Win32::OLE freezing Tk

[Takamoto]

Hello monks

I have the following basic Tk application that uses Win32::OLE to copy a PPT files to another locaction (the task is not important here, it is just to illustrate my problem). The application works fine, but it freezes for a long time, even after the OLE operation has been concluded and the message window "Done!" is shown and closed.

Can this behaviour be solved? If not, how can I show my message "Done!" only after the GUI is reactive? The problem is that the user thinks s/he has control over the GUI as soon as the "Done!" message is shown.

Furthermore: shouldn't $ppt->{Visible} = 0; prevent the PowerPoint application to show up?

use strict;
use warnings;
use utf8;
use Tk;
use Try::Tiny;
use Win32::OLE;
use Win32::OLE::Const qw( Microsoft.PowerPoint );
use Win32::OLE::Enum;

my $mw = Tk::MainWindow->new(
    -width => 160,
    -height => 120,
);
$mw->packPropagate(0);
# Button erstellen:
my $but = $mw->Button(
    -text => "Save PPT", 
    -command => \&save_PPT,
);
$but->pack();
my $quit_btn = $mw->Button(
    -text => "Exit", 
    -command => \&quit_program,
);
$but->pack();
$quit_btn->pack();
$mw->MainLoop();


sub save_PPT {
    my $filename = "C:\\Users\\Taka\\Desktop\\original.pptx";
    my $ppt;
    try { $ppt = Win32::OLE->GetActiveObject('PowerPoint.Application')
+ }
    catch { die $_ }
    ;

    unless ( $ppt ) {
        $ppt = Win32::OLE->new(
            'PowerPoint.Application', sub { $_[0]->Quit }
        ) or return 'error';
    }

$ppt->{Visible} = 0;
my $presentation = $ppt->Presentations->Open($filename, 1);
my $slides = Win32::OLE::Enum->new( $presentation->Slides );

$presentation->SaveAs("SAVED_" . $filename);
$presentation->Close;
$mw->messageBox (-title => "message", -message=>"DONE!", -icon=> 'info
+');
} 

sub quit_program {
    exit(0);
}

Any suggestion would be very much appreciated.

[Corion]

Most likely, the delay is when shutting down Powerpoint as $ppt goes out of scope.

You can test this theory by explicitly clearing out $ppt yourself:

$presentation->SaveAs("SAVED_" . $filename);
$presentation->Close;
undef $ppt; # Clean up Powerpoint
$mw->messageBox (-title => "message", -message=>"DONE!", -icon=> 'info
+');

There is very little way around this, but if you plan to convert more than a single presentation in one go, it might make sense to declare $ppt as a global variable and keep it around:

our $ppt;
sub save_PPT {
# ...
$ppt ||= Win32::OLE->GetActiveObject('PowerPoint.Application');
# ... and also later:
$ppt ||= Win32::OLE->new(
            'PowerPoint.Application', sub { $_[0]->Quit }
        ) or return 'error';
# ---

[Takamoto]

Thank you, Corion. undef $ppt; seems to do the trick. I am not sure how this can let PowerPoint shut down without keeping the GUI occupied, but it works.

[marto]

If you are concerned about performance can't you just copy the file without opening the file in PowerPoint and using the 'save as' option?

[bliako]

Perhaps this (edit: undef $ppt;) just kills PP as opposed to shutdown/close?

[jcb]

The problem is that you are performing a long-running task on the GUI thread and not returning control to the Tk MainLoop often enough. This is a fundamental mismatch, since Tk is event-based and long-running callbacks will hang the GUI. I usually encounter this with network interaction when combining Tk and LWP in the same program; my usual solution is to fork and handle LWP operations in child processes, passing results back over a pair of pipes (one monitored by Tk in non-blocking mode and one in blocking mode for passing large binary results up using Storable) but this probably will not work well on Windows.

I suggest looking into the threads support in perl; you may need a few shared variables for passing state between the threads. I have no idea how to get the Tk event loop to handle thread completion.

[Anonymous Monk]

See Re: Parallel download Tk ( threads Thread::Queue LWP::UserAgent WWW::Mechanize) , Re: Perl Tk nonblocking (threads queue)