CoglFramebuffer: The Framebuffer Interface

## CoglFramebuffer: The Framebuffer Interface CoglFramebuffer: The Framebuffer Interface — A common interface for manipulating framebuffers |

## Functions

#define | COGL_FRAMEBUFFER()
CoglBool | cogl_framebuffer_allocate ()
int | cogl_framebuffer_get_width ()
int | cogl_framebuffer_get_height ()
void | cogl_framebuffer_set_viewport ()
float | cogl_framebuffer_get_viewport_x ()
float | cogl_framebuffer_get_viewport_y ()
float | cogl_framebuffer_get_viewport_width ()
float | cogl_framebuffer_get_viewport_height ()
void | cogl_framebuffer_get_viewport4fv ()
int | cogl_framebuffer_get_red_bits ()
int | cogl_framebuffer_get_green_bits ()
int | cogl_framebuffer_get_blue_bits ()
int | cogl_framebuffer_get_alpha_bits ()
int | cogl_framebuffer_get_depth_bits ()
CoglColorMask | cogl_framebuffer_get_color_mask ()
void | cogl_framebuffer_set_color_mask ()
int | cogl_framebuffer_get_samples_per_pixel ()
void | cogl_framebuffer_set_samples_per_pixel ()
void | cogl_framebuffer_resolve_samples ()
void | cogl_framebuffer_resolve_samples_region ()
CoglContext * | cogl_framebuffer_get_context ()
void | cogl_framebuffer_clear ()
void | cogl_framebuffer_clear4f ()
CoglBool | cogl_framebuffer_read_pixels_into_bitmap ()
CoglBool | cogl_framebuffer_read_pixels ()
void | cogl_framebuffer_set_dither_enabled ()
CoglBool | cogl_framebuffer_get_dither_enabled ()
void | cogl_framebuffer_draw_rectangle ()
void | cogl_framebuffer_draw_textured_rectangle ()
void | cogl_framebuffer_draw_multitextured_rectangle ()
void | cogl_framebuffer_draw_rectangles ()
void | cogl_framebuffer_draw_textured_rectangles ()
void | cogl_framebuffer_discard_buffers ()
void | cogl_framebuffer_finish ()
void | cogl_framebuffer_push_matrix ()
void | cogl_framebuffer_pop_matrix ()
void | cogl_framebuffer_identity_matrix ()
void | cogl_framebuffer_scale ()
void | cogl_framebuffer_translate ()
void | cogl_framebuffer_rotate ()
void | cogl_framebuffer_rotate_euler ()
void | cogl_framebuffer_rotate_quaternion ()
void | cogl_framebuffer_transform ()
void | cogl_framebuffer_get_modelview_matrix ()
void | cogl_framebuffer_set_modelview_matrix ()
void | cogl_framebuffer_perspective ()
void | cogl_framebuffer_frustum ()
void | cogl_framebuffer_orthographic ()
void | cogl_framebuffer_get_projection_matrix ()
void | cogl_framebuffer_set_projection_matrix ()
void | cogl_framebuffer_push_scissor_clip ()
void | cogl_framebuffer_push_rectangle_clip ()
void | cogl_framebuffer_push_primitive_clip ()
void | cogl_framebuffer_pop_clip ()
CoglFramebuffer * | cogl_get_draw_framebuffer ()
void | cogl_set_framebuffer ()
void | cogl_push_framebuffer ()
void | cogl_pop_framebuffer ()

## Types and Values

typedef | CoglFramebuffer

## Description

Framebuffers are a collection of buffers that can be rendered too. A framebuffer may be comprised of one or more color buffers, an optional depth buffer and an optional stencil buffer. Other configuration parameters are associated with framebuffers too such as whether the framebuffer supports multi-sampling (an anti-aliasing technique) or dithering.

There are two kinds of framebuffer in Cogl, CoglOnscreen framebuffers and CoglOffscreen framebuffers. As the names imply offscreen framebuffers are for rendering something offscreen (perhaps to a texture which is bound as one of the color buffers). The exact semantics of onscreen framebuffers depends on the window system backend that you are using, but typically you can expect rendering to a CoglOnscreen framebuffer will be immediately visible to the user.

If you want to create a new framebuffer then you should start by looking at the CoglOnscreen and CoglOffscreen constructor functions, such as `cogl_offscreen_new_with_texture()` or `cogl_onscreen_new()`. The CoglFramebuffer interface deals with all aspects that are common between those two types of framebuffer.

Setup of a new CoglFramebuffer happens in two stages. There is a configuration stage where you specify all the options and ancillary buffers you want associated with your framebuffer and then when you are happy with the configuration you can "allocate" the framebuffer using `cogl_framebuffer_allocate()`. Technically explicitly calling `cogl_framebuffer_allocate()` is optional for convenience and the framebuffer will automatically be allocated when you first try to draw to it, but if you do the allocation manually then you can also catch any possible errors that may arise from your configuration.

## Functions

### COGL_FRAMEBUFFER()

    #define             COGL_FRAMEBUFFER(X)

### cogl_framebuffer_allocate ()

    CoglBool
    cogl_framebuffer_allocate (CoglFramebuffer *framebuffer,
                               CoglError **error);

Explicitly allocates a configured CoglFramebuffer allowing developers to check and handle any errors that might arise from an unsupported configuration so that fallback configurations may be tried.

Many applications don't support any fallback options at least when they are initially developed and in that case the don't need to use this API since Cogl will automatically allocate a framebuffer when it first gets used. The disadvantage of relying on automatic allocation is that the program will abort with an error message if there is an error during automatic allocation.

#### Parameters

framebuffer | A CoglFramebuffer |
error | A pointer to a CoglError for returning exceptions. |

#### Returns

`TRUE` if there were no error allocating the framebuffer, else `FALSE`.

