output: document hotspot coord space

include/wlr/interfaces/wlr_output.h

@@ -32,6 +32,7 @@ struct wlr_output_impl {
 	 * The hotspot indicates the offset that needs to be applied to the
 	 * top-left corner of the image to match the cursor position. In other
 	 * words, the image should be displayed at (x - hotspot_x, y - hotspot_y).
+	 * The hotspot is given in the texture's coordinate space.
 	 *
 	 * If update_texture is true, all parameters need to be taken into account.
 	 * If update_texture is false, only the hotspot is to be updated.