Displaying messages in Visual FoxPro
Developers who have moved into Visual FoxPro from other Windows
development tools and languages tend to rely on the familar
dialog whenever they want to display a short text message to the user.
Visual FoxPro does offer several other ways of showing a warning or giving
some information to the user:
- Status bar
- Wait Window
The Visual FoxPro Status Bar runs across the bottom of the screen, just
above the Windows status bar. Whilst you are developing it gives you
useful information such as which table is open, the position of the
current record in that table, and whether or not that record is locked.
Regular users don't need to know this degree of detail so it is usual
to turn the status bar off at runtime. The early part of the program or
the Init method of an application class will typically have a line of
Set Status Bar Off
Sometimes though it can be more useful to leave the bar on and then to
control what is being displayed there. As its name suggests, the Status
Bar can be useful for keeping the user up to date with the general state
of the system:
Set Status Bar On
Set Message To
'There are ' + lcUnPaid + ' unpaid invoices.'
Note that there is another very similar command:
Set Status On
This is a relic of the DOS versions of FoxPro and displays a status bar
close to, but not quite at, the bottom of the screen. This bar shows
much the same information as the modern-day status bar. Here's a screen
shot of it in FoxBase+ from the late eighties.
If you see something like this in your application then you've missed the
word 'BAR' from the command. An easy mistake to make.
The Wait Window is unique to the FoxPro family and, although it's very
useful, it might be unfamiliar to some users.
These commands display a small grey window in the upper right corner of
"Here's a message"
The basic command will display a window and halt execution until the user
presses a key or clicks the mouse. Some additional clauses make it more
'Display for 5 seconds'
'Change position on screen'
A typical use for the Wait Window with
the timeout clause is to report progress
through a long task.
'Copying customer file...'
Use it to display messages for short periods through the task and
finally use a Wait Clear when
the process completes. If the process hangs or fails for any reason
then the last message will remain visible and this can be useful
for tracing the cause of the fault.
You could use a regular Windows messagebox dialog with its timeout
feature in a similar fashion but this takes more resources and doesn't
always work if the user has assigned a sound scheme to the messages. The
Wait Window can be set to flick on and off the screen in a tenth of a
second so that the user just sees a blur of messages "Copying this",
"Copying that", and so forth.
The Wait command has been around since Fox
for DOS so it does have a couple of foibles:
- The timeout is in seconds - not the usual milliseconds
- The position is in rows and columns - not pixels or twips
Not perhaps the obvious tool for short text messages but it does allow
the user to scroll back through the messages. All you have to do is
add your message to the box as a new line and make that the current
value of the listbox.
The listbox will then scroll up as your messages appear. Very useful
for showing the progress of this sort of housekeeping task, especially if
you use a two-column listbox and display a timestamp alongside each message in the list.