Today, when writing myhoho, the value returned when you could create createplane2d, you must assign a global variable g_pdisplay so that each time you use the function corresponding to the getGraphics (), it is always an error, the illegal memory address of the access.
After breakpoint debugging, it is found that getGraphics () returned to 0 instead of drawing the pointer to display. After several modifications, I finally discovered that in the CreatePlane2D function constructed, I didn't assign G_PDisPlay, so it was always an error when calling getGraphics (). It is estimated that the role of getGraphics () is to return the value of g_pdisplay.
