Solved

Timage descendent - designtime painting

Posted on 2003-11-05
7
325 Views
Last Modified: 2013-11-23
My component has to paint some rectangles on itself's canvas, according to some parameters.

How can my component show the rectangles even at designtime ? (like all vcl components in delphi : when you place/resize/etc the component on the form, you _see_ it , not only the contour.
0
Comment
Question by:Catalin80
[X]
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
  • 3
  • 2
  • 2
7 Comments
 
LVL 5

Expert Comment

by:DeerBear
ID: 9693209
Hi,

Why do you use TImage as base class?
Wouldn't a TPaintBox have been better?

Anyway, the only "pictures" you can see at design time are
loaded files, which get displayed in the "Paint" method or the
Update one, I didn't look at the sources.

So, my guess is that you should look in the TImage class where
this happens and act accordingly.

HTH,

Andrew

P.S. As a last chance, you can always override the WM_PAINT method.
If you want a sample just let me know.
0
 

Author Comment

by:Catalin80
ID: 9693568
If it works, give me the sample code. Thx.
0
 
LVL 5

Accepted Solution

by:
DeerBear earned 70 total points
ID: 9693588
Hi,

This example shows a form intercepting WM_PAINT, but the
same concept applies to controls:

Type

  TMyForm = class( TForm )
   private
      procedure HandleWM_PAINT( var Mesg : TMessage );message WM_PAINT;
  end;

procedure TMyForm.HandleWM_PAINT( var Mesg : TMessage );
begin
  Inherited;// REMEMBER TO CALL INHERITED OTHERWISE THE COMPONENT WON'T WORK!!!!!!!!!!
  // Place your code here!
end;

HTH,

Andrew
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 12

Expert Comment

by:andrewjb
ID: 9694687
?? There's no difference. At design time Delphi runs your code, just like at run time. If you component view OK at runtime, it should work at design time, too.

(Obviously non-visual controls don't display, but then you can't see them at runtime either)

0
 

Author Comment

by:Catalin80
ID: 9696972
@DeerBear : That works fine but : when the strech property is false, the object blinks.
0
 
LVL 5

Expert Comment

by:DeerBear
ID: 9699508
Hi,

Use double buffering to avoid flickering.

Draw your image on a temporary bitmap and then transfer it on the
drawing surface.

HTH,

Andrew
0
 
LVL 12

Expert Comment

by:andrewjb
ID: 9700139
... or one of the vcl base classes has a 'DoubleBuffered' property, and it does it all for you.
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Delphi TcxGrid group footer summary 3 358
update joined tables 2 62
Wincontrol not (correctly) drawn 15 47
Problem working with dynamic array - help 2 35
The uses clause is one of those things that just tends to grow and grow. Most of the time this is in the main form, as it's from this form that all others are called. If you have a big application (including many forms), the uses clause in the in…
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…
Finds all prime numbers in a range requested and places them in a public primes() array. I've demostrated a template size of 30 (2 * 3 * 5) but larger templates can be built such 210  (2 * 3 * 5 * 7) or 2310  (2 * 3 * 5 * 7 * 11). The larger templa…
Attackers love to prey on accounts that have privileges. Reducing privileged accounts and protecting privileged accounts therefore is paramount. Users, groups, and service accounts need to be protected to help protect the entire Active Directory …

749 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