TixHList is the Tix Hierarchical Listbox Widget. You can use it to display any data that have a hierarchical structure. For example, the HList widget in figure 4-1 displays a Unix file system directory tree; the HList widget in figure 4-1 displays the corporate hierarchy of a hypothetical company. As shown in these two figures, the entries inside the TixHList widget are indented can be optionally connected by branch lines according to their positions in the hierarchy.
![]()
Directory Tree Display
![]()
A Corporate Hierarchy (Figure 4-1) Examples of the TixHList Widget
A TixHList widget can be created by the command
tixHList. However, most likely, you would want to create a TixHList
with scrollbars attached. Therefore, usually you will use the
tixScrolledHList command to create a scrolled hierarchical listbox
(line 1 in program 4-2 ). The tixScrolledHList
command is very similar to the TixScrolledListBox command we
saw in section 2.3.1 . It creates a TixHList subwidget
of the name hlist and attaches two scrollbars to it.
As shown in the first five lines in program 4-2 , we
create a scrolled TixHList widget, using the -options switch
(see section 1.3.5 ) to set several options for the
hlist subwidget (we'll talk about these options shortly). Then, we
can access the HList subwidget widget using the subwidget
hlist method (line 7 in program 4-2 ).
tixScrolledHList .sh -options { hlist.itemType text hlist.drawBranch false hlist.indent 8 } pack .sh -expand yes -fill both set hlist [.sh subwidget hlist]$hlist add foo -text "foo" $hlist add foo.bar -text "foo's 1st son" $hlist add foo.bor -text "foo's 2nd son" $hlist add foo.bar.bao -text "foo's 1st son's 1st son" $hlist add foo.bar.kao -text "foo's 1st son's 2nd son" $hlist add dor -text "dor, who has no son"
(Figure 4-2) Creating Entries in a HList Widget
(Figure 4-3) Output of Program 4-2
Each entry in an HList widget has a unique name, called its
entry-path, which determines each entry's position in the HList
widget. The entry-paths of the HList entries are very similar to the
pathnames of Unix files. Each entry-path is a list of string names
separated by a separator character. By default, the separator
character is the period character ( .), but it can be
configured using the -separator option of the HList widget.
In program 4-3 , we add several new entries foo,
foo.bar, foo.bor, foo.bar.bao, .. etc, into the
HList widget using the add method. The relationship between
the entries is signified by their names, in a way similar to how
Unix denotes directories and subdirectories. For example, foo
is the parent of foo.bar and foo.bor;
foo.bar is the parent of foo.bar.bao, and so on. As far as
the terminology goes, we also say that foo.bar a child
of foo; foo is an ancestor of foo.bar.bao
and foo.bar.bao is a descendant of foo.
The output of program 4-2 is shown in figure
4-3 . As we can see, the entries are displayed under
their parents with the amount of indentation control by the
-indent option of the HList widget: foo.bar.bao and
foo.bar.kao are display under foo.bar, which is in turn
displayed under foo.
Entries with no parents, for example, foo and dor in
program 4-2 , are called top-level
entries. Top-level entries are usually entries with no immediate
superiors in a hierarchical. For example, the owner of a company, the
principle of a school or the root directory of a Unix file
system. Toplevel entries are displayed with no indentation.
As evident from program 4-2 , all entries who entry-path does not contain a separator character are top-level entries. The only exception is the separator character itself is also a toplevel entry. This makes it easy to display Unix file and directory names inside the HList widget, as shown in program 4-4 .
set folder [tix getimage folder] tixScrolledHList .sh -options { hlist.separator / hlist.itemType imagetext hlist.drawBranch true hlist.indent 14 hlist.wideSelection false } pack .sh -expand yes -fill both set hlist [.sh subwidget hlist]foreach directory {/ /usr /usr/bin /usr/local /etc /etc/rc.d} { $hlist add $directory -image $folder -text $directory }
(Figure 4-4) Displaying Directories in a HList Widget
(Figure 4-5) Output of Program 4-4
Each entry is associated with a display item (see section
3.2 about display items). We can use the -itemtype
option of the HList widget to specify the default type of display
item to be created by the the add method, as shown in program
4-2 and 4-4 . Alternatively, we can
also specify the type of display item using the -itemtype
option for the add method.
There are two options to control the layout of the entries: the
-showbranch option specifies whether branch lines should be drawn
between parent entries and their children. The -indent option
controls the amount of relative indentation between parent and child
entries. Notice the -drawbranch option is turned on in figure
4-5 but turned off in figure
4-3 . Usually, you need to set a bigger indentation
when the branches are shown --- we used an indentation of 14 pixels
in 4-5 compared to 8 pixels in 4-3 .
The handling of the selection and user events for the HList widget
is very similar to the TList widget (see section
3.3.5 ), except that for the HList widget all the
operations are based on entry-paths, not list indices. The methods
info selection, selection set and selection clear
can be used to query, set or clear the selection; the option
-selectmode controls how many entries can be selected at a time;
the options -browsecmd and -command can be used to
specify a command to be called to handle user events.
There is one more option worth mentioning: the -wideselection
option. When set to true, the selection highlight will be
drawn across the whole HList widget (see figure
4-3 ). When set to false, selection highlight will be
drawn as wide as the selected entry (see figure
4-5 ). Normally, you would set -wideselection
to false when you use imagetext items inside (as we did
in program 4-4 ).
The TixTree widget is based on the TixScrolledHList widget; you can
use it to create a collapsible hierarchical structure so that the
user can conveniently navigate through a large number of list
entries. As shown in figure 4-7 , the TixTree puts
the little `` +'' and `` -'' icons next to the branches of
an HList entry that has descendants. These two icons are knows as
the open and close icons, respectively. When the user presses the
open icon next to an entry, its immediate children of an entry will
be displayed. Conversely, when the user presses the close icon, the
entry's children will become hidden.
Program 4-6 shows how to create a collapsible
tree. We first create a TixTree widget. Then we add the entries in
your hierarchical structure into its hlist subwidget using the
add method of this subwidget. When we are finished with adding the
entries, we just call the autosetmode method of the TixTree
widget, which will automatically adds the open and close icons next
to the entries who have children.
set folder [tix getimage folder] tixTree .tree -command Command -options { hlist.separator / hlist.itemType imagetext hlist.drawBranch true hlist.indent 18 } pack .tree -expand yes -fill both set hlist [.tree subwidget hlist]foreach directory {/ /usr /usr/bin /usr/local /etc /etc/rc.d} { $hlist add $directory -image $folder -text $directory } .tree autosetmode
proc Command {entry} { puts "you have selected $entry" }
(Figure 4-6) Creating a Collapsible Hierarchy
(Figure 4-7) Output of Program 4-6
Note that in program 4-6 we use the -command
option of the TixTree widget, not the -command option of its
hlist subwidget. This is because the TixTree actually used the
-command option of its hlist subwidget to process some
low-level events. In general, if both a mega-widget and its
subwidget have the options of the same name, you would always use
the option that belongs to the mega-widget.