※ [本文转录自 C_and_CPP 看板 #1MnbOvZX ] 作者: ResolaQQ (ResolaQQ) 看板: C_and_CPP 标题: [问题] SDL2 RenderPresent 的叙述看不太懂 时间: Fri Feb 19 07:39:34 2016 额外使用到的函数库(Library Used): (Ex: OpenGL, ...) SDL2 问题(Question)： SDL_RenderPresent 的叙述如下 SDL's rendering functions operate on a backbuffer; that is, calling a rendering function such as SDL_RenderDrawLine() does not directly put a line on the screen, but rather updates the backbuffer. As such, you compose your entire scene and present the composed backbuffer to the screen as a complete picture. Therefore, when using SDL's rendering API, one does all drawing intended for the frame, and then calls this function once per frame to present the final drawing to the user. The backbuffer should be considered invalidated after each present; do not assume that previous contents will exist between frames. You are strongly encouraged to call SDL_RenderClear() to initialize the backbuffer before starting each new frame's drawing, even if you plan to overwrite every pixel. 我不太理解文中的 backbuffer 是指什麽，像底下这应该是错误的 SDL_RenderClear(renderer) // 清除绘图内容 SDL_RenderDrawLine(renderer, 0, 0, 100, 100) // 画条斜线从 (0,0) 到 (100,100) SDL_RenderPresent(renderer) // 显示到萤幕上 SDL_RenderPresent(renderer) // 错误，显示到萤幕上後，绘图内容应该被假设为无效 但底下这个有没有问题呢？我就不确定了 SDL_SetRenderTarget(renderer, texture) // 把绘图目标设定到 texture 上 SDL_RenderDrawLine(renderer, 0, 0, 100, 100) // 画条斜线从 (0,0) 到 (100,100) SDL_SetRenderTarget(renderer, NULL) // 把绘图目标设定回预设值 SDL_RenderCopy(renderer, texture, NULL, NULL) // 把 texture 的内容拷贝进去 SDL_RenderPresent(renderer) // 显示到萤幕上 SDL_RenderCopy(renderer, texture, NULL, NULL) // 这时候，texture 是有效的吗？ SDL_RenderPresent(renderer) // 是否可以这样把之前绘制过的图形再次显示出来？ texture 似乎是一小块显示卡的记忆体 不知道叙述里的 backbuffer 有没有包含 texture？ 还是仅止於预设的绘图目标？ -- 放着养蚊子的部落格 http://resolaqq.blogspot.tw --

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※ 发信站: 批踢踢实业坊(ptt.cc) ※ 转录者: ResolaQQ (114.38.126.41), 02/19/2016 07:40:55