Bug 1365776 - Use the IDWriteFontFace1 interface if available to get glyph advances from DirectWrite more cheaply. r=jrmuizel

gfx/thebes/gfxDWriteFonts.cpp

@@ -5,13 +5,10 @@
 
 #include "gfxDWriteFonts.h"
 
-#include "mozilla/MemoryReporting.h"
-
 #include <algorithm>
 #include "gfxDWriteFontList.h"
 #include "gfxContext.h"
 #include "gfxTextRun.h"
-#include <dwrite.h>
 
 #include "harfbuzz/hb.h"
 
@@ -95,6 +92,11 @@ gfxDWriteFont::gfxDWriteFont(const RefPtr<UnscaledFontDWrite>& aUnscaledFont,
 
     mFontFace = aUnscaledFont->GetFontFace();
 
+    // If the IDWriteFontFace1 interface is available, we can use that for
+    // faster glyph width retrieval.
+    mFontFace->QueryInterface(__uuidof(IDWriteFontFace1),
+                              (void**)getter_AddRefs(mFontFace1));
+
     ComputeMetrics(anAAOption);
 }
 
@@ -630,20 +632,38 @@ gfxDWriteFont::GetMeasuringMode()
 gfxFloat
 gfxDWriteFont::MeasureGlyphWidth(uint16_t aGlyph)
 {
-    DWRITE_GLYPH_METRICS metrics;
     HRESULT hr;
-    if (mUseSubpixelPositions) {
-        hr = mFontFace->GetDesignGlyphMetrics(&aGlyph, 1, &metrics, FALSE);
-        if (SUCCEEDED(hr)) {
-            return metrics.advanceWidth * mFUnitsConvFactor;
+    if (mFontFace1) {
+        int32_t advance;
+        if (mUseSubpixelPositions) {
+            hr = mFontFace1->GetDesignGlyphAdvances(1, &aGlyph, &advance, FALSE);
+            if (SUCCEEDED(hr)) {
+                return advance * mFUnitsConvFactor;
+            }
+        } else {
+            hr = mFontFace1->GetGdiCompatibleGlyphAdvances(
+                      FLOAT(mAdjustedSize), 1.0f, nullptr,
+                      GetMeasuringMode() == DWRITE_MEASURING_MODE_GDI_NATURAL,
+                      FALSE, 1, &aGlyph, &advance);
+            if (SUCCEEDED(hr)) {
+                return NS_lround(advance * mFUnitsConvFactor);
+            }
         }
     } else {
-        hr = mFontFace->GetGdiCompatibleGlyphMetrics(
-                  FLOAT(mAdjustedSize), 1.0f, nullptr,
-                  GetMeasuringMode() == DWRITE_MEASURING_MODE_GDI_NATURAL,
-                  &aGlyph, 1, &metrics, FALSE);
-        if (SUCCEEDED(hr)) {
-            return NS_lround(metrics.advanceWidth * mFUnitsConvFactor);
+        DWRITE_GLYPH_METRICS metrics;
+        if (mUseSubpixelPositions) {
+            hr = mFontFace->GetDesignGlyphMetrics(&aGlyph, 1, &metrics, FALSE);
+            if (SUCCEEDED(hr)) {
+                return metrics.advanceWidth * mFUnitsConvFactor;
+            }
+        } else {
+            hr = mFontFace->GetGdiCompatibleGlyphMetrics(
+                      FLOAT(mAdjustedSize), 1.0f, nullptr,
+                      GetMeasuringMode() == DWRITE_MEASURING_MODE_GDI_NATURAL,
+                      &aGlyph, 1, &metrics, FALSE);
+            if (SUCCEEDED(hr)) {
+                return NS_lround(metrics.advanceWidth * mFUnitsConvFactor);
+            }
         }
     }
     return 0;

gfx/thebes/gfxDWriteFonts.h

@@ -8,7 +8,7 @@
 
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/UniquePtr.h"
-#include <dwrite.h>
+#include <dwrite_1.h>
 
 #include "gfxFont.h"
 #include "gfxUserFontSet.h"
@@ -93,6 +93,8 @@ protected:
     bool GetForceGDIClassic();
 
     RefPtr<IDWriteFontFace> mFontFace;
+    RefPtr<IDWriteFontFace1> mFontFace1; // may be unavailable on older DWrite
+
     cairo_font_face_t *mCairoFontFace;
 
     Metrics *mMetrics;