Making a childwindow transparent or "combining WS_EX_LAYERED with WS_CHILD"

[Marc Giesmann]

Hi!

Little problem: I've got a Childwindow, which is on top of other childwindows. I have to make the topmost childwindow a little bit transparent.

But MSDN says (and is incredibly right)

Note that WS_EX_LAYERED cannot be used for child windows.

Is there a workaround for layered childwindows?

Best regards,
Marc Giesmann

[Michael Mattias]

Maybe you can gin up a demo which would show the effect you wish to achieve; from that, someone may have an idea for you. You can show the effect with a "non-child" window and ask if anyone knows how to do it with a "child" window.

"A little bit transparent" is just a tad to ephemeral for me to visualize.

But just off the top of my head, why not just handle WM_PAINT and/or WM_ERASEBKGND yourself? (Warning: drawing is not my strong suit).

Or, maybe there is something in either GDI or GDIPlus which can help you create the desired effect?

Or, don't make the window a child window; make it no parent, with style WS_EX_TOOLWINDOW to eliminate the task bar entry; and then do "something" with that when painted.




MCM

[Chris Boss]

Child windows can not use the layered window feature of XP or Vista, as far as I know.

A lot depends upon what is on the child window.

If the child window simply needs to let the dialog area show through, while not any of the controls on it., thats relatively easy. You create a region which matchs only the area you want to be visible and then set the window to use that region. A region allows you to have a non-rectangular window of any shape desired.

If you need the backgeound windows to bleed through partially (alphablending the child window to its background windows) I don't think you will be able to do it.

Now you could make the child window a top level window instead (no longer a child) and also topmost. This will keep it above the others and you can using layering.

[Marc Giesmann]

First, thanks to all. After some more research I just made my RECT Window a WS_POPUP window, and clipped with

LOCAL tWindowRect AS RECT
GetWindowRect(hWorkspace, tWindowRect)
ClipCursor(tWindowRect)

the mousecursor in the window. Thats quite the same effect than a childwindow has. Okay, it steals for the time of sizing/moving the focus from my mainwindow (even If I call "DIALOG SHOW STATE hWndSELECTRECT, %SW_SHOWNA" before showing it), but thats okay.

To have an example for what I was trying to immitate, just use WinXP on standard configuration, and highlight some more icons by using the rectangle-feature in the windows explorer. Click on an empty area and drag the mouse over some icons.

There should be a blue, but transparent rectangle.

Thanks again, and have a nice weekend
Marc Giesmann

[Cliff Nichols]

Sounds something more up the line of something Patrice may know about??? (but who knows?)

[Marc Giesmann]

Cliff,
just handled everything as I wished it to be

The only thing I've had to add was

DIALOG SHOW STATE hWndSELECTRECT, %SW_HIDE
DIALOG SHOW MODELESS hWndSELECTRECT
DIALOG SHOW STATE hWndSELECTRECT, %SW_SHOWNA

and now my choosing-rect isn't stealing my focus anymore, works like a charm and lookspretty nice- even on "normal" machine (P4 HT). Some flickers to remove yet, but that won't bother me too much.

Thanks again, best regards,
Marc Giesmann

P.S.:
If anyone still has a workaround for the childwindow with transluency issue, please do it. I still think, that a solution like that would be much more comfortable for me.

[Patrice Terrier]

You must go to plain SDK mode and perform the drawing yourself, using full 32-bit drawing mode.

http://www.jose.it-berater.org/smfforum/index.php?topic=3680.0

And the secret is to work in composited mode:




...