Problem in redrawing Rectangle on "Up Arrow Key Down" in MFC Dialog Based application - C / C++ / MFC Discussion Boards

Re: Important Points for KT

LittleYellowBird10-Jun-10 5:22

LittleYellowBird

10-Jun-10 5:22

Aaahhh, you have a bad case of RADYN's!!! Rose | [Rose]

(Repeated Acronym use Drives You Nuts! Big Grin | :-D

)

Ali

Re: Important Points for KT

Cedric Moonen10-Jun-10 8:11

Cedric Moonen

10-Jun-10 8:11

Precisely...
It is particulary annoying when you have to read some "papers" about any kind of technology (but the worse is for software) Dead | X|

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Re: Important Points for KT

Richard MacCutchan10-Jun-10 5:43

Richard MacCutchan

10-Jun-10 5:43

Cedric Moonen wrote:
where will we end

Exactly; I usually have to go here[^] to find the answer. This was one of the few times when it came to me almost immediately. I must say I agree with you, people who post questions where the main item is a TLA (or TLA) are a PITA.

It's time for a new signature.

Re: Important Points for KT

Niklas L11-Jun-10 2:09

Niklas L

11-Jun-10 2:09

Where PITA of course is an ETLA.

home

Re: Important Points for KT

Richard MacCutchan11-Jun-10 2:44

Richard MacCutchan

11-Jun-10 2:44

Niklas Lindquist wrote:
Where PITA of course is an ETLA.

Personally, I'd describe it as a FLA or a flatbread. Laugh | :laugh:

It's time for a new signature.

Re: Important Points for KT

Tim Craig10-Jun-10 13:48

Tim Craig

10-Jun-10 13:48

A place I worked in the early 80s had at least three acronyms of MRP. It all depended on whom you were talking to.

Once you agree to clans, tribes, governments...you've opted for socialism. The rest is just details.

Re: Important Points for KT

CPallini10-Jun-10 3:00

CPallini

10-Jun-10 3:00

Richard MacCutchan wrote:
I assume you are talking about a Knowledge Transfer;

I suppose is "Klingon Therapy" instead. $Shucks | :-\$

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Problem in redrawing Rectangle on "Up Arrow Key Down" in MFC Dialog Based application

Arindam Tewary9-Jun-10 23:55

Arindam Tewary

9-Jun-10 23:55

Hi,

I am writing a small program in MFC using Dialog based project.
What I want to achive is : On pressing "Up Arrow Key" I want to redraw a rectangle which was already drawn.( want to draw the rectangle in other point).

Can you please help me what I am doing wrong here.

I am setting a variable "iKeyPressed" to "1" "PreTranslateMessage" method when Up Key is pressed.

BOOL CKeyDownTestDlg::PreTranslateMessage(MSG* pMsg)
{
	// TODO: Add your specialized code here and/or call the base class
    iKeyPressed = 0;
	if (pMsg->message == WM_KEYDOWN)
	{
		if(pMsg->wParam==VK_UP)
		{
			iKeyPressed = 1;
			CKeyDownTestDlg::OnPaint();
		 //::AfxMessageBox(_T("Inside"));              
		}
	}
	return CDialog::PreTranslateMessage(pMsg);
}

Then in OnPaint() method I am checking the value of "iKeyPressed". If that is "1", then I intend to "Redraw" (erasing out the previously drawn rectangle)rectangle which was drawn earlier.

void CKeyDownTestDlg::OnPaint()
{
	if (IsIconic())
	{
		//These code is not executed.
	}
	else
	{
		char c[10];
		
		CPaintDC dc(this); // device context for painting
		CString MFCString; 
		MFCString = c;
		if(iKeyPressed==0)
		{
			dc.Rectangle(5,5,100,20);
			AfxMessageBox(_T("iKeyPressed = 0"));     
			/*dc.SelectObject(old_brush);*/
		}

		if(iKeyPressed==1)
		{
			CPaintDC dc(this); // device context for painting
			AfxMessageBox(_T("iKeyPressed = 1"));      
			dc.Rectangle(5,5,20,100);			
		}
		CDialog::OnPaint();
	}
}

Interestingly, while executing I could see Message "iKeyPressed = 1".

Any help is appreciated.

Thanks,
Arindam D Tewary

Re: Problem in redrawing Rectangle on "Up Arrow Key Down" in MFC Dialog Based application

Aescleal10-Jun-10 0:14

Aescleal

10-Jun-10 0:14

You need to understand how WM_PAINT and OnPaint works. If you call your OnPaint at an arbitrary time what happens is it creates a CPaintDC which won't (or rather probably won't) have any invalid region in it. So all your drawing is clipped to a non-existent region and nothing appears on the screen.

Try calling Invalidate() instead of OnPaint() and see if that improves the situation. Can't remember the parameters off the top of me head so you'll have to look them up! This signals that you want to paint the whole window and will cause a redraw (i.e. your OnPaint()) will get called indirectly. When that happens CPaintDC will be set up properly.

Oh, and only have one object of type CPaintDC in a given OnPaint method, you might get some strangeness otherwise.

