=for comment based on iup-3.5 - http://www.tecgraf.puc-rio.br/iup/en/elem/iuptree.html

=head1 NAME

IUP::Tree - [GUI element] tree containing nodes of branches or leaves with associated text/image

=head1 DESCRIPTION 

Creates a tree containing nodes of branches or leaves. Both branches
and leaves can have an associated text and image.

The branches can be expanded or collapsed. When a branch is expanded,
its immediate children are visible, and when it is collapsed they are
hidden.

The leaves can generate an "executed" or "renamed" actions, branches
can only generate a "renamed" action.

The focus node is the node with the focus rectangle, marked nodes have
their background inverted.

=begin HTML

<p>
  <table border="1">
    <col style="background-color: rgb(239, 235, 231);">
    <col style="background-color: rgb(173, 177, 194);">
    <col style="background-color: rgb(212, 208, 200);">
    <col style="background-color: rgb(236, 233, 216);">
    <tbody align="center">
      <tr>
        <th>GTK</th>
        <th>Motif</th>
        <th>Windows</th>
      </tr>
      <tr>
        <td><img src="http://kmx.github.io/perl-iup/img-3.9/elem/iuptree_gtk.png"></td>
        <td><img src="http://kmx.github.io/perl-iup/img-3.9/elem/iuptree_mot.png"></td>
        <td><img src="http://kmx.github.io/perl-iup/img-3.9/elem/iuptree_win.png"></td>
      </tr>
    </tbody>
  </table>
</p>

=end HTML

=head1 USAGE

=head2 CREATION - new() method

 $tree = IUP::Tree->new( TITLE=>'Root node name' );

B<Returns:> the identifier of the created element, or C<undef> if an error occurs.

NOTE: You can pass to C<new()> other C<ATTRIBUTE=E<gt>'value'> or C<CALLBACKNAME=E<gt>\&func> pairs relevant
to this element - see L<IUP::Manual::02_Elements|IUP::Manual::02_Elements/"new()">.

=head2 Tree - Hierarchy

Branches can contain other branches or leaves. When ADDROOT=Yes the
tree has initially one branch, the B<root>. The first node always has
id=0 and depth=0. The tree nodes have a sequential identification
number (id), starting by the first, with id=0, and increases for each
node independent from the node depth. The following picture illustrates
the numbering of the nodes in a tree.

B<Tree nodes and Ids:>

=begin HTML

<p><img src="http://kmx.github.io/perl-iup/spec/iuptree1.png"></p>

=end HTML

Since you have to add each node the creation of this tree can be done
in several ways because the action attributes ADD* and INSERT* use an
existent node to position the new node. The following pseudo code
initializes the tree from top to bottom sequencially:

 TITLE0 = "Figures"
   ADDLEAF0 = "Other"    // Use the previous node as reference
   ADDBRANCH1 = "triangle"
     ADDLEAF2 = "equilateral"
     ADDLEAF3 = "isoceles"
     ADDLEAF4 = "scalenus"
   INSERTBRANCH2 = "parallelogram"  // Use the previous node at the same depth as reference
     ADDLEAF6 = "square"
     ADDLEAF7 = "diamond"
   INSERTBRANCH6 = "2D"
   INSERTBRANCH9 = "3D"

The following pseudo code initializes the tree from bottom to top
sequentially (except for branches), and also uses the focus node:

 VALUE = 0  // Set the focus node at the first (default for a new element)
 TITLE = "Figures"
 ADDBRANCH = "3D"
 ADDBRANCH = "2D"
 ADDBRANCH = "parallelogram"
 ADDLEAF1 = "diamond"
 ADDLEAF1 = "square"
 ADDBRANCH = "triangle"
 ADDLEAF1 = "scalene"
 ADDLEAF1 = "isosceles"
 ADDLEAF1 = "equilateral"
 ADDLEAF = "Other"

Notice that in both cases the initialization of the tree is highly
dependent on the order of the operations. Currently we can NOT garantie
the order before mapping to the native system, so the initialization
must be performed after the tree is mapped.

Scrollbars are automatically displayed if the tree is greater than its
display area.

Branches may be added in IUP::Lua using a Lua Table, see
L<iup.TreeAddNodes|#TreeAddNodes>.

=head2 Tree - Manipulation

Node insertion or removal is done by means of attributes. It is allowed
to remove nodes and branches inside callbacks associated to opening or
closing branches.

This means that the user may insert nodes and branches only when
necessary when the parent branch is opened, allowing the use of a
larger IUP::Tree without too much overhead. Then when the parent branch
is closed the subtree can be removed. But the subtree must have at
least 1 node so the branch can be opened and closed, empty branches can
NOT be opened.

=head2 Tree - User Data

The node id does not always correspond to the same node as the tree is
modified. For example, an id=2 will always refer to the third node in
the tree, so if you add a node before the third node, the node with
id=2 will now refer to the new node, and the old node will now have
id=3. For that reason, each node can store an user data pointer
uniquely identifying the node. To set or retrieve the user data of a
node use the B<USERDATAid> attribute, or the B<L<Extra
Functions|#Extra_Functions>> below to associate a user data to a node
and to find a node given its user data.

