Delphi : Restore a pre-design tabsheet after user has closed it...

Question

Hello,

I have a tPageControl on a form, and have made a nice 'welcome page' as a new ttabsheet at design time for the user to start off with. However, if the user closes this tab, I would like the option to bring it back, as it was in originally (much like the welcome page in the Delphi IDE). This seems like a simple problem...

When the tab closes, the original sheet is freed and set nil. I tried creating the sheet again by name (e.g. tabsheet1 := ttabsheet.create) and assigning it to the pagecontrol, but none of the original components from the sheet are there anymore...

I know designing the welcome page as a separate form, creating it when I need it and slapping it into a new tabsheet would work... but I was just wondering if there was a way to do it with the design time tabsheet.

Thanks all!

Rusty

Answer 1

Re-creating the design-time tab sheet will be quite a challenge because all the information describing its layout is embedded in the DFM resource for your form. It's not like there a separate resource for each tab, so you'd need to read the resource, extract the portion relevant to the tab, and then get ReadComponent to build a new instance; nothing in Delphi is designed to make that very easy, so you should consider other options.

The easiest solution would probably be to design your welcome page on a frame; I've found frames to be a little more cooperative than full-fledged forms when it comes to re-parenting them.

Another option is to create the entire tab in code. GExperts has a tool to make that pretty easy. Select the tab sheet, and then choose DExperts's "components to code" command. That places some code on the clipboard, and you can paste it into a function in your program. The code will contain everything required to re-create the selected components in code instead of building them from the DFM resource. Then, you can use that function to not only re-create the tab after it's been closed, but to create the tab in the first place. That way, you can be assured that you're creating the same thing both times.

The reason your attempt at re-creating the tab didn't work is that the name of the variable used to hold a reference to the form doesn't really define anything. All you did was create a brand new TTabSheet. The fact that you stored a reference to it in the same variable that used to hold a reference to the old tab is irrelevant. (But please feel free to give that variable a more meaningful name; all "TabSheet1" says is that it's the first tab you put on your form, way back when you first started working on this project.)

Answer 2

Rob's right about what's going on, and about using frames to fix it. Bit if you want a simpler solution, you could try just making the tab invisible whan the user closes it, instead of freeing it.

Answer 3

Thank you all for your comments and suggestions. A couple notes :

I tried the GEExperts option (pretty nice, I havent used this one before!) : however, it did not preserve many design time settings (font size and color for example)...also there were components with glyphs that didnt get saved....

Changing the visibility of the tabsheet doesnt seem to work either; the pagecontrol doesn't seem to know what to display, even after calling .Refresh ...it shows whatever is underneath your window.

Anyhow, I might investigate the frames option, but likely will just move the components to a new form and call it when needed...

Thanks again!

Answer 4

As Serg mentioned, you can just set the tabsheet's TabVisible property to false when you want to hide the page. The page control will switch to the next tab if it needs to, the tab will disappear, and the user won't be able to switch back to it until you change TabVisible back.