CODEWITHSUNDEEP
windowsdelphiwinapi
DNR
DNR

Reputation: 1659

How to stop event propagation despite WS_EX_NOACTIVATE?

I have a semi-transparent form (using AlphaBlend) that acts as an overlay. For the user to still be able to interact with the window below I have set WS_EX_NOACTIVATE on my form so all right and left clicks go through to the other window.

However I have a few clickable labels on my form. Clicking those and performing the appropriate action works fine since despite the WS_EX_NOACTIVATE flag the OnClick methods are called, but the click will (obviousely) also propagate to the other window, which I do not want in this case.

So, does anyone know how to "stop" the click being sent through to the window below in case I already handled it in my form ? Basically I would like being able to chose whether the click "belongs to me" and does not get propagated or whether the window below mine receives it.

Upvotes: 0

Views: 526

Answers (2)

David Heffernan
David Heffernan

Reputation: 612993

As Rob explained, WS_EX_NOACTIVATE is not relevant here. Most likely you used WS_EX_TRANSPARENT and that made your window transparent to mouse clicks.

To get finer grained control of mouse click transparency, handle the WM_NCHITTEST message in your top level window. Return HTTRANSPARENT for regions that you want to be "click through". Otherwise return, for example, HTCLIENT.

Upvotes: 4

Rob Kennedy
Rob Kennedy

Reputation: 163287

Wm_ex_NoActivate should be irrelevant here. That just controls whether your window receives the input focus. Indeed, if you start with a scratch program and do nothing but change the extended window style, you'll see that when you click within the bounds of that program's window, the clicks are handled in the usual way, except that the window is never activated; programs behind that window do not receive any click events.

Therefore, to make your label controls eat click events instead of forwarding them to the windows behind them, you need to find out what you did to make them start forwarding those messages and simply stop doing that, whatever that is.

Upvotes: 1

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