Visual Basic 6 Black Book
(Publisher: The Coriolis Group)
Author(s): Steven Holzner
ISBN: 1576102831
Publication Date: 08/01/98

Setting A Form’s Startup Position

You can set the position of a form when it is first displayed by positioning it in the Visual Basic IDE’s forms window, or by setting the StartUpPosition property at design time (this property is not available at runtime):

•  vbStartUpManual—0; no initial setting specified

•  vbStartUpOwner—1; center on the item to which the form belongs

•  vbStartUpScreen—2; center form in the whole screen

•  vbStartUpWindowsDefault—3 (the default); position in the upper-left corner of the screen

Note, of course, that you can also position a form in the form’s Load event handler by setting its Left and Top properties.

Keeping A Form’s Icon Out Of The Windows 95 Taskbar

The Aesthetic Design Department is on the phone again. The dialog boxes in your program, SuperDuperTextPro, are fine, but there’s one little problem: when you display a dialog box, its icon appears in the Windows 95 taskbar, and according to company specs, dialog boxes should not add an icon to the taskbar, even when they’re displayed. Oh, you say.

It’s easy to keep a dialog box’s icon—or other form’s icon—out of the Windows 95 taskbar; just set that form’s ShowInTaskbar property to False at design time (this property is read-only at runtime). In fact, that’s the most common use for this property—to keep dialog box icons out of the taskbar.

Handling Keystrokes In A Form Before Controls Read Them

There’s a subtle war for possession of the focus between forms and controls in Visual Basic. If you click a form, giving the focus to that form, what really happens is that a control in that form (if there are any) gets the focus. But what if you really wanted to give the focus to the form as a whole to use the form’s keystroke events?

It turns out that you can indeed make sure the form gets keystrokes even before the control with the focus gets them by setting the form’s KeyPreview property to True (the default is False). You can set this property at runtime or design time.

Let’s see an example. Here, we add a text box, Text1, to a form. When the users click the form, we’ll start intercepting keystrokes before they go to the text box. Following the Christmas example developed earlier in this book, we’ll remove all occurrences of the letter “L” when the user types that letter (making the text box a No-“L” text box).

Here’s how we start intercepting keystrokes when the user clicks the form:

Private Sub Form_Click()
    KeyPreview = True
End Sub

Now we’ll get the keystrokes first, as the user presses them, no matter what control has the focus. We can remove the letter “L” before it’s passed on to the text box in our example this way:

Private Sub Form_KeyPress(KeyAscii As Integer)
    If KeyAscii = Asc("L") Then
        KeyAscii = 0
    End If
End Sub

Making A Form Immovable

The Aesthetic Design Department is calling. They like the screen position they’ve set for the windows in your program—is there any way to make sure the user can’t move them?

There is. You can set the form’s Moveable property to False. Note, however, that you can only set this property at design time.

Showing Modal Forms

The Testing Department is on the phone again. When you show that form full of options, you shouldn’t let users go back to the main form until they’ve chosen the options they want. Hmm, you think, how does that work?

You can make a form modal, which means that the user has to dismiss it from the screen before working with the other forms in your application. You usually make only dialog boxes modal, but you can make any form modal if you wish. To make a form modal, pass the constant vbModal to the Show method:

Private Sub Command1_Click()
    Form2.Show vbModal
End Sub

Saving Values In The Windows Registry

Placing data in the Windows Registry saves that data for the next time your program runs, and the kind of data you save there usually represents settings for your program, such as window size and location. You can use the Windows Registry directly from Visual Basic. To save a setting in the Windows Registry, you use the SaveSetting statement:

SaveSetting  appname, section, key, setting

Here are the arguments for SaveSetting:

•  appname—String containing the name of the application to which the setting applies.

•  section—String containing the name of the section where the key setting should be saved.

•  key—String containing the name of the key setting being saved.

•  setting—Expression containing the value to set the key to.

Here’s how it works: to save a setting in the Windows Registry, you pass your application’s name, a section name, a key name, and the setting for that key. Using section names allows you to break up an application’s set of keys into different groups, which can be handy in terms of organization. Those keys are the actual variables that you save settings to. We’ll see an example showing how to get and save settings with the Windows Registry in the next topic.

Getting Values From The Windows Registry

You can get settings that you’ve placed in the Windows Registry with the GetSetting function, which returns the value of that setting, or the default value as specified in the list that follows:

GetSetting( appname, section, key[, default])

Here are the arguments passed to this function:

•  appname—String containing the name of the application or project whose key setting is requested.

•  section—String containing the name of the section where the key setting is found.

•  key—String containing the name of the key setting to return.

•  default—Expression containing the value to return if no value is set in the key setting. (If omitted, default is assumed to be a null string, “”.)

Let’s see an example. In Chapter 5, we developed the MRU application, which supports a Most Recently Used (MRU) menu item in the File menu. This item displayed the most recently opened file’s name using data stored in the Registry.