basic delphi programming

This tutorial is a rough guide of how to use the graphics functions in Delphi 7.0 (This should work with minor modifications in Kylix 3 for Linux)

1. The basic code with a blank form in Delphi is this:-

   unit Unit1;
   interface
   uses
     Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
     Dialogs;
   type
     TForm1 = class(TForm)                                    Procedures are defined here!
   private
     { Private declarations }
   public
     { Public declarations }
   end;
   var
     Form1: TForm1;                                           Your Variables Go here!
   implementation
   {$R *.dfm}                                                   Procedures go here!
   end.
             

2. On the left of your screen is the object inspector. Click on your form. Then in the object inspector select the events tab. We want the mouse to draw a line whenever it is over the form. We can use OnMouseMove - double click and in your code window you will get a new procedure like this...

   procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
   begin
    
   end;
             

   Your code goes between the begin and end; End; has a semicolon to show it is not the last end and it only applies to the procedure. The procedure has given us the integers X and Y which are the mouse positions. As in C you must end each line with a semicolon. Because Delphi is object orientated everything is in a heirachy.

3. To draw on the "canvas" use...

   Canvas.lineto(X,Y);
             

   Delphi provides you with a menu exery time you put a full stop in so you can see the available options. If we put the above code into the FormMouseMove procedure then a line would follow the mouse. Supposing we want to set the default color for a line. Click on your form. Then in the object inspector select the events tab. Double click OnCreate. You are provided with a function again. Type Canvas. and a pull-down menu will appear. Select Brush. Your code should now read canvas.brush. . Once again a pull-down will appear so select color from it.... canvas.brush.color .

4. To set a variable in Delphi use := so for example if we use a color dialog to select the color when the form is created (To put the code for a dialog into your program from the drawing toolbar select the dialog tab and then click on it and draw it on the form - this will be invisible when the program is run). Then add this code to your procedure....

   Colordialog1.execute;
   Canvas.Brush.Color:=colordialog1.color;
             

   You can of course put this code under any procedure. You can also set the color manually by using Canvas.Brush.Color:=ClRed .