set_content_update_callbackT_set_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback (Operator)

Name

set_content_update_callbackT_set_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback — Sets the callback for content updates in buffer window.

Signature

Description

set_content_update_callbackset_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback sets a callback CallbackFunctionCallbackFunctionCallbackFunctioncallbackFunctioncallback_function, which is called whenever the contents of the buffer window WindowHandleWindowHandleWindowHandlewindowHandlewindow_handle change. The parameter CallbackContextCallbackContextCallbackContextcallbackContextcallback_context is always passed to the callback.

The type of CallbackFunctionCallbackFunctionCallbackFunctioncallbackFunctioncallback_function is: Herror callback(void *context)

On Windows systems, the __stdcall calling convention is used: Herror __stdcall callback(void *context)

The callback function must not call a HALCON operator. Doing so is undefined behavior. It is advised to perform only computationally inexpensive tasks in the callback, e.g., setting a flag or triggering an asynchronous operation.

In combination with the operators send_mouse_down_eventsend_mouse_down_eventSendMouseDownEventSendMouseDownEventsend_mouse_down_event, send_mouse_up_eventsend_mouse_up_eventSendMouseUpEventSendMouseUpEventsend_mouse_up_event, and send_mouse_double_click_eventsend_mouse_double_click_eventSendMouseDoubleClickEventSendMouseDoubleClickEventsend_mouse_double_click_event, set_content_update_callbackset_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback can be used to create a buffer based control for a GUI Toolkit (such as Qt), where the control passes mouse events to the buffer, while the buffer notifies the control on changes by calling the function CallbackFunctionCallbackFunctionCallbackFunctioncallbackFunctioncallback_function. The control then can obtain the contents of the buffer with dump_window_imagedump_window_imageDumpWindowImageDumpWindowImagedump_window_image and display them.

Attention

set_content_update_callbackset_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback depends on the library libcanvas, which might not be available on embedded systems.

Execution Information

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Multithreading scope: global (may be called from any thread).
• Processed without parallelization.

Parameters

Result

If the window exists and is a buffer window, set_content_update_callbackset_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback returns 2 ( H_MSG_TRUE) .

See also

flush_bufferflush_bufferFlushBufferFlushBufferflush_buffer

Module

Foundation