第15章《乐趣》Page355~375 代码简化版

运行效果：全屏了

简化之后的代码如下：

//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"

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();
}
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
                     //使用空的特性标志
                     , sdl2::WindowFlags().FullScreenDesktop());

    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;
            }
        }//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;
}

//sdl_error.cpp
#include "sdl_error.hpp"

namespace sdl2
{

char const* last_error()
{
    return SDL_GetError();
}

}//sdl2

//sdl_error.hpp
#ifndef SDL_ERROR_HPP_INCLUDED
#define SDL_ERROR_HPP_INCLUDED
#include <SDL2/SDL.h>

namespace sdl2
{
char const* last_error();
}


#endif // SDL_ERROR_HPP_INCLUDED

//sdl_initiator.hpp
#ifndef SDL_INITIATOR_HPP_INCLUDED
#define SDL_INITIATOR_HPP_INCLUDED

namespace sdl2
{

struct Initiator
{
private: //单例模式，外界无需使用构造函数
    Initiator()
        : _init_result(-1)
    {

    }

public:
    static Initiator& Instance()
    {
        static Initiator Instance;
        return Instance;
    }

    ~Initiator()
    {
        SDL_Quit();
    }

    void GetVersion(Uint8& major, Uint8& minor, Uint8& patch)
    {
        SDL_version ver;
        SDL_GetVersion(&ver);

        major = ver.major;
        minor = ver.minor;
        patch = ver.patch;
    }

    bool Init(Uint32 flags = SDL_INIT_EVERYTHING)
    {
        _init_result = SDL_Init(flags);
        return 0 == _init_result;
    }

//    bool operator bool()
    explicit operator bool() const
    {
        return _init_result == 0;
    }

private:
    int _init_result;
};//Initiator

}//sdl2

#endif // SDL_INITIATOR_HPP_INCLUDED

//sdl_renderer.hpp
#ifndef SDL_RENDERER_HPP_INCLUDED
#define SDL_RENDERER_HPP_INCLUDED

namespace sdl2
{
//渲染驱动（方法均为静态）
struct RendererDriver
{
    static bool HintScaleQuality(char const* quality = "linear")
    {
        return SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, quality);
    }
};

struct Renderer
{
    Renderer(SDL_Window* window, int index = -1, Uint32 flags = 0)
    {
        _renderer = SDL_CreateRenderer(window, index, flags);
    }

    ~Renderer()
    {
        SDL_assert(_renderer != nullptr);
        SDL_DestroyRenderer(_renderer);
    }

    bool SetLogicalSize(int w, int h)
    {
        SDL_assert(_renderer != nullptr);
        return 0 == SDL_RenderSetLogicalSize(_renderer, w, h);
    }

    bool CopyFrom(SDL_Texture* src_texture
                  , const SDL_Rect* src_rect = nullptr
                  , const SDL_Rect* dst_rect = nullptr)
    {
        SDL_assert(_renderer != nullptr);
        SDL_assert(src_texture != nullptr);
        return 0 == SDL_RenderCopy(_renderer, src_texture, src_rect, dst_rect);
    }

    void Present()
    {
        SDL_assert(_renderer != nullptr);
        SDL_RenderPresent(_renderer);
    }
    explicit operator bool() const
    {
        return _renderer != nullptr;
    }

    SDL_Renderer* _renderer;
};//Renderer

}//sdl2

#endif // SDL_RENDERER_HPP_INCLUDED

//sdl_surface.hpp
#ifndef SDL_SURFACE_HPP_INCLUDED
#define SDL_SURFACE_HPP_INCLUDED

namespace sdl2
{

struct Surface
{

    //代管外部创建好的surface指针
    explicit Surface(SDL_Surface* surface)
        : _surface(surface)
    {

    }
    /*父类的析构函数使用虚函数的主要原因是为了确保多态时的正确清理。
      在C++中，析构函数主要用于释放动态分配的资源。如果父类的析构函数不是虚函数，
      那么当使用子类指针删除父类对象时，由于没有动态绑定（晚绑定），
      只会调用父类的析构函数，而不会调用子类的析构函数。
      这样，子类中的资源可能不会被正确释放，导致内存泄漏或其他问题。

     如果父类的析构函数是虚函数，那么当使用子类指针删除父类对象时，
     会根据实际对象的类型动态调用相应的析构函数。这样，既可以释放父类占用的资源，
     又可以释放子类占用的资源，确保资源的正确释放。
     因此，为了确保多态时的正确清理，父类的析构函数应该声明为虚函数。*/
    virtual ~Surface()
    {
        SDL_assert(_surface != nullptr);
        SDL_FreeSurface(_surface);
    };

    bool SetAlphaMod(Uint8 alpha)
    {
        SDL_assert(_surface != nullptr);
        return 0 == SDL_SetSurfaceAlphaMod(_surface, alpha);
    }

    bool SetBlendMode(SDL_BlendMode const& mode)
    {
        SDL_assert(_surface != nullptr);
        return 0 == SDL_SetSurfaceBlendMode(_surface, mode);
    }

