initial checkin for experimenting

BUG=skia:

Review URL: https://codereview.chromium.org/696063005

2 files changed, 109 insertions, 0 deletions

diff --git a/src/core/SkCanvasDrawable.cpp b/src/core/SkCanvasDrawable.cpp
new file mode 100644
index 0000000000..7c01738dd6
--- /dev/null
+++ b/src/core/SkCanvasDrawable.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCanvas.h"
+#include "SkCanvasDrawable.h"
+#include "SkThread.h"
+
+static int32_t next_generation_id() {
+    static int32_t gCanvasDrawableGenerationID;
+
+    // do a loop in case our global wraps around, as we never want to
+    // return a 0
+    int32_t genID;
+    do {
+        genID = sk_atomic_inc(&gCanvasDrawableGenerationID) + 1;
+    } while (0 == genID);
+    return genID;
+}
+
+SkCanvasDrawable::SkCanvasDrawable() : fGenerationID(0) {}
+
+void SkCanvasDrawable::draw(SkCanvas* canvas) {
+    SkAutoCanvasRestore acr(canvas, true);
+    this->onDraw(canvas);
+}
+
+uint32_t SkCanvasDrawable::getGenerationID() {
+    if (0 == fGenerationID) {
+        fGenerationID = next_generation_id();
+    }
+    return fGenerationID;
+}
+
+bool SkCanvasDrawable::getBounds(SkRect* boundsPtr) {
+    SkRect bounds;
+    if (!boundsPtr) {
+        boundsPtr = &bounds;
+    }
+    return this->onGetBounds(boundsPtr);
+}
+
+void SkCanvasDrawable::notifyDrawingChanged() {
+    fGenerationID = 0;
+}
+
+
diff --git a/src/core/SkCanvasDrawable.h b/src/core/SkCanvasDrawable.h
new file mode 100644
index 0000000000..8092ea0b7a
--- /dev/null
+++ b/src/core/SkCanvasDrawable.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCanvasDrawable_DEFINED
+#define SkCanvasDrawable_DEFINED
+
+#include "SkRefCnt.h"
+
+class SkCanvas;
+struct SkRect;
+
+/**
+ *  Base-class to capture a set of drawing commands (sent to SkCanvas). Instances of this class
+ *  need not be thread-safe, but they must be able to be used in a thread different from where
+ *  they were created.
+ */
+class SkCanvasDrawable : public SkRefCnt {
+public:
+    SkCanvasDrawable();
+
+    /**
+     *  Draws into the specified content. The drawing sequence will be balanced upon return
+     *  (i.e. the saveLevel() on the canvas will match what it was when draw() was called,
+     *  and the current matrix and clip settings will not be changed.
+     */
+    void draw(SkCanvas*);
+
+    /**
+     *  Return a unique value for this instance. If two calls to this return the same value,
+     *  it is presumed that calling the draw() method will render the same thing as well.
+     *
+     *  Subclasses that change their state should call notifyDrawingChanged() to ensure that
+     *  a new value will be returned the next time it is called.
+     */
+    uint32_t getGenerationID();
+
+    /**
+     *  If the drawable knows a bounds that will contains all of its drawing, return true and
+     *  set the parameter to that rectangle. If one is not known, ignore the parameter and
+     *  return false.
+     */
+    bool getBounds(SkRect*);
+
+    void notifyDrawingChanged();
+
+protected:
+    virtual void onDraw(SkCanvas*) = 0;
+
+    virtual bool onGetBounds(SkRect*) { return false; }
+
+private:
+    int32_t fGenerationID;
+};
+
+#endif