C / C++ / MFC

24-May-04 8:49

Hi,

I'm trying to implement double buffering in my MFC application, but keep running into a (to me) strange problem. I've read through the article "drawing speed in GDI+", and been trying to follow the code from step 2 in this article. My code (see below) compiles, but when I execute my app, I get the "standard" windows dialog, which asks if I want to send an error report, and forces me to terminate the application.

Please remember that I'm a newbie, there are certanly much bad code below, I'm just asking for the error Laugh | :laugh:

...

My view is derived frow CScrollView. Does this have anything to do with anything?

<br />
	// Kode for å tegne opp rapporten<br />
<br />
	// Beregner området å tegne i<br />
	CRect rect;<br />
	GetClientRect(&rect);<br />
	int nWidth = rect.right - rect.left +1;<br />
	int nHeight = rect.bottom - rect.top + 1;<br />
<br />
	CClientDC ClientDC(this);<br />
	Graphics graphics(ClientDC.m_hDC);	// GDI+ Stuff graph(ClientDC.m_hDC);<br />
<br />
	// Test for drawing with double buffering<br />
        // Bitmap* bmp = new Bitmap(nWidth,nHeight); and<br />
        // Bitmap* bmp(nWidth,nHeight); seems to give the same results...<br />
	#ifdef _DEBUG<br />
	#undef new<br />
		Bitmap* bmp = new Bitmap(nWidth,nHeight);<br />
	#define new DEBUG_NEW<br />
	#else<br />
		Bitmap* bmp = new Bitmap(nWidth,nHeight);<br />
	#endif<br />
		Graphics* graph = Graphics::FromImage(bmp);<br />
	<br />
	CRect area( 0, 0, 0, 0);<br />
<br />
        // This works, no questions asked, but it's not double buffering<br />
	area.SetRect( 8, 90, 814, 90); // Skillelinje som skiller elevdata fra resten av skjemaet<br />
	DrawLine(&graphics, area, 1);<br />
<br />
	/*       Test drawing to test double buffering */<br />
	// Takes about 10 seconds without double buffering<br />
	// Takes about xx seconds with double buffering<br />
	Pen pen(Color(200,0,0, 50));<br />
	for( int j=100; j<500;j = j + 5) {<br />
		for (int i=100; i<500; i = i + 5) {<br />
			area.SetRect( 110,110, j, i);<br />
<br />
                        // This works.<br />
			DrawLine(&graphics, area, 1);<br />
<br />
                        // This line causes the crach, when commented out, the code does what it's supposed to do<br />
			// graph->DrawLine(&pen, area.left, area.top, area.Width(), area.Height());<br />
		}<br />
	}<br />
<br />
	graphics.DrawImage( bmp, 0,0, 600, 600);<br />
	delete graph;<br />
	delete bmp;<br />
	/*       End test drawing       */<br />

This is my version of DrawLine Smile | :)

<br />
void CITPAXpertView::DrawLine(Graphics *pdc, CRect rect, int width)<br />
{<br />
	// Beregner hvor vi er "i landskapet" når det gjelder scrolling<br />
	CPoint where = GetDeviceScrollPosition();<br />
<br />
	// Lager en penn å tegne med<br />
	Pen penn(Color(0,0,0), REAL(width));<br />
<br />
	// Takes care of drawing lines<br />
	pdc->DrawLine( &penn, rect.left - where.x, rect.top - where.y, rect.right - where.x, rect.bottom - where.y);<br />
}<br />

567890123424-May-04 19:28

24-May-04 19:28

I try to reproduce your program. In MFC SDI application I added to following code to view OnDraw function:

void CGDITestView::OnDraw(CDC* pDC)
{
CGDITestDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;

CRect rect;
GetClientRect(&rect);
int nWidth = rect.right - rect.left +1;
int nHeight = rect.bottom - rect.top + 1;

CClientDC ClientDC(this);
// Graphics graphics(ClientDC.m_hDC); // GDI+ Stuff graph(ClientDC.m_hDC);
Graphics graphics(pDC->m_hDC); // GDI+ Stuff graph(ClientDC.m_hDC);

// Test for drawing with double buffering
// Bitmap* bmp = new Bitmap(nWidth,nHeight); and
// Bitmap* bmp(nWidth,nHeight); seems to give the same results...
#ifdef _DEBUG
#undef new
Bitmap* bmp = new Bitmap(nWidth,nHeight);
#define new DEBUG_NEW
#else
Bitmap* bmp = new Bitmap(nWidth,nHeight);
#endif
Graphics* graph = Graphics::FromImage(bmp);

CRect area( 0, 0, 0, 0);

// This works, no questions asked, but it's not double buffering
//area.SetRect( 8, 90, 814, 90); // Skillelinje som skiller elevdata fra resten av skjemaet
//DrawLine(&graphics, area, 1);

/* Test drawing to test double buffering */
// Takes about 10 seconds without double buffering
// Takes about xx seconds with double buffering
Pen pen(Color(200,0,0, 50));
for( int j=100; j<500;j = j + 5) {
for (int i=100; i<500; i = i + 5) {
area.SetRect( 110,110, j, i);

// This works.
//DrawLine(&graphics, area, 1);

// This line causes the crach, when commented out, the code does what it's supposed to do
graph->DrawLine(&pen, area.left, area.top, area.Width(), area.Height());
}
}

graphics.DrawImage( bmp, 0,0, 600, 600);
delete graph;
delete bmp;
/* End test drawing */
}

It works. From your post it is difficult to understand what happens. Please remove all lines which are not related to your problem, and post the whole function (including header).

>> I get the "standard" windows dialog, which asks if I want to send an error report.

To get more information run program in Debug congiguration, and use Go command instead of Run. In this case program breaks in Debugger and you can see what exactly happens.

