| Tk::AbstractCanvas - Canvas with Abstract center, zoom, && rotate methods |
Tk::AbstractCanvas - Canvas with Abstract center, zoom, && rotate methods
This documentation refers to version 1.4.A7QFZHF of Tk::AbstractCanvas, which was released on Mon Jul 26 15:35:17:15 2010.
#!/usr/bin/perl -w
use strict;
use Tk;
use Tk::AbstractCanvas;
my $mwin = Tk::MainWindow->new();
my $acnv = $mwin->AbstractCanvas()->pack('-expand' => 1,
'-fill' => 'both');
#$acnv->invertY( 1); # uncomment for inverted y-axis
$acnv->controlNav(1); # advanced CtrlKey+MouseDrag Navigation
$acnv->rectToPoly(1);
#$acnv->ovalToPoly(1); # uncomment for oval to rot w/ canvas
my $rect = $acnv->createRectangle( 7, 8, 24, 23,
'-fill' => 'red');
my $oval = $acnv->createOval( 23, 24, 32, 27,
'-fill' => 'green');
my $line = $acnv->createLine( 0, 1, 31, 32,
'-fill' => 'blue',
'-arrow' => 'last');
my $labl = $mwin->Label('-text' => 'Hello AbstractCanvas! =)');
my $wind = $acnv->createWindow(15, 16, '-window' => $labl);
$acnv->CanvasBind('<Button-1>' => sub { $acnv->zoom(1.04); });
$acnv->CanvasBind('<Button-2>' => sub {
$acnv->rotate($rect, 5);
$acnv->rotate($wind, 5); # this rot should do nothing because
$acnv->rotate($oval, -5); # can't rotate about own center
$acnv->rotate($line, -5);
});
$acnv->CanvasBind('<Button-3>' => sub { $acnv->zoom(0.97); });
$acnv->viewAll();
MainLoop();
AbstractCanvas provides an alternative to a the Tk::Canvas manpage object which partially abstracts the coordinates of objects drawn onto itself. This allows the entire Canvas to be zoomed or rotated. Rotations modify the coordinates that the original object was placed at but zooming the whole canvas does not.
Tk::AbstractCanvas is derived from the excellent modules the Tk::WorldCanvas manpage by Joseph Skrovan <Joseph@Skrovan.Com> (which was itself based on a version by Rudy Albachten <Rudy@Albachten.Com>) && the Tk::RotCanvas manpage by Ala Qumsieh <AQumsieh@CPAN.Org>.
This module is a wrapper around the Canvas widget that maps the user's coordinate system to the now mostly hidden coordinate system of the Canvas widget. There is an option to make the abstract coordinates y-axis increase in the upward direction rather than the default downward.
AbstractCanvas is meant to be a useful alternative to a regular Canvas. Typically, you should call $acnv->viewAll() (or
$acnv->viewArea(@box)) before calling MainLoop().
Most of the AbstractCanvas methods are the same as regular Canvas methods except that they accept && return abstract coordinates instead of widget coordinates.
AbstractCanvas also adds a new rotate() method to allow rotation of canvas objects by arbitrary angles.
$acnv->CanvasBind('<i>' => sub {$acnv->zoom(1.25)});
$acnv->CanvasBind('<o>' => sub {$acnv->zoom(0.8 )});
# If you are using the 'Scrolled' constructor as in:
my $acnv = $mwin->Scrolled('AbstractCanvas', -scrollbars => 'nw',); # ...
# you want to bind the key-presses to the 'AbstractCanvas' Subwidget of Scrolled.
my $scrolled_canvas = $acnv->Subwidget('abstractcanvas'); # note the lowercase
$scrolled_canvas->CanvasBind('<i>' => sub {$scrolled_canvas->zoom(1.25)});
$scrolled_canvas->CanvasBind('<o>' => sub {$scrolled_canvas->zoom(0.8 )});
# If you don't like the scrollbars taking the focus when you
# <ctrl>-tab through the windows, you can:
$acnv->Subwidget('xscrollbar')->configure(-takefocus => 0);
$acnv->Subwidget('yscrollbar')->configure(-takefocus => 0);
$acnv->CanvasBind('<2>' => sub {
$acnv->CanvasFocus();
$acnv->center($acnv->eventLocation());
});
'-exact => 1' will cause the canvas to be scaled twice to get an accurate bounding box. This will be an expensive computation if the canvas contains a large number of objects.
If you do want to change the arrow key-bindings to pan in abstract coordinates using panAbstract you must disable the default arrow key-bindings. Example:
$mwin->bind('AbstractCanvas', '<Up>' => '');
$mwin->bind('AbstractCanvas', '<Down>' => '');
$mwin->bind('AbstractCanvas', '<Left>' => '');
$mwin->bind('AbstractCanvas', '<Right>' => '');
$acnv->CanvasBind( '<Up>' => sub {$acnv->panAbstract(0, 100)});
$acnv->CanvasBind( '<Down>' => sub {$acnv->panAbstract(0, -100)});
$acnv->CanvasBind( '<Left>' => sub {$acnv->panAbstract(-100, 0)});
$acnv->CanvasBind('<Right>' => sub {$acnv->panAbstract( 100, 0)});
This is not usually desired, as the percentage of the display that is shifted will be dependent on the current display magnification.
rotate()
method). The default of this value is 0. An optional parameter can be supplied to set the value.
rotate()
method). The default of this value is 0. An optional parameter can be supplied to set the value.
