From 1ad3f6b8d9e0ef1e921c3ed5526ea352d67265cf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lubo=C5=A1=20Lu=C5=88=C3=A1k?= <l.lunak@collabora.com>
Date: Wed, 18 Mar 2020 12:10:29 +0100
Subject: [PATCH] (do not) use SK_GAMMA_APPLY_TO_A8 also for Skia text on
 Windows
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This is the Windows variant of the SK_GAMMA_APPLY_TO_A8 disabling,
again I don't quite understand why we need to disable this,
but with this patch Skia text rendering on Windows seems to be
pixel-perfect when compared with the VCL gen backend.

Change-Id: Iafc1e6353430e695dafa67d19eefd968d4f02ae2
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90696
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>
---
 external/skia/UnpackedTarball_skia.mk    |  1 +
 external/skia/windows-text-gamma.patch.0 | 28 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 external/skia/windows-text-gamma.patch.0

diff --git a/external/skia/UnpackedTarball_skia.mk b/external/skia/UnpackedTarball_skia.mk
index 58818a840e3d..fd05e8d5b3e3 100644
--- a/external/skia/UnpackedTarball_skia.mk
+++ b/external/skia/UnpackedTarball_skia.mk
@@ -30,6 +30,7 @@ skia_patches := \
     clang-attributes-warning.patch.1 \
     fontconfig-get-typeface.patch.0 \
     windows-hfont-typeface.patch.0 \
+    windows-text-gamma.patch.0 \
 
 $(eval $(call gb_UnpackedTarball_set_patchlevel,skia,1))
 
diff --git a/external/skia/windows-text-gamma.patch.0 b/external/skia/windows-text-gamma.patch.0
new file mode 100644
index 000000000000..366b67f15a65
--- /dev/null
+++ b/external/skia/windows-text-gamma.patch.0
@@ -0,0 +1,28 @@
+--- ./src/ports/SkFontHost_win.cpp.sav	2020-03-18 10:26:52.470184300 +0100
++++ ./src/ports/SkFontHost_win.cpp	2020-03-18 12:08:04.598406700 +0100
+@@ -1215,17 +1215,23 @@
+         // since the caller may require A8 for maskfilters, we can't check for BW
+         // ... until we have the caller tell us that explicitly
+         const SkGdiRGB* src = (const SkGdiRGB*)bits;
++#if defined(SK_GAMMA_APPLY_TO_A8)
+         if (fPreBlend.isApplicable()) {
+             RGBToA8<true>(src, srcRB, glyph, fPreBlend.fG);
+-        } else {
++        } else
++#endif
++        {
+             RGBToA8<false>(src, srcRB, glyph, fPreBlend.fG);
+         }
+     } else {    // LCD16
+         const SkGdiRGB* src = (const SkGdiRGB*)bits;
+         SkASSERT(SkMask::kLCD16_Format == glyph.fMaskFormat);
++#if defined(SK_GAMMA_APPLY_TO_A8)
+         if (fPreBlend.isApplicable()) {
+             RGBToLcd16<true>(src, srcRB, glyph, fPreBlend.fR, fPreBlend.fG, fPreBlend.fB);
+-        } else {
++        } else
++#endif
++        {
+             RGBToLcd16<false>(src, srcRB, glyph, fPreBlend.fR, fPreBlend.fG, fPreBlend.fB);
+         }
+     }