winapi input delay reading events when mouse move and keys are pressed - c++

Question

I'm making a fps based game. Currently I have a wnd_proc function to capture all events for input (WM_MOUSEMOVE, WM_KEYUP, WM_KEYDOWN, ...). My mouse is used to move the camera like in a fps. It works fine when I am only moving the mouse. But when I am pressing on keys to move the character and moving the mouse around at the same time, there is a delay in detecting the mouse movement in the game. I notice the delay also when I press on multiple keys.
For the keyboard events, instead of using my own input class to check whether the keys are pressed, I use GetAsyncKeyState() to read the keyboard stuff and this fixes the multiple keys delay. But my mouse is still the problem. Is there a Async function for the mouse movement?
--EDIT--
This is my input system class which is called during the wndproc function.
class InputSystem : public System
{
...
...
...
void ProcessInput(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
LPBYTE lpb;
UINT dwSize;
RAWINPUT *raw;
switch (message)
{
case WM_INPUT:
{
GetRawInputData((HRAWINPUT)lParam,
RID_INPUT,
NULL,
&dwSize,
sizeof(RAWINPUTHEADER));
lpb = new BYTE[dwSize];
if (lpb == NULL)
return;
if (GetRawInputData((HRAWINPUT)lParam,
RID_INPUT,
lpb,
&dwSize,
sizeof(RAWINPUTHEADER)) != dwSize)
MessageBox(hWnd, L"GetRawInputData returning wrong size!", L"Orhhor! Bao zha liao!", MB_OK);
raw = (RAWINPUT*)lpb;
if (raw->header.dwType == RIM_TYPEKEYBOARD)
{
if (raw->data.keyboard.Message == WM_KEYDOWN ||
raw->data.keyboard.Message == WM_SYSKEYDOWN)
{
input.ReadInput(raw->data.keyboard.VKey);
}
else if (raw->data.keyboard.Message == WM_KEYUP ||
raw->data.keyboard.Message == WM_SYSKEYUP)
{
input.ResetInput(raw->data.keyboard.VKey);
}
}
delete[] lpb;
return;
}
While below is my input class
class Input
{
bool keys[256];
bool prevKeys[256];
...
...
...
}
void Input::InitInput()
{
...
...
...
auto hWnd = CORE->GetSystem<WindowManager>()->GetWindowHandle();
RAWINPUTDEVICE Rid[2];
Rid[0].usUsagePage = 0x01;
Rid[0].usUsage = 0x06; //keyboard
Rid[0].dwFlags = RIDEV_INPUTSINK;
Rid[0].hwndTarget = hWnd;
if (RegisterRawInputDevices(Rid, 1, sizeof(Rid[0])) == false)
assert("Keyboard not registered.");
Rid[0].usUsagePage = 0x01;
Rid[0].usUsage = 0x02; //mouse
Rid[0].dwFlags = RIDEV_INPUTSINK;
Rid[0].hwndTarget = hWnd;
if (RegisterRawInputDevices(Rid, 1, sizeof(Rid[1])) == false)
assert("Mouse not registered.");
for (int i = 0; i < 256; ++i)
{
keys[i] = false;
prevKeys[i] = false;
}
}
void Input::ReadInput(WPARAM w)
{
keys[w] = true;
return;
}
void Input::ResetInput(WPARAM w)
{
keys[w] = prevKeys[w] = false;
return;
}
bool Input::KeyPressed(int key)
{
if (!prevKeys[key] && keys[key])
{
prevKeys[key] = true;
return true;
}
return false;
}
bool Input::KeyDown(int key)
{
return keys[key];
}