Smallest possible desktop application that uses Skia to render stuff.

experimental/SkiaExamples/BaseExample.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 "BaseExample.h"
+
+#include "gl/GrGLUtil.h"
+#include "gl/GrGLDefines.h"
+#include "gl/GrGLInterface.h"
+#include "SkApplication.h"
+#include "SkGpuDevice.h"
+#include "SkGraphics.h"
+
+void application_init() {
+    SkGraphics::Init();
+    SkEvent::Init();
+}
+
+void application_term() {
+    SkEvent::Term();
+    SkGraphics::Term();
+}
+
+BaseExample::BaseExample(void* hWnd, int argc, char** argv)
+    : INHERITED(hWnd), fDelayMs(16) {}
+
+void BaseExample::tearDownBackend() {
+  if (kGPU_DeviceType == fType) {
+        SkSafeUnref(fContext);
+        fContext = NULL;
+
+        SkSafeUnref(fInterface);
+        fInterface = NULL;
+
+        SkSafeUnref(fRenderTarget);
+        fRenderTarget = NULL;
+
+        detach();
+    }
+}
+
+bool BaseExample::setupBackend(DeviceType type) {
+    fType = type;
+
+    this->setConfig(SkBitmap::kARGB_8888_Config);
+    this->setVisibleP(true);
+    this->setClipToBounds(false);
+
+    bool result = attach(kNativeGL_BackEndType, 0 /*msaa*/, &fAttachmentInfo);
+    if (false == result) {
+        SkDebugf("Not possible to create backend.");
+        detach();
+        return false;
+    }
+
+    fInterface = GrGLCreateNativeInterface();
+
+    SkASSERT(NULL != fInterface);
+
+    fContext = GrContext::Create(kOpenGL_GrBackend, (GrBackendContext)fInterface);
+    SkASSERT(NULL != fContext);
+
+    setupRenderTarget();
+
+    return true;
+}
+
+void BaseExample::setupRenderTarget() {
+    GrBackendRenderTargetDesc desc;
+    desc.fWidth = SkScalarRound(width());
+    desc.fHeight = SkScalarRound(height());
+    desc.fConfig = kSkia8888_GrPixelConfig;
+    desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
+    desc.fSampleCnt = fAttachmentInfo.fSampleCount;
+    desc.fStencilBits = fAttachmentInfo.fStencilBits;
+
+    GrGLint buffer;
+    GR_GL_GetIntegerv(fInterface, GR_GL_FRAMEBUFFER_BINDING, &buffer);
+    desc.fRenderTargetHandle = buffer;
+
+    fRenderTarget = fContext->wrapBackendRenderTarget(desc);
+
+    fContext->setRenderTarget(fRenderTarget);
+}
+
+SkCanvas* BaseExample::createCanvas() {
+    if (fType == kGPU_DeviceType &&

[caryclark, 2013/06/17 15:08:39]

note if (fType ... ) here ... but below ...

+            NULL != fContext && NULL != fRenderTarget) {
+        SkAutoTUnref<SkDevice> device(new SkGpuDevice(fContext, fRenderTarget));
+        return new SkCanvas(device);
+    } else {
+        if (fType == kGPU_DeviceType) {
+            tearDownBackend();
+            setupBackend(kRaster_DeviceType);
+        }
+        return INHERITED::createCanvas();
+    }

[caryclark, 2013/06/17 15:08:39]

I would rewrite this as:

if (fType == kGPU_DeviceType) {
  if (NULL != fContext ... {
    ...
    return newSkCanvas(device);
  }
  tearDownBackend();
  ...
}
return INHERITED::createCanvas();

My rationale is that there's less to parse if duplicate conditionals are removed
(both the if () and the else)

[sglez, 2013/06/17 18:04:35]

The else is still needed to handle a nil context or render target, but yes, this
is cleaner.

+}
+
+void BaseExample::draw(SkCanvas* canvas) {
+    if (getDeviceType() == kGPU_DeviceType) {

[caryclark, 2013/06/17 15:08:39]

if (getDeviceType() ... here.
Choose one or the other. (I prefer if (fType ... since it's private and then I
don't have to go look at getDeviceType() to see if it does anything tricky)

+        SkASSERT(NULL != fContext);
+        fContext->flush();
+    }
+    if (kRaster_DeviceType == getDeviceType()) {

[caryclark, 2013/06/17 15:08:39]

reverse compare order

+        // need to send the raster bits to the (gpu) window
+        fContext->setRenderTarget(fRenderTarget);
+        const SkBitmap& bm = getBitmap();
+        fRenderTarget->writePixels(0, 0, bm.width(), bm.height(),
+                                      kSkia8888_GrPixelConfig,
+                                      bm.getPixels(),
+                                      bm.rowBytes());
+    }
+    present();
+}
+
+void BaseExample::onSizeChange() {
+    setupRenderTarget();
+}
+
+void BaseExample::setInvalDelay(SkMSec ms) {
+    fDelayMs = ms;

[caryclark, 2013/06/17 15:08:39]

One line implementations might as well live in the .h file

[sglez, 2013/06/17 18:04:35]

Mike's changes make my delay fix obsolete so I'm taking this out.

+}
+
+#ifdef SK_BUILD_FOR_UNIX
+void BaseExample::onHandleInval(const SkIRect&) {
+    (new SkEvent("inval-imageview", this->getSinkID()))->postDelay(fDelayMs);
+}
+#endif
+
+#ifdef SK_BUILD_FOR_WIN
+void BaseExample::onHandleInval(const SkIRect& rect) {
+        Sleep(fDelayMs);

[caryclark, 2013/06/17 15:08:39]

This suggests that one thread should be doing computation for the next frame
since this thread will always wait 1/60th of a second. Is this your intent?

[sglez, 2013/06/17 18:04:35]

The intent was to mimic the Linux behavior by making the app sleep when
invalidated. I took the call out. 
The rest of this function is still needed to fix the choppiness on Windows.

+        RECT winRect;
+        winRect.top = rect.top();
+        winRect.bottom = rect.bottom();
+        winRect.right = rect.right();
+        winRect.left = rect.left();
+        InvalidateRect((HWND)this->getHWND(), &winRect, false);
+}
+#endif