Chapter 18. A Tk Interface Extension Tour

18.1. Display Items

One of the things we gain when using Tix widgets is the ability to create a display item and then add it to a Tix widget for display. Display items are all rectangular, and the container widget manipulates those rectangles with little regard to anything other than the size of the rectangles and the order in which to display them.

There are four different types of items you can use in Tix widgets: text, imagetext, image, and window. A text item displays only text. An imagetext item can display both an image and text, or only an image, or only text. An image item displays only an image, and a window is another widget.

When creating each item in our TList, we specify the type using the -itemtype option:

$tl = $mw->TList->pack(-expand => 1, -fill => 'both');
foreach my $i (0..19) { 
  $tl->insert('end', -itemtype => 'text', -text => "Display Item #$i");
}

In Figure 18-1, we see there are 20 different display items inserted. Each has an item type of 'text'.

Figure 18-1. A TList widget showing display items

Now let's change our example to show different item types:

$tl = $mw->TList->pack(-expand => 1, -fill => 'both');
my $image = $mw->Getimage('folder');

foreach my $i (0..4) { 
  $tl->insert('end', -itemtype => 'text', -text => "text Item #$i");
  $tl->insert('end', -itemtype => 'imagetext', 
              -text => "imagetext item #$i", -image => $image);
  my $b = $tl->Button(-text => "Window item #$i", 
                      -command => sub { print "Button pressed\n"; });
  $tl->insert('end', -itemtype => 'window', -widget => $b);
}

Figure 18-2 shows our screenshot, generated using the previous code, then manually resized to make it pretty with three items per column.

Figure 18-2. A TList widget showing different display item types

We didn't bother showing the 'image' type in this example, since it's just an image with no text on it. The fonts and colors used to display each item are the defaults for the TList widget, but we could change them on a per item basis using item styles (covered in the next section).

Table 18-1 lists the options you can use when creating each of the display item types. Different widgets use different methods to create item types. In our previous examples, we used TList, so the method to create a new item is insert. If we were using the HList widget, we would call itemCreate to create a new item.

Table 18-1. The options available for item types in Tix widgets

     

Option	Text	Imagetext	Image	Window
-bitmap => bitmap A bitmap to display in the item.
-image => image An image to display in the item.
-showimage => 0 | 1 Determines whether the image will be shown. Even if the image isn't being displayed, space will still be allocated for it.
-showtext => 0 | 1 Determines whether the text will be shown.
-style => $style A reference to a style created using the ItemStyle method. Will change how the item is displayed: font, colors, etc.
-text => string The text to be displayed. If using -showtext => 0 on an imagetext item, the text won't be seen.
-underline => index The character index to underline in the text. First character in the text is at 0.
-window => $widget The widget to display.
-widget => $widget An alias for the -window option. You can use either -window or -widget as the option name.