Rewrite GrTextureMaker to disentangle bitmap case from base class and give GPU object a say in what…

src/gpu/GrTextureParamsAdjuster.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrTextureMaker_DEFINED
+#define GrTextureMaker_DEFINED
+
+#include "GrTextureParams.h"
+#include "GrResourceKey.h"
+
+class GrContext;
+class GrTexture;
+class GrTextureParams;
+class GrUniqueKey;
+class SkBitmap;
+
+/**
+ * Different GPUs and API extensions have different requirements with respect to what texture
+ * sampling parameters may be used with textures of various types. This class facilitates making
+ * texture compatible with a given GrTextureParams. It abstracts the source of the original data
+ * which may be an already existing texture, CPU pixels, a codec, ... so that various sources can
+ * be used with common code that scales or copies the data to make it compatible with a
+ * GrTextureParams.
+ */
+class GrTextureParamsAdjuster {
+public:
+    struct CopyParams {
+        GrTextureParams::FilterMode fFilter;
+        int                         fWidth;
+        int                         fHeight;
+    };
+
+    GrTextureParamsAdjuster(int width, int height) : fWidth(width), fHeight(height) {}
+    virtual ~GrTextureParamsAdjuster() {}
+
+    int width() const { return fWidth; }
+    int height() const { return fHeight; }
+
+    /** Returns a texture that is safe for use with the params */
+    GrTexture* refTextureForParams(GrContext*, const GrTextureParams&);
+
+protected:
+    /**
+     *  Return the maker's "original" texture. It is the responsibility of the maker
+     *  to make this efficient ... if the texture is being generated, the maker must handle
+     *  caching it (if desired).
+     */
+    virtual GrTexture* refOriginalTexture(GrContext*) = 0;
+
+    /**
+     *  If we need to copy the maker's original texture, the maker is asked to return a key
+     *  that identifies its original + the CopyParms parameter. If the maker does not want to cache
+     *  the stretched version (e.g. the maker is volatile), this should simply return without
+     *  initializing the copyKey.
+     */
+    virtual void makeCopyKey(const CopyParams&, GrUniqueKey* copyKey) = 0;
+
+    /**
+     *  Return a new (uncached) texture that is the stretch of the maker's original.
+     *
+     *  The base-class handles general logic for this, and only needs access to the following
+     *  methods:
+     *  - onRefOriginalTexture()
+     *  - onGetROBitmap()
+     *
+     *  Subclass may override this if they can handle creating the texture more directly than
+     *  by copying.
+     */
+    virtual GrTexture* generateTextureForParams(GrContext*, const CopyParams&);
+
+    /**
+     *  If a stretched version of the texture is generated, it may be cached (assuming that
+     *  onMakeParamsKey() returns true). In that case, the maker is notified in case it
+     *  wants to note that for when the maker is destroyed.
+     */
+    virtual void didCacheCopy(const GrUniqueKey& copyKey) = 0;
+
+    /**
+     *  Some GPUs are unreliable w/ very small texture sizes. If we run into that case, this
+     *  method will be called (in service of onGenerateParamsTexture) to return a raster version
+     *  of the original texture.
+     */
+    virtual bool getROBitmap(SkBitmap*) = 0;
+
+    /** Helper for creating a key for a copy from an original key. */
+    static void MakeCopyKeyFromOrigKey(const GrUniqueKey& origKey,
+                                       const CopyParams& copyParams,
+                                       GrUniqueKey* copyKey) {
+        SkASSERT(!copyKey->isValid());
+        if (origKey.isValid()) {
+            static const GrUniqueKey::Domain kDomain = GrUniqueKey::GenerateDomain();
+            GrUniqueKey::Builder builder(copyKey, origKey, kDomain, 3);
+            builder[0] = copyParams.fFilter;
+            builder[1] = copyParams.fWidth;
+            builder[2] = copyParams.fHeight;
+        }
+    }
+
+private:
+    const int fWidth;
+    const int fHeight;
+};
+
+#endif