"Paste" from clipboard can failed (XWin bug)

"Paste" from clipboard can failed (XWin bug)

[rolandc]

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Hi,

>From X application, I select some text. I switch on Windows
application and I try to paste the text.
I do "Ctrl-V" => nothing happens
I do a second "Ctrl-V" => the text is pasted

This problem depends on the X application

When a "paste" occurs, XWin receives a WM_RENDERFORMAT message :
(cf. winClipboardWindowProc())

step 1/ XWin try to get the selection in COMPOUND_TEXT format
    (cf. winProcessXEventsTimeout() calls XConvertSelection("COMPOUND_TEXT "))

step 2/ If the owner of the selection (the X app) can't handle
COMPOUND_TEXT format, XWin try to get the selection in UTF8_STRING
format
    (cf. winClipboardFlushXEvents(), on receive an SelectionNotify
event with "event.xselection.property == None", XWin calls
XConvertSelection("UTF8_STRING"))

step 3/ If the owner of the selection (the X app) can't handle
UTF8_STRING format, XWin try to get the selection in XA_STRING format
    (cf. winClipboardFlushXEvents(), on receive an SelectionNotify
event with "event.xselection.property == None", XWin calls
XConvertSelection("XA_STRING"))

But there is a bug in XWin :
XWin calls winProcessXEventsTimeout() only twice. If the X app handles
only handles XA_STRING format, the "step 3" is never invoked !
As the result, XWin can't get "paste data" and log the message:
    "winClipboardWindowProc - timed out waiting for WIN_XEVENTS_NOTIFY"


XWin.log with my comment:
...
(receive WM_RENDER_FORMAT message)
winClipboardWindowProc - WM_RENDER*FORMAT - Hello.
(call XConvertSelection("COMPOUND_TEXT "))
(first call winProcessXEventsTimeout())
winClipboardFlushXEvents - SelectionNotify
winClipboardFlushXEvents - SelectionNotify - ATOM: PRIMARY
(receive event.xselection.target == atomCompoundText aka COMPOUND_TEXT)
(the X app can't handle COMPOUND_TEXT format)
winClipboardFlushXEvents - SelectionNotify - Requesting conversion of
CompoundText target.
(call XConvertSelection("UTF8_STRING") and return)
(second call winProcessXEventsTimeout())
winClipboardFlushXEvents - SelectionNotify
winClipboardFlushXEvents - SelectionNotify - ATOM: PRIMARY
(receive event.xselection.target == atomUTF8String aka UTF8_STRING)
(the X app can't handle UTF8_STRING format)
winClipboardFlushXEvents - SelectionNotify - Requesting conversion of
UTF8 target.
(call XConvertSelection("XA_STRING") and return)
(XWin can't get paste data, also it logs an error :)
(and reset the clipboard => SetClipboardData (CF_UNICODETEXT,
NULL);SetClipboardData (CF_TEXT, NULL);)
winClipboardWindowProc - timed out waiting for WIN_XEVENTS_NOTIFY
...

Solution 1 :
Call a third time the function winProcessXEventsTimeout()
(see paste_bug_solution1.patch file attached)
but this is not a very elegant solution ...

Solution 2 :
call winProcessXEventsTimeout() only one time
winProcessXEventsTimeout() must process all notification until
* time out expired
* getting the paste data
* error occurred
(see paste_bug_solution2.patch file attached)

note: the actual timeout is set to 1 second.

Greetings,

[-- Attachment #2: paste_bug_solution1.patch --]
[-- Type: application/octet-stream, Size: 709 bytes --]

diff --git a/hw/xwin/winclipboardwndproc.c b/hw/xwin/winclipboardwndproc.c
old mode 100644
new mode 100755
index 9394b04..204eacc
--- a/hw/xwin/winclipboardwndproc.c
+++ b/hw/xwin/winclipboardwndproc.c
@@ -521,6 +521,19 @@ winClipboardWindowProc (HWND hwnd, UINT message,
 						pDisplay,
 						fConvertToUnicode,
 						WIN_POLL_TIMEOUT);
+		if (WIN_XEVENTS_CONVERT == iReturn)
+		{
+			/*
+			* The selection was offered for conversion first, so we have
+			* to process a second SelectionNotify event to get the actual
+			* data in the selection.
+			*/
+			iReturn = winProcessXEventsTimeout (hwnd,
+						iWindow,
+						pDisplay,
+						fConvertToUnicode,
+						WIN_POLL_TIMEOUT);
+		}
 	  }
 	
 	/*

[-- Attachment #3: paste_bug_solution2.patch --]
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diff --git a/hw/xwin/winclipboardwndproc.c b/hw/xwin/winclipboardwndproc.c
old mode 100644
new mode 100755
index 9394b04..18287b7
--- a/hw/xwin/winclipboardwndproc.c
+++ b/hw/xwin/winclipboardwndproc.c
@@ -42,7 +42,6 @@
  * Constants
  */
 
