From f25787b72c20e97cdeb74e037dc1ff56a88b45c6 Mon Sep 17 00:00:00 2001 From: Ben Wagner Date: Tue, 1 Dec 2020 20:22:00 -0500 Subject: [PATCH] Subpixel anti-aliasing in FreeType 2.8.1+ FreeType 2.8.1 and later always provide some form of subpixel anti-aliasing. Bug: skia:10950,skia:6663 Change-Id: I666cc942e73b73073cdabf900c25faa10d9aaf0f Reviewed-on: https://skia-review.googlesource.com/c/skia/+/339861 Reviewed-by: Herb Derby Commit-Queue: Ben Wagner --- src/ports/SkFontHost_FreeType.cpp | 33 ++++++++++++++++++++----------- 1 file changed, 22 insertions(+), 11 deletions(-) diff --git a/src/ports/SkFontHost_FreeType.cpp b/src/ports/SkFontHost_FreeType.cpp index 990eff4f5e..c0aeb792da 100644 --- a/src/ports/SkFontHost_FreeType.cpp +++ b/src/ports/SkFontHost_FreeType.cpp @@ -32,6 +32,7 @@ #include "src/utils/SkMatrix22.h" #include +#include #include #include FT_ADVANCES_H @@ -147,13 +148,16 @@ public: // *reinterpret_cast(&procPtr) = dlsym(self, "proc"); // because clang has not implemented DR573. See http://clang.llvm.org/cxx_dr_status.html . - FT_Int major, minor, patch; - FT_Library_Version(fLibrary, &major, &minor, &patch); + using Version = std::tuple; + Version version; + FT_Library_Version(fLibrary, &std::get<0>(version), + &std::get<1>(version), + &std::get<2>(version)); #if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02070100 fGetVarDesignCoordinates = FT_Get_Var_Design_Coordinates; #elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN - if (major > 2 || ((major == 2 && minor > 7) || (major == 2 && minor == 7 && patch >= 0))) { + if (Version(2,7,0) <= version) { //The FreeType library is already loaded, so symbols are available in process. void* self = dlopen(nullptr, RTLD_LAZY); if (self) { @@ -166,7 +170,7 @@ public: #if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02070200 FT_Set_Default_Properties(fLibrary); #elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN - if (major > 2 || ((major == 2 && minor > 7) || (major == 2 && minor == 7 && patch >= 1))) { + if (Version(2,7,1) <= version) { //The FreeType library is already loaded, so symbols are available in process. void* self = dlopen(nullptr, RTLD_LAZY); if (self) { @@ -185,7 +189,7 @@ public: #if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02080000 fLightHintingIsYOnly = true; #else - if (major > 2 || ((major == 2 && minor > 8) || (major == 2 && minor == 8 && patch >= 0))) { + if (Version(2,8,0) <= version) { fLightHintingIsYOnly = true; } #endif @@ -194,7 +198,7 @@ public: #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))) { + if (Version(2,7,0) <= version) { //The FreeType library is already loaded, so symbols are available in process. void* self = dlopen(nullptr, RTLD_LAZY); if (self) { @@ -204,11 +208,18 @@ public: } #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) { - fIsLCDSupported = true; - fLCDExtra = 2; //Using a filter adds one full pixel to each side. + fIsLCDSupported = + // Subpixel anti-aliasing may be unfiltered until the LCD filter is set. + // Newer versions may still need this, so this test with side effects must come first. + // The default has changed over time, so this doesn't mean the same thing to all users. + (FT_Library_SetLcdFilter(fLibrary, FT_LCD_FILTER_DEFAULT) == 0) || + + // In 2.8.1 and later FreeType always provides some form of subpixel anti-aliasing. + ((SK_FREETYPE_MINIMUM_RUNTIME_VERSION) >= 0x02080100) || + (Version(2,8,1) <= version); + + if (fIsLCDSupported) { + fLCDExtra = 2; // Using a filter may require up to one full pixel to each side. } } ~FreeTypeLibrary() {