=head2 Tree - Images

L<IUP::Tree> has three types of images: one associated to the leaf, one to
the collapsed branch and the other to the expanded branch. Each image
can be changed, both globally and individually.

The predefined images used in IUP::Tree can be obtained by means of
function IUP::GetHandle. The names of the predefined images are: IMGLEAF,
IMGCOLLAPSED, IMGEXPANDED, IMGBLANK (blank sheet of paper) and IMGPAPER
(written sheet of paper). By default:

 "IMAGELEAF" uses "IMGLEAF"
 "IMAGEBRANCHCOLLAPSED" uses "IMGCOLLAPSED"
 "IMAGEBRANCHEXPANDED" uses "IMGEXPANDED"
 "IMGBLANK" and "IMGPAPER" are designed for use as "IMAGELEAF"

=head2 Tree - Simple Marking

Is the IUP::Tree default operation mode (MARKMODE=SINGLE). In this mode
only one node can be selected.

=head2 Tree - Multiple Marking

L<IUP::Tree> allows marking several nodes simultaneously using the Shift and
Control keys. To use multiple marking set MARKMODE=MULTIPLE. In GTK and
Motif multiple nodes can also be selected using a rubber band if
SHOW_DRAGDROP=NO.

When a user keeps the Control key pressed, the individual marking mode
is used. This way, the focus node can be modified without changing the
marked node. To reverse a node marking, the user simply has to press
the space bar.

When the user keeps the Shift key pressed, the block marking mode is
used. This way, all nodes between the focus node and the initial node
are marked, and all others are unmarked. The initial node is changed
every time a node is marked without the Shift key being pressed. This
happens when any movement is done without Shift or Control keys being
pressed, or when the space bar is pressed together with Control.

=head2 Tree - Navigation

Using the keyboard:

=over

=item * B<Arrow Up/Down>: Moves the focus node to the neighbor node,
according to the arrow direction.

=item * B<Home/End>: Moves the focus node to the first/last node.

=item * B<Page Up/Page Down>: Moves the focus node to the node one
visible page above/below the focus node.

=item * B<Enter>: If the focus node is an expanded branch, it is
collapsed; if it is a collapsed branch, it is expanded; if it is a
leaf, it is executed.

=item * B<Ctrl+Arrow Up/Down>: Moves only the focus node.

=item * B<Ctrl+Space>: Marks or unmark the node at focus.

=item * B<F2>: Calls the rename callback or invoke the in place rename.

=item * B<Esc>: cancels in place rename.

=back

In Motif when pressing Tab the focus goes to the next visible node, if
there are no next visible node then the next control in the dialog
receives the focus. In Windows and GTK the focus simply goes directly
to the next control.

Using the left mouse button:

=over

=item * B<Clicking a node>: Moves the focus node to the clicked node.

=item * B<Clicking a (-/+) box>: Makes the branch to the right of the
(-/+) box collapse/expand.

=item * B<Double-clicking a node>: Moves the focus node to the clicked
node. If the node is an expanded branch, it is collapsed; if it is a
collapsed branch, it is expanded; if it is a leaf, it is executed.

=item * B<Clicking twice a node>: Calls the rename callback or invoke
the in place rename.

=item * B<Clicking and dragging a node>: if SHOWDRAGDROP=Yes starts a
drag. When mouse is released, the DRAGDROP_CB callback is called. If
the callback does not exist or if it returns IUP_CONTINUE then the node
is moved to the new position. If Ctrl is pressed then the node is
copied instead of moved. In Motif drag is performed with the middle
mouse button.

=back

=head2 Tree - Removing a Node with "Del"

By default the Del key is not processed, but you can implement it using
a simple K_ANY callback:

B<Callback handler prototype:>

 sub k_any_handler {
   my ($self, $c) = @_
   if ($c == K_DEL) {
     $self->SetAttribute( DELNODE=>"MARKED" );
   }
   return IUP_CONTINUE;
 }

=head2 ATTRIBUTES

For more info about concept of attributes (setting/getting values etc.)
see L<IUP::Manual::03_Attributes|IUP::Manual::03_Attributes>. Attributes specific to this element:

=head3 General

=over

=item B<ADDEXPANDED>

I<(non inheritable)>

Defines if branches will be expanded
when created. The branch will be actually expanded when it receives the
first child. Possible values: "YES" = The branches will be created
expanded; "NO" = The branches will be created collapsed. Default:
"YES".

=item B<ADDROOT>

I<(non inheritable)>

Automatically adds an empty branch as the
first node when the tree is mapped. Default: "YES". (Since 3.1)

=item B<AUTOREDRAW>

I<[Windows] (non inheritable)>

Automatically redraws the
tree when something has change. Set to NO to add many items to the tree
without updating the display. Default: "YES". (since 3.3)

=item L<BGCOLOR|IUP::Manual::03_Attributes/BGCOLOR>

Background color of the tree.
Default: the global attribute TXTBGCOLOR.

