From: nowhere@never.at   
      
   Kerr-Mudd,John wrote:   
   ...   
   >> good, programming question are always welcome here.   
      
   > Ok, What's the smallest mouse driver using only BIOS int 15 or   
   > "keyboard" in/out. I'm thinking back a year to when I made a small   
   > scrollbar menu; be nice to have mouse support for up/down/select.   
      
   I rare use a mouse in text mode.   
      
   some BIOS support also INT33.   
      
   I never fully used the INT15_C2, I only call it to make an USB-mouse   
   behave like a PS/2, so I can use my old setup and driver routines.   
      
   INT15_C2 may save you a lot, you just need to write the handler and   
   let the BIOS work its IRQ-routine as long you remain in RM16.   
      
   My mice nest (setup/structs/IRQs) measure 512 bytes, still including dual   
   serial mouse support and one PS/2 mouse. The draw-part is apart within   
   the event handlers. Mouse-rectangle arrays and many mouse images are also   
   elsewhere in memory.   
      
   You can use less than this of course ie: ignore the 3rd button and/or renounce   
   of button @ pos info.   
   My IRQ driver (same code for RM16 and PM16) incl.accelleration within   
   the routine, fits 256 byte (it's really old and could be shortened):   
      
   My mousebuffer: (was once only 32 byte for two button mice)   
   *altered by IRQ input:   
   00 b input count   
   01 b 1st   
   02 b 2nd   
   03 b 3rd   
   04 b 4th   
   05 b reserved   
   *former reserved, later merged in:   
   06 w signed Z-value   
   *set by screen mode change:   
   08 w ver limit   
   0a w hor limit   
   *calculated/updated (all POS in pixels):   
   0c w ver current pos   
   0e w hor current pos   
   *last pressed/released button at POS:   
   10 q hor+ver Lbut pressed   
   14 q         R   
   18 q         Lbut released   
   1c q         R   
   *this eight bytes were added somehow later:   
   20 q         Mbut pressed   
   24 q         Mbut released   
      
   IRQ_0C:            ;aka '12'   
   push ds   
   push myseg         ;either RM or PM-equivalent   
   pop ds             ;from here on common for both modes   
   pusha   
   in al,[60]   
   sti                ;enable to not loose any other event   
   mov si,mymouse     ;40 byte buffer   
   movzx bx,[si]      ;got bytes count   
   or bx,bx   
   jnz L1             ;already got some   
   test al,08   
   jz L2              ;resync, it's not a 1st   
   L1:   
   inc bx   
   mov [bx+si],al     ;1st...4th byte   
   cmp bl,04          ;got all four ?   
   jc L2              ;no? then wait for next   
   or [mousebits],80  ;set packet complete in global event flags   
   ...   
    position updates and button on/off locations were stored here   
    into my buffer, button state changes alter event flags too.   
    my main idle loop handles all events if/when it wants to do it.   
   ...   
   L2:   
   mov [si],bh        ;make count 0   
   mov al,20          ;eoi   
   out al,[a0]   
   out al,[20]   
   popa   
   pop ds   
   iret   
   __   
   wolfgang   
      
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