add colortable support to imagegenerator

src/lazy/SkDiscardablePixelRef.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDiscardablePixelRef.h"
 #include "SkDiscardableMemory.h"
 #include "SkImageGenerator.h"
@@ skipping 42 matching lines @@
     if (fDMFactory != NULL) {
         fDiscardableMemory = fDMFactory->create(size);
     } else {
         fDiscardableMemory = SkDiscardableMemory::Create(size);
     }
     if (NULL == fDiscardableMemory) {
         return false;  // Memory allocation failed.
     }
 
     void* pixels = fDiscardableMemory->data();
-    if (!fGenerator->getPixels(this->info(), pixels, fRowBytes)) {
+    const SkImageInfo& info = this->info();
+    SkPMColor colors[256];
+    int colorCount = 0;
+
+    if (!fGenerator->getPixels(info, pixels, fRowBytes, colors, &colorCount)) {
         fDiscardableMemory->unlock();
         SkDELETE(fDiscardableMemory);
         fDiscardableMemory = NULL;
         return false;
     }
 
+    if (colorCount > 0) {
+        fCTable.reset(SkNEW_ARGS(SkColorTable, (colors, colorCount)));
+    } else {
+        fCTable.reset(NULL);
+    }
+
     rec->fPixels = pixels;
-    rec->fColorTable = NULL;
+    rec->fColorTable = fCTable.get();

[scroggo, 2014/05/28 15:01:37]

This version does not purge the color table on memory pressure, but maybe that's
okay (it's pretty small, after all).

One way to purge would be to request a larger block of discardable memory and
allocate the color table there. The downside is that someone could take a
reference to it (weren't you interested in removing its inheritance from
SkRefCnt?), and then we might delete/overwrite it underneath them.

[reed1, 2014/05/28 15:48:02]

Agreed, I don't know how to ram the colortable into the discardable block yet,
so that part is not "discardable". I'll add a comment acknowledging this.

     rec->fRowBytes = fRowBytes;
     return true;
 }
 
 void SkDiscardablePixelRef::onUnlockPixels() {
     fDiscardableMemory->unlock();
 }
 
 bool SkInstallDiscardablePixelRef(SkImageGenerator* generator, SkBitmap* dst,
                                   SkDiscardableMemory::Factory* factory) {
@@ skipping 12 matching lines @@
         SkNEW_ARGS(SkDiscardablePixelRef,
                    (info, autoGenerator.detach(), dst->rowBytes(), factory)));
     dst->setPixelRef(ref);
     return true;
 }
 
 // This is the public API
 bool SkInstallDiscardablePixelRef(SkImageGenerator* generator, SkBitmap* dst) {
     return SkInstallDiscardablePixelRef(generator, dst, NULL);
 }