Topics | Functions
libcaca dirty rectangle manipulation
libcaca attribute definitions » libcaca basic functions » libcaca canvas drawing

## Topics
| libcaca canvas transformation

## Functions
__extern int | caca_disable_dirty_rect (caca_canvas_t *)
| Disable dirty rectangles.
__extern int | caca_enable_dirty_rect (caca_canvas_t *)
| Enable dirty rectangles.
__extern int | caca_get_dirty_rect_count (caca_canvas_t *)
| Get the number of dirty rectangles in the canvas.
__extern int | caca_get_dirty_rect (caca_canvas_t *, int, int *, int *, int *, int *)
| Get a canvas's dirty rectangle.
__extern int | caca_add_dirty_rect (caca_canvas_t *, int, int, int, int)
| Add an area to the canvas's dirty rectangle list.
__extern int | caca_remove_dirty_rect (caca_canvas_t *, int, int, int, int)
| Remove an area from the dirty rectangle list.
__extern int | caca_clear_dirty_rect_list (caca_canvas_t *)
| Clear a canvas's dirty rectangle list.

## Detailed Description

These functions manipulate dirty rectangles for optimised blitting.

## Function Documentation

## ◆ caca_disable_dirty_rect()

__extern int caca_disable_dirty_rect | ( | caca_canvas_t * | cv | ) |

Disable dirty rectangle handling for all libcaca graphic calls. This is handy when the calling application needs to do slow operations within a known area. Just call caca_add_dirty_rect() afterwards.

This function is recursive. Dirty rectangles are only reenabled when caca_enable_dirty_rect() is called as many times.

This function never fails.

Parameters

  cv | A libcaca canvas.

Returns
  This function always returns 0.

## ◆ caca_enable_dirty_rect()

__extern int caca_enable_dirty_rect | ( | caca_canvas_t * | cv | ) |

This function can only be called after caca_disable_dirty_rect() was called.

If an error occurs, -1 is returned and errno is set accordingly:

- `EINVAL` Dirty rectangles were not disabled.

Parameters

  cv | A libcaca canvas.

Returns
  0 in case of success, -1 if an error occurred.

## ◆ caca_get_dirty_rect_count()

__extern int caca_get_dirty_rect_count | ( | caca_canvas_t * | cv | ) |

Get the number of dirty rectangles in a canvas. Dirty rectangles are areas that contain cells that have changed since the last reset.

The dirty rectangles are used internally by display drivers to optimise rendering by avoiding to redraw the whole screen. Once the display driver has rendered the canvas, it resets the dirty rectangle list.

Dirty rectangles are guaranteed not to overlap.

This function never fails.

Parameters

  cv | A libcaca canvas.

Returns
  The number of dirty rectangles in the given canvas.

## ◆ caca_get_dirty_rect()

__extern int caca_get_dirty_rect | ( | caca_canvas_t * | cv,
|  | int | r,
|  | int * | x,
|  | int * | y,
|  | int * | width,
|  | int * | height )

Get the canvas's given dirty rectangle coordinates. The index must be within the dirty rectangle count. See caca_get_dirty_rect_count() for how to compute this count.

If an error occurs, no coordinates are written in the pointer arguments, -1 is returned and errno is set accordingly:

- `EINVAL` Specified rectangle index is out of bounds.

Parameters

  cv | A libcaca canvas.
  r | The requested rectangle index.
  x | A pointer to an integer where the leftmost edge of the dirty rectangle will be stored.
  y | A pointer to an integer where the topmost edge of the dirty rectangle will be stored.
  width | A pointer to an integer where the width of the dirty rectangle will be stored.
  height | A pointer to an integer where the height of the dirty rectangle will be stored.

Returns
  0 in case of success, -1 if an error occurred.

## ◆ caca_add_dirty_rect()

__extern int caca_add_dirty_rect | ( | caca_canvas_t * | cv,
|  | int | x,
|  | int | y,
|  | int | width,
|  | int | height )

Add an invalidating zone to the canvas's dirty rectangle list. For more information about the dirty rectangles, see caca_get_dirty_rect().

This function may be useful to force refresh of a given zone of the canvas even if the dirty rectangle tracking indicates that it is unchanged. This may happen if the canvas contents were somewhat directly modified.

If an error occurs, -1 is returned and errno is set accordingly:

- `EINVAL` Specified rectangle coordinates are out of bounds.

Parameters

  cv | A libcaca canvas.
  x | The leftmost edge of the additional dirty rectangle.
  y | The topmost edge of the additional dirty rectangle.
  width | The width of the additional dirty rectangle.
  height | The height of the additional dirty rectangle.

Returns
  0 in case of success, -1 if an error occurred.

Referenced by caca_blit(), caca_clear_canvas(), caca_fill_box(), caca_flip(), caca_flop(), caca_free_frame(), caca_invert(), caca_put_attr(), caca_put_char(), caca_rotate_180(), caca_rotate_left(), caca_rotate_right(), caca_set_canvas_boundaries(), caca_set_frame(), caca_stretch_left(), and caca_stretch_right().

## ◆ caca_remove_dirty_rect()

__extern int caca_remove_dirty_rect | ( | caca_canvas_t * | cv,
|  | int | x,
|  | int | y,
|  | int | width,
|  | int | height )

Mark a cell area in the canvas as not dirty. For more information about the dirty rectangles, see caca_get_dirty_rect().

Values such that xmin > xmax or ymin > ymax indicate that the dirty rectangle is empty. They will be silently ignored.

If an error occurs, -1 is returned and errno is set accordingly:

- `EINVAL` Specified rectangle coordinates are out of bounds.

Parameters

  cv | A libcaca canvas.
  x | The leftmost edge of the clean rectangle.
  y | The topmost edge of the clean rectangle.
  width | The width of the clean rectangle.
  height | The height of the clean rectangle.

Returns
  0 in case of success, -1 if an error occurred.

## ◆ caca_clear_dirty_rect_list()

__extern int caca_clear_dirty_rect_list | ( | caca_canvas_t * | cv | ) |

Empty the canvas's dirty rectangle list.

This function never fails.

Parameters

  cv | A libcaca canvas.

Returns
  This function always returns 0.

Referenced by caca_refresh_display().