ExtCreatePen and Windows 7 GDI

I created DIBPATTERN pens with ExtCreatePen API for custom pattern pens.

It sucessfully draws desired lines on Windows XP,

But on Windows 7 (x64 for my case), it does not draw any lines; no changes on screen.

(Other sim开发者_如何学Goply created pens, for example CreatePen(PS_DOT,1,0), are working.)

I found that calling SetROP2(hdc, R2_XORPEN) makes the following line-drawing API calls draw something but with XOR operation. I don't want XOR drawing.

Here is my code to create the pen. It has no problem on Windows XP:

LOGBRUSH lb;
lb.lbStyle = BS_DIBPATTERN;
lb.lbColor = DIB_RGB_COLORS;
int cb = sizeof(BITMAPINFOHEADER) + sizeof(RGBQUAD) * 2 + 8*4; 
HGLOBAL hg = GlobalAlloc(GMEM_MOVEABLE, cb);                
BITMAPINFO* pbmi = (BITMAPINFO*) GlobalLock(hg);
ZeroMemory(pbmi, cb);
pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER); 
pbmi->bmiHeader.biWidth = 8; 
pbmi->bmiHeader.biHeight = 8; 
pbmi->bmiHeader.biPlanes = 1; 
pbmi->bmiHeader.biBitCount = 1; 
pbmi->bmiHeader.biCompression = BI_RGB;
pbmi->bmiHeader.biSizeImage = 8;
pbmi->bmiHeader.biClrUsed = 2;
pbmi->bmiHeader.biClrImportant = 2;
pbmi->bmiColors[1].rgbBlue =
pbmi->bmiColors[1].rgbGreen =
pbmi->bmiColors[1].rgbRed = 0xFF;
DWORD* p = (DWORD*) &pbmi->bmiColors[2];
for(int k=0; k<8; k++) *p++ = patterns[k];
GlobalUnlock(hg);
lb.lbHatch = (LONG) hg;
s_aSelectionPens[i] = ExtCreatePen(PS_GEOMETRIC, 1, &lb, 0, NULL);
ASSERT(s_aSelectionPens[i]); // success on both XP and Win7
GlobalFree(hg);

Is it bug only on my PC? Please check this problem. Thank you.

This is a known bug with the Windows 7 GDI, though good luck getting Microsoft to acknowledge it.

http://social.technet.microsoft.com/Forums/en-US/w7itproappcompat/thread/a70ab0d5-e404-4e5e-b510-892b0094caa3

-Noel

I will admit, I was dubious as first, but I compiled and ran your program, and it does indeed fail to draw the second line on Windows 7, buy only in aero mode

By switching to Windows basic or classic mode, all four lines are drawn, as expected.

I can only assume that this is some kind of bad interaction with your custom pen and the new way aero mode implements GDI calls. This seems like it might be a Microsoft bug, perhaps you can post this question on one of their message boards?

So you are creating an 8x8 black/white (monochrome) bitmap as a DIB, and then using that to create a pen. I see nothing wrong with this code. this definitely looks like a windows bug, but there may be a workaround.

Try setting

pbmi->bmiHeader.biClrUsed = 0;
pbmi->bmiHeader.biClrImportant = 0;

In this context, setting the values to 0 should mean the same thing as setting them to 2, but 0 is more standard behavior for situations where you have are using the full palette. You still need two entries in your palette, 0 just means "full size based on biBitCount".

Also, each palette entrie is a RGBQUAD, which means there is room for alpha, and your alpha is set to 0, which should be ignored, but maybe it isn't. so try setting the high byte of your two palette entries to 0xFF or 0x80.

Finally, it's possible that your palette is being ignored entirely, and Windows is using the BkMode, BkColor and TextColor of the destination DC for everything, so you need to make sure that they are set to values that you can see.

My guess is that this has something to do with alpha transparency, since GDI ignores alpha entirely, but Aero doesn't.