Add OpenGL support to Linux viewer

tools/viewer/Viewer.cpp

 /*
 * 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 "Viewer.h"
 
 #include "GMSlide.h"
@@ skipping 17 matching lines @@
     return vv->onPaint(canvas);
 }
 
 static bool on_touch_handler(int owner, Window::InputState state, float x, float y, void* userData)
 {
     Viewer* viewer = reinterpret_cast<Viewer*>(userData);
 
     return viewer->onTouch(owner, state, x, y);
 }
 
-DEFINE_bool2(fullscreen, f, true, "Run fullscreen.");
+DEFINE_bool2(fullscreen, f, false, "Run fullscreen.");
 DEFINE_string(key, "", "Space-separated key/value pairs to add to JSON identifying this builder.");
 DEFINE_string2(match, m, nullptr,
                "[~][^]substring[$] [...] of bench name to run.\n"
                "Multiple matches may be separated by spaces.\n"
                "~ causes a matching bench to always be skipped\n"
                "^ requires the start of the bench to match\n"
                "$ requires the end of the bench to match\n"
                "^ and $ requires an exact match\n"
                "If a bench does not match any list entry,\n"
                "it is skipped unless some list entry starts with ~");
 DEFINE_string(skps, "skps", "Directory to read skps from.");
+DEFINE_bool(vulkan, true, "Run with Vulkan.");
 
 const char *kBackendTypeStrings[sk_app::Window::kBackendTypeCount] = {
     " [OpenGL]",
     " [Vulkan]"
 };
 
 Viewer::Viewer(int argc, char** argv, void* platformData)
     : fCurrentMeasurement(0)
     , fDisplayStats(false)
     , fBackendType(sk_app::Window::kVulkan_BackendType)
     , fZoomCenterX(0.0f)
     , fZoomCenterY(0.0f)
     , fZoomLevel(0.0f)
     , fZoomScale(SK_Scalar1)
 {
     memset(fMeasurements, 0, sizeof(fMeasurements));
 
     SkDebugf("Command line arguments: ");
     for (int i = 1; i < argc; ++i) {
         SkDebugf("%s ", argv[i]);
     }
     SkDebugf("\n");
 
     SkCommandLineFlags::Parse(argc, argv);
 
+    fBackendType = FLAGS_vulkan ? sk_app::Window::kVulkan_BackendType
+                                : sk_app::Window::kNativeGL_BackendType;
+
     fWindow = Window::CreateNativeWindow(platformData);
     fWindow->attach(fBackendType, DisplayParams());
 
     // register callbacks
     fCommands.attach(fWindow);
     fWindow->registerPaintFunc(on_paint_handler, this);
     fWindow->registerTouchFunc(on_touch_handler, this);
 
     // add key-bindings
     fCommands.addCommand('s', "Overlays", "Toggle stats display", [this]() {
@@ skipping 25 matching lines @@
         this->setupCurrentSlide(previousSlide);
     });
     fCommands.addCommand(Window::Key::kUp, "Up", "Transform", "Zoom in", [this]() {
         this->changeZoomLevel(1.f / 32.f);
         fWindow->inval();
     });
     fCommands.addCommand(Window::Key::kDown, "Down", "Transform", "Zoom out", [this]() {
         this->changeZoomLevel(-1.f / 32.f);
         fWindow->inval();
     });
+#if 0  // this doesn't seem to work on any platform right now
 #ifndef SK_BUILD_FOR_ANDROID
     fCommands.addCommand('d', "Modes", "Change rendering backend", [this]() {
         fWindow->detach();
 
         if (sk_app::Window::kVulkan_BackendType == fBackendType) {
             fBackendType = sk_app::Window::kNativeGL_BackendType;
         } 
-        // TODO: get Vulkan -> OpenGL working without swapchain creation failure
+        // TODO: get Vulkan -> OpenGL working on Windows without swapchain creation failure
         //else if (sk_app::Window::kNativeGL_BackendType == fBackendType) {
         //    fBackendType = sk_app::Window::kVulkan_BackendType;
         //}
 
         fWindow->attach(fBackendType, DisplayParams());
         this->updateTitle();
+        fWindow->inval();
     });
 #endif
+#endif
 
     // set up slides
     this->initSlides();
 
     fAnimTimer.run();
 
     // set up first frame
     fCurrentSlide = 0;
     setupCurrentSlide(-1);
 
@@ skipping 229 matching lines @@
     // Record measurements
     fMeasurements[fCurrentMeasurement++] = ms;
     fCurrentMeasurement &= (kMeasurementCount - 1);  // fast mod
     SkASSERT(fCurrentMeasurement < kMeasurementCount);
 
     fAnimTimer.updateTime();
     if (fSlides[fCurrentSlide]->animate(fAnimTimer) || fDisplayStats) {
         fWindow->inval();
     }
 }