[lazarus] how to implement TDBListBox.Readonly

Andrew Johnson acjgenius at earthlink.net
Mon Sep 15 08:17:15 EDT 2003

Just to clarify here, we have a readonly property(all db aware controls
do in delphi afaik), this sets the datalink readonly property to true or
false. If its readonly then calling edit will validate false(I think)
and apears to work in the DBEdit. now when the fieldlink is readonly we
don't _want_ changes to happen same as when we aren't in editing(ala in
browse) mode. Since a list set changes the field value to one in the
list then we can't even let it change selection. So to make sure its
properly readonly we need to prevent changing. I overrode click and
keydown, but some messages still seem to be getting through. I tested
this in Delphi4 and got what I expected - if I click something when
readonly, nothing happens, in mine sometimes the selection changes...
thats the issue.

I will try and implement keydown later too see if I can catch arrow,
home page up/down and end there so they don't change selection.

(btw this is in cvs now if you want to look at what I mean)


On Mon, 2003-09-15 at 07:12, Michael Van Canneyt wrote:
> On Mon, 15 Sep 2003, Marc Weustink wrote:
> > + From: Andrew Johnson [mailto:acjgenius at earthlink.net]
> > + Sent: maandag 15 september 2003 3:34
> > +
> > + I just decided to do TDBListBox since I figured it should be another
> > + easy one, but I forgot about readonly. With Edti I could use inherited
> > + readonly to make sure it was uneditable, but with listbox there is no
> > + such thing. So I need to figure out how to handle this. I think I just
> > + need to add events for all mouse and keyboard events which would change
> > + the selection. So I wonder what all I need to be catching. obviously I
> > + need to do a KeyPress like I did with text, just add a test to make sure
> > + TFieldDataLink.Edit validates and if not set the Key to #0. However I am
> > + not sure what all else will need to be handled. aka what functions and
> > + within those functions what needs to be trapped.
> > +
> > + If anyone knows please tell me :)
> > +
> > + KeyPress won't get the arrow keys will it?
> >
> > Nope. KeyDown/Up will get all keys, KeyPress only those keys who return a
> > valid ASCII char.
> >
> > I just had a peek at the VCL and Readonly is handled through the DataLink.
> > If I understand what is happening, the ListBox isn't readonly. Only the
> > dataset isn't set to Edit when changing something in the listbox.
> The listbox should do that using  TFieldDataLink.Edit, this will return
> true if the dataset is successfully set in editmode.
> Michael.
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