Your Active Document has some control over how it's placed and displayed
in the container. Most of this control has to do with the behavior it will exhibit when the
user tries to scroll through it within the container. Remember, because another application (the container)
is hosting your document, your document can't have full control over its own appearance and
behavior. With regards to scrolling, you may specify:
-
Whether or not your object will have scrollbars and what type they will be (Scrollbars
property).
-
How small the container has to shrink before your document will receive horizontal
or vertical scrollbars (MinHeight and MinWidth
properties).
-
How far the scrollbar's "elevator box" will travel when the user clicks
a scroll button (HScrollSmallChange and VScrollSmallChange
properties).
-
How to behave whenever the user scrolls your document (Scroll
event procedure).
-
How frequently to call the Scroll event (ContinuousScroll
property).
Each of the above features is discussed in the following sections.
-
The
Scrollbars Property and
MinHeight and MinWidth
Properties
-
The
HScrollSmallChange and
VScrollSmallChange Properties
-
The
Scroll Event Procedure and the
ContinuousScroll Property
The
Scrollbars Property and MinHeight and MinWidth Properties
You can use the Scrollbars property to determine whether
the Active Document will appear in its container with horizontal scrollbars, vertical scrollbars,
both types of scrollbars, or no scrollbars. Simply set the UserDocument's
Scrollbars property to one of the four settings:
-
vbSBNone (0)
-
vbHorizontal (1)
-
vbVertical (2)
-
vbBoth (3)
Even if you set the Scrollbars property to display
Scrollbars, your Active Document might not always show them. This is because the Active
Document container's height (ViewPortHeight) or width
(ViewPortWidth) must shrink below the values specified in the
MinHeight or MinWidth property respectively. The respective
Height and Width properties of the
UserDocument determine the default values of the MinHeight and
MinWidth properties. If ViewPortHeight is greater than
MinHeight, no vertical scrollbar will appear regardless of the
Scrollbars setting. If ViewPortWidth is greater than
MinWidth, no horizontal scrollbar will appear regardless of the
Scrollbars setting.
If you always want scrollbars to appear around your document application,
simply set MinHeight and MinWidth to arbitrarily large values
(equal to or greater than Screen.Height and
Screen.Width). Your container will always be smaller than these specified sizes, and scrollbars
will, therefore, always appear.
The
HScrollSmallChange and VScrollSmallChange Properties
These properties control the distance that the scrollbar will move when the user clicks
one of the "thumb screws" (the arrow buttons) at either end of the scrollbar. Units
of measure are in twips, and the minimum value for these properties is 15 twips (slightly over
1/100th of an inch).
The
Scroll Event Procedure and the ContinuousScroll Property
The UserDocument's Scroll event fires whenever the user
makes a change on the Scrollbar. In Listing 14.6, the document's background
color whimsically changes every time there is a Scroll event so
you can see how often the event fires.
LISTING 14.6
THE SCROLL EVENT
Private Sub UserDocument_Scroll()
'Whenever the user moves the scroll bar,
'we flash a different background color
BackColor = _
RGB(Rnd * 255, Rnd * 255, Rnd * 255)
End Sub
You can control how often the Scroll event fires by setting the
ContinuousScroll property. The settings of this Boolean property
have the following significance:
-
When ContinuousScroll is False, the
Scroll event will not fire while the user is dragging the Scroll box. The
event will only fire when the user releases the Scroll box.
-
When ContinuousScroll is True, the
Scroll event will fire continuously as the user drags the Scroll box.
The setting of ContinuousScroll has no effect one
way or another on the Scroll event if the user is clicking
the scrollbar arrows or the shaft of the scrollbar. In these cases, the
Scroll event fires once for every click.
