Avoid black flashes when resizing debugger window using MSAA

debugger/QT/SkGLWidget.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkGLWidget.h"
 
 #if SK_SUPPORT_GPU
 
 SkGLWidget::SkGLWidget(SkDebugger* debugger) : QGLWidget() {
-    this->setStyleSheet("QWidget {background-color: white; border: 1px solid #cccccc;}");
     fDebugger = debugger;
     fCurIntf = NULL;
     fCurContext = NULL;
     fGpuDevice = NULL;
     fCanvas = NULL;
 }
 
 SkGLWidget::~SkGLWidget() {
     SkSafeUnref(fCurIntf);
     SkSafeUnref(fCurContext);
     SkSafeUnref(fGpuDevice);
     SkSafeUnref(fCanvas);
 }
 
 void SkGLWidget::setSampleCount(int sampleCount)
 {
     QGLFormat currentFormat = format();
     currentFormat.setSampleBuffers(sampleCount > 0);
     currentFormat.setSamples(sampleCount);
     setFormat(currentFormat);
 }
 
 void SkGLWidget::initializeGL() {
     fCurIntf = GrGLCreateNativeInterface();
     if (!fCurIntf) {
         return;
     }
+    glStencilMask(0xffffffff);
+    glClearStencil(0);
+    glClear(GL_STENCIL_BUFFER_BIT);
+
     fCurContext = GrContext::Create(kOpenGL_GrBackend, (GrBackendContext) fCurIntf);
     GrBackendRenderTargetDesc desc = this->getDesc(this->width(), this->height());
     desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
     GrRenderTarget* curRenderTarget = fCurContext->wrapBackendRenderTarget(desc);
     fGpuDevice = new SkGpuDevice(fCurContext, curRenderTarget);
     fCanvas = new SkCanvas(fGpuDevice);
     curRenderTarget->unref();
-
-    glClearColor(1, 1, 1, 0);
-    glClearStencil(0);
-    glClear(GL_STENCIL_BUFFER_BIT);
 }
 
 void SkGLWidget::resizeGL(int w, int h) {
     if (fCurContext) {
+        glDisable(GL_SCISSOR_TEST);
+        glStencilMask(0xffffffff);
+        glClearStencil(0);
+        glClear(GL_STENCIL_BUFFER_BIT);
+        fCurContext->resetContext();
+
         GrBackendRenderTargetDesc desc = this->getDesc(w, h);
         desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
         GrRenderTarget* curRenderTarget = fCurContext->wrapBackendRenderTarget(desc);
         SkSafeUnref(fGpuDevice);
         SkSafeUnref(fCanvas);
         fGpuDevice = new SkGpuDevice(fCurContext, curRenderTarget);
         fCanvas = new SkCanvas(fGpuDevice);
     }
     fDebugger->resize(w, h);
     draw();
@@ skipping 16 matching lines @@
     GR_GL_GetIntegerv(fCurIntf, GR_GL_SAMPLES, &desc.fSampleCnt);
     GR_GL_GetIntegerv(fCurIntf, GR_GL_STENCIL_BITS, &desc.fStencilBits);
     GrGLint buffer;
     GR_GL_GetIntegerv(fCurIntf, GR_GL_FRAMEBUFFER_BINDING, &buffer);
     desc.fRenderTargetHandle = buffer;
 
     return desc;
 }
 
 #endif