`ALLEGRO_BITMAP_WRAP` settings are not necessarily respected

I wrote a fragment shader in which I read neighboring pixels for a post-processing effect. I expect the texture reads to follow the wrapping settings set with al_set_new_bitmap_wrap(). However, that won't happen as expected when the internal texture allocated by Allegro is larger than the ALLEGRO_BITMAP.

Here is an example of my shader running on Android. Notice the yellow artifacts at the right edge of the screen.

My shader takes as input a texture of a partially rendered scene (I render to an offscreen texture).
The size of the input bitmap is 426x240. I clear it with al_clear_to_color(yellow) - for testing - before it receives the partially rendered scene. The scene covers the entire bitmap.
I set ALLEGRO_SUPPORT_NPOT_BITMAP to 1 before creating the display.

al_get_opengl_texture_size() tells me that the OpenGL texture size is 448x240 on Android (GLES3). I looked into the source code and found that this size is consistent with the following logic: (I can't turn it off)

allegro5/src/opengl/ogl_bitmap.c

Lines 1079 to 1085 in e3ad047

    
           /* glReadPixels requires 32 byte aligned rows */ 
        
           if (IS_ANDROID) { 
        
              int mod = true_w % 32; 
        
              if (mod != 0) { 
        
                 true_w += 32 - mod; 
        
              } 
        
           }

These artifacts do not appear when using OpenGL on a Linux desktop. Texture size is 426x240, as expected.

shader_wrap_demo.mp4

I feel we should just remove that workaround (and probably the minimum-size one above as well?). And in the future if we want hacks like that we should do it for just the specific GPU that needs it (and with a much more detailed comment why exactly it's needed).

We already have a allegro5.cfg setting for minimum bitmap size. We could also add one for this to disable it. Could call it 'android_bitmap_size_align = 32'

	/* glReadPixels requires 32 byte aligned rows */
	if (IS_ANDROID) {
	int mod = true_w % 32;
	if (mod != 0) {
	true_w += 32 - mod;
	}
	}