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Component Writing : TGraphicControl with user (keyboard) input

I am writing a network monitoring screen logging component. Due to the speed of the output, I am using TGraphicControl as the main drawing Canvas in the component, which I've provided Line and Page updates for.

I have used the mouse button up msg to detect when and where the user has clicked on the screen. However, to provide a more professional finish, I really need to let the user navigate the captured data with the arrow keys.

I'm aware of the procedure necessary to grab the arrow keys :
PROCEDURE WMGetDlgCode (VAR MESSAGE : TWMGetDlgCode); MESSAGE WM_GetDlgCode;

But I think I need a method of adding/simulating key down events on this (or a sub/child) control, as TGraphicControl doesn't naturally own a window's handle from which to receive WM_KEYDOWN ?!?

Any ideas would be much appreciated.
Many thanks.
Steve

Lukasz Zielinski

Write WndProc and use AllocateHwnd from Forms unit to get Handle.
ziolko.

steve_hsk

ASKER

Hi ziolko ...

This method appears to work :-)

Have used it before to grab the Window's Caption Control, but for some reason it didn't occur to me here. Needed more coffee ;-)

The points are yours. As a last query, did you have a better way of implementation than below ? (may as well try and make ya work for it :-) ) ...

NOTE : Here for others reference also ...

TYPE TWindowClass = CLASS (TComponent)
PUBLIC
// Declare Class Control Functions
CONSTRUCTOR Create(AOwner: TComponent); OVERRIDE;
DESTRUCTOR Destroy; OVERRIDE;
PRIVATE
// Declare Internal Variables
FForm : TWinControl;
FNewProc : Pointer;
FOldProc : Pointer;
FWinControl : TWinControl;

// Declare Internal Methods
PROCEDURE HookedMsgProc (VAR Msg: TMessage);
PROCEDURE Loaded; OVERRIDE;
PROCEDURE HookWindow;
PROCEDURE UnhookWindow;
END;

CONSTRUCTOR TWindowClass.Create(AOwner: TComponent);
VAR tFormParent : TWinControl;
BEGIN
INHERITED Create(AOwner);
tFormParent := TWinControl(AOwner);

WHILE (tFormParent <> NIL) AND (NOT (tFormParent IS TForm)) DO
BEGIN
tFormParent := tFormParent.Parent;
END;

FForm := tFormParent;

FNewProc := MakeObjectInstance(HookedMsgProc);
END;

DESTRUCTOR TWindowClass.Destroy;
BEGIN
FreeObjectInstance(FNewProc);
UnhookWindow;
inherited Destroy;
END;

PROCEDURE TWindowClass.Loaded;
BEGIN
FWinControl := FForm;
HookWindow;
inherited Loaded;
END;

PROCEDURE TWindowClass.HookedMsgProc (VAR Msg: TMessage);
BEGIN
if (Msg.WParam = VK_UP) or (Msg.WParam = VK_DOWN)then
BEGIN
g_tparent.m_FtDataSelection.DrawSelection(Msg.LParam);
END
ELSE
BEGIN
Msg.Result := CallWindowProc(FOldProc, FWinControl.Handle, Msg.Msg, Msg.WParam, Msg.LParam);
END;

INHERITED;
END;

PROCEDURE TWindowClass.HookWindow;
BEGIN
FOldProc := Pointer(GetWindowLong(FWinControl.Handle, GWL_WNDPROC));
SetWindowLong(FWinControl.Handle, GWL_WNDPROC, Integer(FNewProc));
END;

PROCEDURE TWindowClass.UnhookWindow;
BEGIN
IF FOldProc <> NIL THEN
BEGIN
SetWindowLong(FWinControl.Handle, GWL_WNDPROC, Integer(FOldProc));
FOldProc := nil;
END;
END;

Lukasz Zielinski

Hi steve if You dont mind I'll take a look at it tomorrow morning. I'll rather go to sleep then drink more coffe :-)))
ziolko.

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Lukasz Zielinski

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steve_hsk

ASKER

Job well done ... !

Two different implementations, both which work nicely !

Many thanks Ziolko !

:-)

steve_hsk

ASKER

Nice suggestion, followed by a nice example !

Job well done !

<< have increased my morning coffee intake two-fold ;-)

Many thanks,
Steve

Lukasz Zielinski

glad to be helpfull :-)
ziolko.