Summary
The question revolves around handling WM_INPUT messages with RIM_INPUTSINK in a native Win32 application. Specifically, it asks whether to call DefWindowProc() or return 0 when encountering RIM_INPUTSINK in the WndProc() function.
Root Cause
The root cause of the confusion lies in understanding the roles of WM_INPUT, RIM_INPUT, and RIM_INPUTSINK. Key points include:
- WM_INPUT is a message sent to the window procedure of a window that has registered for raw input.
- RIM_INPUT indicates that the input is from an input device.
- RIM_INPUTSINK indicates that the input is being sent to the application because the application has registered for it, but it’s not directly related to the physical input.
Why This Happens in Real Systems
This situation arises in real systems because applications often need to handle raw input for custom or specialized processing, such as gaming or graphical applications. The handling of RIM_INPUTSINK can affect how these applications process and respond to user input.
Real-World Impact
The impact of incorrectly handling RIM_INPUTSINK can include:
- Unexpected application behavior
- Incorrect input processing
- Potential security vulnerabilities if sensitive input data is not handled properly
- Incompatibility with certain input devices
Example or Code
static LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
switch (msg) {
case WM_INPUT:
switch (GET_RAWINPUT_CODE_WPARAM(wParam)) {
case RIM_INPUT:
// Process the raw input
break;
case RIM_INPUTSINK:
// For RIM_INPUTSINK, the recommended action is to pass the message to DefWindowProc
return DefWindowProcW(hwnd, msg, wParam, lParam);
}
break;
//...
}
return DefWindowProcW(hwnd, msg, wParam, lParam);
}How Senior Engineers Fix It
Senior engineers fix this by understanding the Windows API documentation and the implications of each return value. They recognize that RIM_INPUTSINK is a special case that should be passed to DefWindowProc() for default handling, ensuring compatibility and correctness.
Why Juniors Miss It
Juniors might miss this detail due to:
- Lack of experience with Windows API and raw input handling
- Insufficient understanding of the differences between RIM_INPUT and RIM_INPUTSINK
- Overlooking the importance of passing certain messages to DefWindowProc() for default system handling