dwFlags
dwFlags is a common parameter name used in many Windows API functions to convey a set of optional behaviors or modes. It represents a 32-bit value, typically a DWORD, where each bit or group of bits corresponds to a particular option. The exact meaning of each flag is defined by the function being called, and the same name dwFlags may carry different flag definitions in different APIs.
- Flags are defined as constants (often macros) in header files or documentation. They are intended to
- To enable multiple options, the typical pattern is to combine constants with the bitwise OR operator.
- When a function returns or receives dwFlags, the caller may need to test for individual options
- To disable or unset a flag, you can clear bits with bitwise operations, e.g., dwFlags &= ~FLAG_B.
- In Windows file operations, a parameter named dwFlagsAndAttributes often uses a combination of FILE_ATTRIBUTE_* and FILE_FLAG_*
- In user-interface or windowing APIs, dwFlags may control aspects like visibility, styles, or extended behaviors, using
- The exact set of available flags, their names, and whether they are mutually exclusive depends on
- Always use the provided flag constants rather than magic numbers.
- Consult the function’s documentation to understand the valid flags, their interactions, and any required combinations.
- Be mindful of portability across languages or Windows versions, as flag definitions may evolve.