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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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15
cogl/cogl-sub-texture-private.h
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@ -37,12 +37,11 @@ struct _CoglSubTexture
CoglHandle full_texture;
/* The texture coordinates of the subregion of full_texture */
gfloat tx1, ty1;
gfloat tx2, ty2;
/* Are all of the texture coordinates a multiple of one? */
gboolean tex_coords_are_a_multiple;
/* The region represented by this sub-texture */
gint sub_x;
gint sub_y;
gint sub_width;
gint sub_height;
};
GQuark
@ -50,7 +49,7 @@ _cogl_handle_sub_texture_get_type (void);
CoglHandle
_cogl_sub_texture_new (CoglHandle full_texture,
gfloat tx1, gfloat ty1,
gfloat tx2, gfloat ty2);
gint sub_x, gint sub_y,
gint sub_width, gint sub_height);
#endif /* __COGL_SUB_TEXTURE_H */