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Best way to draw a rectangle around a control (TShape hides behind)

Posted on 2009-05-04
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Last Modified: 2013-11-22
When the user hovers the mouse over a TButton (OnMouseEnter) I want to draw a box around it (actually around a few buttons).
The problem with using a TShape is that it is not a TWinControl - so it will always appear BEHIND things like TPanels, TButtons etc.
I am busy working with another solution that draws on the "DeskTopWindow" canvas, but I'm sure there must be a more direct way (such as using the Form's Canvas) but I can't seem to get it right.

Some help would be appreciated.
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Question by:rfwoolf
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LVL 37

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by:Geert Gruwez
Geert Gruwez earned 250 total points
ID: 24302086
why not use a bevel control ?
and then just set the bevel visible property when hovering to true
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by:Geert Gruwez
Geert Gruwez earned 250 total points
ID: 24302168
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by:Geert Gruwez
Geert Gruwez earned 250 total points
ID: 24302192
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LVL 37

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by:Geert Gruwez
Geert Gruwez earned 250 total points
ID: 24302521
i used that uHoverHook unit to create a sample with 2 bevels and 3 buttons ...
unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, uHoverHook, ComCtrls;
 
type
  TForm1 = class(TForm)
    Panel1: TPanel;
    Panel2: TPanel;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Bevel1: TBevel;
    Bevel2: TBevel;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    fHover: THoverHook;
    procedure HoverMouseOver(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure OnHoverEnter(Sender: TObject);
    procedure OnHoverLeave(Sender: TObject);
  protected
    procedure WndProc(var Message: TMessage); override;
  public
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.FormCreate(Sender: TObject);
begin
  //fHover := THoverHook.Create(HoverMouseOver, True);
  fHover := THoverHook.Create;
  fHover.OnMouseMove := HoverMouseOver;
  fHover.StartHook;
  fHover.AddToHook(Button1);
  fHover.AddToHook(Button2);
  fHover.AddToHook(Button3);
end;
 
procedure TForm1.HoverMouseOver(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  Bevel1.Visible := (Sender = Button1) or (Sender = Button3);
  Bevel2.Visible := (Sender = Button2);
end;
 
procedure TForm1.FormDestroy(Sender: TObject);
begin
  FreeAndNil(fHover);
end;
 
procedure TForm1.WndProc(var Message: TMessage);
var X: TObject;
begin
  inherited WndProc(Message);
  if (Message.Msg = CM_MOUSEENTER) or (Message.Msg = CM_MOUSELEAVE) then
  begin
    X := ControlAtPos(Mouse.CursorPos, False, True);
    if Message.Msg = CM_MOUSEENTER then
      OnHoverEnter(X)
    else
      OnHoverLeave(X);
  end;
end;
 
procedure TForm1.OnHoverEnter(Sender: TObject);
begin
end;
 
procedure TForm1.OnHoverLeave(Sender: TObject);
begin
  Bevel1.Visible := False;
  Bevel2.Visible := False;
end;
 
end.

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Accepted Solution

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rfwoolf earned 0 total points
ID: 24309268
Hi Geert

The bevel solution is unideal because Bevels are not transparent. Of course you could put the bevels behind the buttons, but that is unideal in my case because I have some buttons that fit exactly onto a panel.

I am not sure why everyone is obsessed with 'hovering' in those links you gave me - I can just use the MouseEnter and the MouseLeave events for buttons to detect when the mouse is hovering over the button and when it is not.

And so again it looks like my best solution is to draw on the form's canvas, but that is creating a huge headache because of the titlebar and border!!


Aurrrghh.
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LVL 26

Assisted Solution

by:EddieShipman
EddieShipman earned 250 total points
ID: 24549098
There is a set of controls written by an ex-colleague calle Res-cue controls. They have this capability and you can
learn how he does it and do it with your own controls. I can attach them if you'd like...
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LVL 26

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by:EddieShipman
EddieShipman earned 250 total points
ID: 24549142
From his help file:
"The Focus Technology is a powerful programming technique that allows developers to give a visual cue when a control receives focus.  No more searching for the control that has focus, our Focus Technology draws a rectangle around the control that has focus and can even change the Font attributes of a label for the control.  Developers are given the flexibility to change the appearance of the rectangle by providing many properties that can be altered such as spacing, color, 3D, etc.  In addition, we provide events for when a focus rectangle and label are about to be painted or removed from the screen so that developers can provide other visual cues to the user as to which control has focus.

Another powerful feature of our Focus Technology is the ability to use this technology on any TWinControl.  Thats right, you dont have to replace your current controls in your application to use the great feature.  Simply place a TrscMasterFocus component on a form and select the controls that you want to have this capability.  It is as simple as that."

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