Re: Re: "Always on top" with Win32 and Tk

[elwarren]

A quick Google Search gives me this snippet of VB code. You could possibly do this with the assistance of a Win32::API guru?

http://home.newsfactory.net/~DataGhost/VBing/code/Windows%20Operations/alwaysontop.htm

HTH

[kevin_i_orourke]

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

[donato]

Hi, I'm kind of a newbie in perl but i noticed your code had some trouble running on my pc... the corrections made were in the creation of the api SetWindowPos object which now becomes Win32::API->new('user32', 'SetWindowPos', ['N','N','N','N','N','N','N'], 'N'); or you might as well code it [NNNNNNN], N, i think it will work (havent tested...) and the creation of the FindWindow obj also: Win32::API->new('user32', 'FindWindow', ['P','P'], 'N'); again [PP], N... that made it work on my pc... anyway, thanks for the code!

[kevin_i_orourke]

I tried the VB code, converted to Perl and using Win32::API. (the code isn't the tidiest in the world, I've missed out most of the program):

...
use Tk;
use Win32::API;

# Windows constants
my ($OnTop, $NoTop, $Top) = (-1, -2, 0);
my ($SWP_NOMOVE, $SWP_NOSIZE) = (2, 1);

...

# Create a Win32::API object for SetWindowPos
my $SetWindowPos = new Win32::API("user32", "SetWindowPos", [N,N,N,N,N
+,N,N], N);

...

my $w = new MainWindow;

...

# do the 'always on top' bit
my $hwnd = $w->frame; # frame returns a hex value as a string, e.g. "0
+x1234"
print "$hwnd\n";
$SetWindowPos->Call(hex($hwnd), $OnTop, 0, 0, 0, 0, $SWP_NOMOVE | $SWP
+_NOSIZE);

MainLoop;

Unfortunately $w->frame returns the Tk MainWindow, not the Win32 window containing it. As a result setting $w->frame 'always on top' doesn't have any effect.

Anyone know how to get an HWND for a window's parent out of Win32? Tk::Wm's $w->wrapper doesn't work either.

--
Kevin O'Rourke

[bart]

Anyone know how to get an HWND for a window's parent out of Win32?

Try the GetParent API call.

[kevin_i_orourke]

Thanks, I've had a look at the VB. I assume if I can extract an HWND from Tk I could use this. It's a bit nasty but looks like the only way.

From my reading of Tk::Wm documentation I should be able to get the HWND using $w->frame. Time for a play with Win32::API

--
Kevin O'Rourke