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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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22
cogl/cogl-texture.h
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@ -320,18 +320,18 @@ gboolean cogl_texture_set_region (CoglHandle handle,
/**
* cogl_texture_new_from_sub_texture:
* @full_texture: a #CoglHandle to an existing texture
* @tx1: X coordinate of the top-left of the subregion
* @ty1: Y coordinate of the top-left of the subregion
* @tx2: X coordinate of the bottom-right of the subregion
* @ty2: Y coordinate of the bottom-right of the subregion
* @sub_x: X coordinate of the top-left of the subregion
* @sub_y: Y coordinate of the top-left of the subregion
* @sub_width: Width in pixels of the subregion
* @sub_height: Height in pixels of the subregion
*
* Creates a new texture which represents a subregion of another
* texture. The GL resources will be shared so that no new texture
* data is actually allocated.
*
* You can also specify texture coordinates outside the range of [0,1]
* to make a texture that represents a repeated version of another
* texture.
* Sub textures have undefined behaviour texture coordinates outside
* of the range [0,1] are used. They also do not work with
* CoglVertexBuffers.
*
* Return value: a #CoglHandle to the new texture.
*
@ -339,10 +339,10 @@ gboolean cogl_texture_set_region (CoglHandle handle,
*/
CoglHandle cogl_texture_new_from_sub_texture
(CoglHandle full_texture,
gfloat tx1,
gfloat ty1,
gfloat tx2,
gfloat ty2);
gint sub_x,
gint sub_y,
gint sub_width,
gint sub_height);
#ifndef COGL_DISABLE_DEPRECATED