Bug 948765 - Add a LayerUtils file in gfx/layers. r=nical

This file is currently just a helper for doing PremultiplySurface in
Moz2D. It corresponds to an existing Thebes one in the gfxUtils class.

An upcoming patch will require this PremultiplySurface method. The
existing one in gfxUtils has been renamed internally to
DeprecatedPremultiplyTables.

gfx/layers/LayerUtils.cpp

@@ -0,0 +1,79 @@
+/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LayerUtils.h"
+#include "PremultiplyTables.h"
+
+namespace mozilla {
+namespace layers {
+
+using namespace mozilla::gfx;
+
+static inline const uint8_t PremultiplyValue(uint8_t a, uint8_t v) {
+  return PremultiplyTable[a*256+v];
+}
+
+static inline const uint8_t UnpremultiplyValue(uint8_t a, uint8_t v) {
+  return UnpremultiplyTable[a*256+v];
+}
+
+void
+PremultiplySurface(DataSourceSurface* srcSurface,
+                   DataSourceSurface* destSurface)
+{
+  if (!destSurface)
+    destSurface = srcSurface;
+
+  IntSize srcSize = srcSurface->GetSize();
+  MOZ_ASSERT(srcSurface->GetFormat() == destSurface->GetFormat() &&
+             srcSize.width  == destSurface->GetSize().width &&
+             srcSize.height  == destSurface->GetSize().height &&
+             srcSurface->Stride() == destSurface->Stride(),
+             "Source and destination surfaces don't have identical characteristics");
+
+  MOZ_ASSERT(srcSurface->Stride() == srcSize.width * 4,
+             "Source surface stride isn't tightly packed");
+
+  // Only premultiply ARGB32
+  if (srcSurface->GetFormat() != SurfaceFormat::B8G8R8A8) {
+    if (destSurface != srcSurface) {
+      memcpy(destSurface->GetData(), srcSurface->GetData(),
+             srcSurface->Stride() * srcSize.height);
+    }
+    return;
+  }
+
+  uint8_t *src = srcSurface->GetData();
+  uint8_t *dst = destSurface->GetData();
+
+  uint32_t dim = srcSize.width * srcSize.height;
+  for (uint32_t i = 0; i < dim; ++i) {
+#ifdef IS_LITTLE_ENDIAN
+    uint8_t b = *src++;
+    uint8_t g = *src++;
+    uint8_t r = *src++;
+    uint8_t a = *src++;
+
+    *dst++ = PremultiplyValue(a, b);
+    *dst++ = PremultiplyValue(a, g);
+    *dst++ = PremultiplyValue(a, r);
+    *dst++ = a;
+#else
+    uint8_t a = *src++;
+    uint8_t r = *src++;
+    uint8_t g = *src++;
+    uint8_t b = *src++;
+
+    *dst++ = a;
+    *dst++ = PremultiplyValue(a, r);
+    *dst++ = PremultiplyValue(a, g);
+    *dst++ = PremultiplyValue(a, b);
+#endif
+  }
+}
+
+
+}
+}

gfx/layers/LayerUtils.h

@@ -0,0 +1,21 @@
+/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_LAYERS_LAYERUTILS_H_
+#define MOZILLA_LAYERS_LAYERUTILS_H_
+
+#include "mozilla/gfx/2D.h"
+
+namespace mozilla {
+namespace layers {
+
+void
+PremultiplySurface(gfx::DataSourceSurface* srcSurface,
+                   gfx::DataSourceSurface* destSurface = nullptr);
+
+}
+}
+
+#endif /* MOZILLA_LAYERS_LAYERUTILS_H_ */

gfx/layers/Makefile.in

@@ -13,3 +13,6 @@ CXXFLAGS += \
         $(NULL)
 
 CXXFLAGS += $(MOZ_CAIRO_CFLAGS) $(TK_CFLAGS)
+
+PremultiplyTables.h: $(srcdir)/genTables.py
+	$(PYTHON) $(srcdir)/genTables.py

gfx/layers/genTables.py

@@ -0,0 +1,12 @@
+#!/usr/bin/python
+
+def table_generator(f):
+  return ",\n".join([", ".join(["0x%2.2x" % h for h in [f(i) for i in range(r,r+16)]]) for r in range(0, 65536, 16)])
+
+with open("PremultiplyTables.h", "w") as f:
+  f.write("const uint8_t PremultiplyTable[256*256] = {\n");
+  f.write(table_generator(lambda i: ((i / 256) * (i % 256) + 254) / 255) + "\n")
+  f.write("};\n");
+  f.write("const uint8_t UnpremultiplyTable[256*256] = {\n");
+  f.write(table_generator(lambda i: (i % 256) * 255 / ((i / 256) if (i / 256) > 0 else 255) % 256) + "\n")
+  f.write("};\n");

gfx/layers/moz.build

@@ -261,6 +261,7 @@ UNIFIED_SOURCES += [
     'LayerScope.cpp',
     'LayersLogging.cpp',
     'LayerSorter.cpp',
+    'LayerUtils.cpp',
     'opengl/CompositingRenderTargetOGL.cpp',
     'opengl/CompositorOGL.cpp',
     'opengl/OGLShaderProgram.cpp',
@@ -324,3 +325,7 @@ if CONFIG['MOZ_DEBUG']:
 
 if CONFIG['MOZ_ENABLE_D3D10_LAYER']:
     DEFINES['MOZ_ENABLE_D3D10_LAYER'] = True
+
+GENERATED_FILES = [
+    'PremultiplyTables.h',
+]

gfx/thebes/Makefile.in

@@ -41,5 +41,5 @@ gfxAlphaRecoverySSE2.$(OBJ_SUFFIX): OS_CXXFLAGS += -xarch=sse2 -xO4
 endif
 endif
 
-PremultiplyTables.h: $(srcdir)/genTables.py
+DeprecatedPremultiplyTables.h: $(srcdir)/genTables.py
 	$(PYTHON) $(srcdir)/genTables.py

gfx/thebes/genTables.py

@@ -3,7 +3,7 @@
 def table_generator(f):
     return ",\n".join([", ".join(["0x%2.2x" % h for h in [f(i) for i in range(r,r+16)]]) for r in range(0, 65536, 16)])
 
-with open("PremultiplyTables.h", "w") as f:
+with open("DeprecatedPremultiplyTables.h", "w") as f:
   f.write("const uint8_t gfxUtils::sPremultiplyTable[256*256] = {\n");
   f.write(table_generator(lambda i: ((i / 256) * (i % 256) + 254) / 255) + "\n")
   f.write("};\n");

gfx/thebes/gfxUtils.cpp

@@ -22,7 +22,7 @@ using namespace mozilla;
 using namespace mozilla::layers;
 using namespace mozilla::gfx;
 
-#include "PremultiplyTables.h"
+#include "DeprecatedPremultiplyTables.h"
 
 static const uint8_t PremultiplyValue(uint8_t a, uint8_t v) {
     return gfxUtils::sPremultiplyTable[a*256+v];

gfx/thebes/moz.build

@@ -268,7 +268,7 @@ include('/ipc/chromium/chromium-config.mozbuild')
 FINAL_LIBRARY = 'xul'
 
 GENERATED_FILES = [
-    'PremultiplyTables.h',
+    'DeprecatedPremultiplyTables.h',
 ]
 
 LOCAL_INCLUDES += [