CODEWITHSUNDEEP
windowswinapi
Adam
Adam

Reputation: 637

Pure win32 cross-process child windows

I need to create a transparent overlay window, that goes above another window. The other window is from another vendor. And when the user drags that window mine needs to follow.

WS-CHILD seems like a nice idea but it cannot be combined with WS-EX-LAYERED, which I really need (for transparency). But I still can set a parent without using WS-CHILD.

Parenting does give my winproc notifications (WM-WINDOWPOSCHANGING), but only after dragging is complete, on mouse-up. To give a nice feeling i need to get those notifications (or for example WM-MOVE) continuosly while dragging.

I guess my problem is similar to docking, but the fine docking solution seen fx at CodeProjet uses WS-CHILD. ( http://www.codeproject.com/KB/toolbars/dockwnd.aspx )

I guess I could use polling but that is not what I am looking for. Also I could use ::SetWindowsHook(). But that is my final resort. I am hoping I have missed something trivial and that somebody can point me in a good direction.

Thanx

Upvotes: 2

Views: 2298

Answers (4)

Jens Saathoff
Jens Saathoff

Reputation:

I use a LayeredWindow for that and set the other window as parent.

This is the code I used for that:

::SetWindowLong(GetHwnd(), GWL_EXSTYLE, GetWindowLong(GetHwnd(), GWL_EXSTYLE) |WS_EX_LAYERED);
::SetLayeredWindowAttributes(GetHwnd(), RGB(255,0,255), 255, LWA_COLORKEY | LWA_ALPHA);
::SetWindowLongPtr(GetHwnd(),GWLP_HWNDPARENT,(long)GetParentHWND());
::SetWindowPos(hndOtherWindow, hndOverlayWinow, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE |SWP_NOACTIVATE);

It works for my purposes. There's only one problem left: If my overlaying window loses the focus I want to set the focus, or activate the other window. Do you have an idea?

Upvotes: 1

Maurice Flanagan
Maurice Flanagan

Reputation: 5299

If you want to know when a window in another process is being moved or sized, you need to install a hook,catch the WM_MOVING and WM_SIZING messages and reflect those messages back to your controller process. Sorry it's not the answer you want! I don't blame you for wanting to avoid cross process hooks, its a bit of a pain...

Upvotes: 0

Canopus
Canopus

Reputation: 7457

How about WM_MOVING message? You may try intercepting this message and move your window accordingly.

Upvotes: 0

Phil Booth
Phil Booth

Reputation: 4907

I know it is not your preferred solution, but I think you need to use a global mouse hook. Pass WH_MOUSE_LL to SetWindowsHookEx() and do nothing in the default case of your low-level mouse proc. But when you get the WM_WINDOWPOSCHANGING notification, start tracking the mouse movements and making appropriate calls to MoveWindow() or whatever.

Upvotes: 4

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