🚀 go-pugleaf

"Clayton Arends" <nospam_claytonarends@hotmail.com> wrote:

>For the program that I am creating I do not desire the clipboard to be 
>filled when the app exits.  My question is: what is the typical way that 
>programs handle this situation?  Should I ignore the message (return 
>non-zero)?  Should I empty the clipboard before the app closes or during the 
>WM_RENDERALLFORMATS message?
>
>I really would just like to know the standard way other people handle this.

I don't know what the standard method is, but I have noticed some
programs popping up a dialog on exit asking whether the user wants a
large amount of data left in the clipboard.

I now see why that message pops up.

Alan Bellingham
-- 
ACCU Conference 2006 - 19-22 April, Randolph Hotel, Oxford, UK

Yeah, the lightbulb went off for me too <g>

- Clayton 

Clayton Arends wrote:

>For the program that I am creating I do not desire the clipboard to be 
>filled when the app exits.  My question is: what is the typical way that 
>programs handle this situation?  Should I ignore the message (return 
>non-zero)?  Should I empty the clipboard before the app closes or during the 
>WM_RENDERALLFORMATS message?

This bit from the help seems to indicate that if you don't render
anything, then the clipboard will just forget agout you.

<Win32.hlp - Delayed Rendering>
Any clipboard formats that are not rendered in response to the
WM_RENDERALLFORMATS message cease to be available to other
applications and are no longer enumerated by the clipboard functions. 
</help>

So it would seem that doing nothing would be fine, but return 0,
processed.

ok, that makes sense.  Currently what I'm doing is something like this:

  // in message handler for WM_RENDERALLFORMATS
  ::OpenClipboard(NULL); // not sure if I should use handle or not
  ::EraseClipboard(); // help states that app should always erase

  if (!ComponentState.Contains(csDestroying))
  {
    // add all formats using ::SetClipboardData()
  }

  ::CloseClipboard();

  return 0; // or Msg->Result = 0 for VCL handlers

Unless there's something I'm completely missing I think this is what I will 
go with.  I can't test this right now (different projects to work on, etc).

- Clayton 

Clayton Arends wrote:

>Unless there's something I'm completely missing I think this is what I will 
>go with.

The help says don't open the clipboard when you get a
WM_RENDERALLFORMATS, just SetClipboardData.

<help>
An application should not open the clipboard before calling
SetClipboardData in response to the WM_RENDERFORMAT or
WM_RENDERALLFORMATS message. 
</help>


So the proper response would simply be...

case WM_RENDERFORMAT:
case WM_RENDERALLFORMATS:
	  if (!ComponentState.Contains(csDestroying))
	  {
	    // add all formats using ::SetClipboardData()
	  }
	  return 0; // or Msg->Result = 0 for VCL handlers

From the help for WM_RENDERALLFORMATS:

  When responding to a WM_RENDERALLFORMATS message, the clipboard
  owner must call the OpenClipboard and EmptyClipboard functions before
  calling SetClipboardData.

- Clayton 

Clayton Arends wrote:

>From the help for WM_RENDERALLFORMATS:
>
>  When responding to a WM_RENDERALLFORMATS message, the clipboard
>  owner must call the OpenClipboard and EmptyClipboard functions before
>  calling SetClipboardData.


Ok, I see the conflict.
The general overview as well as the doc for SetClipboardData say DON'T
Open/Close for Both the WM_RENDERx, whereas the docs for
WM_RENDERFORMAT say DON'T and the docs for WM_RENDERALLFORMATS say DO.

This may wrap. SetClipboardData
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/dataexchange/clipboard/clipboardreference/clipboardfunctions/setclipboarddata.asp

Again, may wrap: WM_RENDERALLFORMATS
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/dataexchange/clipboard/clipboardreference/clipboardmessages/wm_renderallformats.asp

Both from MSDN, so which is correct?

This example code from MSDN shows non-Open/Close usage:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/dataexchange/clipboard/usingtheclipboard.asp

In particular:

case WM_RENDERFORMAT: 
    RenderFormat((UINT) wParam); 
    break; 
 
case WM_RENDERALLFORMATS: 
    RenderFormat(uLabelFormat); 
    RenderFormat(CF_TEXT); 
    break;

No Open/Erase/Close in there at all.

Bob,

Nice research, and a handy page.  I don't know if we can say for sure which 
is the preferred method given that the document contradicts itself. 
However, with all of the other uses it is looking more and more like the 
help for WM_RENDERALLFORMATS has the error.  I will try to do both when I 
get around to testing again.  Though, I suspect it will have no affect 
either way and in that case the smaller/faster code wins!

- Clayton