how implement display of fullscreen on QVGA windows mobile when using GAPI

you can use the following codes instead of GXBeginDraw():

RawFrameBufferInfo rfbi;
int hr = ExtEscape(hdc, GETRAWFRAMEBUFFER, 0, NULL, sizeof(RawFrameBufferInfo), (char *)fbi);

g_pPaintBuffer = (BYTE*)rfbi.pFramePointer;

don't use GXBeginDraw() function to get drawing buffer. you should use ExtEscape function to get strcut data, and pFramePointer point is that you want to get drawing buffer point.
when you are ready to draw, you are careful to display Properties struct data. Because they are not fitful for the buffer point which you get through ExtEscape function, you should use data get by ExtEscape function.

Be careful  for data, maybe changed:
g_gxdp.cBPP     ,  rfbi.wBPP;
g_gxdp.cbxPitch      ,  rfbi.cxStride;
g_gxdp.cbyPitch      ,   rfbi.cyStride;
g_gxdp.cxWidth      ,  rfbi.cxPixels;
g_gxdp.cyHeight      ,  rfbi.cyPixels;
g_gxdp.ffFormat      ,   rfbi.wFormat;