In article <38669@palm-dev-forum>, "Richard Burmeister" <[EMAIL PROTECTED]>
wrote:
> > From: Remo Hofer
> >
> > Could you please comment the following function:
> >
> > void UpdateControl(FormPtr f, UInt16 id, Char * s) {
> > ControlType *ctl;
> > Char *label;
> >
> > ctl = FrmGetObjectPtr(f, FrmGetObjectIndex(f, id));
> > label = (Char *) CtlGetLabel(ctl);
> > StrCopy(label, s);
> > CtlSetLabel(ctl, label);
> > }
>
> label is a stack-based (local) variable in the function UpdateControl. As
> soon as you exit UpdateControl, it's contents may change. This is not a
> good way to change the label of a control which will probably outlive the
> function call.
The address of the persistent (global) memory of the controls label (which
lives in the memory allocated by the form) is stored in the local variable
label. And then after tweaking the string, this address (still pointing
into the forms memory) will be set (once again) as the new label location,
just to tell the system that the string has changed and has to be redrawn.
The string itself stays allways in the forms memory. This method works
fine on PalmOS 2 upto 4 (also debug), but I wonder if it is clean enough
for PalmOS 5.
--
Remo Hofer <[EMAIL PROTECTED]>
http://www.geocities.com/SiliconValley/Cable/5206/
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