NAME
   Tk::AbstractCanvas - Canvas with Abstract center, zoom, && rotate
   methods

VERSION
   This documentation refers to version 1.4.A7QFZHF of Tk::AbstractCanvas,
   which was released on Mon Jul 26 15:35:17:15 2010.

SYNOPSIS
     #!/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();

DESCRIPTION
   AbstractCanvas provides an alternative to a Tk::Canvas 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 Tk::WorldCanvas
   by Joseph Skrovan <[email protected]> (which was itself based on a
   version by Rudy Albachten <[email protected]>) && Tk::RotCanvas by Ala
   Qumsieh <[email protected]>.

2DU
   - add Math::Geometry::Planar && others to polygonize, find_CM, test
   intersections, etc.
   - abstract rotations fully away like zoom
   - What else does AbstractCanvas need?

USAGE
DESCRIPTION
   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.

NEW METHODS
   *$acnv*->zoom(*zoom factor*)
     Zooms the display by the specified amount. Example:

       $acnv->CanvasBind('<i>' => sub {$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*->center(*x, y*)
     Centers the display around abstract coordinates x, y. Example:

       $acnv->CanvasBind('<2>' => sub {
         $acnv->CanvasFocus();
         $acnv->center($acnv->eventLocation());
       });

   *$acnv*->centerTags([-exact => {0 | 1}], *TagOrID, [TagOrID, ...]*)
     Centers the display around the center of the bounding box containing
     the specified TagOrIDs without changing the current magnification of
     the display.

     '-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.

   *$acnv*->eventLocation()
     Returns the abstract coordinates (x, y) of the last Xevent.

   *$acnv*->panAbstract(*dx, dy*)
     Pans the display by the specified abstract distances. panAbstract is
     not meant to replace the xview/yview panning methods. Most user
     interfaces will want the arrow keys tied to the xview/yview panning
     methods (the default bindings), which pan in widget coordinates.

     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.

   *$acnv*->invertY([new_value])
     Returns the state of whether the y-axis of the abstract coordinate
     system is inverted. The default of this value is 0. An optional
     parameter can be supplied to set the value.

   *$acnv*->rectToPoly([new_value])
     Returns the state of whether created rectangles should be
     auto-converted into polygons (so that they can be rotated about their
     center by the rotate() method). The default of this value is 0. An
     optional parameter can be supplied to set the value.

   *$acnv*->ovalToPoly([new_value])
     Returns the state of whether created ovals should be auto-converted
     into polygons (so that they can be rotated about their center by the
     rotate() method). The default of this value is 0. An optional
     parameter can be supplied to set the value.

   *$acnv*->controlNav([new_value])
     Returns the state of whether special Control+MouseButton drag
     navigation bindings are set. When true, Control-Button-1 mouse
     dragging rotates the whole AbstractCanvas, 2 pans, && 3 zooms. The
     default of this value is 0 but this option is very useful if you don't
     need Control-Button bindings for some other purpose. An optional
     parameter can be supplied to set the value.

   *$acnv*->controlNavBusy([new_value])
     Returns the state of whether special Control+MouseButton actions are
     busy handling events. An optional parameter can be supplied to set the
     value.

   *$acnv*->controlZoomScale([new_value])
     Returns the value of the special controlNav zoom scale (activated by
     Control-Button-3 dragging). The default value is -0.001. The zoom
     function takes the distance dragged in pixels across the positive x &&
     y axes scaled by the zoom factor to determine the zoom result. If you
     make the scale positive, it will invert the directions which zoom in
     && out. If you make the number larger (e.g., -0.003 or 0.003), zooming
     will become more twitchy. If you make the number smaller (e.g.,
     -0.0007 or 0.0007), zooming will happen more smoothly. An optional
     parameter can be supplied to set the value.

   *$acnv*->controlRotScale([new_value])
     Returns the value of the special controlNav rotation scale (activated
     by Control-Button-1 dragging). The default value is -0.3. The rotation
     function takes the distance dragged in pixels across the positive x &&
     y axes scaled by the rotation factor to determine the rotation result.
     If you make the scale positive, it will invert the directions which
     rotate positive or negative degrees. If you make the number larger
     (e.g., -0.7 or 0.7), rotations will become more twitchy. If you make
     the number smaller (e.g., -0.07 or 0.07), rotations will happen more
     smoothly. An optional parameter can be supplied to set the value.

   *$acnv*->controlRotMoCB([\&new_callback])
     Returns the value of the special controlNav rotation motion callback.
     This will let a user tidy up whatever coordinates are necessary to
     keep sub-groups of widgets in certain orientations together while the
     whole canvas is rotated. An optional parameter can be supplied to set
     the value.

