Displaying changing images in Wx:: produces flicker

[isync]

Hello Monks,

I've got a small problem related to WxPerl: I am constructing a GUI that displays an image in a corner, on top of a WxPanel. Based on actions somewhere else in the app, the app switches the displayed image. And as it seems over the great variety in approaches to display an image, I haven't got it quite right.

$this->{thumb_panel} = Wx::Panel->new($this->{parent}, -1, wxDefaultPo
+sition, [320, 240], wxSUNKEN_BORDER);
$this->{thumb_sb} = Wx::StaticBitmap->new($this->{thumb_panel}, -1, Wx
+::Bitmap->new("somethumb.jpg", wxBITMAP_TYPE_ANY));

Now, when I exchange the displayed image with

my $handler = Wx::JPEGHandler->new();
my $image = Wx::Image->new();
my $bmp;
$handler->LoadFile( $image, $file );
$image->Rescale(320,240);
$bmp = Wx::Bitmap->new($image);
if( $bmp->Ok() ) {
    $this->{thumb_sb} = Wx::StaticBitmap->new($this->{thumb_panel}, -1
+, $bmp);
}

I experience flickering on the exchange. The image disappears for a second, or I can see "the switch taking place" or it starts out as a smaller square and zooms in on the 320x240 size (on windows) or (on Linux) first a formerly displayed image is shown, then replaced by the current one... something like that.

The parent window, a notebook, has wxCLIP_CHILDREN set - no effect. So would anyone please look at the above code and tell me if I am doing something completely wrong here. Or tell me that it is likely that the problem lies elsewhere in my code.

(and yes, I do need the resize on the exchange, as some displayed images might not be of 320x240 size, same with the check, as images might be damaged...)

[zentara]

I can see "the switch taking place" or it starts out as a smaller square and zooms in on the 320x240 size

Thats no bug!! It's a cool graphics effect you get for free. :-)

[isync]

Right... ;-)

[Anonymous Monk]

Its called a StaticBitmap... you really should provide some testable code.

[isync]

Although your hint with *Static*Bitmap could have been a bit more verbose, it actually pointed me into the right direction.

The proper way of displaying images on a panel, that you intend to change, is by using a Wx::PaintDC class, right?

What a bit of thinking about code can do...

my $dc = Wx::PaintDC->new($this->{thumb_panel});
my $bmp = Wx::Bitmap->new(Wx::Image->new("thumb.jpg", wxBITMAP_TYPE_AN
+Y)->Scale(320,240));
$dc->DrawBitmap($bmp, 0, 0, 1);


Although I am still experiencing some flicker (on Linux, Win32 todo) the underlying routine is much cleaner now. Any further notes?

[Anonymous Monk]

Although your hint with *Static*Bitmap could have been a bit more verbose, it actually pointed me into the right direction.
It was a shot in the dark. Without code to test, you're relying a wxWidgets expert, one who has seen it all (and has ESP), will stop by perlmonks. Those guys hang out over here :)

Anyway, I can't make this flicker (needs somethumb.jpg, somethumb2.jpg in cwd).

#!/usr/bin/perl --

use warnings;
use strict;
use Wx 0.86 qw(:everything);

my $app = Wx::SimpleApp->new;
my $f = Wx::Frame->new( undef, -1, "Testing Popup", [ -1, -1 ], [ 555,
+ 555 ] );

Wx::InitAllImageHandlers();

my $p =
  Wx::Panel->new( $f, -1, wxDefaultPosition, [ 320, 240 ], wxSUNKEN_BO
+RDER );

$p->{b} = my $b =
  Wx::Button->new( $p, -1, "GO", wxDefaultPosition, [ 50, 20 ], 0 );

# identify somethumb.jpg
# somethumb.jpg JPEG 105x78 105x78+0+0 8-bit DirectClass 4.24kb 0.000u
+ 0:01
# identify somethumb2.jpg
# somethumb2.jpg JPEG 105x78 105x78+0+0 8-bit DirectClass 4.1kb
$p->{im1} = Wx::Image->new( 'somethumb.jpg',  wxBITMAP_TYPE_ANY, -1 );
$p->{im2} = Wx::Image->new( 'somethumb2.jpg', wxBITMAP_TYPE_ANY, -1 );
$p->{imc} = 'im1';
$p->{sbmp} = my $sbmp =
  Wx::StaticBitmap->new( $p, -1, Wx::Bitmap->new( $p->{im1} ) );

$p->{sbz} = my $sbz =
  Wx::StaticBoxSizer->new( Wx::StaticBox->new( $p, -1, 'Wx::StaticBoxS
+izer' ),
    wxVERTICAL );
$sbz->Add( $b,    0, wxALIGN_RIGHT | wxALL, 5 );
$sbz->Add( $sbmp, 0, wxALIGN_RIGHT | wxALL, 5 );

$p->SetAutoLayout(1);
$p->SetSizer($sbz);
$p->Layout();

$sbz->Fit($f);
$sbz->SetSizeHints($f);

$f->CenterOnScreen;
$f->Show(1);

use Wx::Event 'EVT_BUTTON';
EVT_BUTTON(
    $p, -1,
    sub {
        my ( $p, $e ) = @_;
        if ( $p->{imc} eq 'im1' ) {
            $p->{imc} = 'im2';
        }
        else {
            $p->{imc} = 'im1';
        }
        my $image = $p->{ $p->{imc} };
        $image->Rescale( 320, 240 );
        $image = Wx::Bitmap->new($image);
        if ( $image->Ok() ) {
            $p->{sbmp}->Destroy; ##
            $p->{sbmp} = Wx::StaticBitmap->new( $p, -1, $image );
            $p->{sbz}->Add( $p->{sbmp}, 0, wxALIGN_RIGHT | wxALL, 0 );
            $p->Layout();
            $p->Refresh();
        }
    }
);

$app->SetTopWindow($f);
$app->MainLoop();

__END__

[Anonymous Monk]

maybe do a ->Refresh();