Volume 6A: Motif Programming Manual

Let's take another look at the PG&E scenario that we discussed at the beginning of the chapter. As you recall, the

problem with that particular situation was that the database could retrieve 20% of the county (the work window), but

the graphic resolution was such that only 10% of it could be displayed at one time (the viewport). The fundamental

problem with the application−defined scrolling mode is that the work window cannot be a different size from the

viewport. However, we can work around this problem by complying with the restriction that the work window and

viewport are the same size, but we can use the enlarged pixmap idea from the source code to accomplish the task.

Each database query can be converted and rendered into a sufficiently large pixmap, which can then be rendered into

the work window as necessary. If the scrolling is small enough, another part of the pixmap can be rendered into the

work window, instead of performing a completely new database lookup.

10.5 Working With Keyboard Traversal in ScrolledWindows

As we described in Chapter 8, Manager Widgets, manager widgets play a significant role in handling keyboard

traversal mechanisms. As a manager, the ScrolledWindow supports keyboard traversal. However, one significant

difference is that the widgets in a ScrolledWindow may not be visible at all times. In Motif 1.1, the toolkit does not

provide a mechanism to allow keyboard traversal to widgets that are not visible. While it might be possible to

implement this feature, it ...