=item B<CANFOCUS>

I<(creation only) (non inheritable)>

Enables the focus
traversal of the control. In Windows the control will still get the
focus when clicked. Default: YES. 

=item B<COUNT>

I<(read only) (non inheritable)>

Returns the total number of
nodes in the tree. 

=item B<DRAGDROP>

I<[Windows and GTK Only] (non inheritable)>

Enable or disable
the drag&drop of files. Default: NO, but if DROPFILES_CB is defined
when the element is mapped then it will be automatically enabled. This
is NOT related to the drag&drop of nodes inside the tree. 

=item B<DROPEQUALDRAG>

I<(non inheritable)>

If enabled will allow a drop node
to be equal to the drag node. Used only if SHOWDRAGDROP =Yes. In the
case the nodes are equal the callback return value is ignored and
nothing is done after. (since 3.3)

=item L<EXPAND|IUP::Manual::03_Attributes/EXPAND>

I<(non inheritable)>

The default value is "YES".

=item B<FGCOLOR>

Default text foreground color. Once each node is created it
will not change its color when FGCOLOR is changed. Default: the global
attribute TXTFGCOLOR. 

=item B<HIDEBUTTONS>

I<(creation only)>

Hide the expand and collapse buttons.
In GTK, branches will be only expanded programmatically. In Motif it
did not work and crash the test.  (GTK 2.12)

=item B<HIDELINES>

I<(creation only)>

Hide the lines that connect the nodes in
the hierarchy.  (GTK 2.10)

=item B<INDENTATION>

Sets the indentation level in pixels. The visual effect
of changing the indentation is highly system dependent. In GTK it acts
as an additional indent value, and the lines do not follow the extra
indent. In Windows is limited to a minimum of 5 pixels. 
(GTK 2.12)

=item L<RASTERSIZE|IUP::Manual::03_Attributes/RASTERSIZE>

I<(non inheritable)>

The initial size is "400x200". Set to C<undef> to allow the automatic layout
use smaller values.

=item B<SHOWDRAGDROP>

I<(creation only, non inheritable)>

Enables the drag and
drop of nodes, and enables the B<DRAGDROP_CB> callback. Default: "NO".
Works only if MARKMODE=SINGLE.

=item B<SPACING>

Vertical internal padding for each node. Notice that the
distance between each node will be actually 2x the spacing. 

=item B<TOPITEM>

I<(write-only)>

Position the given node identifier at the top
of the tree or near to make it visible. If any parent node is collapsed
then they are automatically expanded. 

=back

The following L<common attributes|IUP::Manual::03_Attributes/Common Attributes> are also accepted:

=over

=item * L<ACTIVE|IUP::Manual::03_Attributes/ACTIVE>,
L<EXPAND|IUP::Manual::03_Attributes/EXPAND>, L<FONT|IUP::Manual::03_Attributes/FONT>,
L<SCREENPOSITION|IUP::Manual::03_Attributes/SCREENPOSITION>,
L<POSITION|IUP::Manual::03_Attributes/POSITION>,
L<MINSIZE|IUP::Manual::03_Attributes/MINSIZE>,
L<MAXSIZE|IUP::Manual::03_Attributes/MAXSIZE>, L<WID|IUP::Manual::03_Attributes/WID>,
L<TIP|IUP::Manual::03_Attributes/TIP>, L<SIZE|IUP::Manual::03_Attributes/SIZE>,
L<RASTERSIZE|IUP::Manual::03_Attributes/RASTERSIZE>,
L<ZORDER|IUP::Manual::03_Attributes/ZORDER>,
L<VISIBLE|IUP::Manual::03_Attributes/VISIBLE>

The NAME common attribute is still not supported because of a backward
compatibility code. Old applications must change the use of the old
NAME attribute to TITLE, so the new NAME common attribute can be
enabled in future versions.

=back

=head3 Nodes (non inheritable)

For these attributes "id" is the specified branch identifier. If id is
empty, then the focus node is used as the specified node.

=over

=item B<CHILDCOUNT(id)>

I<(read only)> Returns the immediate children count of
the specified branch. It does not count children of child that are
branches. 

=item B<COLOR(id)>

Text foreground color of the specified node. The value
should be a string in the format "R G B" where R, G, B are numbers from
0 to 255.

=item B<DEPTH(id)>

I<(read only)> Returns the depth of the specified node. The
first node has depth=0, its immediate children has depth=1, their
children has depth=2 and so on.

=item B<KIND(id)>

I<(read only)> Returns the kind of the specified node. Possible values:

=over

=item * "LEAF": The node is a leaf

=item * "BRANCH": The node is a branch

=back

=item B<PARENT(id)>

I<(read only)> Returns the identifier of the specified node.

=item B<STATE(id)>

The state of the specified branch. Returns C<undef> for a LEAF.
In Windows, it will be effective only if the branch has children. In
GTK, it will be effective only if the parent is expanded. Possible
values:

=over

=item * "EXPANDED": Expanded branch state (shows its children)

=item * "COLLAPSED": Collapsed branch state (hides its children)

=back

=item B<TITLE(id)>

The text label of the specified node.

