Very Computer

Hi,

HAs anyone an example how to handle to act on the WM_PAINT message

Greetings,

Bart Huls

Quote:>HAs anyone an example how to handle to act on the WM_PAINT message

A window gets that msg when any part of it is exposed. VCL controls
repaint themselves, but any painting you do yourself on a TCanvas
(e.g. in a TForm or TPaintBox or in your own control) must be done
again.

Hi,

I want to catch this message because I want must do someting when the
form is being maximized, Or is there an other way?

Thanks,

Bart Huls

If I understand your question correctly, you want to "catch" the
WM_PAINT message and call your own function. This can easily be done,
but may not really be what you want !

In the class header for your form put the following code:-

class TMyForm : public TForm
{
  ...
private:        // User declarations
  void __fastcall MyPaint(TMessage* Message);
  BEGIN_MESSAGE_MAP
    MESSAGE_HANDLER(WM_PAINT, TMessage*, MyPaint)
  END_MESSAGE_MAP(TForm)
  ...

Quote:};

Then in the form module, write the necessary code that you need to do:-

void __fastcall TMyForm::MyPaint(TMessage *Message)
{
  ...

Quote:}

Now the bad news ! Remember that by depriving the form of it's regular
supply of WM_PAINT messages, you'll have to take care of updating the
form yourself ! (calling Show() won't work since Show throws WM_PAINT
messages which will wind you up !).

Perhaps trapping the WM_SIZE message would be more fruitful. You'll have
to check the wParam part of the message (Message->wParam) to see if the
form has Maximized (wParam==2), Minimized (wParam==1) or Restored
(wParam==0)

Page 8-4 in the BCB 1.0 Component Writer's Guide gives more details.

Good luck !

Quote:>I want to catch this message because I want must do someting when the
>form is being maximized, Or is there an other way?

When a form is maxed your resize handler will be called, and you can
look at WindowState to see if the form is now maxed, minned or normal.
That might be more suitable.

Hi Colin,

I tried to use the WM_SIZE message but when I catch the message it
seems that the corrupts the getting of the WM_GETMINMAX message.
Maybe I'm doing something wrong, but I don't have enough documentation
about this. can you tell me  what the Message parameters are?

Thanks,

Bart Huls

Quote:>>I tried to use the WM_SIZE message but when I catch the message it

seems that the corrupts the getting of the WM_GETMINMAX message.

Be sure you call DefaultHandler(&Message) or TForm::Dispatch(&Message) in
your message handler.

--
Kent (TeamB and TurboPower Software)

Hallo Kent,

Calling TForm::Dispatch(&Message) results in a Stackoverflow calling
the defaulthandler results in a vertical scrollbar. When I click the
vertical scrollbar, The form doesn't move and the scrollbar disappear.
I don't know what is wrong?

Greetings,

Bart Huls

Quote:>Calling TForm::Dispatch(&Message) results in a Stackoverflow

How did you trap WM_PAINT? With a message map, or by overriding the WndProc
function. If you overrode WndProc, call the base class WndProc instead of
calling Dispatch. Dispatch should work from a message map.

If your base class is not TForm, make sure that you replace TForm with the
correct base class.

Harold Howe (TeamB)
http://www.bcbdev.com

Hello Harold,

Quote:

> >Calling TForm::Dispatch(&Message) results in a Stackoverflow

> How did you trap WM_PAINT? With a message map, or by overriding the WndProc

I'm catching the WM_SIZE command in the message map

BEGIN_MESSAGE_MAP
   MESSAGE_HANDLER(WM_SIZE         ,TWMSize           ,WMSize         );
END_MESSAGE_MAP(TForm)

Quote:};

And in the source:

void __fastcall TfrmRadarPresentatie::WMSize(TWMSize &Message)
{
  TfrmRadarPresentatie::Dispatch(&Message);

Quote:}

It creates a stack-overflow. When I'm not calling the default-handler
there is a scrollbar on my form.

Regards,

Bart Huls

Stack overflow not surprizing! When you get the WMSize message, you send
it to yourself then repeat until you die!

void __fastcall TfrmRadarPresentatie::WMSize(TWMSize &Message)
{
  TfrmRadarPresentatie::Dispatch(&Message);

Quote:}

Oops. Try:

  TForm::Dispatch(&Message);

--
Kent (TeamB and TurboPower Software)