OnCustomDrawItem event of TListView doesn't seem to work
lazarus / 31-LCL

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lazjump · 2016-03-14 13:06

Hello,

OnCustomDrawItem event of TListView doesn't seem to work.

To test, please put a ListView and set the ViewStyle property to
vsReport, and put this code in the OnCustomDrawItem event:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
TListView(Sender).Canvas.Font.Style:=[fsStrikeOut];
The code would work fine in Delphi 7.

Tested on Windows XP with the old Lazarus 1.4.0. And also tested on
Windows 8 64 bit with CodeTyphon 5.70.

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lazjump · 2016-03-16 13:11

Since TListView is a common control, this looks like undesirable.

Anyone have a workaround?

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lazjump · 2016-03-28 14:12

So anyone have a workaround?

My need is very simple, I want to make the font of checked items in a
List View become striked out.

But this code don't work:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.ListView1CustomDrawItem(Sender: TCustomListView;  Item:
TListItem; State: TCustomDrawState; var DefaultDraw: Boolean);begin 
if Item.Checked then   
TListView(Sender).Canvas.Font.Style:=[fsStrikeOut];end;
Is this a bug, or wrong way to do it in Lazarus?

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balazsszekely · 2016-03-28 14:55

I'm afraid the component behaves differently in lazarus:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.Button1Click(Sender: TObject);begin  ListView1.OwnerDraw :=
True;  ListView1.Items.Add.Caption := 'Test';end; procedure
TForm1.ListView1DrawItem(Sender: TCustomListView; AItem: TListItem; 
ARect: TRect; AState: TOwnerDrawState);begin  with Sender.Canvas do 
begin    Font.Size := 11;    Font.Name := 'Tahoma';    Font.Style :=
Sender.Canvas.Font.Style + [fsStrikeOut];    TextOut(ARect.Left + 2,
ARect.Top + 2, AItem.Caption);  end;end;      
PS: I would switch to virtual tree instead of you.

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lazjump · 2016-03-28 15:17

Thank you for your kind reply, GetMem.

Yes it looks like ListView behaves differently in Lazarus & Delphi 7.
I thought it would behave the same since it is a "common control". But
it is not.

I am aware of using OwnerDraw:=true and the OnDrawItem event. But
there comes several problems with that; one is that the checkbox in
the ListView must be painted manually. And there are several other
problems (which I don't remember) when I tried to owner draw the List
View.

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howardpc · 2016-03-28 15:49

You don't have to paint the checkbox manually (though you can if you
wish).
Try this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.ListView1CustomDrawItem(Sender: TCustomListView;  Item:
TListItem; State: TCustomDrawState; var DefaultDraw: Boolean);var  lv:
TCustomListView absolute Sender;begin  if not (Sender is
TCustomListView) then    Exit;  if Item.Checked then begin   
lv.Canvas.Font.Style:=lv.Font.Style + [fsBold, fsStrikeOut];   
lv.Canvas.TextRect(Item.DisplayRect(drIcon), 25, 5 + Item.Position.Y,
Item.Caption);    DefaultDraw:=False;  end;end;

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lazjump · 2016-03-29 09:06

Hi howardpc,

Thank you. But that doesn't seem to work with the old Lazarus 1.4.0
(Windows XP) and also with CodeTyphon 5.70 (Windows 8 64 bit)

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howardpc · 2016-03-29 10:16

Yes, my example was compiled on Linux (64-bit).

Ironic that customising the Windows widgetset implementation of GUI
controls first introduced in Windows does not yet work as expected on
Windows, but does on other OSs. I haven't tried this exercise with a
trunk Lazarus on a recent Windows, but Laz 1.4 and CodeTyphon may well
differ from the behaviour of Lazarus trunk Win 32/64 (or even the 1.6
release).