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20 Recording Surfaces

Records all drawing operations

20.1 Overview

A recording surface is a surface that records all drawing operations at the highest level of the surface backend interface, (that is, the level of paint, mask, stroke, fill, and show_text_glyphs). The recording surface can then be "replayed" against any target surface by using it as a source surface.

If you want to replay a surface so that the results in target will be identical to the results that would have been obtained if the original operations applied to the recording surface had instead been applied to the target surface, you can use code like this:

     
          cairo_t *cr;
     
     cr = cairo_create (target);
     cairo_set_source_surface (cr, recording_surface, 0.0, 0.0);
     cairo_paint (cr);
     cairo_destroy (cr);

A recording surface is logically unbounded, i.e. it has no implicit constraint on the size of the drawing surface. However, in practice this is rarely useful as you wish to replay against a particular target surface with known bounds. For this case, it is more efficient to specify the target extents to the recording surface upon creation.

The recording phase of the recording surface is careful to snapshot all necessary objects (paths, patterns, etc.), in order to achieve accurate replay. The efficiency of the recording surface could be improved by improving the implementation of snapshot for the various objects. For example, it would be nice to have a copy-on-write implementation for _cairo_surface_snapshot.

20.2 Usage

— Function: cairo-recording-surface-create (content <cairo-content-t>) (extents <cairo-rectangle-t>) ⇒  (ret <cairo-surface-t >)

Creates a recording-surface which can be used to record all drawing operations at the highest level (that is, the level of paint, mask, stroke, fill and show_text_glyphs). The recording surface can then be "replayed" against any target surface by using it as a source to drawing operations.

The recording phase of the recording surface is careful to snapshot all necessary objects (paths, patterns, etc.), in order to achieve accurate replay.

content
the content of the recording surface
extents
the extents to record in pixels, can be ‘#f’ to record unbounded operations.
ret
a pointer to the newly created surface. The caller owns the surface and should call cairo-surface-destroy when done with it.

Since 1.10

— Function: cairo-recording-surface-ink-extents (surface <cairo-surface-t>) ⇒  (x0 <double>) (y0 <double>) (width <double>) (height <double>)

Measures the extents of the operations stored within the recording-surface. This is useful to compute the required size of an image surface (or equivalent) into which to replay the full sequence of drawing operations.

surface
a <cairo-recording-surface-t>
x0
the x-coordinate of the top-left of the ink bounding box
y0
the y-coordinate of the top-left of the ink bounding box
width
the width of the ink bounding box
height
the height of the ink bounding box

Since 1.10