Implemented middle click to jump-to-location

lib/minimap-element.coffee

@@ -450,9 +450,14 @@ class MinimapElement extends HTMLElement
   # {MinimapElement} canvas.
   #
   # event - The {Event} object.
-  mousePressedOverCanvas: ({which, pageY, target}) ->
-    return if which isnt 1
-
+  mousePressedOverCanvas: (e) ->
+    if e.which is 1
+      @leftMousePressedOverCanvas(e)
+    else if e.which is 2
+      @middleMousePressedOverCanvas(e)
+    else return
+
+  leftMousePressedOverCanvas: ({pageY, target}) ->
     y = pageY - target.getBoundingClientRect().top
     row = Math.floor(y / @minimap.getLineHeight()) + @minimap.getFirstVisibleScreenRow()
 
@@ -469,6 +474,16 @@ class MinimapElement extends HTMLElement
     else
       textEditor.setScrollTop(scrollTop)
 
+  middleMousePressedOverCanvas: ({pageY}) ->
+    {top: offsetTop} = @getBoundingClientRect()
+    y = pageY - offsetTop - @minimap.getTextEditorScaledHeight()/2
+
+    ratio = y /
+      (@minimap.getVisibleHeight() - @minimap.getTextEditorScaledHeight())
+
+    @minimap.textEditor.setScrollTop(
+      ratio * @minimap.getTextEditorMaxScrollTop())
+
   # Internal: A method that relays the `mousewheel` events received by
   # the {MinimapElement} to the {TextEditorElement}.
   #
@@ -491,6 +506,9 @@ class MinimapElement extends HTMLElement
   #
   # event - The {Event} object.
   startDrag: ({which, pageY}) ->
+    if which is 2
+      @mousePressedOverCanvas({which, pageY})
+
     return if which isnt 1
     {top} = @visibleArea.getBoundingClientRect()
     {top: offsetTop} = @getBoundingClientRect()

spec/helpers/events.coffee

@@ -14,8 +14,7 @@ mouseEvent = (type, properties) ->
     shiftKey: false
     metaKey: false
     button: 0
-    relatedTarget: `undefined`
-    which: 1
+    relatedTarget: undefined
   }
 
   properties[k] = v for k,v of defaults when not properties[k]?
@@ -29,14 +28,15 @@ objectCenterCoordinates = (obj) ->
 module.exports = {objectCenterCoordinates, mouseEvent}
 
 ['mousedown', 'mousemove', 'mouseup', 'click'].forEach (key) ->
-  module.exports[key] = (obj, {x, y, cx, cy, which}={}) ->
+  module.exports[key] = (obj, {x, y, cx, cy, btn} = {}) ->
     {x,y} = objectCenterCoordinates(obj) unless x? and y?
 
     unless cx? and cy?
       cx = x
       cy = y
 
-    obj.dispatchEvent(mouseEvent key, {pageX: x, pageY: y, clientX: cx, clientY: cy, which})
+    obj.dispatchEvent(mouseEvent key, {
+      pageX: x, pageY: y, clientX: cx, clientY: cy, button: btn})
 
 module.exports.mousewheel = (obj, deltaX=0, deltaY=0) ->
   obj.dispatchEvent(mouseEvent 'mousewheel', {deltaX, deltaY})

spec/minimap-element-spec.coffee

@@ -305,6 +305,52 @@ describe 'MinimapElement', ->
         it 'relays the events to the editor view', ->
           expect(editorElement.component.presenter.setScrollTop).toHaveBeenCalled()
 
+      describe 'middle clicking the minimap', ->
+        [canvas, visibleArea, originalTop, originalLeft, maxScroll] = []
+
+        beforeEach ->
+          canvas = minimapElement.canvas
+          visibleArea = minimapElement.visibleArea
+          {top, left} = visibleArea.getBoundingClientRect()
+          [originalTop, originalLeft] = [top, left]
+          maxScroll = minimap.getTextEditorMaxScrollTop()
+
+        it 'scrolls to the top using the middle mouse button', ->
+          mousedown(canvas, x: originalLeft + 1, y: 0, btn: 1)
+          expect(editor.getScrollTop()).toEqual(0)
+
+        describe 'scrolling to the middle using the middle mouse button', ->
+          canvasMidY = undefined
+
+          beforeEach ->
+            editorMidY = editor.getHeight() / 2.0
+            {top, height} = canvas.getBoundingClientRect()
+            canvasMidY = top + (height / 2.0)
+            actualMidY = Math.min(canvasMidY, editorMidY)
+            mousedown(canvas, x: originalLeft + 1, y: actualMidY, btn: 1)
+
+          it 'scrolls the editor to the middle', ->
+            middleScrollTop = Math.round((maxScroll) / 2.0)
+            expect(editor.getScrollTop()).toEqual(middleScrollTop)
+
+          it 'updates the visible area to be centered', ->
+            nextAnimationFrame()
+            {top, height} = visibleArea.getBoundingClientRect()
+            visibleCenterY = top + (height / 2)
+            expect(visibleCenterY).toBeCloseTo(canvasMidY, 0)
+
+        it 'scrolls the editor to an arbitrary location', ->
+          scrollTo = 100 # pixels
+          scrollRatio = (scrollTo - minimap.getTextEditorScaledHeight()/2) /
+            (minimap.getVisibleHeight() - minimap.getTextEditorScaledHeight())
+          scrollRatio = Math.max(0, scrollRatio)
+          scrollRatio = Math.min(1, scrollRatio)
+
+          mousedown(canvas, x: originalLeft + 1, y: scrollTo, btn: 1)
+
+          expectedScroll = maxScroll * scrollRatio
+          expect(editor.getScrollTop()).toBeCloseTo(expectedScroll, 0)
+
       describe 'pressing the mouse on the minimap canvas (without scroll animation)', ->
         beforeEach ->
           t = 0