Drawing on top of components

Hi Keijo,

you can draw directly on desktop in the same coordinates where your form located. It will look like drawing over your form.

-----
Igor.

hello Keijo, do you want this rect to be redrawn in the Onpaint of your form. or just drawn temporarily over other controls (until a paint happens)? If you want to draw over controls then putting a control over the other controls (as you said) will do it, if you can't do that then you can hide the controls that are in the same place as your rect and show them when the rect is gone, if you have partially covered controls then they will dissapear (a few controls could be resized to still be visible). I think it's posible to change the update area of a window but if you take the rect area out of the Main Form's update area then the rect won't be drawn. It seems the windows OS is very good at making sure all visible controls are drawn where they are suppose to be. Also you might try a timer event triggered by the OnPaint that allows a few microseconds and then Paints the Rectangle on the Forms Canvas.You may look at windows API

ValidateRect(
    HWND hWnd,     // handle of window
    CONST RECT *lpRect     // address of validation rectangle coordinates
   );

which removes a rect from update

you could try something like
ValidateRect(Button1.Handle, @SmallerRect);
where SmallerRect is the Bounds rect minus the part covered by the Rectangle.

I couldn't get that to be persistant since the update area is renewed on each paint and is not useful on non wincontrols.

There are two kinds of controls in delphi, wincontrols and non-windowed controls, Windowed controls will always show on top of non windowed ones.

Here are a couple of methods not already discussed..

In win2k and above you can use 'alpha blending' and transparency. I think Delphi 6 comes with a transparancy demo, also the delphi magazine did an article on it. If you use a transparent form or panel on top of the image you want then you will see the image but the (invisible) buttons will still work.

Marco Cantu used to have some kind of transparency demo too. I remember some kind of 'click through' where the mouse events get passed through to the windows underneath.

A final way is to use owner draw controls and bitmap buttons, so that each control paints its own piece of the picture, The controls know where they are so they could copy the corresponding parts from a TImage.

as

Oh hang on, here is an easy way..

Put a panel on top of the whole form and the enabled property to false.. All the buttons and Edits still work, you just cant see them. If you want you can grab the underlying form image and blend it with the picture you are displaying, like this.

procedure TForm1.FormPaint(Sender: TObject);
begin
ValidateRect(handle,nil);
if not panel1.Visible then exit;
panel1.Visible:=false;
PaintTo(Image1.Canvas,0,0);
panel1.Visible:=true;
end;

It feels very wierd.

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