Delaying the Creation of New Pages<A NAME=213> </A>

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### Delaying the Creation of New Pages

If your notebook contains many complicated pages, it may take quite a while to create all widgets inside these pages and your program will probably freezes for a few seconds when it pops up the notebook for the first time. To avoid embarrassing moments like this, we can use the ``delayed page creation'' feature of the TixNoteBook widget.

When we create a page using the `add` method, we can specify the optional parameter `-createcmd` so that we only need to create the page when the user wants to see it. This is illustrated in program 2-3:

> `tixNoteBook .n
> .n add hd -label "Hard Disk" -underline 0 -createcmd CreateHd
> .n add net -label "Network" -underline 0 -createCmd CreateNet
> proc CreateHd {frame} {
> tixControl $frame.access -label "Access Time:"
> tixControl $frame.write -label "Write Throughput:"
> tixControl $frame.read -label "Read Througput:"
> tixControl $frame.capacity -label "Capacity:"
> pack $frame.access $frame.write $frame.read $frame.capacity
> -side top -fill x
> }
> proc CreateNet {frame} {
> ...
> }`

(Figure 2-3) Delayed Page Creation

In line 2 of program 2-3, we use the `-createcmd` option to specify that the procedure `CreateHd` should be called when the ``Hard Disk'' page needs to be created. `CreateHd` takes one argument, the frame subwidget of the page. As we can see, program program 2-3 is not very different than program 2-2, except now we can issue less commands during the set-up of the NoteBook widget and the interface can be started up more quickly.