I've got it working now! As before I've removed most of the code from my program.
use Tk;
use Win32::API;
...
# Windows constants
my ($OnTop, $NoTop, $Top) = (-1, -2, 0);
my ($SWP_NOMOVE, $SWP_NOSIZE) = (2, 1);
# 'always on top' state
my $isOnTop = $NoTop;
...
# Create a Win32::API object for SetWindowPos
my $SetWindowPos = new Win32::API("user32", "SetWindowPos", [N,N,N,N,N
+,N,N], N);
# and one for FindWindow
my $FindWindow = new Win32::API("user32", "FindWindow", [P,P], N);
...
my $w = new MainWindow;
...
my $aotCBut = $w->Checkbutton(-text => "Always on top",
-onvalue => $OnTop,
-offvalue => $NoTop,
-variable => \$isOnTop,
-command => sub {
# get a handle to the toplevel window containing our Perl/Tk a
+pp
my $class = "TkTopLevel";
my $name = $w->title;
my $NULL = 0;
my $topHwnd = $FindWindow->Call($class, $name);
if ($topHwnd != $NULL) {
# change 'always on top' state
$SetWindowPos->Call($topHwnd, $isOnTop, 0, 0, 0, 0, $SWP_N
+OMOVE | $SWP_NOSIZE);
};
})
->pack(-side => "bottom", expand => "yes", -fill => "x");
...
# start the UI
MainLoop;
The Win32 FindWindow API call will return a handle to a window with the specified title and class. Perl/Tk creates windows of the class TkTopLevel. You must call this after the window has been mapped (i.e. after MainLoop), otherwise you won't get a valid window handle.
A useful reference when using Win32::API is here, it talks about Visual Basic but you can fairly easily convert it to Perl.
--
Kevin O'Rourke