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_width ()

    int
    cogl_framebuffer_get_width (CoglFramebuffer *framebuffer);

Queries the current width of the given `framebuffer` .

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The width of `framebuffer` .

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_height ()

    int
    cogl_framebuffer_get_height (CoglFramebuffer *framebuffer);

Queries the current height of the given `framebuffer` .

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The height of `framebuffer` .

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_set_viewport ()

    void
    cogl_framebuffer_set_viewport (CoglFramebuffer *framebuffer,
                                   float x,
                                   float y,
                                   float width,
                                   float height);

Defines a scale and offset for everything rendered relative to the top-left of the destination framebuffer.

By default the viewport has an origin of (0,0) and width and height that match the framebuffer's size. Assuming a default projection and modelview matrix then you could translate the contents of a window down and right by leaving the viewport size unchanged by moving the offset to (10,10). The viewport coordinates are measured in pixels. If you left the x and y origin as (0,0) you could scale the windows contents down by specify and width and height that's half the real size of the framebuffer.

Although the function takes floating point arguments, existing drivers only allow the use of integer values. In the future floating point values will be exposed via a checkable feature.

#### Parameters

framebuffer | A CoglFramebuffer |
x | The top-left x coordinate of the viewport origin (only integers supported currently) |
y | The top-left y coordinate of the viewport origin (only integers supported currently) |
width | The width of the viewport (only integers supported currently) |
height | The height of the viewport (only integers supported currently) |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_viewport_x ()

    float
    cogl_framebuffer_get_viewport_x (CoglFramebuffer *framebuffer);

Queries the x coordinate of the viewport origin as set using `cogl_framebuffer_set_viewport()` or the default value which is 0.

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The x coordinate of the viewport origin.

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_viewport_y ()

    float
    cogl_framebuffer_get_viewport_y (CoglFramebuffer *framebuffer);

Queries the y coordinate of the viewport origin as set using `cogl_framebuffer_set_viewport()` or the default value which is 0.

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The y coordinate of the viewport origin.

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_viewport_width ()

    float
    cogl_framebuffer_get_viewport_width (CoglFramebuffer *framebuffer);

Queries the width of the viewport as set using `cogl_framebuffer_set_viewport()` or the default value which is the width of the framebuffer.

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The width of the viewport.

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_viewport_height ()

    float
    cogl_framebuffer_get_viewport_height (CoglFramebuffer *framebuffer);

Queries the height of the viewport as set using `cogl_framebuffer_set_viewport()` or the default value which is the height of the framebuffer.

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The height of the viewport.

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_viewport4fv ()

    void
    cogl_framebuffer_get_viewport4fv (CoglFramebuffer *framebuffer,
                                      float *viewport);

Queries the x, y, width and height components of the current viewport as set using `cogl_framebuffer_set_viewport()` or the default values which are 0, 0, framebuffer_width and framebuffer_height. The values are written into the given `viewport` array.

#### Parameters

framebuffer | A CoglFramebuffer |
viewport | A pointer to an array of 4 floats to receive the (x, y, width, height) components of the current viewport. | [out caller-allocates][array fixed-size=4]

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_red_bits ()

    int
    cogl_framebuffer_get_red_bits (CoglFramebuffer *framebuffer);

Retrieves the number of red bits of `framebuffer`

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

the number of bits

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_green_bits ()

    int
    cogl_framebuffer_get_green_bits (CoglFramebuffer *framebuffer);

Retrieves the number of green bits of `framebuffer`

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

the number of bits

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_blue_bits ()

    int
    cogl_framebuffer_get_blue_bits (CoglFramebuffer *framebuffer);

Retrieves the number of blue bits of `framebuffer`

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

the number of bits

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_alpha_bits ()

    int
    cogl_framebuffer_get_alpha_bits (CoglFramebuffer *framebuffer);

Retrieves the number of alpha bits of `framebuffer`

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

the number of bits

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_depth_bits ()

    int
    cogl_framebuffer_get_depth_bits (CoglFramebuffer *framebuffer);

Retrieves the number of depth bits of `framebuffer`

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

the number of bits

Since 2.0

Stability Level: Unstable

### cogl_framebuffer_get_color_mask ()

    CoglColorMask
    cogl_framebuffer_get_color_mask (CoglFramebuffer *framebuffer);

Gets the current CoglColorMask of which channels would be written to the current framebuffer. Each bit set in the mask means that the corresponding color would be written.

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

A CoglColorMask

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_set_color_mask ()

    void
    cogl_framebuffer_set_color_mask (CoglFramebuffer *framebuffer,
                                     CoglColorMask color_mask);

Defines a bit mask of which color channels should be written to the given `framebuffer` . If a bit is set in `color_mask` that means that color will be written.

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |
color_mask | A CoglColorMask of which color channels to write to the current framebuffer. |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_samples_per_pixel ()

    int
    cogl_framebuffer_get_samples_per_pixel
                                   (CoglFramebuffer *framebuffer);

Gets the number of points that are sampled per-pixel when rasterizing geometry. Usually by default this will return 0 which means that single-sample not multisample rendering has been chosen. When using a GPU supporting multisample rendering it's possible to increase the number of samples per pixel using `cogl_framebuffer_set_samples_per_pixel()`.

Calling `cogl_framebuffer_get_samples_per_pixel()` before the framebuffer has been allocated will simply return the value set using `cogl_framebuffer_set_samples_per_pixel()`. After the framebuffer has been allocated the value will reflect the actual number of samples that will be made by the GPU.

#### Parameters

framebuffer | A CoglFramebuffer framebuffer |

#### Returns

The number of point samples made per pixel when rasterizing geometry or 0 if single-sample rendering has been chosen.

