basic scroll-button support for plan9
andrey

Reference: /n/sources/patch/applied/scroll-mouse
Date: Tue Oct 19 16:29:46 CES 2004

--- /sys/src/9/pc/mouse.c	Tue Oct 19 16:29:46 2004
+++ /sys/src/9/pc/mouse.c	Tue Oct 19 16:29:46 2004
@@ -129,10 +129,16 @@
 				/* fall through to emit previous packet */
 			}else{
 				/* the AccuPoint on the Toshiba 34[48]0CT encodes extra buttons as 4 and 5 */
-				/* they repeat and don't release, however, so user-level timing code is required */
-				if(msg[3] == 0xFF) 
+				/* they repeat and don't release, however, so user-level timing code is required 
+				 * furthermore, intellimice with 3buttons + scroll give a two's complement
+				 * number in the lower 4 bytes (byte 4 is sign extension) that describes
+				 * the amount the scroll wheel has moved during the last sample. here we use only 
+				 * the sign to decide whether the wheel is moving up or down and generate 
+				 * a single button 4 or 5 click accordingly.
+				 */
+				if((msg[3] >> 3) & 1) 
 					buttons |= 1<<3;
-				if(msg[3] == 0x01) 
+				else if(msg[3] & 0x7) 
 					buttons |= 1<<4;
 			}
 		}