Window.createSimilarImageSurface

Create a new image surface that is efficient to draw on the given window.

Initially the surface contents are all 0 (transparent if contents have transparency, black otherwise.)

The width and height of the new surface are not affected by the scaling factor of the window, or by the scale argument; they are the size of the surface in device pixels. If you wish to create an image surface capable of holding the contents of window you can use:

int scale = gdk_window_get_scale_factor (window);
int width = gdk_window_get_width (window) * scale;
int height = gdk_window_get_height (window) * scale;

// format is set elsewhere
cairo_surface_t *surface =
  gdk_window_create_similar_image_surface (window,
                                           format,
                                           width, height,
                                           scale);

Note that unlike cairo.surface.Surface.createSimilarImage, the new surface's device scale is set to scale, or to the scale factor of window if scale is 0.