The hotspot comes from the information stored in the cursor font. The initial colors of a cursor are a black foreground and a white background (see XRecolorCursor).
XCreateFontCursor can generate BadAlloc and BadValue errors.
The XCreatePixmapCursor function creates a cursor and returns the cursor ID associated with it. The foreground and background RGB values must be specified using foreground_color and background_color, even if the X server only has a StaticGray or GrayScale screen. The foreground color is used for the pixels set to 1 in the source, and the background color is used for the pixels set to 0. Both source and mask, if specified, must have depth one (or a BadMatch error results) but can have any root. The mask argument defines the shape of the cursor. The pixels set to 1 in the mask define which source pixels are displayed, and the pixels set to 0 define which pixels are ignored. If no mask is given, all pixels of the source are displayed. The mask, if present, must be the same size as the pixmap defined by the source argument, or a BadMatch error results. The hotspot must be a point within the source, or a BadMatch error results.
The components of the cursor can be transformed arbitrarily to meet display limitations. The pixmaps can be freed immediately if no further explicit references to them are to be made. Subsequent drawing in the source or mask pixmap has an undefined effect on the cursor. The X server might or might not make a copy of the pixmap.
XCreatePixmapCursor can generate BadAlloc and BadPixmap errors.
The XCreateGlyphCursor function is similar to XCreatePixmapCursor except that the source and mask bitmaps are obtained from the specified font glyphs. The source_char must be a defined glyph in source_font, or a BadValue error results. If mask_font is given, mask_char must be a defined glyph in mask_font, or a BadValue error results. The mask_font and character are optional. The origins of the source_char and mask_char (if defined) glyphs are positioned coincidently and define the hotspot. The source_char and mask_char need not have the same bounding box metrics, and there is no restriction on the placement of the hotspot relative to the bounding boxes. If no mask_char is given, all pixels of the source are displayed. You can free the fonts immediately by calling XFreeFont if no further explicit references to them are to be made.
For 2-byte matrix fonts, the 16-bit value should be formed with the byte1 member in the most significant byte and the byte2 member in the least significant byte.