第15章 《乐趣》Page375~379定时器，定时回调，定时回调线程id, 停止后续定时

运行效果：在骏马窗口中，按下ctrl + t 键，就可以看到定时回调，同时可以看出timer_callback和main()真的不在同一线程中运行

代码如下：仅给出main.cpp, 其他的头文件和源文件和Page355~375的代码一样，可参看上一篇博文

//main.cpp
#include <iostream>
#include <SDL2/SDL.h>
#include "sdl_initiator.hpp"
#include "sdl_error.hpp"
#include "sdl_window.hpp"
#include "sdl_surface.hpp"
#include "sdl_renderer.hpp"
#include "sdl_texture.hpp"

#include <SDL2/SDL_timer.h>
#include <thread>

using namespace std;

//加载图片为纹理，并设置透明色
SDL_Texture* LoadBMPTexture(SDL_Renderer* renderer
                           , char const* filename
                           , Uint8 key_r, Uint8 key_g, Uint8 key_b)
{
    sdl2::BitmapSurface bmp(filename);
    if(!bmp)
    {
        return nullptr;
    }
    bmp.EnableColorKey(key_r, key_g, key_b, 0);
    return sdl2::Texture(renderer, bmp._surface).Release();
}
//加载图片为纹理，不透明，不混色
SDL_Texture* LoadBMPTexture(SDL_Renderer* renderer
                            , char const* filename)
{
    sdl2::BitmapSurface bmp(filename);
    if(!bmp)
    {
        return nullptr;
    }

    return sdl2::Texture(renderer, bmp._surface).Release();
}
//加载图片为纹理，并设置透明色和混色
SDL_Texture* LoadBMPTexture(SDL_Renderer* renderer
                , char const* filename
                , Uint8 key_r, Uint8 key_g, Uint8 key_b
                , Uint8 alpha_mod
                , SDL_BlendMode blend_mode = SDL_BLENDMODE_BLEND)
{
    sdl2::BitmapSurface bmp(filename);
    if(!bmp)
    {
        return nullptr;
    }
    bmp.EnableColorKey(key_r, key_g, key_b, 0);
    bmp.SetAlphaMod(alpha_mod);
    bmp.SetBlendMode(blend_mode);
    return sdl2::Texture(renderer, bmp._surface).Release();
}

//回调第二个入参param被注释掉，因为暂时不需要传递附加数据
Uint32 timer_callback(Uint32 interval, void* /*param*/)
{
    cout << "hello sdl timer\r\n";
    cout << "timer_callback thread id: " << std::this_thread::get_id() << endl;
    return interval;
}

int main(int argc, char* argv[])
{
    sdl2::Initiator::Instance().Init(SDL_INIT_VIDEO
                                     | SDL_INIT_AUDIO
                                     | SDL_INIT_EVENTS
                                     | SDL_INIT_TIMER);

    if(!sdl2::Initiator::Instance())//重载转换符
    {
        cerr << "初始化就出错，没得玩了！"
             << sdl2::last_error() << endl;
    }

    //创建并居中显示宽640，高480的游戏窗口
    sdl2::Window wnd("hello sdl"
                     , sdl2::WindowPosition()
                     , 640, 480
                     //去除原来的全屏标志
                     , sdl2::WindowFlags());

    if(!wnd)
    {
        cerr << sdl2::last_error() << endl;
        return -1;
    }

    //准备窗口的渲染器
    sdl2::Renderer renderer(wnd._window);
    if(!renderer)
    {
        cerr << sdl2::last_error() << endl;
        return -1;
    }
    //重要！修改缩放质量配置
    sdl2::RendererDriver::HintScaleQuality();
    //重要！设置虚拟大小
    renderer.SetLogicalSize(640, 480);

    //准备背景图(不需要透明和混色)
    sdl2::Texture bkgnd(LoadBMPTexture(renderer._renderer, "bkgnd.bmp"));

    if(!bkgnd)
    {
        cerr << sdl2::last_error() << endl;
        return -1;
    }

    //准备小马图，透明色为白色
    sdl2::Texture horse(LoadBMPTexture(renderer._renderer
                                       , "sdl.bmp"
                                       , 0xff, 0xff, 0xff));
    if(!horse)
    {
        cerr << sdl2::last_error() << endl;
        return -1;
    }

    //准备白云图纹理，透明色为红色，不透明度188（0~255）
    sdl2::Texture cloud(LoadBMPTexture(renderer._renderer
                                       , "cloud.bmp"
                                       , 0xff, 0, 0, 188));
    if(!cloud)
    {
        cerr << sdl2::last_error() << endl;
        return -1;
    }
    //事件循环
    bool Q = false;
    while(!Q)//一直循环，直到Q为真
    {
        SDL_Event event;
        //会将队列中拖出的event数据存储到event中
        while(SDL_PollEvent(&event))
        {
            switch(event.type)
            {
                case SDL_QUIT:
                    Q = true;
                    break;

                case SDL_KEYDOWN:
                    if(event.key.keysym.sym == SDLK_t)//按键 ctrl + t
                    {
                        SDL_AddTimer(2000, timer_callback, nullptr);
                        cout << "main thread id: " << std::this_thread::get_id() << endl;
                    }
                    break;
            }
        }//内循环

        /*外循环：贴骏马图*/
        //贴背景->窗口
        renderer.CopyFrom(bkgnd._texture);

        //贴第一朵白云
        SDL_Rect cloud_rect_1{200, 20, 156, 78};
        renderer.CopyFrom(cloud._texture, nullptr, &cloud_rect_1);

        //贴第二朵白云
        SDL_Rect cloud_rect_2{340, 6, 156, 78};
        renderer.CopyFrom(cloud._texture, nullptr, &cloud_rect_2);
        //贴骏马
        SDL_Rect dst_rect{86, 65, 468, 350};
        renderer.CopyFrom(horse._texture, nullptr, &dst_rect);

        renderer.Present();
        SDL_Delay(1);//防止cpu占用率太高
//        Q = true; //开发过程中，为方便程序退出，暂时这样
    }//外循环

    return 0;
}

如果将64行的代码改为 return 0，即可停止后续定时，效果如下：