   *$acnv*->controlRotRlCB([\&new_callback])
     Returns the value of the special controlNav rotation release callback.
     This will let a user tidy up whatever coordinates are necessary to
     keep sub-groups of widgets in certain orientations together after the
     whole canvas is done being rotated. An optional parameter can be
     supplied to set the value.

   *$acnv*->controlScale([new_value])
     Returns the scale value of the AbstractCanvas relative to the
     underlying canvas. An optional parameter can be supplied to set the
     value although the zoom function should almost always be employed
     instead of manipulating the scale directly through this accessor.

   *$acnv*->eventX([new_value])
     Returns the x-coordinate of where the last special Control+MouseButton
     event occurred. An optional parameter can be supplied to set the
     value.

   *$acnv*->eventY([new_value])
     Returns the y-coordinate of where the last special Control+MouseButton
     event occurred. An optional parameter can be supplied to set the
     value.

   *$acnv*->rotate(*TagOrID, angle* ?,*x, y*?)
     This method rotates the object identified by TagOrID by *angle*. The
     angle is specified in *degrees*. If an *x, y* coordinate is specified,
     then the object is rotated about that point. Otherwise, the object is
     rotated about its center point, if that can be determined.

   *$acnv*->pixelSize()
     Returns the width (in abstract coordinates) of a pixel (at the current
     magnification).

   *$acnv*->rubberBand(*{0|1|2}*)
     Creates a rubber banding box that allows the user to graphically
     select a region. rubberBand is called with a step parameter '0', '1',
     or '2'. '0' to start a new box, '1' to stretch the box, && '2' to
     finish the box. When called with '2', the specified box is returned
     (x1, y1, x2, y2)

     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*.

   *$acnv*->viewAll([-border => number])
     Displays at maximum possible zoom all objects centered in the
     *AbstractCanvas*. The switch '-border' specifies, as a percentage of
     the screen, the minimum amount of white space to be left on the edges
     of the display. Default '-border' is 0.02.

   *$acnv*->viewArea(x1, y1, x2, y2, [-border => number]))
     Displays at maximum possible zoom the specified region centered in the
     *AbstractCanvas*.

   *$acnv*->viewFit([-border => number], *TagOrID*, [*TagOrID*, ...])
     Adjusts the AbstractCanvas to display all of the specified tags. The
     '-border' switch specifies (as a percentage) how much extra
     surrounding space should be shown.

   *$acnv*->getView()
     Returns the rectangle of the current view (x1, y1, x2, y2)

   *$acnv*->widgetx(*x*)
   *$acnv*->widgety(*y*)
   *$acnv*->widgetxy(*x, y*)
     Convert abstract coordinates to widget coordinates.

   *$acnv*->abstractx(*x*)
   *$acnv*->abstracty(*y*)
   *$acnv*->abstractxy(*x, y*)
     Convert widget coordinates to abstract coordinates.

CHANGED METHODS
   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*)

   *$acnv*->bbox([-exact => {0 | 1}], *TagOrID*, [*TagOrID*, ...])
     '-exact => 1' is only needed if the TagOrID is not 'all'. It will
     cause the canvas to be scaled twice to get an accurate bounding box.
     This will be expensive computationally if the canvas contains a large
     number of objects.

     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.

   *$acnv*->scale(*'all', xOrigin, yOrigin, xScale, yScale*)
     Scale should not be used to 'zoom' the display in && out as it will
     change the abstract coordinates of the scaled objects. Methods zoom,
     viewArea, && viewAll should be used to change the scale of the display
     without affecting the dimensions of the objects.

VIEW AREA CHANGE CALLBACK
   *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');
       }
     }

SCROLL REGION NOTES
   (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.

ROTATION LIMITATIONS
   As it stands, the module can only rotate the following object types
   about their centers:

   * Lines
   * Polygons
   * Rectangles (if rectToPoly(1) is called)
   * Ovals (if 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.

ROTATION DETAILS
   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.

CHANGES
   Revision history for Perl extension Tk::AbstractCanvas:

   - 1.4.A7QFZHF Mon Jul 26 15:35:17:15 2010
     * updated license to GPLv3

   - 1.2.75L75Nr Mon May 21 07:05:23:53 2007
     * added ex/* examples && tidied everything up

     * added Ctrl rot callbacks (mocb, rlcb) && limited Motion && Release
     to just Ctrl + one MouseButton events

   - 1.0.56BHMOt Sat Jun 11 17:22:24:55 2005
     * original version

INSTALL
   Please run:

     `perl -MCPAN -e "install Tk::AbstractCanvas"`

   or uncompress the package && run the standard:

     `perl Makefile.PL; make; make test; make install`

LICENSE
   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.

AUTHORS
   Pip Stuart (*[email protected]*)

   AbstractCanvas is derived from code by: Joseph Skrovan
   (*[email protected]*) Rudy Albachten (*[email protected]*) Ala Qumsieh
   (*[email protected]*)

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