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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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386 enhanced-mode Windows supports mouse input for non-Windows applications
running in a window. To provide this input, Windows works in conjunction
with an extended MS-DOS mouse driver. Windows sends information about the
Windows mouse to the MS-DOS driver and the driver provides this information
to the non-Windows application.
 
To support mouse input in a window, an MS-DOS mouse driver must:
 
♦  Install an Interrupt 2Fh handler and watch for Mouse Device Call Out
   functions (Interrupt 2Fh Function 1607h)
 
♦  Register a mouse-support callback function when Windows broadcasts the
   Mouse Device Call Out function
 
♦  Respond appropriate to requests made by Windows through the mouse-support
   callback function
 
Registering the Mouse-Support Callback
 
An MS-DOS mouse driver must install an interrupt-handling routine for
Interrupt 2Fh when it is first loaded. The handler should watch for the
Mouse Device Call Out function (Interrupt 2Fh Function 1607h) that Windows
broadcasts when it starts up. When it detects the function, it should
respond with the address of its mouse-support callback function.
 
Windows sets the following registers and calls the Mouse Device Call Out
function as follows:
 
mov ax, 1607h
mov bx, 000Ch   ; virtual mouse device ID number
mov cx, 0001h   ; mouse API extension number
int 2Fh
 
The MS-DOS mouse driver must respond by setting the registers as follows:
 
mov ax, seg Callback
mov ds, ax
mov si, offset Callback ; DS:SI contains address of mouse-support
                        ; callback
mov ax, 0               ; zero indicates that support exists
 
Mouse-Support Callback Function
 
Windows calls the mouse-support callback function with requests and
information about the Windows mouse. The value in the AX registers specifies
what request Windows is passing to the callback function. The following
lists the requests.
 
AX     Action
────────────────────────────────────────────────────────────────────────────
0001h  Mouse move/button click
 
0002h  Disable mouse cursor drawing
 
0003h  Enable mouse cursor drawing
 
Before Windows calls, it disables interrupts and the trace flag. The
callback function must return by executing an iret instruction.
 
Mouse Movement and the Button
 
Whenever the mouse moves or a button is pressed, Windows calls the
mouse-support callback (in the proper virtual-machine context) with the
following parameters:
 
Register  Value
────────────────────────────────────────────────────────────────────────────
AX        0001h.
 
BX        x-coordinate in pixels of mouse.
 
CX        y-coordinate in pixels of mouse.
 
DX        Button state (see Interrupt 33h Function 0Ch).
 
SI        Mouse event flags (see Interrupt 33h Function 0Ch).
 
The driver should update its internal state appropriately and call any
user-installed mouse handler.
 
Disable Mouse Cursor Drawing
 
When a non-Windows application is going to run in a window, Windows disables
mouse cursor drawing to prevent two mouse cursors from being drawn. The
user's mouse Enable and Disable functions should behave normally, but the
mouse cursor should not be drawn by the MS-DOS driver. The state variable
that enables and disables mouse-cursor drawing should be instanced so that
each virtual-machine (VM) can have a different state.
 
Enable Mouse Cursor Drawing
 
This is the default state for a full-screen non-Windows application and
should be the initial state for the MS-DOS mouse driver. Windows makes this
request to re-enable the mouse cursor drawing when a non-Windows application
is switched from a window back to full screen.
 
Note:  Applications that draw their own cursors will still have two mouse
       cursors in a window.
 
       Applications which don't depend on the mouse driver will not have
       mouse support in a window.
 
 
                                      ♦