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

VERSION
    This documentation refers to version 1.6 of Tk::AbstractCanvas, which
    was released on Sat Jul 8 14:13:18:12 -0500 2017.

SYNOPSIS
      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 rot8 with 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-3>' => sub { $acnv->zoom(0.97); });
      $acnv->CanvasBind('<Button-2>' => sub {
        $acnv->rotate($rect,  5);
        $acnv->rotate($wind,  5); # this rot8 should do nothing because
        $acnv->rotate($oval, -5); #   window can't go around own center
        $acnv->rotate($line, -5);                                });
      $acnv->viewAll();
      MainLoop();                 # ... then click the 3 mouse buttons

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 <Joseph@Skrovan.Com> (which was itself based on a
    version by Rudy Albachten <Rudy@Albachten.Com>) and Tk::RotCanvas by Ala
    Qumsieh <AQumsieh@CPAN.Org>.

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 and 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, and 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
      and 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 and 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
      and 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, and '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 and 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 and returned to AbstractCanvas methods
    instead of widget coordinates unless otherwise specified. (i.e., These
    methods take and return abstract coordinates: center, panAbstract,
    viewArea, find, coords, scale, move, bbox, rubberBand, eventLocation,
    pixelSize, and 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 and out as it will
      change the abstract coordinates of the scaled objects. Methods zoom,
      viewArea, and 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 and 'zoom
    out' near the edge will zoom out and 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, and 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 and 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, and 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 and ovals, this module is capable of
    intercepting any calls to create(), createRectangle(), and 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.

TODO
    - fix grid item placed in AC to do something appropriate from Josef Wolf
    8 years ago at HTTPS://RT.CPAN.Org/Ticket/Display.html?id=46655
    - add Math::Geometry::Planar and others to polygonize, find_CM, test
    intersections, etc.
    - maybe include Graph::Easy and some file serialization like DiagEMT XML
    but maybe more like a .Hrc format for the future
    - maybe make Diag objects which can scale fonts or state-box sizes
    separately from uniform AC zooms, have EMT side scroll panel, input or
    output arrow ordering, state-box flags region and menu frameworks,
    overview with rubberBand of main view region, jointed arrows, arcs,
    splines, and pal8s
    - abstract rotations fully away like zoom

CHANGES
    Revision history for Perl extension Tk::AbstractCanvas:

    - 1.6 H78MEDIC Sat Jul 8 14:13:18:12 -0500 2017
      * cleaned up examples and tested that grid works from
      <HTTPS://RT.CPAN.Org/Ticket/Display.html?id=46655>. (Thanks Josef!)

      * replaced POD ampersands with 'and' and turned double-spaces after
      periods to single

    - 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 and tidied everything up

      * added Ctrl rot callbacks (mocb, rlcb) and limited Motion and 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 and run the standard:

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

BUGS
    Please report any bugs or feature requests to bug-Tk-AbstractCanvas at
    RT.CPAN.Org, or through the web interface at
    <HTTPS://RT.CPAN.Org/NoAuth/ReportBug.html?Queue=Tk-AbstractCanvas>. I
    will be notified, and then you can be updated of progress on your bug as
    I address fixes.

SUPPORT
    You can find documentation for this module with the perldoc command.

      `perldoc Tk::AbstractCanvas`

    You can also look for information at:

        RT: CPAN's Request Tracker

      HTTPS://RT.CPAN.Org/NoAuth/Bugs.html?Dist=Tk-AbstractCanvas

        AnnoCPAN: Annotated CPAN documentation

      HTTP://AnnoCPAN.Org/dist/Tk-AbstractCanvas

        CPAN Ratings

      HTTPS://CPANRatings.Perl.Org/d/Tk-AbstractCanvas

        Search  CPAN

      HTTP://Search.CPAN.Org/dist/Tk-AbstractCanvas

LICENSE
    Most source code should be Free! Code I have lawful authority over is
    and shall be! Copyright: (c) 2005-2017, Pip Stuart. Copyleft : This
    software is licensed under the GNU General Public License (version 3 or
    later). Please consult <HTTPS://GNU.Org/licenses/gpl-3.0.txt> for
    important information about your freedom. This is Free Software: you are
    free to change and redistribute it. There is NO WARRANTY, to the extent
    permitted by law. See <HTTPS://FSF.Org> for further information.

AUTHORS
    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*)

