Resizable-forms-and-size-grip-Part-2


            Title: Resizable forms and size grip - Part 2
Question: Improving the behaviour...
Answer:
A comment to my previous article (thanks to Skip Bremer) stated that the cursor target area was not enlarged as the status bar would. This is correct. 
In effect the article was simply a suggestion on how to use that API to draw a size grip not on how to reproduce the behaviour of the status bar; anyway the Bremer's comment pushed me to make some testing on how to implement the suggested behaviour.
The solution I found is simple: I used a PaintBox aligned on the bottom-right corner of the form, I set the Cursor property to crSizeNWSE and then intercepted the OnPaint and OnMouseDown events.
During the OnPaint the DrawFrameControl API is used to draw the visual effect.
During the OnMouseDown event the mouse capture is released and the resize of the form is started using the SendMessage API
Here follows the DFM and PAS source code:
This is the DFM:
object Form1: TForm1
 Left = 286
 Top = 106
 Width = 410
 Height = 286
 HorzScrollBar.Visible = False
 VertScrollBar.Visible = False
 Anchors = [akRight, akBottom]
 Caption = 'Grip Tester'
 Color = clBtnFace
 Font.Charset = DEFAULT_CHARSET
 Font.Color = clWindowText
 Font.Height = -11
 Font.Name = 'MS Sans Serif'
 Font.Style = []
 OldCreateOrder = False
 PixelsPerInch = 96
 TextHeight = 13
 object PaintBox1: TPaintBox
 Left = 386
 Top = 242
 Width = 16
 Height = 16
 Cursor = crSizeNWSE
 Anchors = [akRight, akBottom]
 Font.Charset = ANSI_CHARSET
 Font.Color = clWindowText
 Font.Height = -11
 Font.Name = 'MS Sans Serif'
 Font.Style = []
 ParentFont = False
 OnMouseDown = PaintBox1MouseDown
 OnPaint = PaintBox1Paint
 end
 object Label1: TLabel
 Left = 263
 Top = 245
 Width = 119
 Height = 13
 Anchors = [akRight, akBottom]
 Caption = 'This is not a size grip! --'
 end
end
This is the PAS source:
unit Unit1;
interface
uses
 Windows, Messages, Forms, ExtCtrls, Classes, Controls, StdCtrls;
type
 TForm1 = class(TForm)
 PaintBox1: TPaintBox;
 Label1: TLabel;
 procedure PaintBox1Paint(Sender: TObject);
 procedure PaintBox1MouseDown(Sender: TObject; Button: TMouseButton;
 Shift: TShiftState; X, Y: Integer);
 private
 { Private declarations }
 public
 { Public declarations }
 end;
var
 Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.PaintBox1Paint(Sender: TObject);
begin
 DrawFrameControl(PaintBox1.Canvas.Handle,
 PaintBox1.ClientRect,
 DFC_SCROLL,
 DFCS_SCROLLSIZEGRIP);
end;
procedure TForm1.PaintBox1MouseDown(Sender: TObject; Button: TMouseButton;
 Shift: TShiftState; X, Y: Integer);
begin
 if(Button = mbLeft) and (Shift = [ssLeft]) then
 begin
 ReleaseCapture;
 SendMessage(Self.Handle, WM_NCLBUTTONDOWN, HTBOTTOMRIGHT, 0);
 end;
end;
end.
Enjoy
Forms Delphi
