Continue to ask: Why is it so difficult to draw a rectangular frame on the window. depressed

lala1205

Here is the code,
void __fastcall TForm1 :: FormCreate (TObject * Sender)
{
Brush-> Style = bsClear;
}
// ---------------------------------------------
void __fastcall TForm1 :: FormMouseDown (TObject * Sender, TMouseButton Button,
      TShiftState Shift, int X, int Y)
{
   if (Shift.Contains (ssLeft))
   bMouseDownFlag = true;
   pt.x = X;
   pt.y = Y;
}
// ------------------------------------------------ ---
void __fastcall TForm1 :: FormMouseMove (TObject * Sender, TShiftState Shift,
      int X, int Y)
{
if (bMouseDownFlag)
{
this-> Refresh ();
this-> Canvas-> MoveTo (pt.x, pt.y);
this-> Canvas-> LineTo (pt.x, Y);
this-> Canvas-> MoveTo (pt.x, Y);
this-> Canvas-> LineTo (X, Y);
this-> Canvas-> MoveTo (X, Y);
this-> Canvas-> LineTo (X, pt.y);
this-> Canvas-> MoveTo (X, pt.y);
this-> Canvas-> LineTo (pt.x, pt.y);
}
}
// ---------------------------------------
void __fastcall TForm1 :: FormMouseUp (TObject * Sender, TMouseButton Button,
      TShiftState Shift, int X, int Y)
{
    if (bMouseDownFlag)
    {this-> Refresh ();
    this-> Canvas-> Rectangle (pt.x, pt.y, X, Y);
    bMouseDownFlag = false;}
}
Depressed, the problem now is that if you remove the code Brush-> Style = bsClear in FormCreate, then the function of drawing a rectangle on the form can be completely realized, and every time a new rectangle is drawn, the previous rectangle drawn will be erased.
But after adding the code Brush-> Style = bsClear; in FormCreate, the problem came, first 1. There are many overlapping traces in the process of drawing a rectangle, 2. Each time a new rectangle is drawn, the previous rectangle drawn first will not be erased.
Why is this happening? How to deal with it. I want to add the code Brush-> Style = bsClear in FormCreate to draw a rectangle in the form, and overcome the two problems above, please help
Thank you

zhongshuan

Use pmXor to draw once to erase the original, and then draw it again, and use the rectangle directly without using lineto several times
So it ’s better to change your move

mad_diablo

Brush-> Style = bsClear
To
Brush-> Style = bsBlod

baiyunyy

Wow    ! I am also the only one who still uses this software.