Add support for multiple frames in SkCodec

gm/animatedGif.cpp

Index: gm/animatedGif.cpp
diff --git a/gm/animatedGif.cpp b/gm/animatedGif.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..fc6fad08868c6a654066919254487fd790d3d49c
--- /dev/null
+++ b/gm/animatedGif.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkAnimTimer.h"
+#include "SkCanvas.h"
+#include "SkCodec.h"
+#include "SkColor.h"
+#include "SkCommandLineFlags.h"
+#include "SkPaint.h"
+#include "SkString.h"
+#include "Resources.h"
+
+#include <vector>
+
+DEFINE_string(animatedGif, "test640x479.gif", "Animated gif in resources folder");
+
+namespace {
+    void error(SkCanvas* canvas, const SkString& errorText) {
+        constexpr SkScalar kOffset = 5.0f;
+        canvas->drawColor(SK_ColorRED);
+        SkPaint paint;
+        SkRect bounds;
+        paint.measureText(errorText.c_str(), errorText.size(), &bounds);
+        canvas->drawText(errorText.c_str(), errorText.size(), kOffset, bounds.height() + kOffset,
+                         paint);
+    }
+}
+
+class AnimatedGifGM : public skiagm::GM {
+private:
+    std::unique_ptr<SkCodec>        fCodec;
+    size_t                          fFrame;
+    double                          fNextUpdate;
+    size_t                          fTotalFrames;
+    std::vector<SkCodec::FrameInfo> fFrameInfos;
+    std::vector<SkBitmap>           fFrames;
+
+    void drawFrame(SkCanvas* canvas, int frameIndex) {
+        // FIXME: Create from an Image/ImageGenerator?
+        if (frameIndex >= (int) fFrames.size()) {
+            fFrames.resize(frameIndex + 1);
+        }
+        SkBitmap& bm = fFrames[frameIndex];
+        if (!bm.getPixels()) {
+            const SkImageInfo info = fCodec->getInfo().makeColorType(kN32_SkColorType);
+            bm.allocPixels(info);
+
+            SkCodec::Options opts;
+            opts.fFrameIndex = frameIndex;
+            opts.fHasPriorFrame = false;
+            const size_t requiredFrame = fFrameInfos[frameIndex].fRequiredFrame;
+            if (requiredFrame != SkCodec::kNone) {
+                SkASSERT(requiredFrame < fFrames.size());
+                SkBitmap& requiredBitmap = fFrames[requiredFrame];
+                // For simplicity, do not try to cache old frames
+                if (requiredBitmap.getPixels() && requiredBitmap.copyTo(&bm)) {
+                    opts.fHasPriorFrame = true;
+                }
+            }
+
+            if (SkCodec::kSuccess != fCodec->getPixels(info, bm.getPixels(),
+                                                       bm.rowBytes(), &opts,
+                                                       nullptr, nullptr)) {
+                SkDebugf("Could not getPixels for frame %i: %s", frameIndex, FLAGS_animatedGif[0]);
+                return;
+            }
+        }
+
+        canvas->drawBitmap(bm, 0, 0);
+    }
+
+public:
+    AnimatedGifGM()
+    : fFrame(0)
+    , fNextUpdate (-1)
+    , fTotalFrames (-1) {}
+
+private:
+    SkString onShortName() override {
+        return SkString("animatedGif");
+    }
+
+    SkISize onISize() override {
+        if (this->initCodec()) {
+            SkISize dim = fCodec->getInfo().dimensions();
+            // Wide enough to display all the frames.
+            dim.fWidth *= fTotalFrames;
+            // Tall enough to show the row of frames plus an animating version.
+            dim.fHeight *= 2;
+            return dim;
+        }
+        return SkISize::Make(640, 480);
+    }
+
+    void onDrawBackground(SkCanvas* canvas) override {
+        if (this->initCodec()) {
+            SkAutoCanvasRestore acr(canvas, true);
+            for (size_t frameIndex = 0; frameIndex < fTotalFrames; frameIndex++) {
+                this->drawFrame(canvas, frameIndex);
+                canvas->translate(fCodec->getInfo().width(), 0);
+            }
+        }
+    }
+
+    bool initCodec() {
+        if (fCodec) {
+            return true;
+        }
+        if (FLAGS_animatedGif.isEmpty()) {
+            SkDebugf("Nothing specified for --animatedGif!");
+            return false;
+        }
+
+        std::unique_ptr<SkStream> stream(GetResourceAsStream(FLAGS_animatedGif[0]));
+        if (!stream) {
+            return false;
+        }
+
+        fCodec.reset(SkCodec::NewFromStream(stream.release()));
+        if (!fCodec) {
+            SkDebugf("Could create codec from %s", FLAGS_animatedGif[0]);
+            return false;
+        }
+
+        fFrame = 0;
+        fFrameInfos = fCodec->getFrameInfo();
+        fTotalFrames = fFrameInfos.size();
+        return true;
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        if (!fCodec) {
+            SkString errorText = SkStringPrintf("Nothing to draw; %s", FLAGS_animatedGif[0]);
+            error(canvas, errorText);
+            return;
+        }
+
+        SkAutoCanvasRestore acr(canvas, true);
+        canvas->translate(0, fCodec->getInfo().height());
+        this->drawFrame(canvas, fFrame);
+    }
+
+    bool onAnimate(const SkAnimTimer& timer) override {
+        if (!fCodec || fTotalFrames == 1) {
+            return false;
+        }
+
+        double secs = timer.msec() * .1;
+        if (fNextUpdate < double(0)) {
+            // This is a sentinel that we have not done any updates yet.
+            // I'm assuming this gets called *after* onOnceBeforeDraw, so our first frame should
+            // already have been retrieved.
+            SkASSERT(fFrame == 0);
+            fNextUpdate = secs + fFrameInfos[fFrame].fDuration;
+
+            return true;
+        }
+
+        if (secs < fNextUpdate) {
+            return true;
+        }
+
+        while (secs >= fNextUpdate) {
+            // Retrieve the next frame.
+            fFrame++;
+            if (fFrame == fTotalFrames) {
+                fFrame = 0;
+            }
+
+            // Note that we loop here. This is not safe if we need to draw the intermediate frame
+            // in order to draw correctly.
+            fNextUpdate += fFrameInfos[fFrame].fDuration;
+        }
+
+        return true;
+    }
+};
+
+DEF_GM(return new AnimatedGifGM);
+