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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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10
cogl/cogl-texture-private.h
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@ -84,6 +84,8 @@ struct _CoglTextureVtable
void (* transform_coords_to_gl) (CoglTexture *tex,
float *s,
float *t);
gboolean (* transform_quad_coords_to_gl) (CoglTexture *tex,
float *coords);
gboolean (* get_gl_texture) (CoglTexture *tex,
GLuint *out_gl_handle,
@ -94,6 +96,7 @@ struct _CoglTextureVtable
GLenum mag_filter);
void (* ensure_mipmaps) (CoglTexture *tex);
void (* ensure_non_quad_rendering) (CoglTexture *tex);
void (* set_wrap_mode_parameter) (CoglTexture *tex,
GLenum wrap_mode);
@ -137,6 +140,10 @@ void
_cogl_texture_transform_coords_to_gl (CoglHandle handle,
float *s,
float *t);
gboolean
_cogl_texture_transform_quad_coords_to_gl (CoglHandle handle,
float *coords);
GLenum
_cogl_texture_get_gl_format (CoglHandle handle);
@ -152,6 +159,9 @@ _cogl_texture_set_filters (CoglHandle handle,
void
_cogl_texture_ensure_mipmaps (CoglHandle handle);
void
_cogl_texture_ensure_non_quad_rendering (CoglHandle handle);
/* Utility functions to help uploading a bitmap. These are intended to
* be used by CoglTexture implementations or drivers... */