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_set_samples_per_pixel ()

    void
    cogl_framebuffer_set_samples_per_pixel
                                   (CoglFramebuffer *framebuffer,
                                    int samples_per_pixel);

Requires that when rendering to `framebuffer` then `n` point samples should be made per pixel which will all contribute to the final resolved color for that pixel. The idea is that the hardware aims to get quality similar to what you would get if you rendered everything twice as big (for 4 samples per pixel) and then scaled that image back down with filtering. It can effectively remove the jagged edges of polygons and should be more efficient than if you were to manually render at a higher resolution and downscale because the hardware is often able to take some shortcuts. For example the GPU may only calculate a single texture sample for all points of a single pixel, and for tile based architectures all the extra sample data (such as depth and stencil samples) may be handled on-chip and so avoid increased demand on system memory bandwidth.

By default this value is usually set to 0 and that is referred to as "single-sample" rendering. A value of 1 or greater is referred to as "multisample" rendering.

There are some semantic differences between single-sample rendering and multisampling with just 1 point sample such as it being redundant to use the `cogl_framebuffer_resolve_samples()` and `cogl_framebuffer_resolve_samples_region()` apis with single-sample rendering.
It's recommended that `cogl_framebuffer_resolve_samples_region()` be explicitly used at the end of rendering to a point sample buffer to minimize the number of samples that get resolved. By default Cogl will implicitly resolve all framebuffer samples but if only a small region of a framebuffer has changed this can lead to redundant work being done.

#### Parameters

framebuffer | A CoglFramebuffer framebuffer |
samples_per_pixel | The minimum number of samples per pixel |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_resolve_samples ()

    void
    cogl_framebuffer_resolve_samples (CoglFramebuffer *framebuffer);

When point sample rendering (also known as multisample rendering) has been enabled via `cogl_framebuffer_set_samples_per_pixel()` then you can optionally call this function (or `cogl_framebuffer_resolve_samples_region()`) to explicitly resolve the point samples into values for the final color buffer.

Some GPUs will implicitly resolve the point samples during rendering and so this function is effectively a nop, but with other architectures it is desirable to defer the resolve step until the end of the frame.

Since Cogl will automatically ensure samples are resolved if the target color buffer is used as a source this API only needs to be used if explicit control is desired - perhaps because you want to ensure that the resolve is completed in advance to avoid later having to wait for the resolve to complete.

If you are performing incremental updates to a framebuffer you should consider using `cogl_framebuffer_resolve_samples_region()` instead to avoid resolving redundant pixels.

#### Parameters

framebuffer | A CoglFramebuffer framebuffer |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_resolve_samples_region ()

    void
    cogl_framebuffer_resolve_samples_region
                                   (CoglFramebuffer *framebuffer,
                                    int x,
                                    int y,
                                    int width,
                                    int height);

When point sample rendering (also known as multisample rendering) has been enabled via `cogl_framebuffer_set_samples_per_pixel()` then you can optionally call this function (or `cogl_framebuffer_resolve_samples()`) to explicitly resolve the point samples into values for the final color buffer.

Some GPUs will implicitly resolve the point samples during rendering and so this function is effectively a nop, but with other architectures it is desirable to defer the resolve step until the end of the frame.

Use of this API is recommended if incremental, small updates to a framebuffer are being made because by default Cogl will implicitly resolve all the point samples of the framebuffer which can result in redundant work if only a small number of samples have changed.

Because some GPUs implicitly resolve point samples this function only guarantees that at-least the region specified will be resolved and if you have rendered to a larger region then it's possible that other samples may be implicitly resolved.

#### Parameters

framebuffer | A CoglFramebuffer framebuffer |
x | top-left x coordinate of region to resolve |
y | top-left y coordinate of region to resolve |
width | width of region to resolve |
height | height of region to resolve |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_context ()

    CoglContext *
    cogl_framebuffer_get_context (CoglFramebuffer *framebuffer);

Can be used to query the CoglContext a given `framebuffer` was instantiated within. This is the CoglContext that was passed to `cogl_onscreen_new()` for example.

#### Parameters

framebuffer | A CoglFramebuffer |

#### Returns

The CoglContext that the given `framebuffer` was instantiated within.

[transfer none]

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_clear ()

    void
    cogl_framebuffer_clear (CoglFramebuffer *framebuffer,
                            unsigned long  buffers,
                            const CoglColor *color);

Clears all the auxiliary buffers identified in the `buffers` mask, and if that includes the color buffer then the specified `color` is used.

#### Parameters

framebuffer | A CoglFramebuffer |
buffers | A mask of CoglBufferBit's identifying which auxiliary buffers to clear |
color | The color to clear the color buffer too if specified in `buffers` . |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_clear4f ()

    void
    cogl_framebuffer_clear4f (CoglFramebuffer *framebuffer,
                              unsigned long  buffers,
                              float red,
                              float green,
                              float blue,
                              float alpha);

Clears all the auxiliary buffers identified in the `buffers` mask, and if that includes the color buffer then the specified `color` is used.

#### Parameters

framebuffer | A CoglFramebuffer |
buffers | A mask of CoglBufferBit's identifying which auxiliary buffers to clear |
red | The red component of color to clear the color buffer too if specified in `buffers` . |
green | The green component of color to clear the color buffer too if specified in `buffers` . |
blue | The blue component of color to clear the color buffer too if specified in `buffers` . |
alpha | The alpha component of color to clear the color buffer too if specified in `buffers` . |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_read_pixels_into_bitmap ()

    CoglBool
    cogl_framebuffer_read_pixels_into_bitmap
                                   (CoglFramebuffer *framebuffer,
                                    int x,
                                    int y,
                                    CoglReadPixelsFlags source,
                                    CoglBitmap *bitmap);

This reads a rectangle of pixels from the given framebuffer where position (0, 0) is the top left. The pixel at (x, y) is the first read, and a rectangle of pixels with the same size as the bitmap is read right and downwards from that point.

