1);
+    UINT32 coordIndex = 0;
 
     for (UINT32 axisIndex = 0; axisIndex < fontAxisCount; ++axisIndex) {
         if (fontResource->GetFontAxisAttributes(axisIndex) & DWRITE_FONT_AXIS_ATTRIBUTES_VARIABLE) {
-            coordinates[coordinatesIndex].axis = SkEndian_SwapBE32(fontAxisValue[axisIndex].axisTag);
-            coordinates[coordinatesIndex].value = fontAxisValue[axisIndex].value;
-            if (++coordinatesIndex == minCount) break;
+            parameters[coordIndex].tag = SkEndian_SwapBE32(fontAxisDefaultValue[axisIndex].axisTag);
+            parameters[coordIndex].min = fontAxisRange[axisIndex].minValue;
+            parameters[coordIndex].def = fontAxisDefaultValue[axisIndex].value;
+            parameters[coordIndex].max = fontAxisRange[axisIndex].maxValue;
+            parameters[coordIndex].setHidden(fontResource->GetFontAxisAttributes(axisIndex) &
+                                             DWRITE_FONT_AXIS_ATTRIBUTES_HIDDEN);
         }
     }
 
diff --git a/src/ports/SkTypeface_win_dw.h b/src/ports/SkTypeface_win_dw.h
index 2d76b39adb..a671eb4855 100644
--- a/src/ports/SkTypeface_win_dw.h
+++ b/src/ports/SkTypeface_win_dw.h
@@ -117,6 +117,8 @@ protected:
     SkTypeface::LocalizedStrings* onCreateFamilyNameIterator() const override;
     int onGetVariationDesignPosition(SkFontArguments::VariationPosition::Coordinate coordinates[],
                                      int coordinateCount) const override;
+    int onGetVariationDesignParameters(SkFontParameters::Variation::Axis parameters[],
+                                       int parameterCount) const override;
     int onGetTableTags(SkFontTableTag tags[]) const override;
     size_t onGetTableData(SkFontTableTag, size_t offset, size_t length, void* data) const override;