🐎 Implement a basic cache of editor dimension during update

It reduces the cost of computing the height of the text editor several
time during the update.

lib/adapters/beta-adapter.coffee

@@ -1,33 +1,44 @@
-# Internal: 
+# Internal:
 module.exports =
 class BetaAdater
   constructor: (@textEditor) ->
     @textEditorElement = atom.views.getView(@textEditor)
 
+  enableCache: -> @useCache = true
+
+  clearCache: ->
+    @useCache = false
+    delete @heightCache
+    delete @scrollTopCache
+    delete @scrollLeftCache
+    delete @maxScrollTopCache
+
   onDidChangeScrollTop: (callback) ->
     @textEditorElement.onDidChangeScrollTop(callback)
 
   onDidChangeScrollLeft: (callback) ->
     @textEditorElement.onDidChangeScrollLeft(callback)
 
   getHeight: ->
+    return @heightCache ?= @textEditorElement.getHeight() if @useCache
     @textEditorElement.getHeight()
 
   getScrollTop: ->
+    return @scrollTopCache ?= @textEditorElement.getScrollTop() if @useCache
     @textEditorElement.getScrollTop()
 
   setScrollTop: (scrollTop) ->
     @textEditorElement.setScrollTop(scrollTop)
 
   getScrollLeft: ->
+    return @scrollLeftCache ?= @textEditorElement.getScrollLeft() if @useCache
     @textEditorElement.getScrollLeft()
 
-  getHeightWithoutScrollPastEnd: ->
-    @textEditor.displayBuffer.getLineHeightInPixels()
-
   getMaxScrollTop: ->
+    return @maxScrollTopCache if @maxScrollTopCache? and @useCache
     maxScrollTop = @textEditorElement.getScrollHeight() - @getHeight()
     lineHeight = @textEditor.getLineHeightInPixels()
 
     maxScrollTop -= @getHeight() - 3 * lineHeight if @scrollPastEnd
+    return @maxScrollTopCache = maxScrollTop if @useCache
     maxScrollTop

lib/adapters/legacy-adapter.coffee

@@ -1,32 +1,43 @@
-# Internal: 
+# Internal:
 module.exports =
 class LegacyAdater
   constructor: (@textEditor) ->
 
+  enableCache: -> @useCache = true
+
+  clearCache: ->
+    @useCache = false
+    delete @heightCache
+    delete @scrollTopCache
+    delete @scrollLeftCache
+    delete @maxScrollTopCache
+
   onDidChangeScrollTop: (callback) ->
     @textEditor.onDidChangeScrollTop(callback)
 
   onDidChangeScrollLeft: (callback) ->
     @textEditor.onDidChangeScrollLeft(callback)
 
   getHeight: ->
+    return @heightCache ?= @textEditor.getHeight() if @useCache
     @textEditor.getHeight()
 
   getScrollTop: ->
+    return @scrollTopCache ?= @textEditor.getScrollTop() if @useCache
     @textEditor.getScrollTop()
 
   setScrollTop: (scrollTop) ->
     @textEditor.setScrollTop(scrollTop)
 
   getScrollLeft: ->
+    return @scrollLeftCache ?= @textEditor.getScrollLeft() if @useCache
     @textEditor.getScrollLeft()
 
-  getHeightWithoutScrollPastEnd: ->
-    @textEditor.displayBuffer.getLineHeightInPixels()
-
   getMaxScrollTop: ->
+    return @maxScrollTopCache if @maxScrollTopCache? and @useCache
     maxScrollTop = @textEditor.displayBuffer.getMaxScrollTop()
     lineHeight = @textEditor.getLineHeightInPixels()
 
     maxScrollTop -= @getHeight() - 3 * lineHeight if @scrollPastEnd
+    return @maxScrollTopCache = maxScrollTop if @useCache
     maxScrollTop

lib/minimap-element.coffee

@@ -6,6 +6,8 @@ CanvasDrawer = require './mixins/canvas-drawer'
 
 MinimapQuickSettingsElement = null
 
+SPEC_MODE = atom.inSpecMode()
+
 # Public: The {MinimapElement} is the view meant to render a {Minimap} instance
 # in the DOM.
 #
@@ -376,6 +378,7 @@ class MinimapElement
   # Internal: Performs the actual {MinimapElement} update.
   update: ->
     return unless @attached and @isVisible() and @minimap?
+    @minimap.enableCache()
 
     visibleAreaLeft = @minimap.getTextEditorScaledScrollLeft()
     visibleAreaTop = @minimap.getTextEditorScaledScrollTop() - @minimap.getScrollTop()
@@ -386,7 +389,7 @@ class MinimapElement
     else
       @style.flexBasis = null
 
-    if atom.inSpecMode()
+    if SPEC_MODE
       @applyStyles @visibleArea,
         width: visibleWidth + 'px'
         height: @minimap.getTextEditorScaledHeight() + 'px'
@@ -406,7 +409,7 @@ class MinimapElement
     canvasTransform = @makeTranslate(0, canvasTop)
     canvasTransform += " " + @makeScale(1 / devicePixelRatio) if devicePixelRatio isnt 1
 
-    if atom.inSpecMode()
+    if SPEC_MODE
       @applyStyles @canvas, top: canvasTop + 'px'
     else
       @applyStyles @canvas, transform: canvasTransform
@@ -419,7 +422,7 @@ class MinimapElement
       indicatorHeight = minimapScreenHeight * (minimapScreenHeight / @minimap.getHeight())
       indicatorScroll = (minimapScreenHeight - indicatorHeight) * @minimap.getCapedTextEditorScrollRatio()
 
-      if atom.inSpecMode()
+      if SPEC_MODE
         @applyStyles @scrollIndicator,
           height: indicatorHeight + 'px'
           top: indicatorScroll + 'px'
@@ -431,6 +434,7 @@ class MinimapElement
       @disposeScrollIndicator() if not @minimap.canScroll()
 
     @updateCanvas()
+    @minimap.clearCache()
 
   # Defines whether to render the code highlights or not.
   #

lib/minimap.coffee

@@ -424,3 +424,9 @@ class Minimap
 
   # Internal: Emits a change events with the passed-in changes as data.
   emitChanges: (changes) -> @emitter.emit('did-change', changes)
+
+  # Internal:
+  enableCache: -> @adapter.enableCache()
+
+  # Internal:
+  clearCache: -> @adapter.clearCache()

lib/mixins/decoration-management.coffee

@@ -24,6 +24,8 @@ class DecorationManagement extends Mixin
 
     Decoration ?= require '../decoration'
 
+  getDecorations: -> decoration for id,decoration of @decorationsById
+
   # Registers an event listener to the `did-add-decoration` event.
   #
   # callback - The {Function} to call when the event is triggered.
@@ -231,7 +233,7 @@ class DecorationManagement extends Mixin
   #
   # oldStart - The row index of the first range start.
   # oldEnd - The row index of the first range end.
-  # newStart - The row index of the second range start. 
+  # newStart - The row index of the second range start.
   # newEnd - The row index of the second range end.
   #
   # Returns an {Array}.