surfaces

[Steven J Abner]

Start by saying cairo rocks!
I'm doing conversion of an interface drawing project, and love the 
cairo way. But in
doing gdk/gtk encountered something I'd like to see if correct, no 
bumps down the line.
  The design is a window, normally the top-most, with one 'main' 
cairo_surface_t. Rather than a bunch of 'widgets/windows', the 
cairo_surface_t may be broken into multiple 'drawing ports' by means of 
cairo_surface_create_for_rectangle(). On XCB this is a breeze, and 
doesn't force destruction of all the multiple ports, just ones that may 
be effected. This is because of the wonderful 
cairo_xcb_surface_set_size(). For others, the solution eludes me. But I 
did get a working solution to the design.
This solution is where you all come in. Is this a sound method? Is 
there a way to adapt cairo_xcb_surface_set_size() to other surfaces? 
Maybe something hidden or overlooked?
  Here is the questionable:

static void
_interface_configure(PhxInterface *iface, int16_t hD, int16_t vD) {

  iface->mete_box.w += hD;
  iface->draw_box.w += hD;
  iface->mete_box.h += vD;
  iface->draw_box.h += vD;
#ifdef XCB
  cairo_xcb_surface_set_size(iface->surface,
                             iface->mete_box.w,
                             iface->mete_box.h);
#else
  for (int ndx = 0; ndx < iface->ncount; ndx++) {
    PhxNexus *inspect = iface->nexus[ndx];
    inspect->state |= 4;
    cairo_surface_destroy(inspect->surface);
    inspect->surface = NULL;
  }
  cairo_surface_destroy(iface->surface);
    /* create window's drawing surface */
  master_iface->surface = gdk_window_create_similar_surface(
                                 iface->window,
                                 CAIRO_CONTENT_COLOR_ALPHA,
                                 iface->draw_box.w,
                                 iface->draw_box.h);
  cairo_status_t error = cairo_surface_status(iface->surface);
  if (error != CAIRO_STATUS_SUCCESS) {
    fprintf(stderr, "Some weird cairo error...?!");
    return;
  }
#endif
  if (iface->nexus[0] != NULL) {
    _interface_delta_sweep(iface, hD, vD);
    _interface_resurface(iface);
  }
}

  A small description:
iface is global controller/variables, holds 'surface'.
nexus are drawing ports listed within iface, sub-surfaces.
nexus->state | 4 just informs to destroy/resurface the sub-surface.
delta_sweep moves/resizes based on window's changes and marks if needs 
resurface.
resurface destroy/create_for_rectangle a marked nexus.
A visual example of multiple ports is provided to aid in attempt to 
convey.
  The #else ... #endif is the code of needing advice.
Any insight you can share would be highly appreciated.
Steve

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