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

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 instantiatet 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.

       mode STRING = 'auto'
	   The module implements two techniques, standard classic 'xor'	(using
	   .rect_focus method) and a conservative method that uses widgets
	   instead of drawing on a canvas ('full').  The 'auto'	mode checks
	   the system and selects the appropriate mode.

	   Allowed modes: auto,	xor, full

       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
	   Cheks 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>.

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 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.	 It seems that depending on which widget
       received	mouse button just before initialting rubberband	drawing
       matters somehow.	Anyway,	the module tries to see	if we're under Windows
       7 aero, and if so, turns	the 'full' mode	on.

perl v5.24.1			  2017-05-15		  Prima::RubberBand(3)

NAME | DESCRIPTION | SYNOPSIS | API | Prima::Widget interface | AUTHOR | SEE ALSO

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