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Date of registration: Oct 5th 2017

Posts: 30


Thursday, October 5th 2017, 2:53pm

Window to Window comms - Parent to Parent

Dear all
I wondered if you could help me solve this puzzle. Scenario is as follows: there are two unrelated windows (i.e. both windows are parents to different children), defined in two different source files.
For example, I have a main window and a footer window, both visible. Then how do I communicate to the main window that the footer window wants to, for example, display something else on the main window?

I know I can use WM_SendMessageNoPara(hWinMain, WM_FOOTER_BUTTON_BACK); in the footer callback. However that relies on having the main window handle (hWinMain) declared as global. Is there a way to communicate between the two parents without using globals? What's the best way?


This post has been edited 1 times, last edit by "mjanas10" (Oct 5th 2017, 3:11pm)

SEGGER - Schoenen

Super Moderator

Date of registration: Aug 13th 2015

Posts: 496


Friday, October 6th 2017, 3:21pm


Yes, it is possible without global variables. You can simply react on WM_GET_ID in the callback of a window and write a unique ID into pMsg->Data.v. This way you can use WM_GetDialogItem() to get the window handle via the ID.

Attached is an example on how to do this.

As long you know the IDS you could also get the handle of a child window of another window, like:

C/C++ Source code

hItem = WM_GetDialogItem(WM_HBKWIN, ID_MAINWIN);
hItem = WM_GetDialogItem(hItem, ID_CHILD);
hItem = WM_GetDialogItem(hItem, ID_CHILD_OF_CHILD);
hItem = WM_GetDialogItem(hItem, ID_CHILD_OF_CHILD_OF_CHILD);

SEGGER - Schoenen has attached the following file: