bug#20271: 24.4; Can't change cursor type in w32

[joaotavora@gmail.com (João Távora)]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: joaotavora@gmail.com (João Távora)
>> Cc: 20271@debbugs.gnu.org
>> Date: Wed, 08 Apr 2015 12:48:11 +0100
>> 
>> I found the culprit. It's the Windows Magnifier. If you
>> (accidentally ,as in my case) start if *before* you start Emacs, you
>> get the thin 1px wide black vertical bar. There's no real turning it
>> off, so a logout is at least necessary.
>
> Sounds like an entry in etc/PROBLEMS is in order.  Can you propose
> one, with a few details about turning the Magnifier on and off?

Sorry for the delay. Here's a proposed entry, though it does not say
much more than what I have said now. There is apparently no way to "turn
if off" in a way that it doesn't affect more Emacs sessions. All you can
do is close its little window. 

diff --git a/etc/PROBLEMS b/etc/PROBLEMS
index c701ec4..b2dee7d 100644
--- a/etc/PROBLEMS
+++ b/etc/PROBLEMS
@@ -2251,6 +2251,17 @@ If this does not work, please inform bug-gnu-emacs@gnu.org.  Then
 please call support for your X-server and see if you can get a fix.
 If you do, please send it to bug-gnu-emacs@gnu.org so we can list it here.
 
+** Cursor shape incompatibility with Windows Magnifier
+
+For Emacs sessions started _after_ the Windows Magnifier is turned on
+for the first time since the user logged in, the cursor is always a
+thin black blinking vertical caret and does not respond to the
+`cursor-shape' variable or the `set-cursor-color' command. Emacs
+session started _before_ the Magnifier are not affected.
+
+The known workaround is to log out of the user session and start Emacs
+before the Magnifier.
+
 * Build-time problems
 
 ** Configuration

>> > I can tell you how to track the initial cursor drawing using GDB, but
>> > if the problem only happens when Emacs is invoked from a desktop
>> > shortcut, this could be a bit tricky.
>> 
>> This is interesting to track other problems in general. Can I get a
>> "good" precompiled gdb.exe from somewhere in the internet, perhaps your
>> ezwinports repo?
>
> Yes, you can get a 32-bit Windows build of GDB 7.9, the latest
> released version, from ezwinports.

Thanks. I need it to debug the following symptom (completely unrelated
to this bug, maybe not Emacs's fault, should I open a new bug?):

* In a diff-mode buffer, press C-c C-c (`diff-goto-source`)

* _sometimes_, a 5-6 second unquitabble delay occurs.

* Regardless of whether the delay takes place or not, the above command
  always runs to the end *before* the delay occurs, as seen by its
  parting `message' call.

João