Custom drawing in TTreeView

Posted on 2002-06-26
Last Modified: 2010-09-11
I'm using C++ Builder 6. I would like to implement custom item drawing. More specifically, I would like to use several fonts in a single node.

I use the following code on AdvancedCustomItemDraw:
void __fastcall TForm5::pTreeAdvancedCustomDrawItem(
      TCustomTreeView *Sender, TTreeNode *Node, TCustomDrawState State,
      TCustomDrawStage Stage, bool &PaintImages, bool &DefaultDraw)
        DefaultDraw = false;

        TRect Rect = Node->DisplayRect(true);

        Sender->Canvas->Font->Name = "MS Serif";
        Sender->Canvas->Font->Size = 10;
        Sender->Canvas->Font->Color = clRed;
        Sender->Canvas->TextOut(Rect.Left, Rect.Top, "ala");

        Sender->Canvas->Font->Name = "Tahoma";

        Sender->Canvas->Font->Color = clBlack;
        Sender->Canvas->TextOut(Rect.Left+30, Rect.Top, "ala");

But the font does not change.
Please help.
Question by:ia_ia_ia_1
  • 3
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Expert Comment

ID: 7111122
Have a look in BCB's examples. I think theres a project called CustomDraw or CustDraw which should be able to help you. When I get to a machine with BCB on it I will have a go at solving your problem.



Expert Comment

ID: 7111142

I don't do C (only Delphi ;-), but I think this is what you're looking for:

Author Comment

ID: 7111196
The point is that I need to use different fonts in a SINGLE node - and it seems that only the first font I've used to draw text is used - all subsequent changes to the font are disregarded.
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Accepted Solution

Cynna earned 300 total points
ID: 7113152

I'm sorry, I misunderstood you.
When ported to Delphi, your code really has unexpected
results, just like you said. This seems to be a bug
in Delphi (and, obviously, in BC++). You might try installing latest service pack.

But, in the meantime, I did a little investigation about
this behaviour. It seems that problem lies in the fact that
TCustomTreeView replaces the default Brush and Font
OnChange events with its own CanvasChanged . As a
result, Brush and Font are changed only once, before using it. All subsequent changes are ignored by Canvas.

This can be fixed by saving original OnChange events of the
TCustomTreeView.Canvas, and later calling them explicitly to notify TCustomTreeView.Canvas that font has changed.

I tested this with Delphi, and I assume it'll work in BC++ too. Below is a Delphi version that solves this problem.

1. Add this event handlers to the Form declaration:

    { Public declarations }
    OriginalBrushOnChanged: TNotifyEvent;
    OriginalFontOnChanged: TNotifyEvent;


2. Add this to Form's OnCreate event:

    procedure TForm5.FormCreate(Sender: TObject);
      // Save original Canvas OnChange events:
      OriginalBrushOnChanged :=  Tree.Canvas.Brush.OnChange;
       OriginalFontOnChanged := pTree.Canvas.Font.OnChange;


3. Finally, explicitly call event handler after font
   change in AdvancedCustomItemDraw.

   change this line in your example:
        Sender->Canvas->Font->Color = clBlack;

   ... to these two lines:

        Sender->Canvas->Font->Color = clBlack;
        // explicit call to original event handler:

4. If you change brush, same goes for it too, except
   you, of course, call OriginalBrushOnChanged()...

I'm sorry I didn't post C++ version completely, but
I was unsure about declaration of the events in C++, and presumed you know how to translate this to Builder C++, since you posted your question here.

Author Comment

ID: 7113215

Thanks for the investigation. I'm going to give this a try and come later with the results (and points, of course)

Author Comment

ID: 7113267
It works! Thanks :)

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