Operator Reference

HALCON Operator Reference / Graphics / Object
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set_content_update_callbackT_set_content_update_callbackSetContentUpdateCallbackSetContentUpdateCallbackset_content_update_callback (Operator)

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

Signature

set_content_update_callback( : : WindowHandle, CallbackFunction, CallbackContext : )

Herror T_set_content_update_callback(const Htuple WindowHandle, const Htuple CallbackFunction, const Htuple CallbackContext)

void SetContentUpdateCallback(const HTuple& WindowHandle, const HTuple& CallbackFunction, const HTuple& CallbackContext)

void HWindow::SetContentUpdateCallback(void* CallbackFunction, const HTuple& CallbackContext) const

void HWindow::SetContentUpdateCallback(void* CallbackFunction, void* CallbackContext) const

static void HOperatorSet.SetContentUpdateCallback(HTuple windowHandle, HTuple callbackFunction, HTuple callbackContext)

void HWindow.SetContentUpdateCallback(IntPtr callbackFunction, HTuple callbackContext)

void HWindow.SetContentUpdateCallback(IntPtr callbackFunction, IntPtr callbackContext)

def set_content_update_callback(window_handle: HHandle, callback_function: int, callback_context: Union[int, HHandle]) -> None

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

WindowHandleWindowHandleWindowHandlewindowHandlewindow_handle (input_control)  window → HWindow, HTupleHHandleHTupleHtuple (handle) (IntPtr) (HHandle) (handle)

Window handle.

CallbackFunctionCallbackFunctionCallbackFunctioncallbackFunctioncallback_function (input_control)  pointer → HTupleintHTupleHtuple (integer) (IntPtr) (Hlong) (Hlong)

Callback for content updates.

CallbackContextCallbackContextCallbackContextcallbackContextcallback_context (input_control)  pointer → HTupleUnion[int, HHandle]HTupleHtuple (integer / handle) (IntPtr / IntPtr) (Hlong / HHandle) (Hlong / handle)

Parameter to CallbackFunction.

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

ClassesClasses | | Operators