=item B<TITLEFONT(id)>

The text font of the specified node. The format is the
same as the L<FONT|IUP::Manual::03_Attributes/FONT> attribute. 

=item B<TOTALCHILDCOUNT(id)>

I<(read only)> Returns the total children count of
the specified branch. It counts all grandchildren. 

=item B<USERDATA(id)>

The user data associated with the specified node. (since iup-3.0)

=back

=head3 Images (non inheritable)

=over

=item B<IMAGE(id)>

Image name or reference to L<IUP::Image> to be used in the specified node, where id is
the specified node identifier. If id is empty, then the focus node is
used as the specified node. 

See - L<Using Images in Other Elements (via IMAGE Attribute)|IUP::Image/"Using Images in Other Elements (via IMAGE Attribute)">

In Windows and Motif set the BGCOLOR attribute before setting the image.
If node is a branch it is used when collapsed.

=item B<IMAGEEXPANDED(id)>

Same as the IMAGE attribute but used for expanded branches.

=item B<IMAGELEAF>

The image name that will be shown for all leaves.
Default: "IMGLEAF". Internal values "IMGBLANK" and "IMGPAPER" are also
available. If BGCOLOR is set the image is automatically updated.

=item B<IMAGEBRANCHCOLLAPSED>

The image name that will be shown for all
collapsed branches. Default: "IMGCOLLAPSED". If BGCOLOR is set the
image is automatically updated.

=item B<IMAGEBRANCHEXPANDED>

The image name that will be shown for all
expanded branches. Default: "IMGEXPANDED". If BGCOLOR is set the image
is automatically updated.

=back

=head3 Focus Node

=over

=item B<VALUE>

I<(non inheritable)> The focus node identifier. When retrieved
but there isn't a node with focus it returns 0 if there are any nodes,
and returns -1 if there are no nodes. When changed and MARKMODE=SINGLE
the node is also selected. The tree is always scrolled so the node
becomes visible. In Motif the tree will also receive the focus.
Additionally accepts the values:

=over

=item * "ROOT" or "FIRST": the first node

=item * "LAST": the last visible node

=item * "NEXT": the next visible node, one node after the focus node. If at the
last does nothing

=item * "PREVIOUS": the previous visible node, one node before the focus node.
If at the first does nothing

=item * "PGDN": the next visible node, ten nodes node after the focus node. If
at the last does nothing

=item * "PGUP": the previous visible node, ten nodes before the focus node. If
at the first does nothing

=back

=back

=head3 Marks

=over

=item B<MARK>

I<(write only, non inheritable)> Selects a range of nodes in the
format "start-end" (%d-%d). Allowed only when MARKMODE=MULTIPLE. Also
accepts the values:

=over

=item * "INVERT(id)": Inverts the specified node mark state, where id is the
specified node identifier. If id is empty, then the focus node is used
as reference node.

=item * "BLOCK": Marks all nodes between the focus node and the initial
block-marking node defined by MARKSTART

=item * "CLEARALL": Unmark all nodes

=item * "MARKALL": Marks all nodes

=item * "INVERTALL": Inverts the marking of all nodes

=back

=item B<MARKED(id)>

I<(non inheritable)> The selection state of the specified
node, where id is the specified node identifier. If id is empty, then
the focus node is used as reference node. Can be: YES or NO. Default: NO

=item B<MARKEDNODES>

I<(non inheritable)> The selection state of all nodes when
MARKMODE=MULTIPLE. It is/accepts a sequence of '+' and '-' symbols
indicating the state of each item ('+'=selected, '-'=unselected. When
setting this value, if the number of specified symbols is smaller than
the total count then the remaining nodes will not be changed. (since iup-3.1)

=item B<MARKMODE>

Defines how the nodes can be selected. Can be: SINGLE or MULTIPLE. Default: SINGLE.

=item B<MARKSTART>

I<(non inheritable)> Defines the initial node for the block
marking, used when MARK=BLOCK. The value must be the node identifier.
Default: 0 (first node).

=back

=head3 Hierarchy (non inheritable)

=over

=item B<ADDLEAF(id)>

I<(write only)> Adds a new leaf after the reference
node, where id is the reference node identifier. If id is empty, then
the focus node is used as reference node. Use id=-1 to add the first
node in an empty tree. The value is used as the text label of the new
node. The id of the new node will be the id of the reference node + 1.
The attribute B<LASTADDNODE> is set to the new id. The reference node
is marked and all others unmarked. The reference node position remains
the same. If the reference node does not exist, nothing happens. If the
reference node is a branch then the depth of the new node is one depth
increment from the depth of the reference node, if the reference node
is a leaf then the new node has the same depth. If you need to add a
node after a specified node but at a different depth use B<
INSERTLEAF>. Ignored if set before map.