Currently Cogl assumes that the framebuffer is in a premultiplied format so if the format of `bitmap` is non-premultiplied it will convert it. To read the pixel values without any conversion you should either specify a format that doesn't use an alpha channel or use one of the formats ending in PRE.

#### Parameters

framebuffer | A CoglFramebuffer |
x | The x position to read from |
y | The y position to read from |
source | Identifies which auxillary buffer you want to read (only COGL_READ_PIXELS_COLOR_BUFFER supported currently) |
bitmap | The bitmap to store the results in. |

#### Returns

`TRUE` if the read succeeded or `FALSE` otherwise. The function is only likely to fail if the bitmap points to a pixel buffer and it could not be mapped.

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_read_pixels ()

    CoglBool
    cogl_framebuffer_read_pixels (CoglFramebuffer *framebuffer,
                                  int x,
                                  int y,
                                  int width,
                                  int height,
                                  CoglPixelFormat format,
                                  uint8_t *pixels);

This is a convenience wrapper around `cogl_framebuffer_read_pixels_into_bitmap()` which allocates a temporary CoglBitmap to read pixel data directly into the given buffer. The rowstride of the buffer is assumed to be the width of the region times the bytes per pixel of the format. The source for the data is always taken from the color buffer. If you want to use any other rowstride or source, please use the `cogl_framebuffer_read_pixels_into_bitmap()` function directly.

The implementation of the function looks like this:

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    bitmap = cogl_bitmap_new_for_data (context,
                                       width, height,
                                       format,
                                       /<!-- -->* rowstride *<!-- -->/
                                       bpp * width,
                                       pixels);
    cogl_framebuffer_read_pixels_into_bitmap (framebuffer,
                                              x, y,
                                              COGL_READ_PIXELS_COLOR_BUFFER,
                                              bitmap);
    cogl_object_unref (bitmap);

#### Parameters

framebuffer | A CoglFramebuffer |
x | The x position to read from |
y | The y position to read from |
width | The width of the region of rectangles to read |
height | The height of the region of rectangles to read |
format | The pixel format to store the data in |
pixels | The address of the buffer to store the data in |

#### Returns

`TRUE` if the read succeeded or `FALSE` otherwise.

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_set_dither_enabled ()

    void
    cogl_framebuffer_set_dither_enabled (CoglFramebuffer *framebuffer,
                                         CoglBool dither_enabled);

Enables or disabled dithering if supported by the hardware.

Dithering is a hardware dependent technique to increase the visible color resolution beyond what the underlying hardware supports by playing tricks with the colors placed into the framebuffer to give the illusion of other colors. (For example this can be compared to half-toning used by some news papers to show varying levels of grey even though their may only be black and white are available).

If the current display pipeline for `framebuffer` does not support dithering then this has no affect.

Dithering is enabled by default.

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |
dither_enabled | `TRUE` to enable dithering or `FALSE` to disable |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_get_dither_enabled ()

    CoglBool
    cogl_framebuffer_get_dither_enabled (CoglFramebuffer *framebuffer);

Returns whether dithering has been requested for the given `framebuffer` . See `cogl_framebuffer_set_dither_enabled()` for more details about dithering.

This may return `TRUE` even when the underlying `framebuffer` display pipeline does not support dithering. This value only represents the user's request for dithering.

#### Parameters

framebuffer | a pointer to a CoglFramebuffer |

#### Returns

`TRUE` if dithering has been requested or `FALSE` if not.

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_draw_rectangle ()

    void
    cogl_framebuffer_draw_rectangle (CoglFramebuffer *framebuffer,
                                     CoglPipeline *pipeline,
                                     float x_1,
                                     float y_1,
                                     float x_2,
                                     float y_2);

Draws a rectangle to `framebuffer` with the given `pipeline` state and with the top left corner positioned at (`x_1` , `y_1` ) and the bottom right corner positioned at (`x_2` , `y_2` ).

The position is the position before the rectangle has been transformed by the model-view matrix and the projection matrix.
If you want to describe a rectangle with a texture mapped on it then you can use `cogl_framebuffer_draw_textured_rectangle()`.

#### Parameters

framebuffer | A destination CoglFramebuffer |
pipeline | A CoglPipeline state object |
x_1 | X coordinate of the top-left corner |
y_1 | Y coordinate of the top-left corner |
x_2 | X coordinate of the bottom-right corner |
y_2 | Y coordinate of the bottom-right corner |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_draw_textured_rectangle ()

    void
    cogl_framebuffer_draw_textured_rectangle
                                   (CoglFramebuffer *framebuffer,
                                    CoglPipeline *pipeline,
                                    float x_1,
                                    float y_1,
                                    float x_2,
                                    float y_2,
                                    float s_1,
                                    float t_1,
                                    float s_2,
                                    float t_2);

Draws a textured rectangle to `framebuffer` using the given `pipeline` state with the top left corner positioned at (`x_1` , `y_1` ) and the bottom right corner positioned at (`x_2` , `y_2` ). The top left corner will have texture coordinates of (`s_1` , `t_1` ) and the bottom right corner will have texture coordinates of (`s_2` , `t_2` ).

The position is the position before the rectangle has been transformed by the model-view matrix and the projection matrix.

This is a high level drawing api that can handle any kind of CoglMetaTexture texture such as CoglTexture2DSliced textures which may internally be comprised of multiple low-level textures. This is unlike low-level drawing apis such as `cogl_primitive_draw()` which only support low level texture types that are directly supported by GPUs such as CoglTexture2D.

The given texture coordinates will only be used for the first texture layer of the pipeline and if your pipeline has more than one layer then all other layers will have default texture coordinates of `s_1`=0.0 `t_1`=0.0 `s_2`=1.0 `t_2`=1.0

The given texture coordinates should always be normalized such that (0, 0) corresponds to the top left and (1, 1) corresponds to the bottom right. To map an entire texture across the rectangle pass in `s_1` =0, `t_1` =0, `s_2` =1, `t_2` =1.

