Bug 1769279 - Disable FT_LOAD_COLOR when getting glyph metrics for fonts that include an SVG table. r=lsalzman

See https://gitlab.freedesktop.org/freetype/freetype/-/issues/1156
for the issue this is addressing.

Differential Revision: https://phabricator.services.mozilla.com/D146318

gfx/skia/skia/src/ports/SkFontHost_cairo.cpp

@@ -45,6 +45,13 @@ typedef enum FT_LcdFilter_
 #    define FT_PIXEL_MODE_BGRA 7
 #endif
 
+// If compiling with FreeType before 2.12.0
+#ifndef FT_FACE_FLAG_SVG
+// We need the format tag so that we can switch on it and handle a possibly-
+// newer version of the library at runtime.
+static constexpr FT_UInt32 FT_IMAGE_TAG(FT_GLYPH_FORMAT_SVG, 'S', 'V', 'G', ' ');
+#endif
+
 #ifndef SK_CAN_USE_DLOPEN
 #define SK_CAN_USE_DLOPEN 1
 #endif
@@ -587,6 +594,10 @@ void SkScalerContext_CairoFT::generateMetrics(SkGlyph* glyph)
                                        fFTFace->glyph->bitmap.rows);
         }
         break;
+    case FT_GLYPH_FORMAT_SVG:
+        // We don't support getting glyph bounds for SVG, but at least the advance
+        // should be correctly returned, and we don't want to fire an assertion.
+        break;
     default:
         SkDEBUGFAIL("unknown glyph format");
         return;

gfx/thebes/gfxFT2FontBase.cpp

@@ -646,6 +646,17 @@ bool gfxFT2FontBase::GetFTGlyphExtents(uint16_t aGID, int32_t* aAdvance,
   if (!aBounds) {
     flags |= FT_LOAD_ADVANCE_ONLY;
   }
+
+  // Whether to disable subpixel positioning
+  bool roundX = ShouldRoundXOffset(nullptr);
+
+  // Workaround for FT_Load_Glyph not setting linearHoriAdvance for SVG glyphs.
+  // See https://gitlab.freedesktop.org/freetype/freetype/-/issues/1156.
+  if (!roundX &&
+      GetFontEntry()->HasFontTable(TRUETYPE_TAG('S', 'V', 'G', ' '))) {
+    flags &= ~FT_LOAD_COLOR;
+  }
+
   if (Factory::LoadFTGlyph(face.get(), aGID, flags) != FT_Err_Ok) {
     // FT_Face was somehow broken/invalid? Don't try to access glyph slot.
     // This probably shouldn't happen, but does: see bug 1440938.
@@ -655,8 +666,6 @@ bool gfxFT2FontBase::GetFTGlyphExtents(uint16_t aGID, int32_t* aAdvance,
 
   // Whether to interpret hinting settings (i.e. not printing)
   bool hintMetrics = ShouldHintMetrics();
-  // Whether to disable subpixel positioning
-  bool roundX = ShouldRoundXOffset(nullptr);
   // No hinting disables X and Y hinting. Light disables only X hinting.
   bool unhintedY = (mFTLoadFlags & FT_LOAD_NO_HINTING) != 0;
   bool unhintedX =