=item B<ADDBRANCH(id)>

I<(write only)> Same as B<ADDLEAF> for branches. Branches can be created expanded or
collapsed depending on B<ADDEXPANDED>. Ignored if set before map.

=begin HTML

<p>
  <table border="1">
    <tbody align="center">
      <tr>
        <th>Initial layout</th>
        <th>After calling: <pre>$tree->SetAttribute(ADDBRANCH9, "new branch");</pre></th>
      </tr>
      <tr>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree1.png"></td>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree2_addbranch9.png"></td>
      </tr>
    </tbody>
  </table>
</p>

=end HTML

=item B<COPYNODE(id)>

I<(write only)> Copies a node and its children, where id is
the specified node identifier. If id is empty, then the focus node is
used as the specified node. The value is the destination node
identifier. If the destination node is a branch and it is expanded,
then the specified node is inserted as the first child of the
destination node. If the branch is not expanded or the destination node
is a leaf, then it is inserted as the next brother of the leaf. The
specified node is not changed. All node attributes are copied, except
user data. Ignored if set before map. 

=item B<DELNODE(id)>

I<(write only)> Removes a node and/or its children, where id
is the specified node identifier. If id is empty, then the focus node
is used as the specified node. Ignored if set before map. Possible
values:

=over

=item * "ALL": deletes all nodes, id is ignored (Since 3.1)

=item * "SELECTED": deletes the specified node and its children

=item * "CHILDREN": deletes only the children of the specified node

=item * "MARKED": deletes all the selected nodes (and all their children), id is ignored

=back

=item B<EXPANDALL>

I<(write only)> Expand or contracts all nodes. Can be YES (expand all), or NO (contract all). 

=item B<INSERTLEAF(id)>, B<INSERTBRANCH(id)>

I<(write only)> Same as B<ADDLEAF> and B<ADDBRANCH> but the depth of the new node is always the same of
the reference node. If the reference node is a leaf, then the id of the
new node will be the id of the reference node + 1. If the reference
node is a branch the id of the new node will be the id of the reference
node + 1 + the total number of child nodes of the reference node.

=begin HTML

<p>
  <table border="1">
    <tbody align="center">
      <tr>
        <th>Initial layout</th>
        <th>After calling: <pre>$tree->SetAttribute(INSERTBRANCH9, "new branch");</pre></th>
      </tr>
      <tr>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree1.png"></td>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree3_insertbranch9.png"></td>
      </tr>
    </tbody>
  </table>
</p>

=end HTML

=item B<MOVENODE(id)>

I<(write only)> Moves a node and its children, where id is
the specified node identifier. If id is empty, then the focus node is
used as the specified node. The value is the destination node
identifier. If the destination node is a branch and it is expanded,
then the specified node is inserted as the first child of the
destination node. If the branch is not expanded or the destination node
is a leaf, then it is inserted as the next brother of the leaf. The
specified node is removed. User data and all node attributes are
preserved. Ignored if set before map. 

=back

=head3 Editing

=over

=item B<RENAME>

I<(write only)> Forces a rename action to take place. Valid only when SHOWRENAME=YES.

=item B<RENAMECARET>

I<(write only)> The caret's position of the text
box when in-place renaming. Same as the CARET attribute for
L<IUP::Text|IUP::Text>, but here is used only once after
SHOWRENAME_CB is called and before the text box is shown.

=item B<RENAMESELECTION>

I<(write only)> The selection interval of the text box
when in-place renaming. Same as the SELECTION attribute for
L<IUP::Text|IUP::Text>, but here is used only once after
SHOWRENAME_CB is called and before the text box is shown.

=item B<SHOWRENAME>

I<(creation in Windows, non inheritable)> Allows the
in place rename of a node. Default: "NO". Since iup-3.0, F2 and clicking
twice only starts to rename a node if SHOWRENAME=Yes. In Windows must
be set to YES before map, but can be changed later (since iup-3.3).

=back

=head2 CALLBACKS

For more info about concept of callbacks (setting callback handlers etc.)
see L<IUP::Manual::04_Callbacks|IUP::Manual::04_Callbacks>. Callbacks specific to this element:

=over

=item B<SELECTION_CB>

Action generated when a node is selected or
deselected. This action occurs when the user clicks with the mouse or
uses the keyboard with the appropriate combination of keys.

B<Callback handler prototype:>

 sub selection_cb_handler {
   my ($self, $id, $status) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> Node identifier.

B<$status:> 1=node selected, 0=node unselected.

=back

=item B<MULTISELECTION_CB>

Action generated after a continuous range of
nodes is selected in one single operation. If not defined the
SELECTION_CB with status=1 will be called for all nodes in the range.
The range is always completely included, independent if some nodes were
already marked. That single operation also guaranties that all other
nodes outside the range are already not selected. Called only if
MARKMODE=MULTIPLE.

B<Callback handler prototype:>

 sub multiselection_cb_handler {
   my ($self, $ids, $n) = @_;
   #...
 }
 

=over

B<$self:> identifier of the element that activated the event.

