Crash During ChoosePixelFormat in VB6 - windows

Question

I've been tasked to maintain a VB6 app; I've got some OpenGL experience but all using SDL and this one seems to manually handle all it's contexts.
The program appears to crash on a call to ChoosePixelFormat. I'm passing in a non-null handle. It works on most systems, so I'm guessing its a graphics driver issue, but it appears to be up to date.
Does anyone know why this function would crash instead of, say, returning an error code? I understand the PIXELFORMATDESCRIPTOR may have values that don't exist on a given system:
.nSize = Len(glPFD)
.nVersion = 1
.dwFlags = PFD_DRAW_TO_BITMAP Or PFD_SUPPORT_OPENGL Or PFD_SUPPORT_GDI
.iPixelType = PFD_TYPE_RGBA
.cColorBits = 32
.cDepthBits = 16
.iLayerType = PFD_MAIN_PLANE
But would that make it crash?
Edit: On the system on which this fails, it works with a previous version in which this code was identical. I read a forum somewhere that said loading/unloading opengl32.dll can cause gdi32.dll to break things. This might be the case.
Edit: I've attached the full code below (it's kind of ugly, but it helped me narrow down where the crash was). No functions return 0 before ChoosePixelFormat crashes.
hDCdib = CreateCompatibleDC(0) 'DC compatible with screen
Call MsgBox("Create Compatible DC " + CStr(hDCdib))
'Setup a Device Independent Bitmap Section
With bmInfo.bmiHeader
.biSize = Len(bmInfo)
If lngWidth = 0 Then
.biHeight = objDest.ScaleY(objDest.Height, vbTwips, vbPixels)
.biWidth = objDest.ScaleX(objDest.Width, vbTwips, vbPixels)
Else
.biHeight = objDest.ScaleY(lngHeight, vbTwips, vbPixels)
.biWidth = objDest.ScaleX(lngWidth, vbTwips, vbPixels)
End If
.biPlanes = 1
.biBitCount = 32
.biCompression = BI_RGB 'No Compression
.biSizeImage = 0
.biClrImportant = 0
.biClrUsed = 0
.biXPelsPerMeter = 0
.biYPelsPerMeter = 0
End With
Call MsgBox("after header")
hDIBSection = CreateDIBSection(hDCdib, bmInfo, DIB_RGB_COLORS, hBitMapData, _
&O0, &O0)
Call MsgBox("CreateDIBSection" + CStr(hDIBSection))
'Select the DIB into a device context
hBitMapOld = SelectObject(hDCdib, hDIBSection)
Call MsgBox("SelectObject " + CStr(hBitMapOld))
'Create an OpenGL drawing area in that DIB
With glPFD
.nSize = Len(glPFD)
.nVersion = 1
.dwFlags = PFD_DRAW_TO_BITMAP Or PFD_SUPPORT_OPENGL Or PFD_SUPPORT_GDI
.iPixelType = PFD_TYPE_RGBA
.cColorBits = 32
.cDepthBits = 16
.iLayerType = PFD_MAIN_PLANE
End With
Call MsgBox("glPFD ")
'Ignacio issue is in the next line about ChoosePixelFormat
lngFormat = ChoosePixelFormat(hDCdib, glPFD)
Call MsgBox("ChoosePixelFormat " + CStr(lngFormat))
Htemp = SetPixelFormat(hDCdib, lngFormat, glPFD)
Call MsgBox("SetPixelFormat " + CStr(Htemp))
hGLrc = wglCreateContext(hDCdib)
Call MsgBox("wglCreateContext " + CStr(hGLrc))
wglMakeCurrent hDCdib, hGLrc
Call MsgBox("wglMakeCurrent ")

Answer 1

An OpenGL context on a DIB isn't accelerated, so you'll get a software renderer (at least that was the case some years back and I doubt it's changed, although I could be wrong). If you want to do hardware accelerated rendering, create a window and use that to generate your GL context. If you want, hide the window.