View source for Mnemonics in Dialog Boxes

Written by [[Stefan Ruck]]


<p><font COLOR="#669966">[Here is a link to the <a HREF="mnsrc.zip">source
code</a>. Ed.]</font>

<p>We all know them: Mnemonics (I'm glad I just have to write this word
and not pronounce it). When we look at menu bars, we can find them almost
anywhere. These nice underscored characters which make life easier for
those who still use the keyboard instead of the mouse.

<h3>The Problem</h3>

<p>Looking at dialog boxes e.g. of IBM's programs, I'm missing mnemonics a
lot in conjunction with edit controls and other controls that don't have a
text part of their own like radio buttons have.

<p>Believe me, for a long time I thought it was not possible to use them
in static text controls. Just because I hadn't seen it in the OS/2
programs I'm using! Of course I had a look at the docs shipped with the
DevCon I CDs. But searching for the keyword 'Mnemonic' only shows some
very old stuff about mnemonics in menu bars and something about the use of
the Universal Resource Editor (which I'm not using).

<p>So I was thinking about writing a class derived from IFrameWindow
myself. This class should have the ability of putting mnemonics in static
text controls to set the input focus directly e.g. to edit controls just
by pressing the right keys, not by using the mouse.

<p>But there is no need for such a class.

<h3>What's Needed?</h3>

<p>Before I started writing this class, I thought to myself, why not try
to do it the way I know it from Windows programming. There were only two
things to think about.

<p>First there was the question: How to get a character of a static text
control to be underscored?

<p>When you use IBM's dialog editor to design your dialogs, static text
controls do not convert the '~' by default. And because I didn't knew the
meaning of the word 'mnemonic' in the text style page I never tought of
setting this flag. But a short look at the dictionary was very helpful.
(When you use other controls like check boxes or radio button, there is no
mnemonic flag to set to enable mnemonics. Here mnemonics always work.)

<p>So the answer is simple. Just set the DT_MNEMONIC style for the desired
control. Using the IBM's dialog editor you just have to check the mnemonic
check box on the text style page of the control.

<p>The second question is: How does the dialog know where to set the
input focus when the mnemonic of a static text control is being used?


<p>This is similiar to Windows programming (or vice versa). Just take care
with the sequence of the dialog's controls (IBM's dialog editor calls it
'order groups', Microsoft's dialog editor calls it 'tab control'). The
text control has to be directly in front of the corresponding control
which should receive the input focus when the mnemonic is used. This
doesn't mean the position in the dialog box but the sequence in the dialog
description (have a look at the sample below).

<p>As you can see, there is no miracle about mnemonics and static text
controls. No need to do extra programming, just a little bit of dialog box
design.

<h3>The Sample</h3>

<p><img WIDTH=291 HEIGHT=296 SRC="mnsample.gif">

<p><font SIZE=2>
Figure 1: Sample dialog box.
</font>

<p>The dialog description for the dialog box shown in figure 1 looks like
this:

<font COLOR="#0000BB"><font COLOR="#0000BB"><pre>
  DLGTEMPLATE DLG_SAMPLE LOADONCALL MOVEABLE DISCARDABLE
  BEGIN
    DIALOG  "Mnemonic Sample", DLG_SAMPLE, 8, 35, 141, 106,
            WS_VISIBLE, FCF_SYSMENU | FCF_TITLEBAR
    BEGIN
      LTEXT           "~Edit Control", -1, 3, 89, 61, 8,
                      DT_MNEMONIC
      ENTRYFIELD      "", DID_EDIT_CONTROL, 73, 89, 59, 8,
                      ES_MARGIN
      LTEXT           "~Slider", -1, 3, 73, 61, 8,
                      DT_MNEMONIC
      SLIDER          DID_SLIDER, 71, 67, 64, 16,
                      SLS_SNAPTOINCREMENT
                      CTLDATA 12, 0, 20, 0, 0, 0
      GROUPBOX        "~Radiobutton Group", -1, 3, 24, 129, 40,
                      DT_MNEMONIC
      AUTORADIOBUTTON "Radio 1", DID_RADIO_1, 7, 42, 60, 10,
                      WS_TABSTOP | WS_GROUP
      AUTORADIOBUTTON "Radio 2", DID_RADIO_2, 7, 28, 60, 10
      AUTORADIOBUTTON "Radio 3", DID_RADIO_3, 70, 42, 60, 10
      AUTORADIOBUTTON "Radio 4", DID_RADIO_4, 70, 28, 60, 10
      DEFPUSHBUTTON   "~OK", DID_OK, 44, 3, 40, 14, WS_GROUP
    END
  END
</pre></font></font>

<p><font SIZE=2>
Figure 2: Dialog description of the sample dialog box.
</font>

<p>As you can see, group boxes can also be used for mnemonics. And as said
above, it is very important to keep the right sequence among the controls.

<p>When 'Alt+E' is pressed in the dialog box shown in figure 1, the edit
control receives the input focus, 'Alt+S' gives the slider the input focus
and 'Alt+R' sets the input focus to the radio button selected the last
time.

<p>For test purpose, just swap the position of the text control 'Slider'
and 'Edit Control' and see what happens. Because the sequence of the
controls is very important, you can get funny (just for you, not for the
user) effects by changing it.

<p>I feel that using mnemonics in dialog boxes a little bit more than IBM
does is a real help for anyone who is primary using the keyboard. It makes
your programs more 'user friendly'. The user is able to work faster with
your programs and so is more satisfied, and it costs you nearly nothing.
So use them whenever possible.

<p>In the source files there are two makefiles included. The one ending
with .mav was made for IBM's VisualAge for C++. The one ending with .mac
isn't a MAC file but the CSet++ makefile.