Canvas method must be used in the OnAfterDraw event?

[wwp3321]

Hello,
Canvas method must be used in the OnAfterDraw event?

The following codes didn't work well.Nothing was painted on the Chart1.

Code: Select all

void __fastcall TForm1::Button4Click(TObject *Sender)
{
    int X0 = Chart1->Axes->Bottom->CalcXPosValue(10);
    int Y0 = Chart1->Axes->Left->CalcYPosValue(50);

    for(int i=0;i++;i<5)
    {
        Chart1->Canvas->TextOutA(X0,Y0,"OK");
        X0 += 20;
        Y0 += 20;
    }
}

Best Regards
wwp3321

[wwp3321]

The following codes also don't work very well, sometimes the "OK" text just flashed on the Chart1 and disappeared; sometimes the "OK" text can be well painted ,but It disappeared when I Minimize the Form .

Code: Select all

void __fastcall TForm1::Button4Click(TObject *Sender) 
{ 
    int X0 = Chart1->Axes->Bottom->CalcXPosValue(10); 
    int Y0 = Chart1->Axes->Left->CalcYPosValue(50); 

    Chart1->Canvas->TextOutA(X0,Y0,"OK"); 
} 

[Narcís]

Hi wwp3321,

Yes, you need to use this in the OnAfterDraw event because calls like Chart1->Axes->Bottom->CalcXPosValue(10) need the chart being painted before so they can be correctly calculated and provide valid values. A simple example using a pie series:

Code: Select all

procedure TForm1.Chart1AfterDraw(Sender: TObject);
begin
  Chart1.Title.Text.Add(IntToStr(Series1.XRadius));
  Chart1.Title.Text.Add(IntToStr(Series1.YRadius));
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Series1.FillSampleValues();
  Chart1.Draw;
end;

Hope this helps!

[wwp3321]

Now customers want to add the mark by themself.
For example,they want to add a mark at some position by pushing
the Button1.But the following codes don't work well.

Code: Select all

void __fastcall TForm1::Button1Click(TObject *Sender) 
{ 
    int X0 = Chart1->Axes->Bottom->CalcXPosValue(10); 
    int Y0 = Chart1->Axes->Left->CalcYPosValue(50); 

    Chart1->Canvas->TextOutA(X0,Y0,"OK"); 
} 

[Narcís]

Hi wwp3321,

This works fine for me here using code below TeeChart Pro v8.04 VCL. Which TeeChart version are you using?

Code: Select all

//---------------------------------------------------------------------------
void __fastcall TForm3::Button1Click(TObject *Sender)
{
	int X0 = Chart1->Axes->Bottom->CalcXPosValue(10);
	int Y0 = Chart1->Axes->Left->CalcYPosValue(50);

	Chart1->Canvas->TextOutA(X0,Y0,"OK");
}
//---------------------------------------------------------------------------
void __fastcall TForm3::FormCreate(TObject *Sender)
{
	Series1->Clear();

	for (int i=0; i < 100; i++) {
		Series1->Add(i);
	}
}
//---------------------------------------------------------------------------

You may also want to try calling Draw method before retrieving axes positions, for example:

Code: Select all

void __fastcall TForm3::Button1Click(TObject *Sender)
{
	Chart1->Draw();

	int X0 = Chart1->Axes->Bottom->CalcXPosValue(10);
	int Y0 = Chart1->Axes->Left->CalcYPosValue(50);

	Chart1->Canvas->TextOutA(X0,Y0,"OK");
}

Thanks in advance.

[wwp3321]

My TeeChart version is 6.01

[Narcís]

Hi wwp3321,

Could you please try calling Draw method as I suggested?

Thanks in advance.

[wwp3321]

Code: Select all

void __fastcall TForm3::Button1Click(TObject *Sender) 
{ 
   Chart1->Draw(); 

   int X0 = Chart1->Axes->Bottom->CalcXPosValue(10); 
   int Y0 = Chart1->Axes->Left->CalcYPosValue(50); 

   Chart1->Canvas->TextOutA(X0,Y0,"OK"); 
}

When I Minimize the form ,"OK" disappeared.

[Narcís]

Hi wwp3321,

Yes, because the chart has been repainted and custom text has not been painted this time. You'd better use this code in the OnAfterDraw event with a flag being enabled in the button clicked event, something like this:

Code: Select all

//---------------------------------------------------------------------------
void __fastcall TForm3::Button1Click(TObject *Sender)
{
	DrawText=true;
	Chart1->Draw();
}
//---------------------------------------------------------------------------
void __fastcall TForm3::Chart1AfterDraw(TObject *Sender)
{
   if (DrawText) {
	   int X0 = Chart1->Axes->Bottom->CalcXPosValue(10);
	   int Y0 = Chart1->Axes->Left->CalcYPosValue(50);

	   Chart1->Canvas->TextOutA(X0,Y0,"OK");
   }
}
//---------------------------------------------------------------------------

[wwp3321]

Code: Select all

    Chart1->Draw();
    int X0 = Chart1->Axes->Bottom->CalcXPosValue(10);
    int Y0 = Chart1->Axes->Left->CalcYPosValue(50);

    for(int i=0;i++;i<5)
    {
        Chart1->Canvas->TextOutA(X0,Y0,"OK");
        X0 += 20;
        Y0 += 20;
    }

The codes above painted nothting,even one "OK".

[Narcís]

Hi wwp3321,

We may have crossed posts. Could you please check my last reply?

Thanks in advance.

[wwp3321]

Code: Select all

    Chart1->Draw();
    int X0 = Chart1->Axes->Bottom->CalcXPosValue(10);
    int Y0 = Chart1->Axes->Left->CalcYPosValue(50);

    for(int i=0;i++;i<5)
    {
        Chart1->Canvas->TextOutA(X0,Y0,"OK");
        X0 += 20;
        Y0 += 20;
    }

Please check the codes above.
The codes above painted nothting,even one "OK".

The codes above should paint five "OK".

BTW: I didn't resize the form.

[Narcís]

Hi wwp3321,

Please send us a simple example project we can run "as-is" to reproduce the problem here.

You can either post your files at news://www.steema.net/steema.public.attachments newsgroup or at our upload page.

Thanks in advance.

[wwp3321]

I have upload the source.
BCB6.0,Teechart6.01

Received TestTchartCanvas.zip Content Type application/x-zip-compressed Length 1903376

[Narcís]

Hi wwp3321,

Thanks for the example project but I'm not able to run it because a.tee is not included. Could you please send the tee file too?

Thanks in advance.