skia2/example/SkiaSDLExample.cpp

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/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*
*/
#include "GrContext.h"
#include "SDL.h"
#include "SkCanvas.h"
#include "SkRandom.h"
#include "SkSurface.h"
#include "gl/GrGLInterface.h"
#include "gl/GrGLUtil.h"
#if defined(SK_BUILD_FOR_ANDROID)
#include <GLES/gl.h>
#elif defined(SK_BUILD_FOR_UNIX)
#include <GL/gl.h>
#elif defined(SK_BUILD_FOR_MAC)
#include <OpenGL/gl.h>
#endif
/*
* This application is a simple example of how to combine SDL and Skia it demonstrates:
* how to setup gpu rendering to the main window
* how to perform cpu-side rendering and draw the result to the gpu-backed screen
* draw simple primitives (rectangles)
* draw more complex primitives (star)
*/
struct ApplicationState {
ApplicationState() : fQuit(false) {}
// Storage for the user created rectangles. The last one may still be being edited.
SkTArray<SkRect> fRects;
bool fQuit;
};
static void handle_error() {
const char* error = SDL_GetError();
SkDebugf("SDL Error: %s\n", error);
SDL_ClearError();
}
static void handle_events(ApplicationState* state, SkCanvas* canvas) {
SDL_Event event;
while(SDL_PollEvent(&event)) {
switch (event.type) {
case SDL_MOUSEMOTION:
if (event.motion.state == SDL_PRESSED) {
SkRect& rect = state->fRects.back();
rect.fRight = event.motion.x;
rect.fBottom = event.motion.y;
}
break;
case SDL_MOUSEBUTTONDOWN:
if (event.button.state == SDL_PRESSED) {
state->fRects.push_back() = SkRect::MakeLTRB(SkIntToScalar(event.button.x),
SkIntToScalar(event.button.y),
SkIntToScalar(event.button.x),
SkIntToScalar(event.button.y));
}
break;
case SDL_KEYDOWN: {
SDL_Keycode key = event.key.keysym.sym;
if (key == SDLK_ESCAPE) {
state->fQuit = true;
}
break;
}
case SDL_QUIT:
state->fQuit = true;
break;
default:
break;
}
}
}
// Creates a star type shape using a SkPath
static SkPath create_star() {
static const int kNumPoints = 5;
SkPath concavePath;
SkPoint points[kNumPoints] = {{0, SkIntToScalar(-50)} };
SkMatrix rot;
rot.setRotate(SkIntToScalar(360) / kNumPoints);
for (int i = 1; i < kNumPoints; ++i) {
rot.mapPoints(points + i, points + i - 1, 1);
}
concavePath.moveTo(points[0]);
for (int i = 0; i < kNumPoints; ++i) {
concavePath.lineTo(points[(2 * i) % kNumPoints]);
}
concavePath.setFillType(SkPath::kEvenOdd_FillType);
SkASSERT(!concavePath.isConvex());
concavePath.close();
return concavePath;
}
#if defined(SK_BUILD_FOR_ANDROID)
int SDL_main(int argc, char** argv) {
#else
int main(int argc, char** argv) {
#endif
uint32_t windowFlags = 0;
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
SDL_GLContext glContext = nullptr;
#if defined(SK_BUILD_FOR_ANDROID)
// For Android we need to set up for OpenGL ES and we make the window hi res & full screen
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
windowFlags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE |
SDL_WINDOW_BORDERLESS | SDL_WINDOW_FULLSCREEN_DESKTOP |
SDL_WINDOW_ALLOW_HIGHDPI;
#else
// For all other clients we use the core profile and operate in a window
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
windowFlags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE;
#endif
static const int kStencilBits = 8; // Skia needs 8 stencil bits
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, kStencilBits);
SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
// If you want multisampling, uncomment the below lines and set a sample count
static const int kMsaaSampleCount = 0; //4;
// SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
// SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, kMsaaSampleCount);
/*
* In a real application you might want to initialize more subsystems
*/
if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS) != 0) {
handle_error();
return 1;
}
// Setup window
// This code will create a window with the same resolution as the user's desktop.
