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cogl: Make CoglSubTexture only work for quad rendering

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The sub texture backend doesn't work well as a completely general
texture backend because for example when rendering with cogl_polygon
it needs to be able to tranform arbitrary texture coordinates without
reference to the other coordintes. This can't be done when the texture
coordinates are a multiple of one because sometimes the coordinate
should represent the left or top edge and sometimes it should
represent the bottom or top edge. For example if the s coordinates are
0 and 1 then 1 represents the right edge but if they are 1 and 2 then
1 represents the left edge.

Instead the sub-textures are now documented not to support coordinates
outside the range [0,1]. The coordinates for the sub-region are now
represented as integers as this helps avoid rounding issues. The
region can no longer be a super-region of the texture as this
simplifies the code quite a lot.

There are two new texture virtual functions:

transform_quad_coords_to_gl - This transforms two pairs of coordinates
     representing a quad. It will return FALSE if the coordinates can
     not be transformed. The sub texture backend uses this to detect
     coordinates that require repeating which causes cogl-primitives
     to use manual repeating.

ensure_non_quad_rendering - This is used in cogl_polygon and
     cogl_vertex_buffer to inform the texture backend that
     transform_quad_to_gl is going to be used. The atlas backend
     migrates the texture out of the atlas when it hits this.
This commit is contained in:
Neil Roberts
2010-01-18 09:22:04 +00:00
parent 963afa88c5
commit ae7825275e
10 changed files with 324 additions and 373 deletions
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21
cogl/cogl-primitives.c
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@ -278,14 +278,14 @@ _cogl_multitexture_quad_single_primitive (float x_1,
the coordinates (such as in the sub texture backend). This
should be safe to call because we know that the texture only
has one slice. */
for (coord_num = 0; coord_num < 2; coord_num++)
{
float *s = out_tex_coords + coord_num * 2;
float *t = s + 1;
_cogl_texture_transform_coords_to_gl (tex_handle, s, t);
if (*s < 0.0f || *s > 1.0f || *t < 0.0f || *t > 1.0f)
need_repeat = TRUE;
}
if (!_cogl_texture_transform_quad_coords_to_gl (tex_handle,
out_tex_coords))
/* If the backend can't support these coordinates then bail out */
return FALSE;
for (coord_num = 0; coord_num < 4; coord_num++)
if (out_tex_coords[coord_num] < 0.0f ||
out_tex_coords[coord_num] > 1.0f)
need_repeat = TRUE;
/* If the texture has waste or we are using GL_TEXTURE_RECT we
* can't handle texture repeating so we can't use the layer if
@ -867,6 +867,11 @@ cogl_polygon (const CoglTextureVertex *vertices,
if (tex_handle == COGL_INVALID_HANDLE)
continue;
/* Give the texture a chance to know that we're rendering
non-quad shaped primitives. If the texture is in an atlas it
will be migrated */
_cogl_texture_ensure_non_quad_rendering (tex_handle);
if (i == 0 && cogl_texture_is_sliced (tex_handle))
{
#if defined (HAVE_COGL_GLES) || defined (HAVE_COGL_GLES2)