How do you draw a circle? Wait online! !!

卡尔特德

The requirement is that the point where the mouse starts to depress is the center coordinate, the point after moving is a point on the circle, and the radius is the distance between these two points!
Thank you!

沧浪123

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, jpeg, ExtCtrls, StdCtrls;

type
  TForm1 = class (TForm)
    procedure FormMouseDown (Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseUp (Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove (Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    fselecting: boolean;
    fbeginpt, fendpt: tpoint;
    {Private declarations}
  public
    {Public declarations}
  end;

var
  Form1: TForm1;

implementation

{$ R * .dfm}

procedure TForm1.FormMouseDown (Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  fselecting: = true;
  fbeginpt: = Form1.ScreenToClient (mouse.CursorPos);
end;
procedure TForm1.FormMouseUp (Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  fselecting: = false;
  fendpt: = Form1.ScreenToClient (mouse.CursorPos);
  Self.Repaint;
end;
procedure TForm1.FormMouseMove (Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
 fendpt: = Form1.ScreenToClient (mouse.CursorPos);
 if fselecting then
 begin
   Canvas.FillRect (Canvas.ClipRect);
   //Canvas.Rectangle(rect(fbeginpt,fendpt));
   canvas.Ellipse (rect (fbeginpt, fendpt));
   canvas.Pen.Color: = clred;
   Canvas.Pen.Width: = 1;
 end;
end;

end.

desprez

Agree upstairs

wjopwinboy

Just drag and drop with controls. It's that simple
Use visual graph to do

foxdog2005

All good suggestions! Worth learning