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The C Users' Group Library 1994 August
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8n12062a
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1990-10-18
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Comment #
extern void far handler(void); /* a mouse event handler */
------------------------------
Version: 1.0
Date: 1/13/90
Author: Michael Kelly
Environment:
Specific to mice compatible with the Microsoft Mouse Driver Interface
External Variables: _head, _tail: near pointers to links
in a circular queue. Each link has the
form mirrored by the event_q struc defined
below.
even ;use word data alignment
event_q struc ;mirrors EVENT link defined in mouseq.h
xc dw ? ;x mouse coordinate
yc dw ? ;y mouse coordinate
butstat dw ? ;mouse button status
evmask dw ? ;event mask ( active events at time of entry )
vflag dw ? ;"valid" flag
nextptr dw ? ;pointer to next link
event_q ends
_head and _tail are defined in mouseq.h
and iniitialized in the file mouseq.c,
which is responsible for the creation and
destruction of the queue.
------------------------------
Mouse Event Handler called as a far function from the mouse driver
when it senses an event for which the event mask has a bit set.
Designed to be linked to a Small Memory Model C Program
This example uses Turbo C V. 2.0
****************************************
On Entry:
AX = bit mask for current events
where a 1 in bit position:
0 = mouse cursor movement
1 = left button press
2 = right button press
3 = left button release
4 = right button release
5 - 15: unused
BX = button status
CX = X mouse coordinate
DX = Y mouse coordinate
****************************************
#
name _handler
_TEXT segment byte public 'CODE'
DGROUP group _DATA,_BSS
assume cs:_TEXT,ds:DGROUP
_TEXT ends
_DATA segment word public 'DATA'
extrn _head:word,_tail:word
even ;use word data alignment
event_q struc
xc dw ?
yc dw ?
butstat dw ?
evmask dw ?
vflag dw ?
nextptr dw ?
event_q ends
sav_ax dw ?
_DATA ends
_BSS segment word public 'BSS'
_b@ label byte
_BSS ends
_TEXT segment byte public 'CODE'
;***********
;Entry Point
;***********
_handler proc far
cli ;disable interrupts to avoid re-entry
push ds ;save registers
push di
mov di,DGROUP ;point DS to application's data segment
mov ds,di
mov sav_ax,ax ;we're called from inside the mouse driver
;so keep stack pushes to a minimum
mov di,_tail
mov ax,[di].nextptr ;get tail->next pointer
mov di,_head
cmp ax,[di] ;if it equals head then queue is full
jne hndlr1
jmp handl_exit ;exit if queue is full
hndlr1:
mov di,_tail ;we sacrifice one slot in queue to simplify
;code, similar to PC BIOS keyboard buffer
;routine
;***********************************
;store mouse event info in the queue
;***********************************
mov [di].xc,cx ;x mouse coordinate from CX reg
mov [di].yc,dx ;y mouse coordinate from DX reg
mov [di].butstat,bx ;mouse button status from BX reg
mov ax,sav_ax ;event mask from AX reg
mov [di].evmask,ax
mov [di].vflag,1 ;mark queue entry "valid"
mov ax,[di].nextptr
mov _tail,ax ;bump tail pointer
;******************
;Handler Exit Point
;******************
handl_exit:
pop di ;restore registers
pop ds
sti ;enable interrupts
ret ;far return to mouse driver
_handler endp
_TEXT ends
_DATA segment word public 'DATA'
_s@ label byte
_DATA ends
_TEXT segment byte public 'CODE'
public _handler
_TEXT ends
end