2d610c2300
First a few notes about Cogl coordinate systems: - Cogl defines the window origin, viewport origin and texture coordinates origin to be top left unlike OpenGL which defines them as bottom left. - Cogl defines the modelview and projection identity matrices in exactly the same way as OpenGL. - I.e. we believe that for 2D centric constructs: windows/framebuffers, viewports and textures developers are more used to dealing with a top left origin, but when modeling objects in 3D; an origin at the center with y going up is quite natural. The way Cogl handles textures is by uploading data upside down in OpenGL terms so that bottom left becomes top left. (Note: This also has the benefit that we don't need to flip the data we get from image decoding libraries since they typically also consider top left to be the image origin.) The viewport and window coords are mostly handled with various y = height - y tweaks before we pass y coordinates to OpenGL. Generally speaking though the handling of coordinate spaces in Cogl is a bit fragile. I guess partly because none of it was design to be, it just evolved from how Clutter defines its coordinates without much consideration or testing. I hope to improve this over a number of commits; starting here. This commit deals with the fact that offscreen draw buffers may be bound to textures but we don't "upload" the texture data upside down, and so if you texture from an offscreen draw buffer you need to manually flip the texture coordinates to get it the right way around. We now force offscreen rendering to be flipped upside down by tweaking the projection matrix right before we submit it to OpenGL to scale y by -1. The tweak is entirely hidden from the user such that if you call cogl_get_projection you will not see this scale.
127 lines
3.6 KiB
C
127 lines
3.6 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) 2007,2008,2009 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_CONTEXT_H
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#define __COGL_CONTEXT_H
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#include "cogl-internal.h"
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#include "cogl-context-driver.h"
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#include "cogl-primitives.h"
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#include "cogl-clip-stack.h"
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#include "cogl-matrix-stack.h"
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#include "cogl-material-private.h"
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typedef struct
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{
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GLfloat v[3];
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GLfloat t[2];
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GLubyte c[4];
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} CoglTextureGLVertex;
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typedef struct
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{
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/* Features cache */
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CoglFeatureFlags feature_flags;
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gboolean features_cached;
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/* Enable cache */
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gulong enable_flags;
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guint8 color_alpha;
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gboolean enable_backface_culling;
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gboolean indirect;
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/* A few handy matrix constants */
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CoglMatrix identity_matrix;
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CoglMatrix y_flip_matrix;
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/* Client-side matrix stack or NULL if none */
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CoglMatrixMode flushed_matrix_mode;
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GList *texture_units;
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/* Cache of inverse projection matrix */
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float inverse_projection[16];
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/* Materials */
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CoglHandle default_material;
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CoglHandle source_material;
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/* Textures */
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CoglHandle default_gl_texture_2d_tex;
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CoglHandle default_gl_texture_rect_tex;
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/* Batching geometry... */
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/* We journal the texture rectangles we want to submit to OpenGL so
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* we have an oppertunity to optimise the final order so that we
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* can batch things together. */
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GArray *journal;
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GArray *logged_vertices;
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GArray *polygon_vertices;
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/* Some simple caching, to minimize state changes... */
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CoglHandle current_material;
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gulong current_material_flags;
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CoglMaterialFlushOptions current_material_flush_options;
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GArray *current_layers;
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guint n_texcoord_arrays_enabled;
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/* Draw Buffers */
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GSList *draw_buffer_stack;
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CoglHandle window_buffer;
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gboolean dirty_bound_framebuffer;
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gboolean dirty_viewport;
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/* Primitives */
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floatVec2 path_start;
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floatVec2 path_pen;
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GArray *path_nodes;
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guint last_path;
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floatVec2 path_nodes_min;
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floatVec2 path_nodes_max;
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CoglHandle stencil_material;
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/* Pre-generated VBOs containing indices to generate GL_TRIANGLES
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out of a vertex array of quads */
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CoglHandle quad_indices_byte;
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guint quad_indices_short_len;
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CoglHandle quad_indices_short;
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gboolean in_begin_gl_block;
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CoglHandle texture_download_material;
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CoglContextDriver drv;
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} CoglContext;
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CoglContext *
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_cogl_context_get_default ();
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/* Obtains the context and returns retval if NULL */
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#define _COGL_GET_CONTEXT(ctxvar, retval) \
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CoglContext *ctxvar = _cogl_context_get_default (); \
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if (ctxvar == NULL) return retval;
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#define NO_RETVAL
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#endif /* __COGL_CONTEXT_H */
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