-#define WIN_CLIPBOARD_PROP	"cyg_clipboard_prop"
 #define WIN_POLL_TIMEOUT	1
 
 
@@ -126,10 +125,9 @@ winProcessXEventsTimeout (HWND hwnd, int iWindow, Display *pDisplay,
 					      iWindow,
 					      pDisplay,
 					      fUseUnicode);
-	  if (WIN_XEVENTS_NOTIFY == iReturn
-	      || WIN_XEVENTS_CONVERT == iReturn)
+	  if (WIN_XEVENTS_NOTIFY == iReturn)
 	    {
-	      /* Bail out if convert or notify processed */
+	      /* Bail out if notify processed */
 	      return iReturn;
 	    }
 	}
@@ -509,22 +507,9 @@ winClipboardWindowProc (HWND hwnd, UINT message,
 					    pDisplay,
 					    fConvertToUnicode,
 					    WIN_POLL_TIMEOUT);
-	if (WIN_XEVENTS_CONVERT == iReturn)
-	  {
-	    /*
-	     * The selection was offered for conversion first, so we have
-	     * to process a second SelectionNotify event to get the actual
-	     * data in the selection.
-	     */
-	    iReturn = winProcessXEventsTimeout (hwnd,
-						iWindow,
-						pDisplay,
-						fConvertToUnicode,
-						WIN_POLL_TIMEOUT);
-	  }
-	
+
 	/*
-	 * The last of the up-to two calls to winProcessXEventsTimeout
+	 * The last call to winProcessXEventsTimeout
 	 * from above had better have seen a notify event, or else we
 	 * are dealing with a buggy or old X11 app.  In these cases we
 	 * have to paste some fake data to the Win32 clipboard to

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Re: "Paste" from clipboard can failed (XWin bug)

[Jon TURNEY]

On 30/09/2010 15:28, rolandc wrote:
>  From X application, I select some text. I switch on Windows
> application and I try to paste the text.
> I do "Ctrl-V" =>  nothing happens
> I do a second "Ctrl-V" =>  the text is pasted
>
> This problem depends on the X application

For testing purposes, do you have an example of an application which only 
offers XA_STRING?

> When a "paste" occurs, XWin receives a WM_RENDERFORMAT message :
> (cf. winClipboardWindowProc())
>
> step 1/ XWin try to get the selection in COMPOUND_TEXT format
>      (cf. winProcessXEventsTimeout() calls XConvertSelection("COMPOUND_TEXT "))
>
> step 2/ If the owner of the selection (the X app) can't handle
> COMPOUND_TEXT format, XWin try to get the selection in UTF8_STRING
> format
>      (cf. winClipboardFlushXEvents(), on receive an SelectionNotify
> event with "event.xselection.property == None", XWin calls
> XConvertSelection("UTF8_STRING"))
>
> step 3/ If the owner of the selection (the X app) can't handle
> UTF8_STRING format, XWin try to get the selection in XA_STRING format
>      (cf. winClipboardFlushXEvents(), on receive an SelectionNotify
> event with "event.xselection.property == None", XWin calls
> XConvertSelection("XA_STRING"))
>
> But there is a bug in XWin :
> XWin calls winProcessXEventsTimeout() only twice. If the X app handles
> only handles XA_STRING format, the "step 3" is never invoked !
> As the result, XWin can't get "paste data" and log the message:
>      "winClipboardWindowProc - timed out waiting for WIN_XEVENTS_NOTIFY"
>

Thanks very much for investigating this problem.

> Solution 1 :
> Call a third time the function winProcessXEventsTimeout()
> (see paste_bug_solution1.patch file attached)
> but this is not a very elegant solution ...
>
> Solution 2 :
> call winProcessXEventsTimeout() only one time
> winProcessXEventsTimeout() must process all notification until
> * time out expired
> * getting the paste data
> * error occurred
> (see paste_bug_solution2.patch file attached)
>
> note: the actual timeout is set to 1 second.

Thanks very much for the patch.  I agree that (2) is the more elegant solution.

I am actually a bit concerned about the size of the timeout, it's conceivable 
a remote X application could take longer than that to respond.

However, since we are trying to do this conversion synchronously in the 
clipboard thread's message pump, I'm not sure we want to block longer.


-- 
Jon TURNEY
Volunteer Cygwin/X X Server maintainer

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Re: "Paste" from clipboard can failed (XWin bug)

[rolandc]

2010/10/23 Jon TURNEY wrote:
>
> For testing purposes, do you have an example of an application which only
> offers XA_STRING?

I discover this problem with nxproxy.exe (from www.nomachine.com)

[...]
>> note: the actual timeout is set to 1 second.
>
> I am actually a bit concerned about the size of the timeout, it's
> conceivable a remote X application could take longer than that to respond.
>
> However, since we are trying to do this conversion synchronously in the
> clipboard thread's message pump, I'm not sure we want to block longer.
Yes, I agree with you

Regards,

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Re: "Paste" from clipboard can failed (XWin bug)

[Enoksrd]

Hi,

I was having trouble with pasting from Windows 7 to Cygwin/X and was getting

  winClipboardWindowProc - timed out waiting for WIN_XEVENTS_NOTIFY

in the log.  The solution was to disable focus-follows-mouse:

  Control Panel -> Ease of Access -> Change How Your Mouse Works

and uncheck "Activate a window by hovering over it with the mouse".

(I'm replying to this thread since it came up near the top of my search for 
that log error.)

-enoksrd


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