B<$ids:> Reference to array of node identifiers. This array is kept for backward
compatibility, the range is simply defined by C<$ids->[0]> to C<$ids->[$n-1]>, where
C<$ids->[$i+1]=$ids->[$i]+1>.

B<$n:> Number of nodes in the array.

=back

=item B<MULTIUNSELECTION_CB>

Action generated before multiple nodes are
unselected in one single operation. If not defined the SELECTION_CB
with status=0 will be called for all nodes in the range. The range is
not necessarily continuous. Called only if MARKMODE=MULTIPLE. (Since
3.1)

B<Callback handler prototype:>

 sub multiunselection_cb_handler {
   my ($self, $ids, $n) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$ids:> Reference to array of node identifiers.

B<$n:> Number of nodes in the array (should correspond to the size of $ids).

=back

=item B<BRANCHOPEN_CB>

Action generated when a branch is expanded. This
action occurs when the user clicks the "+" sign on the left of the
branch, or when double clicks the branch, or hits Enter on a collapsed
branch.

B<Callback handler prototype:>

 sub branchopen_cb_handler {
   my ($self, $id) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> node identifier.

B<Returns:> IUP_IGNORE for the branch not to be opened, or IUP_DEFAULT for
the branch to be opened.

=back

=item B<BRANCHCLOSE_CB>

Action generated when a branch is collapsed. This
action occurs when the user clicks the "-" sign on the left of the
branch, or when double clicks the branch, or hits Enter on an expanded
branch.

B<Callback handler prototype:>

 sub branchclose_cb_handler {
   my ($self, $id) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> node identifier.

B<Returns:> IUP_IGNORE for the branch not to be closed, or IUP_DEFAULT for
the branch to be closed.

=back

=item B<EXECUTELEAF_CB>

Action generated when a leaf is to be executed. This
action occurs when the user double clicks a leaf, or hits Enter on a
leaf.

B<Callback handler prototype:>

 sub executeleaf_cb_handler {
   my ($self, $id) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> node identifier.

=back

=item B<SHOWRENAME_CB>

Action generated when a node is about to be renamed.
It occurs when the user clicks twice the node or press B<F2>. Called
only if SHOWRENAME=YES.

B<Callback handler prototype:>

 sub showrename_cb_handler {
   my ($self, $id) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> node identifier.

B<Returns:> if IUP_IGNORE is returned, the rename is canceled (in GTK the
rename continuous but the edit box is read-only).

=back

=item B<RENAME_CB>

Action generated after a node was renamed in place. It
occurs when the user press B<Enter> after editing the name, or when the
text box looses it focus. Called only if SHOWRENAME=YES.

B<Callback handler prototype:>

 sub rename_cb_handler {
   my ($self, $id, $title) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> node identifier.

B<$title:> new node title.

B<Returns:> The new title is accepted only if the callback returns
IUP_DEFAULT. If the callback does not exists the new title is always
accepted. If the user pressed B<Enter> and the callback returns
IUP_IGNORE the editing continues. If the text box looses its focus the
editing stops always.

=back

=item B<DRAGDROP_CB>

Action generated when a drag & drop is executed. Only
active if B<SHOWDRAGDROP=YES.>

B<Callback handler prototype:>

 sub dragdrop_cb_handler {
   my ($self, $drag_id, $drop_id, $isshift, $iscontrol) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$drag_id:> Identifier of the clicked node where the drag start.

B<$drop_id:> Identifier of the clicked node where the drop were executed.

B<$isshift:> Boolean flag indicating the shift key state.

B<$iscontrol:> Boolean flag indicating the control key state.

B<Returns:> if returns IUP_CONTINUE, or if the callback is not defined and
B<SHOWDRAGDROP=YES>, then the node is moved to the new position. If
Ctrl is pressed then the node is copied instead of moved. If the drop
node is a branch and it is expanded, then the drag node is inserted as
the first child of the node. If the branch is not expanded or the node
is a leaf, then the drag node is inserted as the next brother of the
drop node.

=back

=item B<NODEREMOVED_CB>

Action generated when a node is going to be removed.
It is only a notification, the action can not be aborted. No node
dependent attribute can be consulted during the callback. Not called
when the tree is unmapped. 

B<Callback handler prototype:>

 sub noderemoved_cb_handler {
   my ($self, $userdata_ref) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$userdata_ref:> perl reference associated via L<TreeSetUserId|/"TreeSetUserId()"> with a node being removed

=back

=item B<RIGHTCLICK_CB>

Action generated when the right mouse button is pressed over a node.

B<Callback handler prototype:>

 sub rightclick_cb_handler {
   my ($self, $id) = @_;
   #...
 }

=over

B<$self:> identifier of the element that activated the event.

B<$id:> node identifier.

=back

=item L<BUTTON_CB|IUP::Manual::04_Callbacks/BUTTON_CB>

Action generated when any
mouse button is pressed or released inside the element. Use
L<ConvertXYToPos|IUP::Manual::02_Elements/"ConvertXYToPos()"> to convert (x,y)
coordinates in the node identifier. 

