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Prima::Widget::RubberBand(3) User Contributed Perl Documentation Prima::Widget::RubberBand(3)

NAME

Prima::Widget::RubberBand - dynamic rubberbands

DESCRIPTION

The motivation for this module was that I was tired of seeing corrupted screens on Windows 7 when dragging rubberbands in Prima code. Even though MS somewhere warned of not doing any specific hacks to circumvent the bug, I decided to give it a go anyway.

This module thus is a "Prima::Widget/rect_focus" with a safeguard. The only thing it can do is to draw a static rubberband - but also remember the last coordinates drawn, so cleaning and animation come for free.

The idea is that a rubberband object is meant to be a short-lived one: as soon as it gets instantiated it draws itself on the screen. When it is destroyed, the rubberband is erased too.

SYNOPSIS

        use strict;
        use Prima qw(Application Widget::RubberBand);
        sub xordraw
        {
                my ($self, @new_rect) = @_;
                $::application-> rubberband( @new_rect ?
                        ( rect => \@new_rect ) :
                        ( destroy => 1 )
                );
        }
        Prima::MainWindow-> new(
                onMouseDown => sub {
                        my ( $self, $btn, $mod, $x, $y) = @_;
                        $self-> {anchor} = [$self-> client_to_screen( $x, $y)];
                        xordraw( $self, @{$self-> {anchor}}, $self-> client_to_screen( $x, $y));
                        $self-> capture(1);
                },
                onMouseMove => sub {
                        my ( $self, $mod, $x, $y) = @_;
                        xordraw( $self, @{$self-> {anchor}}, $self-> client_to_screen( $x, $y)) if $self-> {anchor};
                },
                onMouseUp => sub {
                        my ( $self, $btn, $mod, $x, $y) = @_;
                        xordraw if delete $self-> {anchor};
                        $self-> capture(0);
                },
        );
        run Prima;

API

Creates a new RubberBand instance. See the description of its properties below.

Properties

Defines the rubberband breadth in pixels.
Sets the painting surface, and also the widget (it must be a widget) used for drawing.
Defines the clipping rectangle in inclusive-inclusive coordinates. If set to [-1,-1,-1,-1], means no clipping is needed.
Defines the band geometry in inclusive-inclusive coordinates. The band is drawn so that its body is always inside these coordinates, no matter what the breadth is.

Methods

Hides the band
Checks whether clipRect contains an actual clipping rectangle or it is empty.
Applies all properties
The same shortcuts as in "Prima::Widget", but read-only.
Shows the band

Prima::Widget interface

The module adds a single method to the "Prima::Widget" namespace, "rubberband" (see example of use in the synopsis).

Instantiates a "Prima::RubberBand" object with %profile, also sets "canvas" to $self ( unless "canvas" is set explicitly ).
Returns the existing "Prima::RubberBand" object
Destroys the existing "Prima::Widget::RubberBand" object

AUTHOR

Dmitry Karasik, <dmitry@karasik.eu.org>.

SEE ALSO

"rect_focus" in Prima::Widget, "grip.pl" in examples

Windows 7 Aero mode

Quote from <http://blogs.msdn.com/b/greg_schechter/archive/2006/05/02/588934.aspx> :

"One particularly dangerous practice is writing to the screen, either through the use of GetDC(NULL) and writing to that, or attempting to do XOR rubber-band lines, etc ... Since the UCE doesn't know about it, it may get cleared in the next frame refresh, or it may persist for a very long time, depending on what else needs to be updated on the screen. (We really don't allow direct writing to the primary anyhow, for that very reason... if you try to access the DirectDraw primary, for instance, the DWM will turn off until the accessing application exits)"

This quote seems to explain the effect of why the screen sometimes gets badly corrupted when using a normal xor rubberband. UCE ( Update Compatibility Evaluator ?? ) seems to be hacky enough to recognize some situations, but not all.

2024-08-20 perl v5.40.0