obtaining MOUSE_DX MOUSE_DY in winapi - windows

Question

I need obtain a MOUSE_DX and MOUSE_DY values where
MOUSE_DX is a difference between MOUSE_X and MOUSE_PREV_X
someone give stupid answer to my that i can hide cursor substract
succesive MOUSE_X between mouse move events, and when cursor
goes away from the centre of the sceen call ShowCursorPost to the
cantre of the screen - but this is a real hell : it is stupid perself also
calling ShowCursorPost generate fake mouse move events so
then I would need to filter out this fake movements then (It is hell)
Is there some more reasonable way of obtaining the MOUSE_DX
MOUSE_DY I need?
//EDIT (more explaining for questions )
I want to use mouse as a steering device - something like mowing yaw/pitch/roll of the camera
For this purpose I need to gest something like MOUSE_DELTA_X MOUSE_DELTA_Y
where such numbers are indeed the MOUSE_X-MOUSE_PREV_X where MOUSE_X/Y are
coordinates of the mouse cursor given to me by WM_MOUSEMOVE
allright - this works to some extent but not much:
I need the DX DY walues related to mouse movements but do not need
a mouse cursor at all, when mouse cursor hits the screen edge i will
not gest full DX but some cutted and then all zeros
To prevent this i call (as somebody advice me) SetCursorPos when
the cursor nears to the edge of the desktop (the window really becouse
I do not want him to exit my window) then I call SetCursorPos
to the centre of the client area (I also make cursor invisible, and
also clip it to the window size but it also brings a lot of
trouble, need to unclip the areo on alt+tab etc it is all tiresome
and it is all a complex workaround for such simple thing like obtaining
DX DY) I just do not need this f*cking invisible cursor moving on screen
at all here - but I need mouse DX DY only
but let assume that this machinery with invisible cursor is tiresomely
coded and debugged
the other trouble is that when I call SetCursorPos It also generates
fake mouse movement backward and it generates fake DX and DY then
(it is hard to filter - at least i do not know how to do it all
in a robust way)
(can this fake mouse move been easily filtered out?)
I did it all this invisible cursor clipping SetCursorPos and filtering
out the false DX DY but it is very ugly thing very error prone and
confusing - all this for simple obtaining (cursor independant/mouse
related)DX DY for every move - this is hell It made me a long hours to
debug this stuff so I am angry - this is coding hell - this is terribly
wrong so I am angry and need a good way of doing it

Answer 1

The WM_MOUSEMOVE event tells you the current position of the cursor. Well, it's actually the position of the cursor when the event was placed in the message queue, not quite the same thing. But the system does not keep track of the position of the cursor associated with the previous WM_MOUSEMOVE message. From this you can conclude that you will need to keep track of that.
So, do the following:
Declare variables to hold the previous cursor position.
Initialize those variables to the current cursor position.
Whenever you process WM_MOUSEMOVE you can compare the current position with the previous.
Once you have done that, update the previous cursor position to be equal to the current position, ready for the next WM_MOUSEMOVE message.

Answer 2

What you could try:
Use the ClipCursor function to confine the cursor inside your window, or a sub-rect.
When the mouse hit your "border", start a timer. Stop the timer when the mouse leaves the border.
On each timer tick, you could generate a fake DX or DY.
The idea is to have the behavior of many games: you move the mouse, hitting a border, and then all behave as if you were still moving the mouse.