=item L<MOTION_CB|IUP::Manual::04_Callbacks/MOTION_CB>

Action generated when the
mouse is moved over the element. Use
L<ConvertXYToPos|IUP::Manual::02_Elements/"ConvertXYToPos()"> to convert (x,y)
coordinates in item the node identifier. 

=item L<DROPFILES_CB|IUP::Manual::04_Callbacks/DROPFILES_CB>

I<[Windows and GTK Only]>

Action generated when one or more files are dropped in the element.

=back

The following L<common callbacks|IUP::Manual::04_Callbacks/Common Callbacks> are also accepted:

=over

=item * L<MAP_CB|IUP::Manual::04_Callbacks/MAP_CB>,
L<UNMAP_CB|IUP::Manual::04_Callbacks/UNMAP_CB>,
L<GETFOCUS_CB|IUP::Manual::04_Callbacks/GETFOCUS_CB>,
L<KILLFOCUS_CB|IUP::Manual::04_Callbacks/KILLFOCUS_CB>,
L<ENTERWINDOW_CB|IUP::Manual::04_Callbacks/ENTERWINDOW_CB>,
L<LEAVEWINDOW_CB|IUP::Manual::04_Callbacks/LEAVEWINDOW_CB>,
L<K_ANY|IUP::Manual::04_Callbacks/K_ANY>,
L<HELP_CB|IUP::Manual::04_Callbacks/HELP_CB>

In Motif the tree always resets the focus to the first node when
receive the focus. The KILLFOCUS_CB callback is called only when the
focus is at the first node. Also in Motif some LEAVEWINDOW_CB events
are delayed to when the user enter again, firing a leave and enter
events at enter time.

=back

=head1 NOTES

=head2 Extra Functions

L<IUP::Tree> has functions that allow associating a perl reference to a node.
In order to do that, you provide the id of the node and the reference to userdata; even
if the node's id changes later on, the reference to userdata will still be associated with the given node.
These functions use the B<USERDATA(id)> attribute.

B<IMPORTANT:> Do not manipulate B<USERDATA(id)> attribute directly, always
use L<TreeSetUserId/"TreeSetUserId()"> and L<TreeGetUserId|/"TreeGetUserId()">.

=head3 TreeSetUserId()

 $userdata_ref = { item1=>1, item2=>2 };
 $tree->TreeSetUserId($id, $userdata_ref);

B<$id:> Node identifier.

B<$userdata_ref:> reference (to scalar, array, hash ... whatever) to be associated with the node.
Use C<undef> to remove the association.

B<Returns:> a non zero value if the node was found.

Associates an userdata_ref with a given id. If the id of the node is changed,
the userdata_ref remains the same.

=head3 TreeGetUserId()

 $userdata_ref = $tree->TreeGetUserId($id);

B<$id:> Node identifier.

Returns the reference to data associated to the node or C<undef> if none
was associated. L<SetUserId|/"SetUserId()"> must have been called for the node with
the given id.

=head3 TreeGetId()

 $id = $tree->TreeGetId($userdata_ref);

B<$userdata_ref:> Reference to data associated to the node.

Returns the id of the node that has the userdata_ref on success or C<undef>
if not found. L<SetUserId|/"SetUserId()"> must have been called with the same userdata_ref.

B<BEWARE:> If you wanna use this function keep in mind that you probably want to assure
that the same reference will not be associated with more that 1 node.

=head3 TreeAddNodes()

 $tree->TreeAddNodes($tree2add, $id);
 #or
 $tree->TreeAddNodes($tree2add);

B<$tree2add:> table of nodes (required structure see below)

B<$id:> optional existing node. The default is the first (0).

Initializes the tree using the hash or hash reference as values for the tree
nodes using ADDBRANCH and ADDLEAF. For example:

 $t_singleroot = {
   TITLE=>"Animals", child=>[
     "0.Extra",
     { TITLE=>"1.Mammals",     child=>["Horse",  "Whale"] },
     "2.Extra",
     { TITLE=>"3.Crustaceans", child=>["Shrimp", "Lobster"] },
     "4.Extra",
   ],
 };

 $t_rootless = [
   "0.Extra",
   { TITLE=>"1.Mammals",     child=>["Horse",  "Whale"] },
   { TITLE=>"2.Crustaceans", child=>["Shrimp", "Lobster"] },
   "3.Extra",
   "4.Extra",
   { TITLE=>"5.Extra", child=>["Dog", "Cat"] },
 ];
 
 $dlg->Map();
 $tree1->TreeAddNodes($t_rootless,-1);   #has to go after dialog->Map()
 $tree2->TreeAddNodes($t_singleroot,-1); #has to go after dialog->Map()
 $dlg->Show();

XXX-FIXME-not-true-for-perl
Inside a table B<BRANCHNAME> defines a branch and its title,
B<LEAFNAME> defines a leaf and its title. When a node inside a branch
is not a table then it is a leaf and only defines the leaf title. When
B<LEAFNAME> or B<BRANCHNAME> are used you can also define other node
attributes: B<COLOR>, B<STATE>, B<TITLEFONT>, B<MARKED>, B<IMAGE> and
B<IMAGEEXPANDED>; without specifying the node id. You can also use
B<USERID> to associate an userdata or table just like in B<TREESETUSERID>. 