Even if you have associated a CoglTextureRectangle texture with one of your `pipeline` layers which normally implies working with non-normalized texture coordinates this api should still be passed normalized texture coordinates.

#### Parameters

framebuffer | A destination CoglFramebuffer |
pipeline | A CoglPipeline state object |
x_1 | x coordinate upper left on screen. |
y_1 | y coordinate upper left on screen. |
x_2 | x coordinate lower right on screen. |
y_2 | y coordinate lower right on screen. |
s_1 | S texture coordinate of the top-left coorner |
t_1 | T texture coordinate of the top-left coorner |
s_2 | S texture coordinate of the bottom-right coorner |
t_2 | T texture coordinate of the bottom-right coorner |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_draw_multitextured_rectangle ()

    void
    cogl_framebuffer_draw_multitextured_rectangle
                                   (CoglFramebuffer *framebuffer,
                                    CoglPipeline *pipeline,
                                    float x_1,
                                    float y_1,
                                    float x_2,
                                    float y_2,
                                    const float *tex_coords,
                                    int tex_coords_len);

Draws a textured rectangle to `framebuffer` with the given `pipeline` state with the top left corner positioned at (`x_1` , `y_1` ) and the bottom right corner positioned at (`x_2` , `y_2` ). As a pipeline may contain multiple texture layers this interface lets you supply texture coordinates for each layer of the pipeline.

The position is the position before the rectangle has been transformed by the model-view matrix and the projection matrix.

This is a high level drawing api that can handle any kind of CoglMetaTexture texture for the first layer such as CoglTexture2DSliced textures which may internally be comprised of multiple low-level textures. This is unlike low-level drawing apis such as `cogl_primitive_draw()` which only support low level texture types that are directly supported by GPUs such as CoglTexture2D.

This api can not currently handle multiple high-level meta texture layers. The first layer may be a high level meta texture such as CoglTexture2DSliced but all other layers much be low level textures such as CoglTexture2D and additionally they should be textures that can be sampled using normalized coordinates (so not CoglTextureRectangle textures).

The top left texture coordinate for layer 0 of any pipeline will be (tex_coords[0], tex_coords[1]) and the bottom right coordinate will be (tex_coords[2], tex_coords[3]). The coordinates for layer 1 would be (tex_coords[4], tex_coords[5]) (tex_coords[6], tex_coords[7]) and so on...

The given texture coordinates should always be normalized such that (0, 0) corresponds to the top left and (1, 1) corresponds to the bottom right. To map an entire texture across the rectangle pass in tex_coords[0]=0, tex_coords[1]=0, tex_coords[2]=1, tex_coords[3]=1.

Even if you have associated a CoglTextureRectangle texture which normally implies working with non-normalized texture coordinates this api should still be passed normalized texture coordinates.

The first pair of coordinates are for the first layer (with the smallest layer index) and if you supply less texture coordinates than there are layers in the current source material then default texture coordinates (0.0, 0.0, 1.0, 1.0) are generated.

#### Parameters

framebuffer | A destination CoglFramebuffer |
pipeline | A CoglPipeline state object |
x_1 | x coordinate upper left on screen. |
y_1 | y coordinate upper left on screen. |
x_2 | x coordinate lower right on screen. |
y_2 | y coordinate lower right on screen. |
tex_coords | An array containing groups of 4 float values: [s_1, t_1, s_2, t_2] that are interpreted as two texture coordinates; one for the top left texel, and one for the bottom right texel. Each value should be between 0.0 and 1.0, where the coordinate (0.0, 0.0) represents the top left of the texture, and (1.0, 1.0) the bottom right. | [in][array][transfer none]
tex_coords_len | The length of the `tex_coords` array. (For one layer and one group of texture coordinates, this would be 4) |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_draw_rectangles ()

    void
    cogl_framebuffer_draw_rectangles (CoglFramebuffer *framebuffer,
                                      CoglPipeline *pipeline,
                                      const float *coordinates,
                                      unsigned int n_rectangles);

Draws a series of rectangles to `framebuffer` with the given `pipeline` state in the same way that `cogl_framebuffer_draw_rectangle()` does.

The top left corner of the first rectangle is positioned at (coordinates[0], coordinates[1]) and the bottom right corner is positioned at (coordinates[2], coordinates[3]). The positions for the second rectangle are (coordinates[4], coordinates[5]) and (coordinates[6], coordinates[7]) and so on...

The position is the position before the rectangle has been transformed by the model-view matrix and the projection matrix.

As a general rule for better performance its recommended to use this this API instead of calling `cogl_framebuffer_draw_textured_rectangle()` separately for multiple rectangles if all of the rectangles will be drawn together with the same `pipeline` state.

#### Parameters

framebuffer | A destination CoglFramebuffer |
pipeline | A CoglPipeline state object |
coordinates | an array of coordinates containing groups of 4 float values: [x_1, y_1, x_2, y_2] that are interpreted as two position coordinates; one for the top left of the rectangle (x1, y1), and one for the bottom right of the rectangle (x2, y2). | [in][array][transfer none]
n_rectangles | number of rectangles defined in `coordinates` . |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_draw_textured_rectangles ()

    void
    cogl_framebuffer_draw_textured_rectangles
                                   (CoglFramebuffer *framebuffer,
                                    CoglPipeline *pipeline,
                                    const float *coordinates,
                                    unsigned int n_rectangles);

Draws a series of rectangles to `framebuffer` with the given `pipeline` state in the same way that `cogl_framebuffer_draw_textured_rectangle()` does.

The position is the position before the rectangle has been transformed by the model-view matrix and the projection matrix.

