Question

I was wondering why Delphi (2007) provides three widgets that seem to do the same thing, and what the advantages/disadvantages are for each.

On the same topic, if I want to display different sets of controls, why should I favor eg. PageControl + TabSheets + Frames, instead of just displaying different frames directly on the parent form?

Thank you.

Answer 1

From the helpfile on TTabSet:

Tab set controls are commonly used to
display tabbed pages within a dialog
box. TTabSet is provided for backward
compatibility. Use TTabControl
component in 32-bit Windows
applications.

So the real question is, what’s the difference between TTabControl and TPageControl? The difference is that TTabControl only has one “page”, whereas TPageControl has one page for each tab. This makes them useful in different situations.

TPageControl is useful for dialogs where you want to fit more UI on the screen than you have screen space to fit it in. Organize your UI into categories and put each category on one page. You see this pattern a lot in Options dialogs, for example.

TTabControl, on the other hand, works well for working on an array/list of objects. Create a UI to display and edit the properties of a single object, and place it on a TTabControl, then create one tab for each object and set up the event handlers so it’ll load a new object from the array into the controls whenever you change tabs.

As for the frames question, the main reason to use a TPageControl in conjunction with frames is because it provides a prebuilt way to decide which frame to display. That way you don’t have to reinvent a mechanism for it.