Clean up.

1 files changed, 17 insertions, 2 deletions

diff --git a/win/tkWinX.c b/win/tkWinX.c
index 4b34a1c..9583335 100644
--- a/win/tkWinX.c
+++ b/win/tkWinX.c
@@ -20,6 +20,7 @@
 #   pragma comment (lib, "advapi32.lib")
 #endif
 
+
 /*
  * The zmouse.h file includes the definition for WM_MOUSEWHEEL.
  */
@@ -35,6 +36,20 @@
 #define WM_MOUSEHWHEEL 0x020E
 #endif
 
+/* This flag is set in the state of the MouseWheelEvent to indicate
+ * that the value stored in the keycode field should be interpreted
+ * as the number of pixels to scroll.  A WM_MOUSEWHEEL message sent
+ * by a trackpad contains the number of pixels as the delta value,
+ * while low precision scrollwheels always send an integer multiple
+ * of WHEELDELTA (= 120) as the delta value.  We set this flag
+ * whenever the WM_MOUSEWHEEL delta is not a multiple of 120.  This
+ * ignores the (rare) possibility that a trackpad might generate
+ * a message with delta a multiple of 120, intended to be interpreted
+ * as pixels.  If that proves annoying it will need to be addressed.
+ */
+
+#define HiresScrollMask (1 << 9)
+
 /*
  * imm.h is needed by HandleIMEComposition
  */
@@ -1139,7 +1154,7 @@ GenerateXEvent(
 	    event.key.nbytes = 0;
 	    event.x.xkey.keycode = (unsigned int)delta;
 	    if ( delta % 120 != 0) {
-		event.x.xkey.state |= (1 << 9);
+		event.x.xkey.state |= HiresScrollMask;
 	    }
 	    break;
 	}
@@ -1164,7 +1179,7 @@ GenerateXEvent(
 	    event.x.xkey.state |= ShiftMask;
 	    event.x.xkey.keycode = delta;
 	    if ( delta % 120 != 0) {
-		event.x.xkey.state |= (1 << 9);
+		event.x.xkey.state |= HiresScrollMask;
 	    }
 	    break;
 	}