Example:

=begin HTML

<p>
  <table border="1">
    <tbody align="center">
      <tr>
        <th>Initial layout</th>
        <th>After calling: <pre>$tree->TreeAddNodes( {TITLE=>"subtree", child=>["item1","item2"]}, 9);</pre></th>
      </tr>
      <tr>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree1.png"></td>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree4_TreeAddNodes9.png"></td>
      </tr>
    </tbody>
  </table>
</p>

=end HTML

=head3 TreeInsertNodes()

 $tree->TreeInsertNodes($tree2add, $id);
 #or
 $tree->TreeInsertNodes($tree2add);

Same as L<TreeAddNodes|/"TreeAddNodes()"> but the depth of the new node is always the same of
the reference node. If the reference node is a leaf, then the id of the
new node will be the id of the reference node + 1. If the reference
node is a branch the id of the new node will be the id of the reference
node + 1 + the total number of child nodes of the reference node.

=begin HTML

<p>
  <table border="1">
    <tbody align="center">
      <tr>
        <th>Initial layout</th>
        <th>After calling: <pre>$tree->TreeInsertNodes( {TITLE=>"subtree", child=>["item1","item2"]}, 9);</pre></th>
      </tr>
      <tr>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree1.png"></td>
        <td><img src="http://kmx.github.io/perl-iup/spec/iuptree5_TreeInsertNodes9.png"></td>
      </tr>
    </tbody>
  </table>
</p>

=end HTML

=head3 TreeSetNodeAttributes()

 $tree->TreeSetNodeAttributes($id, $attrs);

B<$id:> existing node.

B<$attrs:> table of attributes.

Sets a group of attributes stored in a table in the form:

 $attrs = {
   TITLE => "Text",
   COLOR => "0 0 220",
   IMAGE => $img,   
 }
 $tree->TreeSetNodeAttributes($id, $attrs); 
 #which sets:
 # $tree->SetAttribute( "TITLE$id" => "Text" );
 # $tree->SetAttribute( "COLOR$id" => "0 0 220" );
 # $tree->SetAttribute( "IMAGE$id" => $img );

=head3 TreeSetAncestorsAttributes()

 $tree->TreeSetAncestorsAttributes($id, $attrs);

B<$id:> existing node

B<$attrs:> table of attributes

Calls L<TreeSetNodeAttributes|/"TreeSetNodeAttributes()"> for all ancestors of the given node
(not including the node).

=head3 TreeSetDescentsAttributes()

 $tree->TreeSetDescentsAttributes($id, $attrs);

B<$id:> existing node

B<$tree:> table of attributes

Calls L<TreeSetNodeAttributes|/"TreeSetNodeAttributes()"> for all descendents of the given
node (not including the node).

=head2 Utility Functions

These functions can be used to set and get attributes from the element:

 $elem->SetAttributeId($name, $id, $value);
 $elem->GetAttributeId($name, $id);

They work just like the respective traditional set and get functions.
But the attribute string is complemented with the id value. For ex:

 $elem->SetAttributeId("KIND", 30, $value) ~~ $elem->SetAttribute("KIND30", $value);
 
 $elem->SetAttributeId("ADDLEAF", 10, $value) ~~ $elem->SetAttribute("ADDLEAF10", $value);

But these functions are faster than the traditional functions because
they do not need to parse the attribute name string and the application
does not need to concatenate the attribute name with the id.

=head1 EXAMPLES


The element B<IUP::Tree> is used in the following sample scripts:

=over

=item * L<0-basic/cbox.pl|https://metacpan.org/source/KMX/IUP-0.303/examples/0-basic/cbox.pl> - IUP::Cbox example

=item * L<0-basic/sbox2.pl|https://metacpan.org/source/KMX/IUP-0.303/examples/0-basic/sbox2.pl> - IUP::Sbox example

=item * L<0-basic/tree1.pl|https://metacpan.org/source/KMX/IUP-0.303/examples/0-basic/tree1.pl> - IUP::Tree example (animals) - using helper methods e.g. TreeAddNodes()

=item * L<0-basic/tree2.pl|https://metacpan.org/source/KMX/IUP-0.303/examples/0-basic/tree2.pl> - IUP::Tree example (figures) - using attribute only interface

=item * L<0-basic/tree3.pl|https://metacpan.org/source/KMX/IUP-0.303/examples/0-basic/tree3.pl> - IUP::Tree example (figures) - using attribute only interface

=item * L<0-basic/tree_set_attrs.pl|https://metacpan.org/source/KMX/IUP-0.303/examples/0-basic/tree_set_attrs.pl> - IUP::Tree example (attributes)

=back 



=head1 SEE ALSO

The original doc: L<iuptree.html|http://www.tecgraf.puc-rio.br/iup/en/elem/iuptree.html>
 

=cut