Jorgen E.25-May-04 3:30

25-May-04 3:30

<br />
void CITPAXpertView::OnDraw(CDC* /*pDC*/)<br />
{<br />
	CITPAXpertDoc* pDoc = GetDocument();<br />
	ASSERT_VALID(pDoc);<br />
	if (!pDoc)<br />
		return;<br />
<br />
	// Kode for å tegne opp rapporten<br />
<br />
	// Beregner området å tegne i<br />
	CRect rect;<br />
	GetClientRect(&rect);<br />
	int nWidth = rect.right - rect.left +1;<br />
	int nHeight = rect.bottom - rect.top + 1;<br />
<br />
	CClientDC ClientDC(this);<br />
	Graphics graphics(ClientDC.m_hDC);	// GDI+ Stuff graph(ClientDC.m_hDC);<br />
<br />
	#ifdef _DEBUG<br />
	#undef new<br />
		Bitmap* bmp = new Bitmap(nWidth,nHeight);<br />
	#define new DEBUG_NEW<br />
	#else<br />
		Bitmap* bmp = new Bitmap(nWidth,nHeight);<br />
	#endif<br />
		Graphics* graph = Graphics::FromImage(bmp);<br />
	<br />
	CRect area( 0, 0, 0, 0);<br />
<br />
	/*       Test drawing to test double buffering */<br />
	Pen pen(Color(200,0,0, 50));<br />
	for( int j=100; j<500;j = j + 5) {<br />
		for (int i=100; i<500; i = i + 5) {<br />
			area.SetRect( 110,110, j, i);<br />
// Using the next line, by removing the // will work fine, only to slow for my needs<br />
		//	graphics.DrawLine(&pen, area.left, area.top, area.Width(), area.Height());<br />
// Using the next line, by removing the // will CRACH to program<br />
			//graph->DrawLine(&pen, area.left, area.top, area.Width(), area.Height());<br />
		}<br />
	}<br />
	graphics.DrawImage( bmp, 0,0, 600, 600);<br />
	delete graph;<br />
	delete bmp;<br />
	/*       End test drawing       */<br />
}<br />

This is the function in question. As you can see, I've commented out both lines that draw in the view. If I use the first line, things work fine. If I use the second line, I get in trouble D'Oh! | :doh:

The rest of the class is basically a standard CView class, except that I've made a few changes to change it to CScrollView. Things seem to be working fine, so I assume that I haven't missed anything, and the class is in fact a CScrollView class, but I might be wrong?

As in your test, the application is SDI.

Thanks, I really appreciate your efforts.

567890123425-May-04 4:06

25-May-04 4:06

Please correct obvious error:

CClientDC ClientDC(this);
Graphics graphics(ClientDC.m_hDC);

replace with
Graphics graphics(pDC->m_hDC);

Uncomment pDC in the function header. I don't beleive this is a reason, but I want to be sure that all code is OK. If problem is not fixed, post here.
I want some other information: debug this function and be sure that after the lines:

Bitmap* bmp = new Bitmap(nWidth,nHeight);
Graphics* graph = Graphics::FromImage(bmp);

bmp and graph are not NULL.

Jorgen E.25-May-04 4:45

25-May-04 4:45

Alex Farber wrote:
CClientDC ClientDC(this);
Graphics graphics(ClientDC.m_hDC);

replace with
Graphics graphics(pDC->m_hDC);

Ok, I've done this, and uncommented pDC in the header. The results are the same... Unsure | :~

I sat a breakpoint at the line "CRect area(0,0,0,0);", and checked bmp and graph... I'm quite sure this is the problem, I just don't know what to do about it Smile | :)

bmp gave me 0x00000000.
graph gave me the status "0x00000000 {nativeGraphics=??? lastResult=??? }"

I might be misunderstanding these results, but I hope it's what you asked for. (Not quite used to using the debugger, you might say Smile | :)

)

567890123425-May-04 5:05

25-May-04 5:05

Bitmap is not created. Interesting, why. What are nWidth and nHeight values? Try this:
Bitmap* pMemBitmap = new Bitmap(nWidth, nHeight, PixelFormat24bppRGB );

Jorgen E.25-May-04 5:12

25-May-04 5:12

nWidth are right-left+1 in the rect returned by GetClientRect, and the similar goes for nHeight.

Using another Pixel Format didn't help, unfortunately.

567890123425-May-04 5:17

25-May-04 5:17

>> nWidth are right-left+1 in the rect returned by GetClientRect, and the similar goes for nHeight.

I know, I asked what are their values in debugger? 10, 100 etc.

Jorgen E.25-May-04 5:22

25-May-04 5:22

Sorry, my bad Eek! | :eek:

nHeight = 654
nWidth = 1023

However, VStudio marks these values in red. Any particular reason?

567890123425-May-04 5:43

25-May-04 5:43

They are marked in red because they are used in current program line.
I really don't have idea what happens. The last thing I can suggest is to see the whole project. If you can make it available for download, post me link to it. Or you can e-mail it to me.

Jorgen E.25-May-04 6:01

25-May-04 6:01

Yeah, "check"'s in the mail :P

567890123425-May-04 6:46

25-May-04 6:46

Move GDI+ initialization code in InitInstance to the place before creating of main frame. Currently it is placed after creating and showing of main frame, and first time view is redrawn, GDI+ is not initialized.
By the way, I didn't know that CodeProject allows to post e-mail with attachments. Since you mahaged to do this, you get an answer immidiately.

Jorgen E.25-May-04 6:55

25-May-04 6:55

Works, thanks!

About the e-mail: I don't quite understand. I simply found your e-mail from the mail I got with the alert connected to this thread, and sendt you a ordinary mail Big Grin | :-D

Thanks for all help!

Jorgen E.23-Jun-04 8:21