SDL_RENDERSETSETSCALE和SDL_RENDERDRAWLINE如何交互

How do SDL_RenderSetScale and SDL_RenderDrawLine interact?

本文关键字：SDL 交互 RENDERSETSETSCALE RENDERDRAWLINE 何交互      更新时间：2023-10-16

来自sdl_rendersetscale（）的简短描述（）和sdl2 wiki上的sdl_rendersetLogicalSize（），我的印象是这些命令是这些命令缩放整个帧与其内容独立于其内容的方式，从而扩展了您的内容，从而扩展了您的内容的规模，从而扩展了您的尺度图形编辑器中的图像。

在我以前的程序中，我只在缩放和渲染sdl_rects和sdl_textures，这似乎就是这种情况。但是，仅部分使用RenderDrawLine（）绘制线路。

如果线平行于X或Y轴，则该线的缩放率正确，但是在任何其他情况下，它根本不缩放。

SDL_RenderSetScale( gRenderer, gScaler, gScaler ); 
SDL_SetRenderDrawColor( gRenderer, 0x00, 0x00, 0x00, 0xFF );
SDL_RenderClear( gRenderer );
SDL_SetRenderDrawColor( gRenderer, 0xFF, 0xFF, 0xFF, 0xFF );
SDL_RenderDrawLine( gRenderer, x1, y1, x2, y2 );
SDL_RenderPresent( gRenderer );

与SDL_RenderSetscale（）角度无关，有没有办法缩放线路？该函数如何确定缩放的规模和忽略的范围？

这是SDL渲染器的已知错误，行绘图函数不会缩放，然后以自由角度绘制。它仍然存在于最近发布的SDL-2.0.6（请参阅/* FIXME: We can't use a rect for this line... */）：

static int
RenderDrawLinesWithRects(SDL_Renderer * renderer,
                     const SDL_Point * points, int count)
{
    SDL_FRect *frect;
    SDL_FRect *frects;
    SDL_FPoint fpoints[2];
    int i, nrects;
    int status;
    frects = SDL_stack_alloc(SDL_FRect, count-1);
    if (!frects) {
        return SDL_OutOfMemory();
    }
    status = 0;
    nrects = 0;
    for (i = 0; i < count-1; ++i) {
        if (points[i].x == points[i+1].x) {
            int minY = SDL_min(points[i].y, points[i+1].y);
            int maxY = SDL_max(points[i].y, points[i+1].y);
            frect = &frects[nrects++];
            frect->x = points[i].x * renderer->scale.x;
            frect->y = minY * renderer->scale.y;
            frect->w = renderer->scale.x;
            frect->h = (maxY - minY + 1) * renderer->scale.y;
        } else if (points[i].y == points[i+1].y) {
            int minX = SDL_min(points[i].x, points[i+1].x);
            int maxX = SDL_max(points[i].x, points[i+1].x);
            frect = &frects[nrects++];
            frect->x = minX * renderer->scale.x;
            frect->y = points[i].y * renderer->scale.y;
            frect->w = (maxX - minX + 1) * renderer->scale.x;
            frect->h = renderer->scale.y;
        } else {
            /* FIXME: We can't use a rect for this line... */
            fpoints[0].x = points[i].x * renderer->scale.x;
            fpoints[0].y = points[i].y * renderer->scale.y;
            fpoints[1].x = points[i+1].x * renderer->scale.x;
            fpoints[1].y = points[i+1].y * renderer->scale.y;
            status += renderer->RenderDrawLines(renderer, fpoints, 2);
        }
    }
    status += renderer->RenderFillRects(renderer, frects, nrects);
    SDL_stack_free(frects);
    if (status < 0) {
        status = -1;
    }
    return status;
}

我认为这不会很快解决，因为这是一个很少使用的功能。

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