Bug 1073363, part 2 - Add a GeneralPattern class to Moz2D to solve the problem of writing general pattern creating functions. r=Bas

gfx/2d/PatternHelpers.h

@@ -0,0 +1,137 @@
+/* -*- Mode: C++; tab-width: 20; 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_GFX_PATTERNHELPERS_H
+#define _MOZILLA_GFX_PATTERNHELPERS_H
+
+#include "mozilla/Alignment.h"
+#include "mozilla/gfx/2D.h"
+
+namespace mozilla {
+namespace gfx {
+
+/**
+ * This class is used to allow general pattern creation functions to return
+ * any type of pattern via an out-paramater without allocating a pattern
+ * instance on the free-store (an instance of this class being created on the
+ * stack before passing it in to the creation function). Without this class
+ * writing pattern creation functions would be a pain since Pattern objects are
+ * not reference counted, making lifetime management of instances created on
+ * the free-store and returned from a creation function hazardous. Besides
+ * that, in the case that ColorPattern's are expected to be common, it is
+ * particularly desirable to avoid the overhead of allocating on the
+ * free-store.
+ */
+class GeneralPattern
+{
+public:
+  explicit GeneralPattern()
+    : mPattern(nullptr)
+  {}
+
+  GeneralPattern(const GeneralPattern& aOther)
+    : mPattern(nullptr)
+  {}
+
+  ~GeneralPattern() {
+    if (mPattern) {
+      mPattern->~Pattern();
+    }
+  }
+
+  Pattern* Init(const Pattern& aPattern) {
+    MOZ_ASSERT(!mPattern);
+    switch (aPattern.GetType()) {
+    case PatternType::COLOR:
+      mPattern = new (mColorPattern.addr())
+        ColorPattern(static_cast<const ColorPattern&>(aPattern));
+      break;
+    case PatternType::LINEAR_GRADIENT:
+      mPattern = new (mLinearGradientPattern.addr())
+        LinearGradientPattern(static_cast<const LinearGradientPattern&>(aPattern));
+      break;
+    case PatternType::RADIAL_GRADIENT:
+      mPattern = new (mRadialGradientPattern.addr())
+        RadialGradientPattern(static_cast<const RadialGradientPattern&>(aPattern));
+      break;
+    case PatternType::SURFACE:
+      mPattern = new (mSurfacePattern.addr())
+        SurfacePattern(static_cast<const SurfacePattern&>(aPattern));
+      break;
+    default:
+      MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unknown pattern type");
+    }
+    return mPattern;
+  }
+
+  ColorPattern* InitColorPattern(const Color &aColor) {
+    MOZ_ASSERT(!mPattern);
+    mPattern = new (mColorPattern.addr()) ColorPattern(aColor);
+    return mColorPattern.addr();
+  }
+
+  LinearGradientPattern* InitLinearGradientPattern(const Point &aBegin,
+                                                   const Point &aEnd,
+                                                   GradientStops *aStops,
+                                                   const Matrix &aMatrix = Matrix()) {
+    MOZ_ASSERT(!mPattern);
+    mPattern = new (mLinearGradientPattern.addr())
+      LinearGradientPattern(aBegin, aEnd, aStops, aMatrix);
+    return mLinearGradientPattern.addr();
+  }
+
+  RadialGradientPattern* InitRadialGradientPattern(const Point &aCenter1,
+                                                   const Point &aCenter2,
+                                                   Float aRadius1,
+                                                   Float aRadius2,
+                                                   GradientStops *aStops,
+                                                   const Matrix &aMatrix = Matrix()) {
+    MOZ_ASSERT(!mPattern);
+    mPattern = new (mRadialGradientPattern.addr())
+      RadialGradientPattern(aCenter1, aCenter2, aRadius1, aRadius2, aStops, aMatrix);
+    return mRadialGradientPattern.addr();
+  }
+
+  SurfacePattern* InitSurfacePattern(SourceSurface *aSourceSurface,
+                                     ExtendMode aExtendMode,
+                                     const Matrix &aMatrix = Matrix(),
+                                     Filter aFilter = Filter::GOOD,
+                                     const IntRect &aSamplingRect = IntRect()) {
+    MOZ_ASSERT(!mPattern);
+    mPattern = new (mSurfacePattern.addr())
+      SurfacePattern(aSourceSurface, aExtendMode, aMatrix, aFilter, aSamplingRect);
+    return mSurfacePattern.addr();
+  }
+
+  Pattern* GetPattern() {
+    return mPattern;
+  }
+
+  const Pattern* GetPattern() const {
+    return mPattern;
+  }
+
+  operator Pattern&() {
+    if (!mPattern) {
+      MOZ_CRASH("GeneralPattern not initialized");
+    }
+    return *mPattern;
+  }
+
+private:
+  union {
+    AlignedStorage2<ColorPattern> mColorPattern;
+    AlignedStorage2<LinearGradientPattern> mLinearGradientPattern;
+    AlignedStorage2<RadialGradientPattern> mRadialGradientPattern;
+    AlignedStorage2<SurfacePattern> mSurfacePattern;
+  };
+  Pattern *mPattern;
+};
+
+} // namespace gfx
+} // namespace mozilla
+
+#endif //  _MOZILLA_GFX_PATTERNHELPERS_H
+

gfx/2d/moz.build

@@ -27,6 +27,7 @@ EXPORTS.mozilla.gfx += [
     'Logging.h',
     'Matrix.h',
     'PathHelpers.h',
+    'PatternHelpers.h',
     'Point.h',
     'Rect.h',
     'Scale.h',