Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Draw line on Panel

Posted on 2001-08-21
12
462 Views
Last Modified: 2010-04-06
Hi

How can i draw line on panel (TPanel does not have canvas like TForm) ?!


10x
Asi
0
Comment
Question by:asi
  • 5
  • 3
  • 2
  • +1
12 Comments
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6409202
just drop a tshape on it or a picturebox and draw there a line
0
 
LVL 3

Accepted Solution

by:
Slavak earned 50 total points
ID: 6409217
or you can create a canvas :

Var
 ACanvas : TCanvas;
............................
  ACanvas := TControlCanvas.Create;
  TControlCanvas(ACanvas).Control := Panel;

 
0
 

Expert Comment

by:Aleq
ID: 6409234
TPanel has no DeviceContext, so only way to do this is to put TImage, TShape or similar component on the panel, set align to alClient (and optionally send it to the back).
----
procedure TForm1.Button1Click(Sender: TObject);
var
  Image: TImage;
begin
  Image:=TImage.Create(Panel1);
  Image.Align:=alClient;
  Image.Parent:=Panel1;
  Image.Transparent:=True;
  Image.Canvas.LineTo(Panel1.Width, Panel1.Height);
end;
0
Free Tool: Postgres Monitoring System

A PHP and Perl based system to collect and display usage statistics from PostgreSQL databases.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 

Expert Comment

by:Aleq
ID: 6409237
ooops, I'm late...
ok, sorry.
0
 
LVL 3

Expert Comment

by:Slavak
ID: 6409293
all window (TWinControl) have device context.

You can create canvas also as,

 ACanvas := TCanvas.Create;
 ACanvas.Handle := GetDC(Panel1.Handle);

but, i prefer a first way.

Note,
 GetDC(Panel1.Handle) give you a device context, that you can use with window API functions
0
 
LVL 8

Expert Comment

by:TOndrej
ID: 6409343
The inheritance chain is the following:
TPanel <- TCustomPanel <- TCustomControl <- ...

TCustomControl has protected Canvas property, the problem is only that none of the descendants make it public.
A quick workaround:

type
  THackPanel = class(TPanel);

  with THackPanel(Panel1) do
  begin
    // you now have access to all protected properties
    Canvas.MoveTo(0, 0);
    Canvas.LineTo(ClientWidth, ClientHeight);
  end;

HTH
TOndrej
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6409385
thats it, tondrej :-)
0
 
LVL 8

Expert Comment

by:TOndrej
ID: 6409395
yes kretzschmar :-)
I went through all the previous comments several times to make sure that none of them mentioned this well-known trick...
I was surprised :-P
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6409403
i know the trick, but thought not on it :-)
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6409415
btw tondrej (sorry to be off topic)
how are you?
what about mike lischke?
are you two working already together?

(many more questions in mind)
0
 
LVL 8

Expert Comment

by:TOndrej
ID: 6409427
1. fine, busy, thanks :-)
2. fine too, busy, too :-)
3. yes! :-P
sorry for offtopic, I've included my e-mail in my profile, if you want to write
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6409453
i will email you, tondrej
0

Featured Post

Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Creating an auto free TStringList The TStringList is a basic and frequently used object in Delphi. On many occasions, you may want to create a temporary list, process some items in the list and be done with the list. In such cases, you have to…
Introduction I have seen many questions in this Delphi topic area where queries in threads are needed or suggested. I know bumped into a similar need. This article will address some of the concepts when dealing with a multithreaded delphi database…
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…

790 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question