NAME

Prima::RubberBand - draw rubberbands

DESCRIPTION

The motivation for this module was that I was tired to see 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 comes for free.

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

SYNOPSIS

        use strict;
        use Prima qw(Application RubberBand);

        sub xordraw
        {
                my ($self, @new_rect) = @_;
                $::application-> rubberband( @new_rect ?
                        ( rect => \@new_rect ) :
                        ( destroy => 1 )
                );
        }

        Prima::MainWindow-> create(
                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

new %properties: Creates a new RubberBand instance. See description of properties below.

Properties

breadth INTEGER = 1: Defines rubberband breadth, in pixels.
canvas = $::application: Sets the painting surface, and also the widget (it must be a widget) used for drawing.
clipRect X1, Y1, X2, Y2: Defines the clipping rectangle, in inclusive-inclusive coordinates. If set to [-1,-1,-1,-1], means no clipping is done.
rect X1, Y1, X2, Y2: Defines the band geometry, in inclusive-inclusive coordinates. The band is drawn so that its body is always inside these coordinates, no matter what breadth is.

Methods

hide: Hides the band, if drawn
has_clip_rect: Checks whether clipRect contains an actual clippring rectange or it is empty.
set %profile: Applies all properties
left, right, top, bottom, width, height, origin, size: Same shortcuts as in "Prima::Widget", but read-only.
show: Show the band, if invisible

Prima::Widget interface

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

rubberband(%profile): Instantiates a "Prima::RubberBand" with %profile, also sets "canvas" to $self unless "canvas" is set explicitly.
rubberband(): Returns the existing "Prima::RubberBand" object
rubberband(destroy => 1): Destroys the existing "Prima::RubberBand" object

AUTHOR

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

"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 why 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.