allow for stepping through a picture with 'n' and 'p'

samplecode/SamplePictFile.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SampleCode.h"
 #include "SkDumpCanvas.h"
 #include "SkView.h"
@@ skipping 14 matching lines @@
 #include "SkTime.h"
 #include "SkTypeface.h"
 #include "SkXfermode.h"
 
 #include "SkStream.h"
 #include "SkSurface.h"
 #include "SkXMLParser.h"
 
 #include "SkGlyphCache.h"
 
+#include "SkDrawFilter.h"
+class SkCounterDrawFilter : public SkDrawFilter {
+public:
+    SkCounterDrawFilter(int count) : fCount(count) {}
+
+    bool filter(SkPaint*, Type t) override {
+        return --fCount >= 0;
+    }
+
+    int fCount;
+};
+
 class PictFileView : public SampleView {
 public:
     PictFileView(const char name[] = NULL)
         : fFilename(name)
         , fBBox(kNo_BBoxType)
         , fTileSize(SkSize::Make(0, 0)) {
         for (int i = 0; i < kBBoxTypeCount; ++i) {
             fPictures[i] = NULL;
         }
+        fCount = 0;
     }
 
     virtual ~PictFileView() {
         for (int i = 0; i < kBBoxTypeCount; ++i) {
             SkSafeUnref(fPictures[i]);
         }
     }
 
     void onTileSizeChanged(const SkSize &tileSize) override {
         if (tileSize != fTileSize) {
@@ skipping 15 matching lines @@
             case kRTree_BBoxType:
                 name.append(" <bbox: R>");
                 break;
             default:
                 SkASSERT(false);
                 break;
             }
             SampleCode::TitleR(evt, name.c_str());
             return true;
         }
+        SkUnichar uni;
+        if (SampleCode::CharQ(*evt, &uni)) {
+            switch (uni) {
+                case 'n': fCount += 1; this->inval(nullptr); return true;
+                case 'p': fCount -= 1; this->inval(nullptr); return true;
+                case 's': fCount =  0; this->inval(nullptr); return true;
+                default: break;
+            }
+        }
         return this->INHERITED::onQuery(evt);
     }
 
     bool onEvent(const SkEvent& evt) override {
         if (evt.isType("PictFileView::toggleBBox")) {
             fBBox = (BBoxType)((fBBox + 1) % kBBoxTypeCount);
             return true;
         }
         return this->INHERITED::onEvent(evt);
     }
 
     void onDrawContent(SkCanvas* canvas) override {
         SkASSERT(static_cast<int>(fBBox) < kBBoxTypeCount);
         SkPicture** picture = fPictures + fBBox;
 
 #ifdef SK_GLYPHCACHE_TRACK_HASH_STATS
         SkGraphics::PurgeFontCache();
 #endif
 
         if (!*picture) {
             *picture = LoadPicture(fFilename.c_str(), fBBox);
         }
         if (*picture) {
+            SkCounterDrawFilter filter(fCount);
+            if (fCount > 0) {
+                canvas->setDrawFilter(&filter);
+            }
             canvas->drawPicture(*picture);
+            canvas->setDrawFilter(NULL);
         }
 
 #ifdef SK_GLYPHCACHE_TRACK_HASH_STATS
         SkGlyphCache::Dump();
         SkDebugf("\n");
 #endif
     }
 
 private:
     enum BBoxType {
         kNo_BBoxType,
         kRTree_BBoxType,
 
         kLast_BBoxType = kRTree_BBoxType,
     };
     static const int kBBoxTypeCount = kLast_BBoxType + 1;
 
     SkString    fFilename;
     SkPicture*  fPictures[kBBoxTypeCount];
     BBoxType    fBBox;
     SkSize      fTileSize;
+    int         fCount;
 
     SkPicture* LoadPicture(const char path[], BBoxType bbox) {
         SkAutoTUnref<SkPicture> pic;
 
         SkBitmap bm;
         if (SkImageDecoder::DecodeFile(path, &bm)) {
             bm.setImmutable();
             SkPictureRecorder recorder;
             SkCanvas* can = recorder.beginRecording(SkIntToScalar(bm.width()),
                                                     SkIntToScalar(bm.height()),
@@ skipping 52 matching lines @@
 SampleView* CreateSamplePictFileView(const char filename[]) {
     return new PictFileView(filename);
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
 #if 0
 static SkView* MyFactory() { return new PictFileView; }
 static SkViewRegister reg(MyFactory);
 #endif