How to determine when a mouse moves away from TPanel in Delphi 6?

Question

I use the OnMouseMove event to determine when the mouse pointer is over my TPanel, is there a way to find out when the mouse pointer moved away from it?

Do I need a panel to change color when the mouse pointer is over it and return to the original color when it moved away from it?

I am using Delphi 6 by the way.

Please, help.

Regards.

Answer 1

Another solution, using TrackMouseEventto get WM_MOUSELEAVE;

type
  TMyPanel = class(TPanel)
  private
    FMouseTracking: Boolean;
    FOnMouseLeave: TNotifyEvent;
    procedure WMMouseLeave(var Msg: TMessage); message WM_MOUSELEAVE;
  protected
    procedure MouseMove(Shift: TShiftState; X, Y: Integer); override;
  published
    property OnMouseLeave: TNotifyEvent read FOnMouseLeave write FOnMouseLeave;
  end;

procedure TMyPanel.MouseMove(Shift: TShiftState; X, Y: Integer);
var
  mEvnt: TTrackMouseEvent;
begin
  inherited;
  if not FMouseTracking then begin
    mEvnt.cbSize := SizeOf(mEvnt);
    mEvnt.dwFlags := TME_LEAVE;
    mEvnt.hwndTrack := Handle;
    TrackMouseEvent(mEvnt);
    FMouseTracking := True;
  end;
end;

procedure TMyPanel.WMMouseLeave(var Msg: TMessage);
begin
  Msg.Result := 0;
  FMouseTracking := False;
  if Assigned(FOnMouseLeave) then
    FOnMouseLeave(Self);
end;

Answer 2

You can use the OnMouseEnter / OnMouseLeave event pair to detect the mouse

procedure TForm1.Panel1MouseEnter(Sender: TObject);
begin
  Panel1.Caption:= 'IN';
  Panel1.Color:= clBlue;
end;

procedure TForm1.Panel1MouseLeave(Sender: TObject);
begin
  Panel1.Caption:= 'OUT';
  Panel1.Color:= clWhite;
end;

---

Delphi 6, ,

TrackMouseEvent - Sertac Akyuz

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Panel1MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    { Private declarations }
    FOldWndProc: TWndMethod;
    FMouseInPanel: Boolean;
    procedure PanelWndProc(var Message: TMessage);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  FOldWndProc:= Panel1.WindowProc;
  Panel1.WindowProc:= PanelWndProc;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  Panel1.WindowProc:= FOldWndProc;
end;

procedure TForm1.Panel1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
var
  mEvnt: TTrackMouseEvent;
begin
  if not FMouseInPanel then begin
    mEvnt.cbSize := SizeOf(mEvnt);
    mEvnt.dwFlags := TME_LEAVE;
    mEvnt.hwndTrack := Panel1.Handle;
    TrackMouseEvent(mEvnt);
    Panel1.Caption:= 'IN';
    FMouseInPanel:= True;
  end;
end;

// if not defined in Delphi 6, WM_MOUSELEAVE = $02A3
procedure TForm1.PanelWndProc(var Message: TMessage);
begin
  if Message.Msg = WM_MOUSELEAVE then begin
    Panel1.Caption:= 'OUT';
    FMouseInPanel:= False;
  end;
  FOldWndProc(Message);
end;

end.

Answer 3

OnMouseEnter OnMouseLeave, OnMouseMove . , .

procedure Form1.Panel1MouseMove(Sender:TObject; Shift:TShiftState; X,Y:Integer);
begin
  if (X >= 0) and (Y >= 0) and (X < Panel1.Width) and (Y < Panel1.Height) then
    begin
      // Movement within the panel
      if GetCapture <> Panel1.Handle then
      begin
        // The mouse just moved over the panel. Do your "on enter" stuff
        // over here.
        SetCapture(Panel1.Handle); // Capture the mouse so we'll receive
                                   // mouse move messages even if the cursor
                                   // is no longer over our panel.
      end;
    end
  else
    begin
      // Movement outside the panel! This is possible because I've previously
      // captured the mouse.
      // Do your "move out" stuff over here.
      ReleaseCapture; // release mouse capture
    end;
end;

Answer 4

OnMouseLeave. , , , OnMouseLeave, , , .

Answer 5

, TCustomPanel ( TPanel), Delphi 6 MouseEnter MouseLeave, . :

procedure CMMouseEnter(var Message: TMessage); message CM_MOUSEENTER;
procedure CMMouseLeave(var Message: TMessage); message CM_MOUSELEAVE;

mouseenter mouseleave:

procedure TMyPanel.CMMouseEnter(var msg: TMessage);
begin
  inherited;
  Color := clBlue;
  { Do Whatever }
end;

procedure TMyPanel.CMMouseLeave(var msg: TMessage);
begin
  inherited;
  Color := clRed;
  { Do Whatever }
end; 

, . , :

ControlStyle := ControlStyle - [csParentBackground] + [csOpaque];

Answer 6

. , -, bitbtn, , Delphi 7. :

TBitBtnPanel = class(TBitBtn)
  private
    { Private declarations }
    FOnMouseLeave: TNotifyEvent;
    FOnMouseEnter: TNotifyEvent;
    FActivateMouseLeave: boolean;
    procedure CMMouseEnter(var Msg: TMessage); message CM_MOUSEENTER;
    procedure CMMouseLeave(var Msg: TMessage); message CM_MOUSELEAVE;
  protected
    { Protected declarations }
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
  published
    { Published declarations }
    property OnMouseLeave: TNotifyEvent read FOnMouseLeave write FOnMouseLeave;
    property OnMouseEnter: TNotifyEvent read FOnMouseEnter write FOnMouseEnter;
  end;

{ TBitBtnPanel }

procedure TBitBtnPanel.CMMouseEnter(var Msg: TMessage);
begin
  Msg.Result := WM_CANCELMODE;
  FActivateMouseLeave:=True;
  if Assigned(FOnMouseEnter) then FOnMouseEnter(Self);
end;

procedure TBitBtnPanel.CMMouseLeave(var Msg: TMessage);
begin
  if (FActivateMouseLeave) then
  begin
    Msg.Result := WM_CANCELMODE;
    FActivateMouseLeave:=False;
    if Assigned(FOnMouseLeave) then FOnMouseLeave(Self);
  end;
end;

constructor TBitBtnPanel.Create(AOwner: TComponent);
begin
  FActivateMouseLeave:=True;
  inherited;
end;

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