attach_background_to_window — Attach a background image to a HALCON window.
attach_background_to_window(Image : : WindowHandle : )
This operator attaches the background image passed in Image to a HALCON window defined in WindowHandle. The input image is copied. Thus it can be freed safely.
The background image is instantly displayed in the HALCON window when calling attach_background_to_window. All HALCON objects that were previously displayed in the window will still be displayed when calling this operator. Thus the previous window content will not be overwritten.
The window contents are displayed in the following order: first the background image, then HALCON objects, and finally the drawing objects. Thus, the drawing object is displayed always on top. Note that the window will be redrawn for each user interaction within the window and each call of set_part. HALCON objects can be deleted from the window with clear_window.
The background image can be removed from the window with the operator detach_background_from_window.
Note that using any synchronous operator which actively probe the event queue, e.g., get_mbutton or read_char, will conflict with the interaction with the drawing objects. In case the state of the cursor has to be read, please refer to the documentation of your framework of choice for an appropriate, non-invasive alternative.
Furthermore, the event based functionality should not be used together with the former blocking operators draw_rectangle1, draw_rectangle2, draw_region, draw_xld or draw_circle. They conflict with the event based functionality, since they actively fetch all events sent to the HALCON window.
If the window exists and the specified parameters are correct attach_background_to_window returns 2 (H_MSG_TRUE). If necessary an exception is raised.