This is a high level drawing api that can handle any kind of CoglMetaTexture texture such as CoglTexture2DSliced textures which may internally be comprised of multiple low-level textures. This is unlike low-level drawing apis such as `cogl_primitive_draw()` which only support low level texture types that are directly supported by GPUs such as CoglTexture2D.

The top left corner of the first rectangle is positioned at (coordinates[0], coordinates[1]) and the bottom right corner is positioned at (coordinates[2], coordinates[3]). The top left texture coordinate is (coordinates[4], coordinates[5]) and the bottom right texture coordinate is (coordinates[6], coordinates[7]). The coordinates for subsequent rectangles are defined similarly by the subsequent coordinates.

As a general rule for better performance its recommended to use this this API instead of calling `cogl_framebuffer_draw_textured_rectangle()` separately for multiple rectangles if all of the rectangles will be drawn together with the same `pipeline` state.

The given texture coordinates should always be normalized such that (0, 0) corresponds to the top left and (1, 1) corresponds to the bottom right. To map an entire texture across the rectangle pass in tex_coords[0]=0, tex_coords[1]=0, tex_coords[2]=1, tex_coords[3]=1.

Even if you have associated a CoglTextureRectangle texture which normally implies working with non-normalized texture coordinates this api should still be passed normalized texture coordinates.

#### Parameters

framebuffer | A destination CoglFramebuffer |
pipeline | A CoglPipeline state object |
coordinates | an array containing groups of 8 float values: [x_1, y_1, x_2, y_2, s_1, t_1, s_2, t_2] that have the same meaning as the arguments for `cogl_framebuffer_draw_textured_rectangle()`. | [in][array][transfer none]
n_rectangles | number of rectangles to `coordinates` to draw |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_discard_buffers ()

    void
    cogl_framebuffer_discard_buffers (CoglFramebuffer *framebuffer,
                                      unsigned long  buffers);

Declares that the specified `buffers` no longer need to be referenced by any further rendering commands. This can be an important optimization to avoid subsequent frames of rendering depending on the results of a previous frame.

For example; some tile-based rendering GPUs are able to avoid allocating and accessing system memory for the depth and stencil buffer so long as these buffers are not required as input for subsequent frames and that can save a significant amount of memory bandwidth used to save and restore their contents to system memory between frames.

It is currently considered an error to try and explicitly discard the color buffer by passing `COGL_BUFFER_BIT_COLOR`. This is because the color buffer is already implicitly discard when you finish rendering to a CoglOnscreen framebuffer, and it's not meaningful to try and discard the color buffer of a CoglOffscreen framebuffer since they are single-buffered.

#### Parameters

framebuffer | A CoglFramebuffer |
buffers | A CoglBufferBit mask of which ancillary buffers you want to discard. |

Since 1.8

Stability Level: Unstable

### cogl_framebuffer_finish ()

    void
    cogl_framebuffer_finish (CoglFramebuffer *framebuffer);

This blocks the CPU until all pending rendering associated with the specified framebuffer has completed. It's very rare that developers should ever need this level of synchronization with the GPU and should never be used unless you clearly understand why you need to explicitly force synchronization.

One example might be for benchmarking purposes to be sure timing measurements reflect the time that the GPU is busy for not just the time it takes to queue rendering commands.

#### Parameters

framebuffer | A CoglFramebuffer pointer |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_push_matrix ()

    void
    cogl_framebuffer_push_matrix (CoglFramebuffer *framebuffer);

Copies the current model-view matrix onto the matrix stack. The matrix can later be restored with `cogl_framebuffer_pop_matrix()`.

#### Parameters

framebuffer | A CoglFramebuffer pointer |

Since 1.10

### cogl_framebuffer_pop_matrix ()

    void
    cogl_framebuffer_pop_matrix (CoglFramebuffer *framebuffer);

Restores the model-view matrix on the top of the matrix stack.

#### Parameters

framebuffer | A CoglFramebuffer pointer |

Since 1.10

### cogl_framebuffer_identity_matrix ()

    void
    cogl_framebuffer_identity_matrix (CoglFramebuffer *framebuffer);

Resets the current model-view matrix to the identity matrix.

#### Parameters

framebuffer | A CoglFramebuffer pointer |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_scale ()

    void
    cogl_framebuffer_scale (CoglFramebuffer *framebuffer,
                            float x,
                            float y,
                            float z);

Multiplies the current model-view matrix by one that scales the x, y and z axes by the given values.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
x | Amount to scale along the x-axis |
y | Amount to scale along the y-axis |
z | Amount to scale along the z-axis |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_translate ()

    void
    cogl_framebuffer_translate (CoglFramebuffer *framebuffer,
                                float x,
                                float y,
                                float z);

Multiplies the current model-view matrix by one that translates the model along all three axes according to the given values.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
x | Distance to translate along the x-axis |
y | Distance to translate along the y-axis |
z | Distance to translate along the z-axis |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_rotate ()

    void
    cogl_framebuffer_rotate (CoglFramebuffer *framebuffer,
                             float angle,
                             float x,
                             float y,
                             float z);

Multiplies the current model-view matrix by one that rotates the model around the axis-vector specified by `x` , `y` and `z` . The rotation follows the right-hand thumb rule so for example rotating by 10 degrees about the axis-vector (0, 0, 1) causes a small counter-clockwise rotation.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
angle | Angle in degrees to rotate. |
x | X-component of vertex to rotate around. |
y | Y-component of vertex to rotate around. |
z | Z-component of vertex to rotate around. |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_rotate_euler ()

    void
    cogl_framebuffer_rotate_euler (CoglFramebuffer *framebuffer,
                                   const CoglEuler *euler);

Multiplies the current model-view matrix by one that rotates according to the rotation described by `euler` .

