Attach wheel measuring properties to display, not directly to CM instance

Issue #1151

Author: marijnh

lib/codemirror.js

@@ -166,6 +166,9 @@ window.CodeMirror = (function() {
     // detected
     d.pasteIncoming = false;
 
+    // Used for measuring wheel scrolling granularity
+    d.wheelDX = d.wheelDY = d.wheelStartX = d.wheelStartY = null;
+
     return d;
   }
 
@@ -1666,7 +1669,7 @@ window.CodeMirror = (function() {
       }
     }
 
-    var scroll = cm.display.scroller;
+    var display = cm.display, scroll = display.scroller;
     // On some browsers, horizontal scrolling will cause redraws to
     // happen before the gutter has been realigned, causing it to
     // wriggle around in a most unseemly way. When we have an
@@ -1678,35 +1681,35 @@ window.CodeMirror = (function() {
         setScrollTop(cm, Math.max(0, Math.min(scroll.scrollTop + dy * wheelPixelsPerUnit, scroll.scrollHeight - scroll.clientHeight)));
       setScrollLeft(cm, Math.max(0, Math.min(scroll.scrollLeft + dx * wheelPixelsPerUnit, scroll.scrollWidth - scroll.clientWidth)));
       e_preventDefault(e);
-      cm.wheelStartX = null; // Abort measurement, if in progress
+      display.wheelStartX = null; // Abort measurement, if in progress
       return;
     }
 
     if (dy && wheelPixelsPerUnit != null) {
       var pixels = dy * wheelPixelsPerUnit;
-      var top = cm.view.scrollTop, bot = top + cm.display.wrapper.clientHeight;
+      var top = cm.view.scrollTop, bot = top + display.wrapper.clientHeight;
       if (pixels < 0) top = Math.max(0, top + pixels - 50);
       else bot = Math.min(cm.view.doc.height, bot + pixels + 50);
       updateDisplay(cm, [], {top: top, bottom: bot});
     }
 
     if (wheelSamples < 20) {
-      if (cm.wheelStartX == null) {
-        cm.wheelStartX = scroll.scrollLeft; cm.wheelStartY = scroll.scrollTop;
-        cm.wheelDX = dx; cm.wheelDY = dy;
+      if (display.wheelStartX == null) {
+        display.wheelStartX = scroll.scrollLeft; display.wheelStartY = scroll.scrollTop;
+        display.wheelDX = dx; display.wheelDY = dy;
         setTimeout(function() {
-          if (cm.wheelStartX == null) return;
-          var movedX = scroll.scrollLeft - cm.wheelStartX;
-          var movedY = scroll.scrollTop - cm.wheelStartY;
-          var sample = (movedY && cm.wheelDY && movedY / cm.wheelDY) ||
-            (movedX && cm.wheelDX && movedX / cm.wheelDX);
-          cm.wheelStartX = cm.wheelStartY = null;
+          if (display.wheelStartX == null) return;
+          var movedX = scroll.scrollLeft - display.wheelStartX;
+          var movedY = scroll.scrollTop - display.wheelStartY;
+          var sample = (movedY && display.wheelDY && movedY / display.wheelDY) ||
+            (movedX && display.wheelDX && movedX / display.wheelDX);
+          display.wheelStartX = display.wheelStartY = null;
           if (!sample) return;
           wheelPixelsPerUnit = (wheelPixelsPerUnit * wheelSamples + sample) / (wheelSamples + 1);
           ++wheelSamples;
         }, 200);
       } else {
-        cm.wheelDX += dx; cm.wheelDY += dy;
+        display.wheelDX += dx; display.wheelDY += dy;
       }
     }
   }