242
If mode is PropModePrepend or PropModeAppend, XIChangeProperty inserts the specified data before the beginning of the existing data or onto the end of the existing data, respectively\&. The type and format must match the existing property value, or a BadMatch error results\&. If the property is undefined, it is treated as defined with the correct type and format with zero\-length data\&.
242
If mode is XIPropModePrepend or XIPropModeAppend, XIChangeProperty inserts the specified data before the beginning of the existing data or onto the end of the existing data, respectively\&. The type and format must match the existing property value, or a BadMatch error results\&. If the property is undefined, it is treated as defined with the correct type and format with zero\-length data\&.
245
245
If the specified format is 8, the property data must be a char array\&. If the specified format is 16, the property data must be a uint16_t array\&. If the specified format is 32, the property data must be a uint32_t array\&.