Add support for Page Up and Page Down keys

spec/app/editor-spec.coffee

@@ -1654,3 +1654,41 @@ describe "Editor", ->
       editor.edit(project.buildEditSessionForPath())
       paths = editor.getOpenBufferPaths().map (path) -> project.relativize(path)
       expect(paths).toEqual = ['sample.js', 'sample.txt', 'two-hundred.txt']
+
+  describe "paging up and down", ->
+    beforeEach ->
+      editor.attachToDom()
+
+    it "moves to the last line when page down is repeated from the first line", ->
+      rows = editor.getLineCount() - 1
+      expect(rows).toBeGreaterThan(0)
+      row = editor.getCursor(0).getScreenPosition().row
+      expect(row).toBe(0)
+      while row < rows
+        editor.pageDown()
+        newRow = editor.getCursor(0).getScreenPosition().row
+        expect(newRow).toBeGreaterThan(row)
+        if (newRow <= row)
+          break
+        row = newRow
+      expect(row).toBe(rows)
+
+    it "moves to the first line when page up is repeated from the last line", ->
+      editor.moveCursorToBottom()
+      row = editor.getCursor().getScreenPosition().row
+      expect(row).toBeGreaterThan(0)
+      while row > 0
+        editor.pageUp()
+        newRow = editor.getCursor().getScreenPosition().row
+        expect(newRow).toBeLessThan(row)
+        if (newRow >= row)
+          break
+        row = newRow
+      expect(row).toBe(0)
+
+    it "resets to original position when down is followed by up", ->
+      expect(editor.getCursor().getScreenPosition().row).toBe(0)
+      editor.pageDown()
+      expect(editor.getCursor().getScreenPosition().row).toBeGreaterThan(0)
+      editor.pageUp()
+      expect(editor.getCursor().getScreenPosition().row).toBe(0)

src/app/cursor.coffee

@@ -54,16 +54,16 @@ class Cursor
   refreshScreenPosition: ->
     @anchor.refreshScreenPosition()
 
-  moveUp: ->
+  moveUp: (rowCount = 1) ->
     { row, column } = @getScreenPosition()
     column = @goalColumn if @goalColumn?
-    @setScreenPosition({row: row - 1, column: column})
+    @setScreenPosition({row: row - rowCount, column: column})
     @goalColumn = column
 
-  moveDown: ->
+  moveDown: (rowCount = 1) ->
     { row, column } = @getScreenPosition()
     column = @goalColumn if @goalColumn?
-    @setScreenPosition({row: row + 1, column: column})
+    @setScreenPosition({row: row + rowCount, column: column})
     @goalColumn = column
 
   moveLeft: ->

src/app/edit-session.coffee

@@ -427,11 +427,11 @@ class EditSession
   getTextInBufferRange: (range) ->
     @buffer.getTextInRange(range)
 
-  moveCursorUp: ->
-    @moveCursors (cursor) -> cursor.moveUp()
+  moveCursorUp: (lineCount) ->
+    @moveCursors (cursor) -> cursor.moveUp(lineCount)
 
-  moveCursorDown: ->
-    @moveCursors (cursor) -> cursor.moveDown()
+  moveCursorDown: (lineCount) ->
+    @moveCursors (cursor) -> cursor.moveDown(lineCount)
 
   moveCursorLeft: ->
     @moveCursors (cursor) -> cursor.moveLeft()

src/app/editor.coffee

@@ -131,6 +131,8 @@ class Editor extends View
       'select-to-end-of-word': @selectToEndOfWord
       'select-to-beginning-of-word': @selectToBeginningOfWord
       'select-all': @selectAll
+      'page-down': @pageDown
+      'page-up': @pageUp
 
     if not @mini
       _.extend editorBindings,
@@ -246,6 +248,20 @@ class Editor extends View
   bufferRowsForScreenRows: (startRow, endRow) -> @activeEditSession.bufferRowsForScreenRows(startRow, endRow)
   stateForScreenRow: (row) -> @activeEditSession.stateForScreenRow(row)
 
+  pageDown: ->
+    [top, rows] = @getPageSize()
+    @activeEditSession.moveCursorDown(rows)
+    @scrollTop(top,  adjustVerticalScrollbar: true)
+  pageUp: ->
+    [top, rows] = @getPageSize()
+    @activeEditSession.moveCursorUp(rows)
+    @scrollTop(top,  adjustVerticalScrollbar: true)
+  getPageSize: ->
+    scrollViewHeight = @scrollView[0].clientHeight
+    newScrollTop = @scrollTop() + scrollViewHeight
+    rows = Math.max(1, Math.ceil(scrollViewHeight / @lineHeight))
+    [newScrollTop, rows]
+
   setText: (text) -> @getBuffer().setText(text)
   getText: -> @getBuffer().getText()
   getPath: -> @getBuffer().getPath()

src/app/keymaps/atom.coffee

@@ -5,3 +5,5 @@ window.keymap.bindKeys '*'
   left: 'move-left'
   down: 'move-down'
   up: 'move-up'
+  pagedown: 'page-down'
+  pageup: 'page-up'