skia2/example/HelloWorld.cpp

/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/

#include "HelloWorld.h"

#include "GrContext.h"
#include "SkCanvas.h"
#include "SkGradientShader.h"
#include "SkGraphics.h"

using namespace sk_app;

Application* Application::Create(int argc, char** argv, void* platformData) {
    return new HelloWorld(argc, argv, platformData);
}

static void on_backend_created_func(void* userData) {
    HelloWorld* hw = reinterpret_cast<HelloWorld*>(userData);
    return hw->onBackendCreated();
}

static void on_paint_handler(SkCanvas* canvas, void* userData) {
    HelloWorld* hw = reinterpret_cast<HelloWorld*>(userData);
    return hw->onPaint(canvas);
}

static bool on_char_handler(SkUnichar c, uint32_t modifiers, void* userData) {
    HelloWorld* hw = reinterpret_cast<HelloWorld*>(userData);
    return hw->onChar(c, modifiers);
}

HelloWorld::HelloWorld(int argc, char** argv, void* platformData)
        : fBackendType(Window::kNativeGL_BackendType)
        , fRotationAngle(0) {
    SkGraphics::Init();

    fWindow = Window::CreateNativeWindow(platformData);
    fWindow->setRequestedDisplayParams(DisplayParams());

    // register callbacks
    fWindow->registerBackendCreatedFunc(on_backend_created_func, this);
    fWindow->registerPaintFunc(on_paint_handler, this);
    fWindow->registerCharFunc(on_char_handler, this);

    fWindow->attach(fBackendType);
}

HelloWorld::~HelloWorld() {
    fWindow->detach();
    delete fWindow;
}

void HelloWorld::updateTitle() {
    if (!fWindow || fWindow->sampleCount() < 0) {
        return;
    }

    SkString title("Hello World ");
    title.append(Window::kRaster_BackendType == fBackendType ? "Raster" : "OpenGL");
    fWindow->setTitle(title.c_str());
}

void HelloWorld::onBackendCreated() {
    this->updateTitle();
    fWindow->show();
    fWindow->inval();
}

void HelloWorld::onPaint(SkCanvas* canvas) {
    // Clear background
    canvas->clear(SK_ColorWHITE);

    SkPaint paint;
    paint.setColor(SK_ColorRED);

    // Draw a rectangle with red paint
    SkRect rect = SkRect::MakeXYWH(10, 10, 128, 128);
    canvas->drawRect(rect, paint);

    // Set up a linear gradient and draw a circle
    {
        SkPoint linearPoints[] = { { 0, 0 }, { 300, 300 } };
        SkColor linearColors[] = { SK_ColorGREEN, SK_ColorBLACK };
        paint.setShader(SkGradientShader::MakeLinear(linearPoints, linearColors, nullptr, 2,
                                                     SkShader::kMirror_TileMode));
        paint.setAntiAlias(true);

        canvas->drawCircle(200, 200, 64, paint);

        // Detach shader
        paint.setShader(nullptr);
    }

    // Draw a message with a nice black paint
    paint.setSubpixelText(true);
    paint.setColor(SK_ColorBLACK);
    paint.setTextSize(20);

    canvas->save();
    static const char message[] = "Hello World";

    // Translate and rotate
    canvas->translate(300, 300);
    fRotationAngle += 0.2f;
    if (fRotationAngle > 360) {
        fRotationAngle -= 360;
    }
    canvas->rotate(fRotationAngle);

    // Draw the text
    canvas->drawText(message, strlen(message), 0, 0, paint);

    canvas->restore();
}

void HelloWorld::onIdle() {
    // Just re-paint continously
    fWindow->inval();
}

bool HelloWorld::onChar(SkUnichar c, uint32_t modifiers) {
    if (' ' == c) {
        fBackendType = Window::kRaster_BackendType == fBackendType ? Window::kNativeGL_BackendType
                                                                   : Window::kRaster_BackendType;
        fWindow->detach();
        fWindow->attach(fBackendType);
    }
    return true;
}