The band color is set with the AbstractCanvas option '-bandColor'. The default color is 'red'. Example specifying a region to delete:
$acnv->configure(-bandColor => 'purple');
$acnv->CanvasBind('<3>' => sub {$acnv->CanvasFocus;
$acnv->rubberBand(0)});
$acnv->CanvasBind('<B3-Motion>' => sub {$acnv->rubberBand(1)});
$acnv->CanvasBind('<ButtonRelease-3>' => sub {
my @box = $acnv->rubberBand(2);
my @ids = $acnv->find('enclosed', @box);
for my $id (@ids) {$acnv->delete($id)} });
# Note: '<B3-ButtonRelease>' will be called for any ButtonRelease! Use '<ButtonRelease-3>' instead.
# If you want the rubber band to look smooth during panning && zooming, add
# rubberBand(1) update calls to the appropriate key-bindings:
$acnv->CanvasBind( '<Up>' => sub { $acnv->rubberBand(1)});
$acnv->CanvasBind( '<Down>' => sub { $acnv->rubberBand(1)});
$acnv->CanvasBind( '<Left>' => sub { $acnv->rubberBand(1)});
$acnv->CanvasBind('<Right>' => sub { $acnv->rubberBand(1)});
$acnv->CanvasBind( '<i>' => sub {$acnv->zoom(1.25); $acnv->rubberBand(1)});
$acnv->CanvasBind( '<o>' => sub {$acnv->zoom(0.8 ); $acnv->rubberBand(1)});
This box avoids the overhead of bounding box calculations that can occur if you create your own rubberBand outside of AbstractCanvas.
Abstract coordinates are supplied && returned to AbstractCanvas methods instead of widget coordinates unless otherwise specified. (i.e., These methods take && return abstract coordinates: center, panAbstract, viewArea, find, coords, scale, move, bbox, rubberBand, eventLocation, pixelSize, && create*)
Neither setting of exact will produce exact results because the underlying canvas bbox method returns a slightly larger box to insure that everything is contained. It appears that a number close to '2' is added or subtracted. The '-exact => 1' zooms in to reduce this error.
If the underlying canvas bbox method returns a bounding box that is small (high error percentage) then '-exact => 1' is done automatically.
Tk::AbstractCanvas option '-changeView' can be used to specify a callback for a change of the view area. This is useful for updating a second AbstractCanvas which is displaying the view region of the first AbstractCanvas.
The callback subroutine will be passed the coordinates of the displayed box (x1, y1, x2, y2). These arguments are added after any extra arguments specifed by the user calling 'configure'. Example:
$acnv->configure(-changeView => [\&changeView, $acn2]);
# viewAll if 2nd AbstractCanvas widget is resized.
$acn2->CanvasBind('<Configure>' => sub {$acn2->viewAll});
{
my $viewBox;
sub changeView {
my($canvas2, @coords) = @_;
$canvas2->delete($viewBox) if $viewBox;
$viewBox = $canvas2->createRectangle(@coords, -outline => 'orange');
}
}
(1) The underlying Tk::Canvas has a '-confine' option which is set to '1' by default there. With '-confine => 1' the canvas will not allow the display to go outside of the scroll region. This causes some methods not to work accurately, for example, the 'center' method will not be able to center on coordinates near to the edge of the scroll region && 'zoom out' near the edge will zoom out && pan towards the center.
Tk::AbstractCanvas sets '-confine => 0' by default to avoid these problems. You can change it back with:
$acnv->configure(-confine => 1);
(2) '-scrollregion' is maintained by AbstractCanvas to include all objects on the canvas. '-scrollregion' will be adjusted automatically as objects are added, deleted, scaled, moved, etc.. (You can create a static scrollregion by adding a border rectangle to the canvas.)
(3) The bounding box of all objects is required to set the scroll region. Calculating this bounding box is expensive if the canvas has a large number of objects. So for performance reasons these operations will not immediately change the bounding box if they potentially shrink it:
coords delete move scale
Instead they will mark the bounding box as invalid, && it will be updated at the next zoom or pan operation. The only downside to this is that the scrollbars will be incorrect until the update.
If these operations increase the size of the box, changing the box is trivial && the update is immediate.
As it stands, the module can only rotate the following object types about their centers:
rectToPoly(1) is called)ovalToPoly(1) is called)All other object types (bitmap, image, arc, text, && window) can only be rotated about another point. A warning is issued if the user tries to rotate one of these object types about their center. Hopefully, more types will be able to center-rotate in the future.
To be able to rotate rectangles && ovals, this module is capable of intercepting any calls to create(), createRectangle(), && createOval() to change them to polygons. The user should not be alarmed if type() returns polygon when a rectangle or oval was created. Additionally, if you call coords() on a polygonized object, expect to have to manipulate all the additionally generated coordinates.
Revision history for Perl extension Tk::AbstractCanvas:
* added Ctrl rot callbacks (mocb, rlcb) && limited Motion && Release to just Ctrl + one MouseButton events
Please run:
`perl -MCPAN -e "install Tk::AbstractCanvas"`
or uncompress the package && run the standard:
`perl Makefile.PL; make; make test; make install`
Most source code should be Free! Code I have lawful authority over is && shall be! Copyright: (c) 2005-2010, Pip Stuart. Copyleft : This software is licensed under the GNU General Public License (version 3). Please consult the Free Software Foundation (HTTP://FSF.Org) for important information about your freedom.
Pip Stuart (Pip@CPAN.Org)
AbstractCanvas is derived from code by: Joseph Skrovan (Joseph@Skrovan.Com) Rudy Albachten (Rudy@Albachten.Com) Ala Qumsieh (AQumsieh@CPAN.Org)
| Tk::AbstractCanvas - Canvas with Abstract center, zoom, && rotate methods |