德尔福：将TImage带到前面

Question

Look at the image below:

As you can see I cannot send Buttons to back. This only works for labels.

So how can I send TImage to front with its transparency .

By the way I've read This related question but didn't help me. Because you cannot even click on a button after running Andreas Rejbrand's code. Not only buttons, everything (like the scrollbar in this image)

Edit: I don't want to make the button reachable after I send that back to the image. Just want to bring TImage to front of everything.

Thanks.

Answer 1

One way which could you near the goal would be to use interposer classes for the TWincontrols and paint the image moved on them, after they have been painted already, using a TControlCanvas and "hooking" WM_PAINT.
The code is showing a raw draft using a semitransparent PNG image and may be enhanced.

unit Unit2;

interface

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

type
  TButton=Class (StdCtrls.TButton)
      Procedure WMPaint(var MSG:TMessage);Message WM_Paint;
  End;
  TEdit=Class (StdCtrls.TEdit)
      Procedure WMPaint(var MSG:TMessage);Message WM_Paint;
  End;

  TForm2 = class(TForm)
    Image1: TImage;
    SpeedButton1: TSpeedButton;
    Button1: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

{ TButton }

procedure TButton.WMPaint(var MSG: TMessage);
var
  cc:TControlCanvas;
begin
   inherited;
    CC:=TControlCanvas.Create;
    CC.Control := TControl(Self);
    CC.Draw(-Left,-Top,Form2.Image1.Picture.Graphic);
    CC.Free;
end;

procedure TEdit.WMPaint(var MSG: TMessage);
var
  cc:TControlCanvas;
begin
   inherited;
    CC:=TControlCanvas.Create;
    CC.Control := TControl(Self);
    CC.Draw(-Left,-Top,Form2.Image1.Picture.Graphic);
    CC.Free;

end;

end.

Another (better) place to "hook" would be overriding PaintWindow

unit Unit2;

interface

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

type
  TButton=Class (StdCtrls.TButton)
      procedure PaintWindow(DC: HDC);override;
  End;
  TEdit=Class (StdCtrls.TEdit)
      procedure PaintWindow(DC: HDC);override;
  End;

  TForm2 = class(TForm)
    Image1: TImage;
    SpeedButton1: TSpeedButton;
    Button1: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

{ TButton }

procedure TButton.PaintWindow(DC: HDC);
var
  cc:TCanvas;
begin
   inherited;
    CC:=TCanvas.Create;
    CC.Handle := DC;
    CC.Draw(-Left,-Top,Form2.Image1.Picture.Graphic);
    CC.Free;
end;

procedure TEdit.PaintWindow(DC: HDC);
var
  cc:TCanvas;
begin
   inherited;
    CC:=TCanvas.Create;
    CC.Handle := DC;
    CC.Draw(-Left,-Top,Form2.Image1.Picture.Graphic);
    CC.Free;

end;

end.

Answer 2

You do not want the Image brought to front (which by the way is impossible over a windowed control), because you want the button also reachable.

Although your question is contradicting itself, and it is not at all clear what exactly you want to achieve, I think you mean to have a transparent button over an image.

If so, then use a TSpeedButton , and set its Transparent and Flat property to True.

Here an example with the three button states: normal, hovered, pressed:

Answer 3

You can use the solution you linked in your question. For the controls that you want the clicks go through - disable them. Since you're putting the image on a panel, disabling both the panel and the image will let the button to be clicked.