nanogui: Thread: Pen Colors

Hi,

After my earlier questions regarding the transparent and alpha blended
windows, I've modified the malpha demo to start to try to get the hang of
the Win32 GDI. I now have everything coming up initially the way that I want
it (window size, attributes, backgrounds, etc.).  One of the windows will
display an x-y plot of data.

To test the plotting functions, I just picked a few and tried to draw on the
window.  One of the results in particular is puzzling me.  I did the
following:

ChanA = CreatePen(PS_SOLID, 0, rgb(0,255,0));
SelectObject(PenPlot, ChanA);
MoveToEx(PenPlot, 0,100, NULL);
LineTo(PenPlot, 300,120);

No matter what the color is changed to I always get a black line.  I did
post the above code to a Win32 GDI newsgroup where someone tested it and
reported that they got a green line with the above code.

I've also tried SetPixel and SetPixelIV.  I cannot get these two functions
to plot anything.

I'm still missing something very basic.

Thanks for any insight.

Keith

: ChanA = CreatePen(PS_SOLID, 0, rgb(0,255,0));
: SelectObject(PenPlot, ChanA);
: MoveToEx(PenPlot, 0,100, NULL);
: LineTo(PenPlot, 300,120);

Check out the implementation of LineTo in src/mwin/wingdi.c.
I would place a couple of printf's in the function, as well
as in src/engine/devopen.c::GdFindColor(), which can show
you the colors that Microwindows is converting the rgb()
macro into a PIXELVAL value.  (You should use RGB(),
not rgb())

This debugging will tell you whether it's a hardware conversion
issue for your particular framebuffer, or a bug in Microwindows
internal code.  You are also not checking the return value for SelectObject,
or CreatePen, so there could be other failure modes.

Regards,

Greg