SDL_DisplayMode dm;
if (SDL_GetDesktopDisplayMode(0, &dm) != 0) {
handle_error();
return 1;
}
SDL_Window* window = SDL_CreateWindow("SDL Window", SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED, dm.w, dm.h, windowFlags);
if (!window) {
handle_error();
return 1;
}
// To go fullscreen
// SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN);
// try and setup a GL context
glContext = SDL_GL_CreateContext(window);
if (!glContext) {
handle_error();
return 1;
}
int success = SDL_GL_MakeCurrent(window, glContext);
if (success != 0) {
handle_error();
return success;
}
glViewport(0, 0, dm.w, dm.h);
glClearColor(1, 1, 1, 1);
glClearStencil(0);
glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
// setup GrContext
SkAutoTUnref<const GrGLInterface> interface(GrGLCreateNativeInterface());
// To use NVPR, comment this out
interface.reset(GrGLInterfaceRemoveNVPR(interface));
SkASSERT(interface);
// setup contexts
SkAutoTUnref<GrContext> grContext(GrContext::Create(kOpenGL_GrBackend,
(GrBackendContext)interface.get()));
SkASSERT(grContext);
// Wrap the frame buffer object attached to the screen in a Skia render target so Skia can
// render to it
GrBackendRenderTargetDesc desc;
desc.fWidth = dm.w;
desc.fHeight = dm.h;
desc.fConfig = kSkia8888_GrPixelConfig;
desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
desc.fSampleCnt = kMsaaSampleCount;
desc.fStencilBits = kStencilBits;
GrGLint buffer;
GR_GL_GetIntegerv(interface, GR_GL_FRAMEBUFFER_BINDING, &buffer);
desc.fRenderTargetHandle = buffer;
// setup SkSurface
// To use distance field text, use commented out SkSurfaceProps instead
// SkSurfaceProps props(SkSurfaceProps::kUseDeviceIndependentFonts_Flag,
// SkSurfaceProps::kLegacyFontHost_InitType);
SkSurfaceProps props(SkSurfaceProps::kLegacyFontHost_InitType);
sk_sp<SkSurface> surface(SkSurface::MakeFromBackendRenderTarget(grContext, desc, &props));
SkCanvas* canvas = surface->getCanvas();
ApplicationState state;
const char* helpMessage = "Click and drag to create rects. Press esc to quit.";
SkPaint paint;
// create a surface for CPU rasterization
sk_sp<SkSurface> cpuSurface(SkSurface::MakeRaster(canvas->imageInfo()));
SkCanvas* offscreen = cpuSurface->getCanvas();
offscreen->save();
offscreen->translate(50.0f, 50.0f);
offscreen->drawPath(create_star(), paint);
offscreen->restore();
sk_sp<SkImage> image = cpuSurface->makeImageSnapshot();
int rotation = 0;
while (!state.fQuit) { // Our application loop
SkRandom rand;
canvas->clear(SK_ColorWHITE);
handle_events(&state, canvas);
paint.setColor(SK_ColorBLACK);
canvas->drawText(helpMessage, strlen(helpMessage), SkIntToScalar(100),
SkIntToScalar(100), paint);
for (int i = 0; i < state.fRects.count(); i++) {
paint.setColor(rand.nextU() | 0x44808080);
canvas->drawRect(state.fRects[i], paint);
}
// draw offscreen canvas
canvas->save();
canvas->translate(dm.w / 2.0, dm.h / 2.0);
canvas->rotate(rotation++);
canvas->drawImage(image, -50.0f, -50.0f);
canvas->restore();
canvas->flush();
SDL_GL_SwapWindow(window);
}
if (glContext) {
SDL_GL_DeleteContext(glContext);
}
//Destroy window
SDL_DestroyWindow(window);
//Quit SDL subsystems
SDL_Quit();
return 0;
}