Install an Interrupt 2Fh handler and watch for Mouse Device Call Out functions (Interrupt 2Fh Function 1607h)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
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
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.