#### Parameters

framebuffer | A CoglFramebuffer pointer |
euler | A CoglEuler |

Since 2.0

Stability Level: Unstable

### cogl_framebuffer_rotate_quaternion ()

    void
    cogl_framebuffer_rotate_quaternion (CoglFramebuffer *framebuffer,
                                        const CoglQuaternion *quaternion);

Multiplies the current model-view matrix by one that rotates according to the rotation described by `quaternion` .

#### Parameters

framebuffer | A CoglFramebuffer pointer |
quaternion | A CoglQuaternion |

Since 2.0

Stability Level: Unstable

### cogl_framebuffer_transform ()

    void
    cogl_framebuffer_transform (CoglFramebuffer *framebuffer,
                                const CoglMatrix *matrix);

Multiplies the current model-view matrix by the given matrix.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
matrix | the matrix to multiply with the current model-view |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_get_modelview_matrix ()

    void
    cogl_framebuffer_get_modelview_matrix (CoglFramebuffer *framebuffer,
                                           CoglMatrix *matrix);

Stores the current model-view matrix in `matrix` .

#### Parameters

framebuffer | A CoglFramebuffer pointer |
matrix | return location for the model-view matrix. | [out]

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_set_modelview_matrix ()

    void
    cogl_framebuffer_set_modelview_matrix (CoglFramebuffer *framebuffer,
                                           const CoglMatrix *matrix);

Sets `matrix` as the new model-view matrix.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
matrix | the new model-view matrix |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_perspective ()

    void
    cogl_framebuffer_perspective (CoglFramebuffer *framebuffer,
                                  float fov_y,
                                  float aspect,
                                  float z_near,
                                  float z_far);

Replaces the current projection matrix with a perspective matrix based on the provided values.

You should be careful not to have to great a `z_far` / `z_near` ratio since that will reduce the effectiveness of depth testing since there wont be enough precision to identify the depth of objects near to each other.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
fov_y | Vertical field of view angle in degrees. |
aspect | The (width over height) aspect ratio for display |
z_near | The distance to the near clipping plane (Must be positive, and must not be 0) |
z_far | The distance to the far clipping plane (Must be positive) |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_frustum ()

    void
    cogl_framebuffer_frustum (CoglFramebuffer *framebuffer,
                              float left,
                              float right,
                              float bottom,
                              float top,
                              float z_near,
                              float z_far);

Replaces the current projection matrix with a perspective matrix for a given viewing frustum defined by 4 side clip planes that all cross through the origin and 2 near and far clip planes.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
left | X position of the left clipping plane where it intersects the near clipping plane |
right | X position of the right clipping plane where it intersects the near clipping plane |
bottom | Y position of the bottom clipping plane where it intersects the near clipping plane |
top | Y position of the top clipping plane where it intersects the near clipping plane |
z_near | The distance to the near clipping plane (Must be positive) |
z_far | The distance to the far clipping plane (Must be positive) |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_orthographic ()

    void
    cogl_framebuffer_orthographic (CoglFramebuffer *framebuffer,
                                   float x_1,
                                   float y_1,
                                   float x_2,
                                   float y_2,
                                   float near,
                                   float far);

Replaces the current projection matrix with an orthographic projection matrix.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
x_1 | The x coordinate for the first vertical clipping plane |
y_1 | The y coordinate for the first horizontal clipping plane |
x_2 | The x coordinate for the second vertical clipping plane |
y_2 | The y coordinate for the second horizontal clipping plane |
near | The distance to the near clipping plane (will be negative if the plane is behind the viewer) |
far | The distance to the far clipping plane (will be negative if the plane is behind the viewer) |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_get_projection_matrix ()

    void
    cogl_framebuffer_get_projection_matrix
                                   (CoglFramebuffer *framebuffer,
                                    CoglMatrix *matrix);

Stores the current projection matrix in `matrix` .

#### Parameters

framebuffer | A CoglFramebuffer pointer |
matrix | return location for the projection matrix. | [out]

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_set_projection_matrix ()

    void
    cogl_framebuffer_set_projection_matrix
                                   (CoglFramebuffer *framebuffer,
                                    const CoglMatrix *matrix);

Sets `matrix` as the new projection matrix.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
matrix | the new projection matrix |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_push_scissor_clip ()

    void
    cogl_framebuffer_push_scissor_clip (CoglFramebuffer *framebuffer,
                                        int x,
                                        int y,
                                        int width,
                                        int height);

Specifies a rectangular clipping area for all subsequent drawing operations. Any drawing commands that extend outside the rectangle will be clipped so that only the portion inside the rectangle will be displayed. The rectangle dimensions are not transformed by the current model-view matrix.

The rectangle is intersected with the current clip region. To undo the effect of this function, call `cogl_framebuffer_pop_clip()`.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
x | left edge of the clip rectangle in window coordinates |
y | top edge of the clip rectangle in window coordinates |
width | width of the clip rectangle |
height | height of the clip rectangle |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_push_rectangle_clip ()

    void
    cogl_framebuffer_push_rectangle_clip (CoglFramebuffer *framebuffer,
                                          float x_1,
                                          float y_1,
                                          float x_2,
                                          float y_2);

Specifies a modelview transformed rectangular clipping area for all subsequent drawing operations. Any drawing commands that extend outside the rectangle will be clipped so that only the portion inside the rectangle will be displayed. The rectangle dimensions are transformed by the current model-view matrix.

The rectangle is intersected with the current clip region. To undo the effect of this function, call `cogl_framebuffer_pop_clip()`.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
x_1 | x coordinate for top left corner of the clip rectangle |
y_1 | y coordinate for top left corner of the clip rectangle |
x_2 | x coordinate for bottom right corner of the clip rectangle |
y_2 | y coordinate for bottom right corner of the clip rectangle |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_push_primitive_clip ()

    void
    cogl_framebuffer_push_primitive_clip (CoglFramebuffer *framebuffer,
                                          CoglPrimitive *primitive,
                                          float bounds_x1,
                                          float bounds_y1,
                                          float bounds_x2,
                                          float bounds_y2);

Sets a new clipping area using a 2D shaped described with a CoglPrimitive. The shape must not contain self overlapping geometry and must lie on a single 2D plane. A bounding box of the 2D shape in local coordinates (the same coordinates used to describe the shape) must be given. It is acceptable for the bounds to be larger than the true bounds but behaviour is undefined if the bounds are smaller than the true bounds.

