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Hi chaps,

Sorry to both you again, I have a little problem here. The following works fine, stretching a whole image across the whole screen:
SDL_RenderCopy(renderer, sprite, NULL, NULL);


If I try to specific where to draw the sprite though, that is its destination rectangle, I get just a black square under Android:
SDL_RenderCopy(renderer, sprite, NULL, &rect);


Under Linux everything works fine. Any idea what might be causing this?

I'm thinking it has to do with how the window's size is overridden by the mobile's screen-size...

William

I don't know anything about the specifics of what is going on there, but keep in mind that copying image data is not a strongpoint of GLES, perhaps the SDL_RendererCopy implementation is using
functionality not present on GLES?

On 07/29/2011 04:34 AM, William Dyce wrote:


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Dunno - it works fine if the image gets to monopolise the render-srface but not if if can't, but I can't think why that would be. I'll have a look at the implementation tomorrow when I've had some sleep. Are there any other ways of blitting images I can try, without using the compat mode (which doesn't seem to work on my hardware)?

William



On 29 July 2011 21:36, Forest Hale wrote:

I think I'm closing down on the problem: using SDL_image I was able to test with images with alpha, my theory being that the image must monopolise the renderer to be draw. Sure enough compositing two images with transparency, even using NULL, NULL (whole render-surface) for both doesn't work properly: I get a black screen.

I'll keep digging.

On 30 July 2011 02:09, William Dyce wrote:

I've been having a look at the actual SDL_RenderCopy function in SDL_render.c:

    real_dstrect.x = 0;
    real_dstrect.y = 0;
    real_dstrect.w = renderer->viewport.w;
    real_dstrect.h = renderer->viewport.h;
    if (dstrect) {
        if (!SDL_IntersectRect(dstrect, &real_dstrect, &real_dstrect)) {
            return 0;
        }
        /* Clip srcrect by the same amount as dstrect was clipped */
        if (dstrect->w != real_dstrect.w) {
            int deltax = (real_dstrect.x - dstrect->x);
            int deltaw = (real_dstrect.w - dstrect->w);
            real_srcrect.x += (deltax * real_srcrect.w) / dstrect->w;
            real_srcrect.w += (deltaw * real_srcrect.w) / dstrect->w;
        }
        if (dstrect->h != real_dstrect.h) {
            int deltay = (real_dstrect.y - dstrect->y);
            int deltah = (real_dstrect.h - dstrect->h);
            real_srcrect.y += (deltay * real_srcrect.h) / dstrect->h;
            real_srcrect.h += (deltah * real_srcrect.h) / dstrect->h;
        }
    }

I can't help but think that somehow the renderer->viewport.w; type functions are behaving strangely with Android, causing the source rect to chosen incorrectly whenever a destination rect is specified. That would explain why there's nothing in the logs: it's not actually an error. But I tried commenting out this whole block of code just to see what would happen and it didn't change a thing.

The function call RenderCopy (rather than SDL_RenderCopy) which is implemented by GLES_RenderCopy in SDL_render_gles.c (that's GLES version 1). I suppose I can only assume that the problem lies here if there is one...

William

On 30 July 2011 12:30, William Dyce wrote:

Eureka! I think I'm really on to something now

So, the problem occurs when multiple images are blitted one on top of the other. I was drawing a background texture first, followed by a sprite, then SDL_RenderPresent:

    // Clear the entire screen to the Renderer's base colour
    SDL_RenderClear(renderer);

    // Render the background
    SDL_RenderCopy(renderer, background, NULL, NULL);

    // Draw the game objects
    thing->draw(renderer);

    // Flip the buffers to update the screen
    SDL_RenderPresent(renderer);


where Thing::draw(SDL_renderer* renderer) is:

    static SDL_Rect draw_dest, draw_src;
    draw_dest.x = position.x - size.x/2;
    draw_dest.y = position.y - size.y/2;
    draw_dest.w = size.x;
    draw_dest.h = size.y;

    draw_src.x = draw_src.y = 0;
    draw_src.w = draw_src.h = 32;

    SDL_RenderCopy(renderer, sprite, &draw_src, &draw_dest);

It seems that I can draw one texture OR the other, but not both one on top of eachother, unless the second completely covers up the first. Am I using RenderCopy and RenderPresent the wrong way? And if so, why does it work on Ubuntu?

William

Now using OpenGL directly:

    // Clear the entire screen
    glClear(GL_COLOR_BUFFER_BIT);

    // Set up position, rotation, colour
    glTranslatef(window_size.x/2, window_size.y/2, 0.0);
    glRotatef(45.0, 0.0, 0.0, 1.0);

    // Bind the texture to which subsequent calls refer to
    glBindTexture(GL_TEXTURE_2D, background);

    // Start drawing texture
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    GLfloat size[9], coords[9];
    glVertexPointer(3, GL_FLOAT, 0, size);
    glTexCoordPointer(2, GL_FLOAT, 0, coords);

    // Top-left triangle
    size = {-16,-16,0, 16,-16,0, 16,16,0};
    coords = {0,0, 1,0, 1,1};
    glDrawArrays(GL_TRIANGLES, 0, 3);

    // Bottom-right triangle
    size = {-16,-16,0, -16,16,0, 16,16,0};
    coords = {0,0, 0,1, 1,1};
    glDrawArrays(GL_TRIANGLES, 0, 3);

    // Stop drawing texture
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);

    // Reset back to the origin
    glLoadIdentity();

    // Flip the buffers to update the screen
    SDL_GL_SwapWindow(window);

Exactly the same problem is occuring.

<insanity>

William

On 1 August 2011 15:43, William Dyce wrote: