To allocate an XIconSize structure, use XAllocIconSize().
The XIconSize structure contains:
typedef struct {
int min_width, min_height;
int max_width, max_height;
int width_inc, height_inc;
} XIconSize;
The width_inc and height_inc members define an arithmetic progression of sizes (minimum to maximum) that represent the supported icon sizes.
To set a window's WM_ICON_SIZE property, use XSetIconSizes().
To read a window's WM_ICON_SIZE property, use XGetIconSizes().