## 3.5 Label Widgets

A label widget displays a text string or a bitmap. Options for frames are also valid options for labels, additional options determine what the label displays. The reference documentation for labels is `label`.

  `L1={New Tk.label tkInit(parent:W bitmap:info)}
  L2={New Tk.label tkInit(parent:W text:'Labels: bitmaps and text')}
  {Tk.send pack(L1 L2 side:left padx:2#m pady:2#m)}`

Figure 3.3: Example for labels displaying bitmaps and text.

Figure 3.3 shows an example where the label `L1` displays a bitmap and the label `L2` displays text. As with other widgets, the options of a label widget can be reconfigured by sending the widget object a `tk` message with the command `configure`. Execution of the following expression changes the bitmap to an exclamation mark:

  `{L1 tk(configure bitmap:warning)}`

### 3.5.1 Bitmap Options

Label widgets and several other widgets allow to display bitmaps. There are two different kinds of bitmaps: predefined bitmaps and bitmaps stored in files.

If the first character of the `bitmap` option value is an `@`, the value is interpreted as filename. For instance, feeding

  `{L2 tk(configure bitmap: '@'#{Property.get 'oz.home'}#
  '/doc/wp/queen.xbm'
  foreground: orange)}`

displays a bitmap stored in a file. Here the file name is given relative to where the Mozart system has been installed, that is relative to `{Property.get 'oz.home'}` (for the system module `Property` see Chapter 23 of ``System Modules'').

predefined bitmaps

If the first character is different from `@`, it is interpreted as the name of a predefined bitmap. A program that displays all predefined bitmaps and their names you can see in Figure 3.4. The program uses the grid geometry manager which is discussed in Section 4.3.

  `{List.forAllInd [error gray75 gray50 gray25 gray12
  hourglass info questhead question warning]
  proc {$ I D}
  R=(I-1) div 5
  C=(I-1) mod 5
  in
  {Tk.batch [grid(row:R*2 column:C
  {New Tk.label tkInit(parent:W bitmap:D)})
  grid(row:R*2+1 column:C
  {New Tk.label tkInit(parent:W text:D)})]}
  end}`

Figure 3.4: Predefined bitmaps.

bitmap colors

Bitmaps have two colors. These colors can be configured with the `foreground` and `background` options. The color of the bitmaps' pixels is given by the foreground color.

### 3.5.2 Font Options

A font to be used for displaying text can be specified by the `font` option. Valid values for the `font` option are either platform specific font names or instances of the class `Tk.font`. An instance of the class `Tk.font` is also a tickle object but is not a widget.

Platform dependent font names are for example X font names. If you are running a Unix based system, you can for example display the available names by using the `xlsfonts` program.

However the preferred way to specify fonts is to be platform independent of course. The program in Figure 3.5 uses this technique.

  `{ForAll [times helvetica courier]
  proc {$ Family}
  {ForAll [normal bold]
  proc {$ Weight}
  F={New Tk.font tkInit(family: Family
  weight: Weight
  size: 12)}
  L={New Tk.label tkInit(parent: W
  text: 'A '#Weight#' '#Family#' font.'
  font: F)}
  in
  {Tk.send pack(L)}
  end}
  end}`

Figure 3.5: Example for different fonts.

The init message for creating a font determines with the options `family` (the style of the font), `weight` (whether it is bold or normal), and `size` (how large is the font in point, if the number is positive, in pixels if it is less than zero) how the font looks. `Tk.font` supports more options, for a complete overview consult `font`.

Regardless of the platform, the families `courier`, `times`, and `helvetica` are supported.