Implement basic large file mode for editor

* Don’t tokenize
* Don’t build metadata to support folds and soft wraps

Remaining issues:

* Max line length is hard coded
* Foldable indicators should be disabled
* Folding via API should be disallowed

src/display-buffer.coffee

@@ -24,13 +24,13 @@ class DisplayBuffer extends Model
   horizontalScrollMargin: 6
   scopedCharacterWidthsChangeCount: 0
 
-  constructor: ({tabLength, @editorWidthInChars, @tokenizedBuffer, buffer, ignoreInvisibles}={}) ->
+  constructor: ({tabLength, @editorWidthInChars, @tokenizedBuffer, buffer, ignoreInvisibles, @largeFileMode}={}) ->
     super
 
     @emitter = new Emitter
     @disposables = new CompositeDisposable
 
-    @tokenizedBuffer ?= new TokenizedBuffer({tabLength, buffer, ignoreInvisibles})
+    @tokenizedBuffer ?= new TokenizedBuffer({tabLength, buffer, ignoreInvisibles, @largeFileMode})
     @buffer = @tokenizedBuffer.buffer
     @charWidthsByScope = {}
     @markers = {}
@@ -478,7 +478,10 @@ class DisplayBuffer extends Model
   #
   # Returns {TokenizedLine}
   tokenizedLineForScreenRow: (screenRow) ->
-    @screenLines[screenRow]
+    if @largeFileMode
+      @tokenizedBuffer.tokenizedLineForRow(screenRow)
+    else
+      @screenLines[screenRow]
 
   # Gets the screen lines for the given screen row range.
   #
@@ -487,13 +490,19 @@ class DisplayBuffer extends Model
   #
   # Returns an {Array} of {TokenizedLine}s.
   tokenizedLinesForScreenRows: (startRow, endRow) ->
-    @screenLines[startRow..endRow]
+    if @largeFileMode
+      @tokenizedBuffer.tokenizedLinesForRows(startRow, endRow)
+    else
+      @screenLines[startRow..endRow]
 
   # Gets all the screen lines.
   #
   # Returns an {Array} of {TokenizedLine}s.
   getTokenizedLines: ->
-    new Array(@screenLines...)
+    if @largeFileMode
+      @tokenizedBuffer.tokenizedLinesForRows(0, @getLastRow())
+    else
+      new Array(@screenLines...)
 
   indentLevelForLine: (line) ->
     @tokenizedBuffer.indentLevelForLine(line)
@@ -506,8 +515,11 @@ class DisplayBuffer extends Model
   #
   # Returns an {Array} of buffer rows as {Numbers}s.
   bufferRowsForScreenRows: (startScreenRow, endScreenRow) ->
-    for screenRow in [startScreenRow..endScreenRow]
-      @rowMap.bufferRowRangeForScreenRow(screenRow)[0]
+    if @largeFileMode
+      [startScreenRow..endScreenRow]
+    else
+      for screenRow in [startScreenRow..endScreenRow]
+        @rowMap.bufferRowRangeForScreenRow(screenRow)[0]
 
   # Creates a new fold between two row numbers.
   #
@@ -611,10 +623,16 @@ class DisplayBuffer extends Model
   #
   # Returns a {Number}.
   screenRowForBufferRow: (bufferRow) ->
-    @rowMap.screenRowRangeForBufferRow(bufferRow)[0]
+    if @largeFileMode
+      bufferRow
+    else
+      @rowMap.screenRowRangeForBufferRow(bufferRow)[0]
 
   lastScreenRowForBufferRow: (bufferRow) ->
-    @rowMap.screenRowRangeForBufferRow(bufferRow)[1] - 1
+    if @largeFileMode
+      bufferRow
+    else
+      @rowMap.screenRowRangeForBufferRow(bufferRow)[1] - 1
 
   # Given a screen row, this converts it into a buffer row.
   #
@@ -622,7 +640,10 @@ class DisplayBuffer extends Model
   #
   # Returns a {Number}.
   bufferRowForScreenRow: (screenRow) ->
-    @rowMap.bufferRowRangeForScreenRow(screenRow)[0]
+    if @largeFileMode
+      screenRow
+    else
+      @rowMap.bufferRowRangeForScreenRow(screenRow)[0]
 
   # Given a buffer range, this converts it into a screen position.
   #
@@ -724,7 +745,10 @@ class DisplayBuffer extends Model
   #
   # Returns a {Number}.
   getLineCount: ->
-    @screenLines.length
+    if @largeFileMode
+      @tokenizedBuffer.getLineCount()
+    else
+      @screenLines.length
 
   # Gets the number of the last screen line.
   #
@@ -736,13 +760,19 @@ class DisplayBuffer extends Model
   #
   # Returns a {Number}.
   getMaxLineLength: ->
-    @maxLineLength
+    if @largeFileMode
+      100
+    else
+      @maxLineLength
 
   # Gets the row number of the longest screen line.
   #
   # Return a {}
   getLongestScreenRow: ->
-    @longestScreenRow
+    if @largeFileMode
+      0
+    else
+      @longestScreenRow
 
