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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.
56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
/*
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* Cogl
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*
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* An object oriented GL/GLES Abstraction/Utility Layer
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*
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* Copyright (C) 2009 Intel Corporation.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#ifndef __COGL_SUB_TEXTURE_H
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#define __COGL_SUB_TEXTURE_H
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#include "cogl-handle.h"
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#include "cogl-texture-private.h"
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#define COGL_SUB_TEXTURE(tex) ((CoglSubTexture *) tex)
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typedef struct _CoglSubTexture CoglSubTexture;
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struct _CoglSubTexture
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{
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CoglTexture _parent;
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CoglHandle full_texture;
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/* The region represented by this sub-texture */
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gint sub_x;
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gint sub_y;
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gint sub_width;
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gint sub_height;
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};
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GQuark
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_cogl_handle_sub_texture_get_type (void);
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CoglHandle
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_cogl_sub_texture_new (CoglHandle full_texture,
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gint sub_x, gint sub_y,
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gint sub_width, gint sub_height);
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#endif /* __COGL_SUB_TEXTURE_H */
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