Cheers,

Ash

Re: Problem in redrawing Rectangle on "Up Arrow Key Down" in MFC Dialog Based application

CPallini10-Jun-10 0:26

CPallini

10-Jun-10 0:26

Arindam Tewary wrote:
BOOL CKeyDownTestDlg::PreTranslateMessage(MSG* pMsg)
{
// TODO: Add your specialized code here and/or call the base class
iKeyPressed = 0;

I think the iKeyPressed = 0 in the above code is you problem. Remove it and change the following piece of code

Arindam Tewary wrote:
if(iKeyPressed==1)
{
CPaintDC dc(this); // device context for painting
AfxMessageBox(_T("iKeyPressed = 1"));
dc.Rectangle(5,5,20,100);
}

This way

if(iKeyPressed==1)
{
  iKeyPressed = 0
  CPaintDC dc(this); // device context for painting
  AfxMessageBox(_T("iKeyPressed = 1"));
  dc.Rectangle(5,5,20,100);
}

BTW calling OnPaint directly is a bad idea: you should replace it with

InvalidateRect(...);
UpdateWindow();

sequence.

Re: Problem in redrawing Rectangle on "Up Arrow Key Down" in MFC Dialog Based application

Arindam Tewary10-Jun-10 0:38

Arindam Tewary

10-Jun-10 0:38

Thanks Mr. Palini for reply.

I just started VC++ MFC couple of days back. I am still not very much comfortable in it after comming from C# background. So I directly called that OnPaint method. I would keep learning about it in comming days for sure.

I used your suggestion but still it does not repaint it. Frown | :(

. Any other idea sir?

Thanks,
Arindam D Tewary

Re: Problem in redrawing Rectangle on "Up Arrow Key Down" in MFC Dialog Based application

CPallini10-Jun-10 1:02

CPallini

10-Jun-10 1:02

You should remove the Message Boxes calls to see it.
Also you're using too many device contexts in OnPaint.
Smile | :)

catching new

Sakhalean9-Jun-10 22:56

Sakhalean

9-Jun-10 22:56

Hi All,

How to catch the new allocation failure exception in MFC

I am using CMemoryException but it is not catching.
I am using bad_alloc exception that also it is not catching.

Re: catching new

rp_suman9-Jun-10 23:19

rp_suman

9-Jun-10 23:19

With ellipsis you can catch all exceptions, if you are not sure about exception type:

catch (...) { 
   // ... 
}

--
"Programming is an art that fights back!"

Re: catching new

Sakhalean9-Jun-10 23:27

Sakhalean

9-Jun-10 23:27

thank you
it is working

Re: catching new

rp_suman10-Jun-10 6:00

rp_suman

10-Jun-10 6:00

You are welcome!! Smile | :)

--
"Programming is an art that fights back!"

Re: catching new

Aescleal9-Jun-10 23:25

Aescleal

9-Jun-10 23:25

Here's a question to consider...

If you're not catching the exception, how do you know it's being thrown? Are you sure it's a memory allocation failure or could it be something else?

Cheers,

Ash

PS: Okay, that was two questions...

PPS: Just out of interest, where are you trying to handle the exception that may or may not have happened? You shouldn't throw exceptions through DLLs supplied by the operating system, so make sure you're trying the catch around all your window procedures or message handlers.

Re: catching new

Sakhalean9-Jun-10 23:28

Sakhalean

9-Jun-10 23:28

catch(...)
is working

Re: catching new

Aescleal9-Jun-10 23:43

Aescleal

9-Jun-10 23:43

Okay, so what exception is being thrown and what effects does it have on the rest of your program? After the exception has been thrown are you sure you can carry on?

There's really only two uses for catch(...):

- Right at the top of main to make sure you report something's happened, you've got no idea what but you're telling the maintenance programmer they're in for a long slog sorting it out

- At the boundary of a subsystem and you want to convert something catastrophic into something slightly less catastrophic so the program can gracefully(ish) bail out with an error message

Ash

Re: catching new

Sakhalean10-Jun-10 0:22

Sakhalean

10-Jun-10 0:22

I want to catch that exception.

So that it should not give outofmemory messagebox.

Temporarly I will continue
but later (afer few days ) I will try to stop that exception.
Now I am doing some other thing.
I Will meet you again.
thank you

Re: catching new

Stephen Hewitt10-Jun-10 14:07

Stephen Hewitt

10-Jun-10 14:07

catch (...) is the wrong way to go about displaying an out of memory dialog box since it will catch all exceptions including ones that don't indicate allocation failure.

Steve

Popup Menu

VVVimal9-Jun-10 22:37

VVVimal

9-Jun-10 22:37

when the context menu is dismissed my application takes a long time to redraw the area that was obscured by the menu. Can anyone give solution to this.

Re: Popup Menu

Niklas L9-Jun-10 22:54

Niklas L

9-Jun-10 22:54

Continue the other thread you started. You can add more info to that instead of opening a new one.

home

Re: Popup Menu

rp_suman9-Jun-10 22:59

rp_suman

9-Jun-10 22:59

Try calling UpdateWindow Function.

--
"Programming is an art that fights back!"

Re: Popup Menu

David Crow10-Jun-10 3:04

David Crow

10-Jun-10 3:04

You waited 89 minutes before posting the same question again. Why so impatient? This forum is read by folks from around the globe. Give them a chance to see your question before reposting.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.