refactor bitmapshader to use a controller

src/core/SkBitmapController.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 SkBitmapController_DEFINED
+#define SkBitmapController_DEFINED
+
+#include "SkBitmap.h"
+#include "SkFilterQuality.h"
+#include "SkMatrix.h"
+
+class SkInPlace;
+
+/**
+ *  Handles request to scale, filter, and lock a bitmap to be rasterized.
+ */
+class SkBitmapController {

[scroggo, 2015/06/02 21:17:33]

I tend to default to making classes noncopyable. I think the default is fine
(although unnecessary and likely wrong) to copy, but maybe if it held a cache
that would be a problem?

[reed1, 2015/06/04 13:17:03]

Done.

+public:
+    class State {

[scroggo, 2015/06/02 21:17:34]

Should this be noncopyable?

The only harm/weirdness I can imagine in copying is that presumably
fLockedBitmap should actually be locked, but if you copied a State the copy's
fLockedBitmap would not be (although its SkPixelRef would be).

[reed1, 2015/06/04 13:17:03]

Done.

+    public:
+        virtual ~State() {}
+
+        const SkBitmap& lockedBitmap() const { return fLockedBitmap; }
+        const SkMatrix& invMatrix() const { return fInvMatrix; }
+        SkFilterQuality quality() const { return fQuality; }
+    
+    protected:
+        SkBitmap        fLockedBitmap;
+        SkMatrix        fInvMatrix;
+        SkFilterQuality fQuality;
+    
+    private:
+        friend class SkBitmapController;
+    };
+
+    virtual ~SkBitmapController() {}
+
+    State* requestBitmap(const SkBitmap&, const SkMatrix& inverse, SkFilterQuality,

[scroggo, 2015/06/02 21:17:33]

This will matter more once it's public:

Add a comment here that State needs to be SkInPlace->destroy()ed unless the
SkInPlace is NULL, in which case it can be deleted (/SkDELETEd?)

Maybe that's obvious, though, if you know what an SkInPlace is.

+                         SkInPlace* = NULL);
+
+protected:
+    virtual State* onRequestBitmap(const SkBitmap&, const SkMatrix& inverse, SkFilterQuality,
+                                   SkInPlace&) = 0;
+};
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+class SkDefaultBitmapController : public SkBitmapController {
+public:
+    SkDefaultBitmapController() {}
+    
+protected:
+    State* onRequestBitmap(const SkBitmap&, const SkMatrix& inverse, SkFilterQuality,
+                           SkInPlace&) override;
+};
+
+#endif