[Lazarus] TComboBox.ReadOnly

[Ondrej Pokorny]

On 01.05.2020 23:36, Juha Manninen via lazarus wrote:
> I applied my own patch. It removes the deprecated published property 
> so it will be gone in Lazarus 2.2. A public ReadOnly property remains 
> but is cannot be assigned any more. Thus ReadOnly property is itself 
> readonly. :)
> Please test.

 From what I can see the ReadOnly property is still published. I would 
remove it completely, there is no reason to have it anymore if it was 
deprecated for 3 years. Not even in the public section. (Again, even 
with ReadOnly=True you can still change the value with the drop down.)

As for Jamie's issue. I took a look at the state before I deprecated it 
and it was a way to disable editing for csOwnerDrawFixed, 
csOwnerDrawVariable styles - so actually a duplicate property for the 
Style property. It had no other function.

It was not an equivalent for a "readonly edit" (=you can select text but 
cannot change it by typing) and enabled drop-down list. Something that 
can be achieved with EM_SETREADONLY as described in 
http://mc-computing.com/Languages/Delphi/ReadOnly.html

This works in Lazarus as well:
procedure TForm1.Button1Click(Sender: TObject);
begin
   // make combobox read-only (make sure ComboBox1.Style=csDropDown)
   SendMessage(GetWindow(ComboBox1.Handle, GW_CHILD), EM_SETREADONLY, 
Ord(True), 0);
end;

So, IMO the removal of the ReadOnly property is valid because it was not 
implemented with EM_SETREADONLY as Jamie expected and was only confusing 
the way it was implemented.

Ondrej