用到的API

• SDL_SetRenderDrawColor(SDL_Renderer* renderer, Uint8 r,
  Uint8 g, Uint8 b, Uint8 a)
• SDL_RenderClear(SDL_Renderer* renderer)
• SDL_RenderFillRect(SDL_Renderer* renderer, const SDL_Rect *rect)
• SDL_RenderDrawRect(SDL_Renderer* renderer, const SDL_Rect *rect)
• SDL_RenderDrawLine(SDL_Renderer* renderer,int x1,int y1,int x2,int y2)
• SDL_RenderDrawPoint(SDL_Renderer* renderer,int x,int y)
• SDL_RenderPresent(SDL_Renderer* renderer);

API介绍

• SDL_SetRenderDrawColor 接收的四个参数分别是RGB通道和alpha通道
• SDL_RenderClear 用设置的绘画颜色清理目标渲染器
• SDL_RenderFillRect 用设置的绘画颜色填充矩形
• SDL_RenderDrawRect 用设置的绘画颜色绘制矩形边框
• SDL_RenderDrawLine 用设置的绘画颜色绘制线段
• SDL_RenderDrawPoint 用设置的绘画颜色绘制点
• SDL_RenderPresent 用渲染器中的内容更新屏幕

SDL_Rect 介绍

SDL_Rect 是一个结构体，其中有四个int型的成员，x,y,w,h
x,y 为坐标， w,h 为宽和高
SDL中的x，y坐标系如图片所示

代码

#include <SDL.h>

#define SCREEN_W 800
#define SCREEN_H 600

int main(int argc, char **argv) {
    SDL_Window *pWindow = NULL;
    SDL_Renderer *pRenderer = NULL;
    SDL_Init(SDL_INIT_EVERYTHING);
    pWindow = SDL_CreateWindow("Geometry Rendering",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,SCREEN_W,SCREEN_H,SDL_WINDOW_OPENGL);
    pRenderer = SDL_CreateRenderer(pWindow, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);

    bool quit = false;
    SDL_Event e;
    while( !quit ) {
        while( SDL_PollEvent(&e) != 0 ) {
            if(e.type == SDL_QUIT)
                quit = true;
        }
        SDL_SetRenderDrawColor(pRenderer,0xFF,0xFF,0xFF,0xFF);
        SDL_RenderClear(pRenderer);

        SDL_Rect fillRect = {SCREEN_W / 4, SCREEN_H / 4, SCREEN_W / 2, SCREEN_H / 2};   
        SDL_SetRenderDrawColor(pRenderer, 0xFF, 0x00, 0x00, 0xFF);
        SDL_RenderFillRect(pRenderer, &fillRect);       //填充矩形

        SDL_Rect outlineRect = {SCREEN_W / 6, SCREEN_H / 6, SCREEN_W * 2 / 3, SCREEN_H * 2 / 3};
        SDL_SetRenderDrawColor(pRenderer,0x00,0xFF,0x00,0xFF);
        SDL_RenderDrawRect(pRenderer,&outlineRect);     //绘制矩形边框

        SDL_SetRenderDrawColor(pRenderer,0x00,0x00,0xFF,0xFF);
        SDL_RenderDrawLine(pRenderer,SCREEN_W * 4 / 5,SCREEN_H * 4 / 5,SCREEN_W * 1 / 5,SCREEN_H * 1 / 5);  //绘制线段

        SDL_SetRenderDrawColor(pRenderer,0xFF,0xFF,0x00,0xFF);
        for(int i = 0; i <= SCREEN_H; i += 10) {
            SDL_RenderDrawPoint(pRenderer, SCREEN_W / 2, i);    //绘制点
        }


        SDL_RenderPresent(pRenderer);
    }

    SDL_DestroyWindow(pWindow);
    SDL_DestroyRenderer(pRenderer);
    SDL_Quit();
    return 0;
}

效果