I'm trying to create a simple component to draw rows/columns of
buttons. The first thing I'm trying to get done is the mouse event
handling. I was able to figure out how to catch the windows messages
and have them trigger published events from some examples I've found,
but I'm having a problem it. If you click very quickly in rapid
succession, the control seems to steal the mouse input for the entire
application. You can't even click on the form's close button as the
click gets taken.
In a test project, I notice that in a listbox that displays the
events when they are fired, when it shows a MouseUp event firing
without a corresponding MouseDown, that's when the control will begin
to steal all mouse input from that point onward. You have to kill the
app at that point. I read a post through a Google search about
problems like this happening with TGraphicControl descendants, so I
tried changing it to a TCustomPanel, but the problem is still there.
Can anyone tell me what is causing this and how I can fix it?
Here's a stripped down version of the component code with only the
relevant parts:
unit MyButtonPanel;
interface
uses
Types, Classes, Messages, Controls, Graphics, ExtCtrls;
type
TMouseDownEvent = procedure(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer) of object;
TMouseUpEvent = procedure(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer) of object;
TMouseClickEvent = procedure(Sender: TObject; Btn: Integer) of
object;
TMyButtonPanel = class(TGraphicControl)
private
FOnMouseDown: TMouseDownEvent;
FOnMouseUp: TMouseUpEvent;
FOnMouseClick: TMouseClickEvent;
protected
procedure WM_LBUTTONDOWN(var Msg: TWMLButtonDown); Message
WM_LBUTTONDOWN;
procedure WM_LBUTTONUP(var Msg: TWMLButtonUp); message
WM_LBUTTONUP;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
property OnMouseClick: TMouseClickEvent read FOnMouseClick write
FOnMouseClick;
property OnMouseDown: TMouseDownEvent read FOnMouseDown write
FOnMouseDown;
property OnMouseUp: TMouseUpEvent read FOnMouseUp write
FOnMouseUp;
end;
procedure Register;
implementation
uses
Forms, Consts, SysUtils, CommCtrl, Themes, Dialogs;
Constructor TMyButtonPanel.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
end;
Destructor TMyButtonPanel.Destroy;
begin
inherited destroy;
end;
procedure TMyButtonPanel.WM_LBUTTONDOWN(Var Msg: TWMLButtonDown);
begin
if Assigned(FOnMouseDown) then FOnMouseDown(Self, mbLeft,
KeysToShiftState(Msg.Keys), Msg.XPos, Msg.YPos);
if Assigned(FOnMouseClick) then FOnMouseClick(Self, 0);
end;
procedure TMyButtonPanel.WM_LBUTTONUP(Var Msg: TWMLButtonDown);
begin
if Assigned(FOnMouseUp) then FOnMouseUp(Self, mbLeft,
KeysToShiftState(Msg.Keys), Msg.XPos, Msg.YPos);
end;
procedure Register;
begin
RegisterComponents('Samples', [TMyButtonPanel]);
end;
end.
--------------------------------------------
Events in Test Project:
procedure TMain.MyButtonPanel1MouseClick(Sender: TObject; Btn:
Integer);
begin
ListBox1.Items.Add( IntToStr(Btn) );
end;
procedure TMain.MyButtonPanel1MouseDown(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
ListBox1.Items.Add('MouseDown');
end;
procedure TMain.MyButtonPanel1MouseUp(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
ListBox1.Items.Add('MouseUp');
end;
---------------------------------------------
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