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Use linear metrics with new FreeType light autohint.

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Starting in FreeType 2.8 the light hinting setting only hints in the y
direction and can be used with linear metrics and subpixel positioning.

Change-Id: I6e478a904001216ade7f319fe98aa863ac6bd672
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/211105
Auto-Submit: Ben Wagner <bungeman@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
This commit is contained in:
Ben Wagner 2019-04-29 15:31:09 -04:00 committed by Skia Commit-Bot
parent 494aa3db9e
commit c752054981
1 changed files with 16 additions and 0 deletions
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16
src/ports/SkFontHost_FreeType.cpp
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@ -129,6 +129,7 @@ public:
, fGetVarAxisFlags(nullptr)
, fLibrary(nullptr)
, fIsLCDSupported(false)
, fLightHintingIsYOnly(false)
, fLCDExtra(0)
{
if (FT_New_Library(&gFTMemory, &fLibrary)) {
@ -176,6 +177,16 @@ public:
}
#endif
// The 'light' hinting is vertical only starting in 2.8.0.
#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02080000
fLightHintingIsYOnly = true;
#else
if (major > 2 || ((major == 2 && minor > 8) || (major == 2 && minor == 8 && patch >= 0))) {
fLightHintingIsYOnly = true;
}
#endif
#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02080100
fGetVarAxisFlags = FT_Get_Var_Axis_Flags;
#elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN
@ -205,6 +216,7 @@ public:
FT_Library library() { return fLibrary; }
bool isLCDSupported() { return fIsLCDSupported; }
int lcdExtra() { return fLCDExtra; }
bool lightHintingIsYOnly() { return fLightHintingIsYOnly; }
// FT_Get_{MM,Var}_{Blend,Design}_Coordinates were added in FreeType 2.7.1.
// Prior to this there was no way to get the coordinates out of the FT_Face.
@ -222,6 +234,7 @@ public:
private:
FT_Library fLibrary;
bool fIsLCDSupported;
bool fLightHintingIsYOnly;
int fLCDExtra;
// FT_Library_SetLcdFilterWeights was introduced in FreeType 2.4.0.
@ -864,6 +877,9 @@ SkScalerContext_FreeType::SkScalerContext_FreeType(sk_sp<SkTypeface> typeface,
break;
case kSlight_SkFontHinting:
loadFlags = FT_LOAD_TARGET_LIGHT; // This implies FORCE_AUTOHINT
if (gFTLibrary->lightHintingIsYOnly()) {
linearMetrics = true;
}
break;
case kNormal_SkFontHinting:
loadFlags = FT_LOAD_TARGET_NORMAL;