func (self *Surface) ClipExtents() (left, top, right, bottom float64) {
var x1, y1, x2, y2 float64
px1 := (*C.double)(&x1)
py1 := (*C.double)(&y1)
px2 := (*C.double)(&x2)
py2 := (*C.double)(&y2)
C.cairo_clip_extents(self.context, px1, py1, px2, py2)
left = float64(*px1)
top = float64(*py1)
right = float64(*px2)
bottom = float64(*py2)
return
}
//export our_area_draw_callback
func our_area_draw_callback(widget *C.GtkWidget, cr *C.cairo_t, data C.gpointer) C.gboolean {
var x0, y0, x1, y1 C.double
var maxwid, maxht C.gint
s := (*sysData)(unsafe.Pointer(data))
// thanks to desrt in irc.gimp.net/#gtk+
// these are in user coordinates, which match what coordinates we want by default, even out of a draw event handler (thanks johncc3, mclasen, and Company in irc.gimp.net/#gtk+)
C.cairo_clip_extents(cr, &x0, &y0, &x1, &y1)
// we do not need to clear the cliprect; GtkDrawingArea did it for us beforehand
cliprect := image.Rect(int(x0), int(y0), int(x1), int(y1))
// the cliprect can actually fall outside the size of the Area; clip it by intersecting the two rectangles
C.gtk_widget_get_size_request(widget, &maxwid, &maxht)
cliprect = image.Rect(0, 0, int(maxwid), int(maxht)).Intersect(cliprect)
if cliprect.Empty() { // no intersection; nothing to paint
return C.FALSE // signals handled without stopping the event chain (thanks to desrt again)
}
i := s.handler.Paint(cliprect)
surface := C.cairo_image_surface_create(
C.CAIRO_FORMAT_ARGB32, // alpha-premultiplied; native byte order
C.int(i.Rect.Dx()),
C.int(i.Rect.Dy()))
if status := C.cairo_surface_status(surface); status != C.CAIRO_STATUS_SUCCESS {
panic(fmt.Errorf("cairo_create_image_surface() failed: %s\n",
C.GoString(C.cairo_status_to_string(status))))
}
// the flush and mark_dirty calls are required; see the cairo docs and https://git.gnome.org/browse/gtk+/tree/gdk/gdkcairo.c#n232 (thanks desrt in irc.gimp.net/#gtk+)
C.cairo_surface_flush(surface)
toARGB(i, uintptr(unsafe.Pointer(C.cairo_image_surface_get_data(surface))),
int(C.cairo_image_surface_get_stride(surface)))
C.cairo_surface_mark_dirty(surface)
C.cairo_set_source_surface(cr,
surface,
0, 0) // origin of the surface
// that just set the brush that cairo uses: we have to actually draw now
// (via https://developer.gnome.org/gtkmm-tutorial/stable/sec-draw-images.html.en)
C.cairo_rectangle(cr, x0, y0, x1, y1) // breaking the nrom here since we have the coordinates as a C double already
C.cairo_fill(cr)
C.cairo_surface_destroy(surface) // free surface
return C.FALSE // signals handled without stopping the event chain (thanks to desrt again)
}
func (self *Surface) ClipExtents() (left, top, right, bottom float64) {
C.cairo_clip_extents(self.context,
(*C.double)(&left), (*C.double)(&top),
(*C.double)(&right), (*C.double)(&bottom))
return left, top, right, bottom
}
// ClipExtents is a wrapper around cairo_clip_extents().
func (v *Context) ClipExtents() (x1, y1, x2, y2 float64) {
var cx1, cy1, cx2, cy2 C.double
C.cairo_clip_extents(v.native(), &cx1, &cy1, &cx2, &cy2)
return float64(cx1), float64(cy1), float64(cx2), float64(cy2)
}
//ClipExtents computes a bounding box in user coordinates covering the area
//inside the current clip.
//
//Originally cairo_clip_extents.
func (c *Context) ClipExtents() Rectangle {
var x0, y0, x1, y1 C.double
C.cairo_clip_extents(c.c, &x0, &y0, &x1, &y1)
return cRect(x0, y0, x1, y1)
}