The primitive is transformed by the current model-view matrix and the silhouette is intersected with the previous clipping area. To restore the previous clipping area, call `cogl_framebuffer_pop_clip()`.

#### Parameters

framebuffer | A CoglFramebuffer pointer |
primitive | A CoglPrimitive describing a flat 2D shape |
bounds_x1 | x coordinate for the top-left corner of the primitives bounds |
bounds_y1 | y coordinate for the top-left corner of the primitives bounds |
bounds_x2 | x coordinate for the bottom-right corner of the primitives bounds. |
bounds_y2 | y coordinate for the bottom-right corner of the primitives bounds. |

Since 1.10

Stability Level: Unstable

### cogl_framebuffer_pop_clip ()

    void
    cogl_framebuffer_pop_clip (CoglFramebuffer *framebuffer);

Reverts the clipping region to the state before the last call to `cogl_framebuffer_push_scissor_clip()`, `cogl_framebuffer_push_rectangle_clip()` `cogl_framebuffer_push_path_clip()`, or `cogl_framebuffer_push_primitive_clip()`.

#### Parameters

framebuffer | A CoglFramebuffer pointer |

Since 1.10

Stability Level: Unstable

### cogl_get_draw_framebuffer ()

    CoglFramebuffer *
    cogl_get_draw_framebuffer (void);

Gets the current CoglFramebuffer as set using `cogl_push_framebuffer()`

#### Returns

The current CoglFramebuffer.

[transfer none]

Since 1.8

Stability Level: Unstable

### cogl_set_framebuffer ()

    void
    cogl_set_framebuffer (CoglFramebuffer *buffer);

`cogl_set_framebuffer` has been deprecated since version 1.16 and should not be used in newly-written code.

The latest drawing apis take explicit CoglFramebuffer arguments so this stack of framebuffers shouldn't be used anymore.

This redirects all subsequent drawing to the specified framebuffer. This can either be an offscreen buffer created with `cogl_offscreen_new_to_texture()` or in the future it may be an onscreen framebuffers too.

#### Parameters

buffer | A CoglFramebuffer object, either onscreen or offscreen. |

Since 1.2

### cogl_push_framebuffer ()

    void
    cogl_push_framebuffer (CoglFramebuffer *buffer);

`cogl_push_framebuffer` has been deprecated since version 1.16 and should not be used in newly-written code.

The latest drawing apis take explicit CoglFramebuffer arguments so this stack of framebuffers shouldn't be used anymore.

Redirects all subsequent drawing to the specified framebuffer. This can either be an offscreen buffer created with `cogl_offscreen_new_to_texture()` or in the future it may be an onscreen framebuffer too.

You should understand that a framebuffer owns the following state:

- The projection matrix
- The modelview matrix stack
- The viewport
- The clip stack

So these items will automatically be saved and restored when you push and pop between different framebuffers.

Also remember a newly allocated framebuffer will have an identity matrix for the projection and modelview matrices which gives you a coordinate space like OpenGL with (-1, -1) corresponding to the top left of the viewport, (1, 1) corresponding to the bottom right and +z coming out towards the viewer.

If you want to set up a coordinate space like Clutter does with (0, 0) corresponding to the top left and (framebuffer_width, framebuffer_height) corresponding to the bottom right you can do so like this:

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    static void
    setup_viewport (unsigned int width,
                    unsigned int height,
                    float fovy,
                    float aspect,
                    float z_near,
                    float z_far)
    {
      float z_camera;
      CoglMatrix projection_matrix;
      CoglMatrix mv_matrix;

      cogl_set_viewport (0, 0, width, height);
      cogl_perspective (fovy, aspect, z_near, z_far);

      cogl_get_projection_matrix (&projection_matrix);
      z_camera = 0.5 * projection_matrix.xx;

      cogl_matrix_init_identity (&mv_matrix);
      cogl_matrix_translate (&mv_matrix, -0.5f, -0.5f, -z_camera);
      cogl_matrix_scale (&mv_matrix, 1.0f / width, -1.0f / height, 1.0f / width);
      cogl_matrix_translate (&mv_matrix, 0.0f, -1.0 * height, 0.0f);
      cogl_set_modelview_matrix (&mv_matrix);
    }

    static void
    my_init_framebuffer (ClutterStage *stage,
                         CoglFramebuffer *framebuffer,
                         unsigned int framebuffer_width,
                         unsigned int framebuffer_height)
    {
      ClutterPerspective perspective;

      clutter_stage_get_perspective (stage, &perspective);

      cogl_push_framebuffer (framebuffer);
      setup_viewport (framebuffer_width,
                      framebuffer_height,
                      perspective.fovy,
                      perspective.aspect,
                      perspective.z_near,
                      perspective.z_far);
    }

The previous framebuffer can be restored by calling `cogl_pop_framebuffer()`

#### Parameters

buffer | A CoglFramebuffer object, either onscreen or offscreen. |

Since 1.2

### cogl_pop_framebuffer ()

    void
    cogl_pop_framebuffer (void);

`cogl_pop_framebuffer` has been deprecated since version 1.16 and should not be used in newly-written code.

The latest drawing apis take explicit CoglFramebuffer arguments so this stack of framebuffers shouldn't be used anymore.

Restores the framebuffer that was previously at the top of the stack. All subsequent drawing will be redirected to this framebuffer.

Since 1.2

## Types and Values

### CoglFramebuffer

    typedef void CoglFramebuffer;