    //    EnableColorKey(Uint32 r, Uint32 g, Uint32 b, Uint32 a)
    bool EnableColorKey(Uint8 r, Uint8 g, Uint8 b, Uint8 a)
    {
        SDL_assert(_surface != nullptr);
        Uint32 key = SDL_MapRGBA(_surface->format, r, g, b, a);
        return 0 == SDL_SetColorKey(_surface, SDL_TRUE, key);
    }

    bool BlitTo(SDL_Surface* dst_surface, SDL_Rect* src_rect, SDL_Rect* dst_rect)
    {
        SDL_assert(_surface != nullptr);
        return 0 == SDL_BlitSurface(_surface, src_rect, dst_surface, dst_rect);
    }

    explicit operator bool() const
    {
        return _surface != nullptr;
    }

    SDL_Surface* _surface;
};

//来自位图的表层
struct BitmapSurface : public Surface
{
    explicit BitmapSurface (char const* filename)
        : Surface(SDL_LoadBMP(filename))
    {

    }
};

}//sdl2

#endif // SDL_SURFACE_HPP_INCLUDED

//sdl_texture.hpp
#ifndef SDL_TEXTURE_HPP_INCLUDED
#define SDL_TEXTURE_HPP_INCLUDED

namespace sdl2
{

struct Texture
{
    Texture(SDL_Texture* texture)
        : _texture(texture)
    {

    }

    Texture(SDL_Renderer* renderer, SDL_Surface* surface)
        : _texture(SDL_CreateTextureFromSurface(renderer, surface))
    {

    }

    ~Texture()
    {
//        SDL_assert(_texture != nullptr);
        //_texture不一定就不空，所以需要修改
        if(_texture)
        SDL_DestroyTexture(_texture);
    }

    SDL_Texture* Release()
    {
        SDL_Texture* tmp;
        tmp = _texture;
//        *tmp = *_texture; //tmp和_texture已经指向同一数据了
        _texture = nullptr;
        return tmp;
    }

    explicit operator bool() const
    {
        return _texture != nullptr;
    }

    SDL_Texture* _texture;
};//Texture

}//sdl2

#endif // SDL_TEXTURE_HPP_INCLUDED

//sdl_window.hpp
#ifndef SDL_WINDOW_HPP_INCLUDED
#define SDL_WINDOW_HPP_INCLUDED

#include <SDL2/SDL.h>

namespace sdl2
{

struct WindowPosition
{
    WindowPosition()//默认构造
        : _x(SDL_WINDOWPOS_CENTERED), _y(SDL_WINDOWPOS_CENTERED)
    {

    }

    WindowPosition(int x, int y)//常规初始化
        : _x(x), _y(y)
    {

    }

    ~WindowPosition()
    {

    }

    WindowPosition& Centered(bool x_centered = true
                             , bool y_centered = true)
    {
        if(x_centered)
            _x = SDL_WINDOWPOS_CENTERED;
        if(y_centered)
            _y = SDL_WINDOWPOS_CENTERED;
    }

    int _x, _y;
};

struct WindowFlags
{
    //默认构造，用于构建一个没有指定任何特性的普通窗口
    WindowFlags()
        : _flags(0)
    {

    }

    ~WindowFlags()
    {

    }

    WindowFlags& FullScreenDesktop()
    {
        _flags &= ~SDL_WINDOW_FULLSCREEN;
        _flags |= SDL_WINDOW_FULLSCREEN_DESKTOP;
        return *this;
    }

    Uint32 _flags;
};

struct Window
{
    Window(char const* title
           , WindowPosition const& win_position
           , int x, int y
           , WindowFlags const& win_flags) //必须有const，否则无法引用右值()
    {
        _window = SDL_CreateWindow(title
                                   , win_position._x, win_position._y
                                   , x, y
                                   , win_flags._flags);
    }

    ~Window()
    {
        SDL_DestroyWindow(_window);
    }

    bool UpdateSurface()
    {
        SDL_assert(_window != nullptr);
        return 0 == SDL_UpdateWindowSurface(_window);
    }

    SDL_Surface* GetSurface()
    {
        SDL_assert(_window);
        return SDL_GetWindowSurface(_window);
    }

    explicit operator bool() const
    {
        return _window != nullptr;
    }

    Uint32 GetID()
    {
        SDL_assert(_window != nullptr);
        return SDL_GetWindowID(_window);
    }

    bool SetOpacity(float opacity)
    {
        SDL_assert(_window != nullptr);
        return 0 == SDL_SetWindowOpacity(_window, opacity);
    }

    void Hide()
    {
        SDL_assert(_window != nullptr);
        SDL_HideWindow(_window);
    }

    void Show()
    {
        SDL_assert(_window != nullptr);
        SDL_ShowWindow(_window);
    }

    SDL_Window* _window;
};

}//sdl2

#endif // SDL_WINDOW_HPP_INCLUDED