How do you set no row selected on TDrawGrid?

[PiedSoftware 3]

Hi

 

With TListBox and TComboBox, if you set ItemIndex to -1, nothing is selected. I tried setting DrawGrid.Row := -1 but that gives an error. Is there some other way to show nothing selected yet?

[dummzeuch 1517]

1 hour ago, PiedSoftware said:

With TListBox and TComboBox, if you set ItemIndex to -1, nothing is selected. I tried setting DrawGrid.Row := -1 but that gives an error. Is there some other way to show nothing selected yet?

You can't. What you can do is do the drawing yourself (isn't that necessary for TDrawGrid anyway?) and if nothing is supposed to be selected, don't draw the focus rectangle. But that would only be visual, If you read row and column they will still have some value. And it would also be necessary to somehow detect when something is being selected. It's easy to detect when the user clicks on something with the mouse, but more difficult when he wants to use the keyboard.

 

It might be easier to have a special row that contains the entry "<nothing>" or similar instead.

[PiedSoftware 3]

2 hours ago, dummzeuch said:

You can't. What you can do is do the drawing yourself (isn't that necessary for TDrawGrid anyway?)

There are some default things set, like font colour and background colour, and I am trying to stay as close to the defaults as I can,

[Remy Lebeau 1436]

Quote

Is there some other way to show nothing selected yet?

Set the Selection property to a TGridRect containing all -1's.

var
  gr: TGridRect;

gr.Left := -1;
gr.Right := -1;
gr.Top := -1;
gr.Bottom := -1;

DrawGrid.Selection := gr; 

 

Edited July 20, 2021 by Remy Lebeau

[PiedSoftware 3]

On 7/20/2021 at 5:46 PM, dummzeuch said:

You can't. What you can do is do the drawing yourself (isn't that necessary for TDrawGrid anyway?)

There are some default things set, like font colour and background colour, and I am trying to stay as close to the defaults as I can,

[PiedSoftware 3]

On 7/21/2021 at 2:00 AM, Remy Lebeau said:

Set the Selection property to a TGridRect containing all -1's.

var
  gr: TGridRect;

gr.Left := -1;
gr.Right := -1;
gr.Top := -1;
gr.Bottom := -1;

DrawGrid.Selection := gr; 

  

Thanks, that is the way I went and it had the desired effect on the appearance.

At first I tried to use a constant:

const
  EmptyRect: TGridRect = (Left: -1; Top: -1; Right: -1; Bottom: -1); // Copied from implementation of vcl.grids

procedure TGridDataRtti<T>.PopulateGrid(...);
begin
 ...
  grid.Selection := EmptyRect; 
 end;

But that gave me the spurious error message:
 E2506 Method of parameterized type declared in interface section must not use local symbol 'EmptyRect'