CODEWITHSUNDEEP
c#windowswinapiclipboard
Steffan Donal
Steffan Donal

Reputation: 2354

How to tell if my application has been removed from the clipboard listener chain?

I am writing a small utility application to monitor my clipboard. This at current works quite well, but a friend has told me that it randomly will stop showing alerts upon clipboard change, and that restarting fixes it.
I couldn't reproduce, but eventually I ran into it myself - the application had stopped recieving WM_DRAWCLIPBOARD events.

How can I tell when my application has been removed from the listener chain?

Upvotes: 2

Views: 248

Answers (2)

RJP
RJP

Reputation: 11

If you are debugging an application that uses SetClipboardViewer and the application crashes or you stop the application in the debugger, or in some other way bypass the restoration of the clipboard chain, there is performance degradation in Windows, to the point that seemingly unrelated features of Windows, such as Alt-Tab, or restoring a minimized window, stop working. They come back if you restart Windows.

An application that inserts itself into the clipboard chain this way should be calling ChangeClipboardChain during Dispose of the main form, or at another appropriate time, to avoid this issue. Dispose isn't called if you stop the app in the debugger.

I have not tried AddClipboardFormatListener; first time I've heard of it; I'm going to try it to see if I can avoid the issue in my own app while I'm debugging.

Upvotes: 1

Raymond Chen
Raymond Chen

Reputation: 45172

This is one of the hazards of the clipboard listener chain: One bad application can damage the chain. Instead of using the SetClipboardViewer function, use AddClipboardFormatListener which does not have this problem.

Upvotes: 6

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