Terminate selection drag on text input

On recent versions of OS X Yosemite, there is a delay before we receive
the `mouseup` event when dragging selections with the trackpad. This
means that we’re frequently accidentally inserting text before the
selection process terminates, leading to unexpected selections after the
text insertion. This fixes that behavior and makes the behavior more
straightforward even in the case where the mouse button is remains held
down during text insertion.

spec/text-editor-component-spec.coffee

@@ -1792,6 +1792,24 @@ describe "TextEditorComponent", ->
         expect(nextAnimationFrame).toBe noAnimationFrame
         expect(editor.getSelectedScreenRange()).toEqual [[2, 4], [6, 8]]
 
+      it "stops selecting if a textInput event occurs during the drag", ->
+        linesNode.dispatchEvent(buildMouseEvent('mousedown', clientCoordinatesForScreenPosition([2, 4]), which: 1))
+        linesNode.dispatchEvent(buildMouseEvent('mousemove', clientCoordinatesForScreenPosition([6, 8]), which: 1))
+        nextAnimationFrame()
+        expect(editor.getSelectedScreenRange()).toEqual [[2, 4], [6, 8]]
+
+        inputEvent = new Event('textInput')
+        inputEvent.data = 'x'
+        Object.defineProperty(inputEvent, 'target', get: -> componentNode.querySelector('.hidden-input'))
+        componentNode.dispatchEvent(inputEvent)
+        nextAnimationFrame()
+
+        expect(editor.getSelectedScreenRange()).toEqual [[2, 5], [2, 5]]
+
+        linesNode.dispatchEvent(buildMouseEvent('mousemove', clientCoordinatesForScreenPosition([8, 0]), which: 1))
+        expect(nextAnimationFrame).toBe noAnimationFrame
+        expect(editor.getSelectedScreenRange()).toEqual [[2, 5], [2, 5]]
+
       describe "when the command key is held down", ->
         it "adds a new selection and selects to the nearest screen position, then merges intersecting selections when the mouse button is released", ->
           editor.setSelectedScreenRange([[4, 4], [4, 9]])
@@ -1979,6 +1997,24 @@ describe "TextEditorComponent", ->
         nextAnimationFrame()
         expect(editor.getScrollTop()).toBe maxScrollTop
 
+      it "stops selecting if a textInput event occurs during the drag", ->
+        gutterNode.dispatchEvent(buildMouseEvent('mousedown', clientCoordinatesForScreenRowInGutter(2)))
+        gutterNode.dispatchEvent(buildMouseEvent('mousemove', clientCoordinatesForScreenRowInGutter(6)))
+        nextAnimationFrame()
+        expect(editor.getSelectedScreenRange()).toEqual [[2, 0], [7, 0]]
+
+        inputEvent = new Event('textInput')
+        inputEvent.data = 'x'
+        Object.defineProperty(inputEvent, 'target', get: -> componentNode.querySelector('.hidden-input'))
+        componentNode.dispatchEvent(inputEvent)
+        nextAnimationFrame()
+
+        expect(editor.getSelectedScreenRange()).toEqual [[2, 1], [2, 1]]
+
+        gutterNode.dispatchEvent(buildMouseEvent('mousemove', clientCoordinatesForScreenRowInGutter(12)))
+        expect(nextAnimationFrame).toBe noAnimationFrame
+        expect(editor.getSelectedScreenRange()).toEqual [[2, 1], [2, 1]]
+
     describe "when the gutter is meta-clicked and dragged", ->
       beforeEach ->
         editor.setSelectedScreenRange([[3, 0], [3, 2]])

src/text-editor-component.coffee

@@ -523,15 +523,17 @@ class TextEditorComponent
       onMouseUp() if event.which is 0
 
     onMouseUp = (event) =>
-      stopDragging()
-      @editor.finalizeSelections()
-      @editor.mergeIntersectingSelections()
+      if dragging
+        stopDragging()
+        @editor.finalizeSelections()
+        @editor.mergeIntersectingSelections()
       pasteSelectionClipboard(event)
 
     stopDragging = ->
       dragging = false
       window.removeEventListener('mousemove', onMouseMove)
       window.removeEventListener('mouseup', onMouseUp)
+      willInsertTextSubscription.dispose()
 
     pasteSelectionClipboard = (event) =>
       if event?.which is 2 and process.platform is 'linux'
@@ -540,6 +542,7 @@ class TextEditorComponent
 
     window.addEventListener('mousemove', onMouseMove)
     window.addEventListener('mouseup', onMouseUp)
+    willInsertTextSubscription = @editor.onWillInsertText(onMouseUp)
 
   isVisible: ->
     @domNode.offsetHeight > 0 or @domNode.offsetWidth > 0