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Task/Simple-windowed-application/Delphi/simple-windowed-application.delphi

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+-- begin file --
+
+   Program SingleWinApp ;
+
+   // This is the equivalent of the C #include
+   Uses Forms, Windows, Messages, Classes, Graphics, Controls, StdCtrls ;
+
+
+   type
+
+     // The only reason for this declaration is to allow the connection of the
+     // on click method to the forms button object. This class declaration adds
+     // a procedure.
+
+     TMainForm class(tform)
+       Procedure AddClicks(sender : tObject);
+     end;
+
+
+   // Use these globals.
+   var
+
+     MainForm : tForm ;
+     aLabel   : tLabel ;
+     aButton  : tButton ;
+     i        : integer = 0 ;
+
+
+    // This is the Method call that we connect to the button object
+    // to start counting the clicks.
+    Procedure tMainForm.AddClicks(sender :tObject)
+    begin
+      inc(i);
+      aLabel.Caption := IntToStr(i) + ' Clicks since startup' ;
+    end;
+
+
+    Begin
+      // Do all the behind the scenes stuff that sets up the Windows environment
+      Application.Initialize ;
+
+      // Create the form
+
+      // Forms can either be created with an owner, like I have done here, or with
+      // the owner set to Nil. In pascal (all versions of Borland) '''NIL''' is a
+      // reserved, (the equivalent of '''NULL''' in Ansi C) word and un-sets any pointer
+      // variable. Setting the owner to the application object will ensure that the form is
+      // freed by the application object when the application shuts down. If I had set
+      // the owner to NIL then i would have had to make sure I freed the form explicitly
+      // or it would have been orphaned, thus creating a memory leak.
+
+      // I must direct your attention to the CreateNew constructor.  This is
+      // a non standard usage.  Normally the constructor Create() will call this
+      // as part of the initialization routine for the form. Normally as you drop
+      // various components on a form in deign mode, a DFM file is created with
+      // all the various initial states of the controls. This bypasses the
+      // DFM file altogether although all components AND the form are created
+      // with default values. (see the Delphi help file).
+
+      MainForm          := tMainForm.CreateNew(Application);
+      MainForm.Parent   := Application ;
+      MainForm.Position := poScreenCenter ;
+      MainForm.Caption  := 'Single Window Application' ;
+
+      // Create the Label, set its owner as MaiaForm
+      aLabel          := tLabel.Create(mainForm);
+      aLabel.Parent   := MainForm;
+      aLabel.Caption  := IntToStr(i) + ' Clicks since startup' ;
+      aLabel.Left     := 20 ;
+      aLabel.Top      := MainForm.ClientRect.Bottom div 2 ;
+
+      // Create the button, set its owner to MainForm
+      aButton         := tButton.Create(MainForm);
+      aButton.Parent  := MainForm ;
+      aButton.Caption := 'Click Me!';
+      aButton.Left    := (MainForm.ClientRect.Right div 2)-(aButton.Width div 2 );
+      aButton.Top     := MainForm.ClientRect.Bottom - aButton.Height - 10 ;
+      aButton.OnClick := AddClicks ;
+
+      // Show the main form, Modaly. The ONLY reason to do this is because in this
+      // demonstration if you only call the SHOW method, the form will appear and
+      // disappear in a split second.
+      MainForm.ShowModal ;
+
+      Application.Run ;
+
+   end. // Program