Question

根据SDL2维基上的SDL_RenderSetScale（）和SDL_RenderSetLogicalSize（）的简短描述，我认为这些命令可以独立于其内容缩放整个帧，基本上就是在图形编辑器中缩放图像的方式。 / p>

在我以前只使用SDL_Rects和SDL_Textures进行缩放和渲染的程序中，似乎就是这种情况。但是，使用RenderDrawLine（）绘制线条只是部分情况。

如果线与x轴或y轴平行，则线会正确缩放，但在任何其他情况下，线都不会缩放。

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 );

有没有办法使用SDL_RenderSetScale（）无论角度如何缩放线？该函数如何决定缩放什么以及忽略什么？

Answer 1

这是SDL渲染器的已知错误，线条绘制功能不会缩放，然后以自由角度绘制。它最近发布的SDL-2.0.6仍然存在（见/* 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;
}

我认为这很快就会被修复，因为这是一个很少使用的功能。

SDL_RenderSetScale和SDL_RenderDrawLine如何交互？

1 个答案: