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[cogl-vertex-buffer] Add cogl_vertex_buffer_indices_get_for_quads
This function can be used as an efficient way of drawing groups of quads without using GL_QUADS. It generates a VBO containing the indices needed to render using pairs of GL_TRIANGLES. The VBO is globally cached so that it only needs to be uploaded whenever more indices are requested than ever before.
This commit is contained in:
Neil Roberts
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2f319ad839
commit
39cb36ba01
@ -394,6 +394,46 @@ cogl_vertex_buffer_ref (CoglHandle handle);
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void
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cogl_vertex_buffer_unref (CoglHandle handle);
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/**
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* cogl_vertex_buffer_indices_get_for_quads:
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* @n_indices: the number of indices in the vertex buffer.
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*
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* Creates a vertex buffer containing the indices needed to draw pairs
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* of triangles from a list of vertices grouped as quads. There will
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* be at least @n_indices entries in the buffer (but there may be
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* more).
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*
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* The indices will follow this pattern:
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*
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* 0, 1, 2, 0, 2, 3, 4, 5, 6, 4, 6, 7 ... etc
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*
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* For example, if you submit vertices for a quad like this:
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*
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* |[
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* 0 3
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* ########
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* # #
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* # #
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* ########
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* 1 2
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* ]|
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*
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* Then you can request 6 indices to render two triangles like this:
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*
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* |[
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* 0 0 3
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* ## ########
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* # ## ## #
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* # ## ## #
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* ######## ##
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* 1 2 2
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* ]|
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*
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* Returns: A %CoglHandle containing the indices. The handled is
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* owned by Cogl and should not be modified or unref'd.
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*/
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CoglHandle
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cogl_vertex_buffer_indices_get_for_quads (guint n_indices);
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G_END_DECLS
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@ -1880,3 +1880,83 @@ _cogl_vertex_buffer_free (CoglVertexBuffer *buffer)
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g_slice_free (CoglVertexBuffer, buffer);
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}
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CoglHandle
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cogl_vertex_buffer_indices_get_for_quads (guint n_indices)
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{
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_COGL_GET_CONTEXT (ctx, COGL_INVALID_HANDLE);
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/* Check if the indices would fit in a byte array */
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if (n_indices <= 256 / 4 * 6)
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{
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/* Generate the byte array if we haven't already */
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if (ctx->quad_indices_byte == COGL_INVALID_HANDLE)
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{
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guint8 *byte_array = g_malloc (256 / 4 * 6 * sizeof (guint8));
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guint8 *p = byte_array;
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int i, vert_num = 0;
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for (i = 0; i < 256 / 4; i++)
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{
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*(p++) = vert_num + 0;
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*(p++) = vert_num + 1;
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*(p++) = vert_num + 2;
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*(p++) = vert_num + 0;
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*(p++) = vert_num + 2;
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*(p++) = vert_num + 3;
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vert_num += 4;
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}
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ctx->quad_indices_byte
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= cogl_vertex_buffer_indices_new (COGL_INDICES_TYPE_UNSIGNED_BYTE,
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byte_array,
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256 / 4 * 6);
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g_free (byte_array);
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}
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return ctx->quad_indices_byte;
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}
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else
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{
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if (ctx->quad_indices_short_len < n_indices)
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{
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guint16 *short_array;
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guint16 *p;
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int i, vert_num = 0;
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if (ctx->quad_indices_short != COGL_INVALID_HANDLE)
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cogl_handle_unref (ctx->quad_indices_short);
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/* Pick a power of two >= MAX (512, n_indices) */
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if (ctx->quad_indices_short_len == 0)
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ctx->quad_indices_short_len = 512;
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while (ctx->quad_indices_short_len < n_indices)
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ctx->quad_indices_short_len *= 2;
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/* Over-allocate to generate a whole number of quads */
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p = short_array = g_malloc ((ctx->quad_indices_short_len
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+ 5) / 6 * 6
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* sizeof (guint16));
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/* Fill in the complete quads */
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for (i = 0; i < ctx->quad_indices_short_len; i += 6)
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{
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*(p++) = vert_num + 0;
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*(p++) = vert_num + 1;
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*(p++) = vert_num + 2;
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*(p++) = vert_num + 0;
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*(p++) = vert_num + 2;
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*(p++) = vert_num + 3;
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vert_num += 4;
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}
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ctx->quad_indices_short
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= cogl_vertex_buffer_indices_new (COGL_INDICES_TYPE_UNSIGNED_SHORT,
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short_array,
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ctx->quad_indices_short_len);
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g_free (short_array);
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}
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return ctx->quad_indices_short;
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}
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}
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@ -313,6 +313,7 @@ CoglIndicesType
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cogl_vertex_buffer_add_indices
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cogl_vertex_buffer_delete_indices
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cogl_vertex_buffer_draw_elements
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cogl_vertex_buffer_indices_get_for_quads
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<SUBSECTION Private>
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CoglVertexBufferAttribFlags
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COGL_VERTEX_BUFFER_ATTRIB_FLAG_GL_TYPE_MASK
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@ -171,6 +171,10 @@ cogl_create_context ()
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_cogl_material_get_cogl_enable_flags (_context->source_material);
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cogl_enable (enable_flags);
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_context->quad_indices_byte = COGL_INVALID_HANDLE;
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_context->quad_indices_short = COGL_INVALID_HANDLE;
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_context->quad_indices_short_len = 0;
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return TRUE;
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}
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@ -207,6 +211,11 @@ _cogl_destroy_context ()
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if (_context->current_layers)
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g_array_free (_context->current_layers, TRUE);
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if (_context->quad_indices_byte)
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cogl_handle_unref (_context->quad_indices_byte);
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if (_context->quad_indices_short)
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cogl_handle_unref (_context->quad_indices_short);
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g_free (_context);
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}
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@ -102,6 +102,12 @@ typedef struct
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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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/* Relying on glext.h to define these */
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COGL_PFNGLGENRENDERBUFFERSEXTPROC pf_glGenRenderbuffersEXT;
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COGL_PFNGLDELETERENDERBUFFERSEXTPROC pf_glDeleteRenderbuffersEXT;
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@ -129,6 +129,10 @@ cogl_create_context ()
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_cogl_material_get_cogl_enable_flags (_context->source_material);
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cogl_enable (enable_flags);
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_context->quad_indices_byte = COGL_INVALID_HANDLE;
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_context->quad_indices_short = COGL_INVALID_HANDLE;
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_context->quad_indices_short_len = 0;
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return TRUE;
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}
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@ -165,6 +169,11 @@ _cogl_destroy_context ()
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if (_context->current_layers)
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g_array_free (_context->current_layers, TRUE);
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if (_context->quad_indices_byte)
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cogl_handle_unref (_context->quad_indices_byte);
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if (_context->quad_indices_short)
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cogl_handle_unref (_context->quad_indices_short);
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g_free (_context);
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}
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@ -104,6 +104,12 @@ typedef struct
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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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#ifdef HAVE_COGL_GLES2
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CoglGles2Wrapper gles2;
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@ -111,7 +117,6 @@ typedef struct
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supported */
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GLint viewport_store[4];
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#endif
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} CoglContext;
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CoglContext *
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