TListItem.MinWidth doesn't work

[David P 2]

Hello

 

I'm using a TListView in Report mode and I'm creating columns dynamically.  I am setting TListItem.MinWidth = 50, but when ran, this is being ignored.

 

What am I missing?

 

Thanks

 

David

[Remy Lebeau 1263]

TListItem does not have a MinWidth property, you meant TListColumn instead.

 

In any case, what version of Delphi are you using?  I can reproduce the problem in Delphi 12 w/ Patch 1 installed.  When dragging a column divider in the header, the TListColumn.MinWidth and TListColumn.MaxWidth values get ignored when the TListView is processing an HDN_ITEMCHANGING notification from the header.  TListView looks for HDN_ITEMCHANGING to trigger a redraw of the active TListItem, but there is an 'else' that skips the MinWidth/MaxWidth processing:

if (Mask and HDI_WIDTH) <> 0 then
  begin
    if code = HDN_ITEMCHANGING then
      EnsureItemRedrawn(nil)
    else // <-- HERE!!
    begin
      Col := GetColumnFromTag(Item);
      if Col.MinWidth >= cxy then
        cxy := Col.MinWidth
      else
        if (Col.MaxWidth > 0) and (Col.MaxWidth <= cxy) then
          cxy := Col.MaxWidth;
        Col.Width := cxy;
    end;
  end;

When I take that 'else' out, the MinWidth/MaxWidth values work properly as expected:

if (Mask and HDI_WIDTH) <> 0 then
  begin
    if code = HDN_ITEMCHANGING then
      EnsureItemRedrawn(nil);
    //else // <-- HERE!!!
    begin
      Col := GetColumnFromTag(Item);
      if Col.MinWidth >= cxy then
        cxy := Col.MinWidth
      else
        if (Col.MaxWidth > 0) and (Col.MaxWidth <= cxy) then
          cxy := Col.MaxWidth;
        Col.Width := cxy;
    end;
  end;

This bug does not exist in Delphi 10.3, so it was introduced sometime after that version:

if (Mask and HDI_WIDTH) <> 0 then
  begin
    // NO redraw LOGIC HERE!!!
    Col := GetColumnFromTag(Item);
    if Col.MinWidth >= cxy then
      cxy := Col.MinWidth
    else
      if (Col.MaxWidth > 0) and (Col.MaxWidth <= cxy) then
        cxy := Col.MaxWidth;
      Col.Width := cxy;
  end;

I would suggest filing a bug report with Embarcadero, but Quality Portal is still down.  I'll report it privately.

Edited March 1 by Remy Lebeau

[David P 2]

Thanks. I'm using CB 11.3

 

In the interim I thought I'd detect the column widths changing and then enforce the min width, but there doesn't appear to be any event that fires when a colmn has changed size.

 

Never mind, found a solution you wrote in 2012.

Edited March 6 by David P

[Remy Lebeau 1263]

1 hour ago, David P said:

In the interim I thought I'd detect the column widths changing and then enforce the min width, but there doesn't appear to be any event that fires when a colmn has changed size.

Correct, there is no event published for this.  You would have to subclass the ListView to handle the HDN_ITEMCHANGING notification directly.  Alternatively, if you are building with Runtime Packages disabled, you can make a copy of Vcl.ComCtrls.pas and add it to your project, and then make the code change I mentioned earlier to fix the bug.

1 hour ago, David P said:

Never mind, found a solution you wrote in 2012.

[David P 2]

I submitted this as a bug and they could not reproduce it in 11.3. Now, neither can I.  I can reduce the column width to below MinWidth but as soon as I release the mouse button it springs back to MinWidth.  I'm  starting to doubt my sanity.

[Remy Lebeau 1263]

As I said, I confirmed the bug does not exist in 10.3, but does exist in 12.0, so it's possible that it does not exist in 11.3 either. I don't have that version to check with. If you look in your IDE's copy of the Vcl.ComCtrls.pas source file, do you see the code I showed earlier?

Edited April 9 by Remy Lebeau

[David P 2]

Both 11.3 and 12.1 have that 'else' in place and both enforce the MinWidth setting.

 

It is possible to drag to a smaller width than MinWidth but upon release it springs to MinWidth width.  I'm now wondering if I was just fixating on the dragging and not when the mouse was released.

[Remy Lebeau 1263]

On 4/9/2024 at 7:44 AM, David P said:

It is possible to drag to a smaller width than MinWidth but upon release it springs to MinWidth width.  I'm now wondering if I was just fixating on the dragging and not when the mouse was released.

Interesting.  I just tested that in 12.0 Patch 1 and sure enough the springing works.  However, removing the 'else' does prevent the dragging from going smaller than the MinWidth to begin with.