Temporarily redirects drawing to an intermediate surface known as a
group. The redirection lasts until the group is completed by a call
to cairo_pop_group() or cairo_pop_group_to_source(). These calls
provide the result of any drawing to the group as a pattern,
(either as an explicit object, or set as the source pattern).
This group functionality can be convenient for performing
intermediate compositing. One common use of a group is to render
objects as opaque within the group, (so that they occlude each
other), and then blend the result with translucence onto the
destination.
Groups can be nested arbitrarily deep by making balanced calls to
cairo_push_group()/cairo_pop_group(). Each call pushes/pops the new
target group onto/from a stack.
The cairo_push_group() function calls cairo_save() so that any
changes to the graphics state will not be visible outside the
group, (the pop_group functions call cairo_restore()).
By default the intermediate group will have a content type of
CAIRO_CONTENT_COLOR_ALPHA. Other content types can be chosen for
the group by using cairo_push_group_with_content() instead.
As an example, here is how one might fill and stroke a path with
translucence, but without any portion of the fill being visible
Since 1.2
Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to cairo_pop_group() or cairo_pop_group_to_source(). These calls provide the result of any drawing to the group as a pattern, (either as an explicit object, or set as the source pattern). This group functionality can be convenient for performing intermediate compositing. One common use of a group is to render objects as opaque within the group, (so that they occlude each other), and then blend the result with translucence onto the destination. Groups can be nested arbitrarily deep by making balanced calls to cairo_push_group()/cairo_pop_group(). Each call pushes/pops the new target group onto/from a stack. The cairo_push_group() function calls cairo_save() so that any changes to the graphics state will not be visible outside the group, (the pop_group functions call cairo_restore()). By default the intermediate group will have a content type of CAIRO_CONTENT_COLOR_ALPHA. Other content types can be chosen for the group by using cairo_push_group_with_content() instead. As an example, here is how one might fill and stroke a path with translucence, but without any portion of the fill being visible Since 1.2