cairoPushGroup             package:RGtk2             R Documentation

_c_a_i_r_o_P_u_s_h_G_r_o_u_p

_D_e_s_c_r_i_p_t_i_o_n:

     Temporarily redirects drawing to an intermediate surface known as
     a group. The redirection lasts until the group is completed by a
     call to 'cairoPopGroup' or 'cairoPopGroupToSource'. 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).

_U_s_a_g_e:

     cairoPushGroup(cr)

_A_r_g_u_m_e_n_t_s:

    'cr': ['Cairo']  a cairo context

_D_e_t_a_i_l_s:

     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
     'cairoPushGroup'/'cairoPopGroup'. Each call pushes/pops the new
     target group onto/from a stack.

     The 'cairoPushGroup' function calls 'cairoSave' so that any
     changes to the graphics state will not be visible outside the
     group, (the pop_group functions call 'cairoRestore').

     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 'cairoPushGroupWithContent' 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
     under the stroke:


     cr$pushGroup()
     cr$setSource(fill_pattern)
     cr$fillPreserve()
     cr$setSource(stroke_pattern)
     cr$stroke()
     cr$popGroupToSource(cr)
     cr$paintWithAlpha(alpha)


     Since  1.2

_A_u_t_h_o_r(_s):

     Derived by RGtkGen from GTK+ documentation

