Yes this is true Max BUT...really all I am savingt to the registry is
wether the checkbox is checled or not, ot he color selected in a color
combo, or the text in a text box...I am not saving ALL the properties of
a control.
Have I given the impression that I was saving ALL the properties of a
control? I hope I didnt.....
Jeremy
-----Original Message-----
From: "Max Nilson" <[EMAIL PROTECTED]>
To: Multiple recipients of list delphi <[EMAIL PROTECTED]>
Date: Wed, 2 Oct 2002 10:28:43 +1200
Subject: RE: [DUG]: Checkbox
> Jeremy Coulter asks:
>
> > What I want it for is a properties page where the user sets up what
> they
> > want the app to look like etc. so saving specific properties like
> > IndexItem, Value, text etc. of the components based on their type, is
> > the best way to go.
>
> and later mentioned:
>
> > Ok, but how do I access the values? i.e. How do I read say
> > checkbox10...as an example to see if its checked or not?
>
> so it looks like he is essentially trying to read and write component
> properties to the registry.
>
> There are two basic methods that you can use to achieve this sort of
> thing,
> and the differencve lies in how you want to handle backwards
> compatibility
> when component are updated over time.
>
> The first mechanism is to simply overload the standard Delphi streaming
> code
> and read and write the DFM stuff into a registry value. Code something
> like
> this is a start:
>
> Mem := TMemoryStream.Create;
> Mem.WriteComponent(ACheckBox); // Dumps propertes into stream
> with TRegistry.Create do
> try
> if not OpenKey('Software\MyApplication\Componentdata') then
> raise Exception.Create('Registry failure!');
> WriteBinaryData(ACheckBox.Name, PChar(Mem.Memory)^, Mem.Size);
> finally
> Destroy
> end
>
> and do the reverse on the way back in, that is read the registry data
> into a
> memory stream, reset the memory stream to the start and use
> ReadComponent to
> read the properties back in again. For more on this sort of technique
> you
> need to read around in Classes.pas to see how Borland wrote all teh
> Delphi
> streaming code.
>
> The only problem with this is that is you rename, delete or change the
> allowable values of a property you have all sorts of problems reading
> the
> old format values back in again, because Delphi has no mechamism to
> allow
> for recovering from errors during property streaming. If you are never
> going
> tio change your properties then you have no problem otherwise you need
> to
> change the format of the saved vales from Delphi's DFM to your own
> scheme.
>
> The basis of doing this is to do the above, but rather than using
> WriteComponent you preform your own enumeration through the published
> proporties and then write their values out in your format. I actually
> do
> this for our custom report designer and write the values I need to out
> into
> a sort of butchered CVS file and it works well. I have coded things so
> that
> I can detect versions of file and as the format changes I can adapt the
> reader to handle old versions cleanly.
>
> Extra bonus marks would be to store all the enumerated property values
> into
> an XML file, as this would be the perfect combination of readable
> output,
> backwards compatibility and style, and have maximum sexyness.
>
> Cheers, Max.
>
>
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