Atom middle mouse scrolling hack

init.coffee

atom.workspace.observeTextEditors (item) ->
  
  # Sets up middle button scroll on the given editor component
  middleMouseScrollSetup = (editorComponent) ->
    lastClick = {x: 0, y: 0}
    lastPosition = {x: 0, y: 0}
    
    {scrollContainer} = editorComponent.refs
    
    onMouseMove = (event) ->
      [lastPosition.x, lastPosition.y] = [event.x, event.y]

    doScroll = ->
      sensitivity = 0.5

      dx = sensitivity * (lastClick.x - lastPosition.x)
      dy = sensitivity * (lastClick.y - lastPosition.y)
      
      previousScrollLeft = editorComponent.getScrollLeft()
      previousScrollTop = editorComponent.getScrollTop()

      updatedScrollLeft = previousScrollLeft - Math.round(dx)
      updatedScrollTop = previousScrollTop - Math.round(dy)

      editorComponent.setScrollLeft(updatedScrollLeft)
      editorComponent.setScrollTop(updatedScrollTop)
      
      editorComponent.updateSync()
      
    # We prevent regular scrolling on the scroll-container since it interferes with
    # the scrolling on the editor-component  
    scrollContainer.addEventListener 'scroll', (event) ->
      if process.platform is 'win32'
        scrollContainer.scrollTop = 0
        scrollContainer.scrollLeft = 0
    
    scrollContainer.addEventListener 'mousedown', (event) ->
      # click with middle button
      if event.button is 1 and process.platform is 'win32'
        [lastClick.x, lastClick.y] = [event.x, event.y]
        [lastPosition.x, lastPosition.y] = [event.x, event.y]

        intervalId = setInterval doScroll, 50

        onMouseUp = ->
          clearInterval(intervalId)
          window.removeEventListener 'mousemove', onMouseMove
          window.removeEventListener 'mouseup', onMouseUp

        window.addEventListener 'mousemove', onMouseMove
        window.addEventListener 'mouseup', onMouseUp
        
  init = () -> 
    editorView = atom.views.getView(item)
    if editorView && editorView.constructor.name == 'atom-text-editor'
      editorComponent = editorView.component
      middleMouseScrollSetup(editorComponent)
      
  init()

styles.less

.platform-win32 atom-text-editor.editor:not(.mini) {
  div {
    div.scroll-view {
      overflow: auto !important;
    }
  }

  .scroll-view::-webkit-scrollbar {
    display: none;
  }
}

I created a package that does this scroll-editor-on-middle-click

I've fixed the Gist to work with the newer Atom versions. Still hacky, so maybe the package linked above will be a better solution.