   # Given a buffer position, this converts it into a screen position.
   #
@@ -759,7 +789,7 @@ class DisplayBuffer extends Model
     {row, column} = @buffer.clipPosition(bufferPosition)
     [startScreenRow, endScreenRow] = @rowMap.screenRowRangeForBufferRow(row)
     for screenRow in [startScreenRow...endScreenRow]
-      screenLine = @screenLines[screenRow]
+      screenLine = @tokenizedLineForScreenRow(screenRow)
 
       unless screenLine?
         throw new BufferToScreenConversionError "No screen line exists when converting buffer row to screen row",
@@ -792,7 +822,7 @@ class DisplayBuffer extends Model
   bufferPositionForScreenPosition: (screenPosition, options) ->
     {row, column} = @clipScreenPosition(Point.fromObject(screenPosition), options)
     [bufferRow] = @rowMap.bufferRowRangeForScreenRow(row)
-    new Point(bufferRow, @screenLines[row].bufferColumnForScreenColumn(column))
+    new Point(bufferRow, @tokenizedLineForScreenRow(row).bufferColumnForScreenColumn(column))
 
   # Retrieves the grammar's token scopeDescriptor for a buffer position.
   #
@@ -856,13 +886,13 @@ class DisplayBuffer extends Model
     else if column < 0
       column = 0
 
-    screenLine = @screenLines[row]
+    screenLine = @tokenizedLineForScreenRow(row)
     maxScreenColumn = screenLine.getMaxScreenColumn()
 
     if screenLine.isSoftWrapped() and column >= maxScreenColumn
       if wrapAtSoftNewlines
         row++
-        column = @screenLines[row].clipScreenColumn(0)
+        column = @tokenizedLineForScreenRow(row).clipScreenColumn(0)
       else
         column = screenLine.clipScreenColumn(maxScreenColumn - 1)
     else if screenLine.isColumnInsideSoftWrapIndentation(column)
@@ -870,7 +900,7 @@ class DisplayBuffer extends Model
         column = screenLine.clipScreenColumn(0)
       else
         row--
-        column = @screenLines[row].getMaxScreenColumn() - 1
+        column = @tokenizedLineForScreenRow(row).getMaxScreenColumn() - 1
     else if wrapBeyondNewlines and column > maxScreenColumn and row < @getLastRow()
       row++
       column = 0
@@ -1137,6 +1167,8 @@ class DisplayBuffer extends Model
     @setScrollTop(Math.min(@getScrollTop(), @getMaxScrollTop())) if delta < 0
 
   updateScreenLines: (startBufferRow, endBufferRow, bufferDelta=0, options={}) ->
+    return if @largeFileMode
+
     startBufferRow = @rowMap.bufferRowRangeForBufferRow(startBufferRow)[0]
     endBufferRow = @rowMap.bufferRowRangeForBufferRow(endBufferRow - 1)[1]
     startScreenRow = @rowMap.screenRowRangeForBufferRow(startBufferRow)[0]

src/project.coffee

@@ -376,11 +376,6 @@ class Project extends Model
   #
   # Returns a promise that resolves to the {TextBuffer}.
   buildBuffer: (absoluteFilePath) ->
-    if fs.getSizeSync(absoluteFilePath) >= 2 * 1048576 # 2MB
-      error = new Error("Atom can only handle files < 2MB for now.")
-      error.code = 'EFILETOOLARGE'
-      throw error
-
     buffer = new TextBuffer({filePath: absoluteFilePath})
     @addBuffer(buffer)
     buffer.load()
@@ -410,7 +405,8 @@ class Project extends Model
     buffer?.destroy()
 
   buildEditorForBuffer: (buffer, editorOptions) ->
-    editor = new TextEditor(_.extend({buffer, registerEditor: true}, editorOptions))
+    largeFileMode = fs.getSizeSync(buffer.getPath()) >= 2 * 1048576 # 2MB
+    editor = new TextEditor(_.extend({buffer, largeFileMode, registerEditor: true}, editorOptions))
     editor
 
   eachBuffer: (args...) ->

src/text-editor.coffee

@@ -75,7 +75,7 @@ class TextEditor extends Model
     'autoDecreaseIndentForBufferRow', 'toggleLineCommentForBufferRow', 'toggleLineCommentsForBufferRows',
     toProperty: 'languageMode'
 
-  constructor: ({@softTabs, initialLine, initialColumn, tabLength, softWrapped, @displayBuffer, buffer, registerEditor, suppressCursorCreation, @mini, @placeholderText, lineNumberGutterVisible}={}) ->
+  constructor: ({@softTabs, initialLine, initialColumn, tabLength, softWrapped, @displayBuffer, buffer, registerEditor, suppressCursorCreation, @mini, @placeholderText, lineNumberGutterVisible, largeFileMode}={}) ->
     super
 
     @emitter = new Emitter
@@ -84,7 +84,7 @@ class TextEditor extends Model
     @selections = []
 
     buffer ?= new TextBuffer
-    @displayBuffer ?= new DisplayBuffer({buffer, tabLength, softWrapped, ignoreInvisibles: @mini})
+    @displayBuffer ?= new DisplayBuffer({buffer, tabLength, softWrapped, ignoreInvisibles: @mini, largeFileMode})
     @buffer = @displayBuffer.buffer
     @softTabs = @usesSoftTabs() ? @softTabs ? atom.config.get('editor.softTabs') ? true
 

src/tokenized-buffer.coffee

@@ -24,7 +24,7 @@ class TokenizedBuffer extends Model
   visible: false
   configSettings: null
 
-  constructor: ({@buffer, @tabLength, @ignoreInvisibles}) ->
+  constructor: ({@buffer, @tabLength, @ignoreInvisibles, @largeFileMode}) ->
     @emitter = new Emitter
     @disposables = new CompositeDisposable
     @tokenIterator = new TokenIterator
@@ -209,6 +209,8 @@ class TokenizedBuffer extends Model
     return
 
   invalidateRow: (row) ->
+    return if @largeFileMode
+
     @invalidRows.push(row)
     @invalidRows.sort (a, b) -> a - b
     @tokenizeInBackground()
@@ -230,7 +232,10 @@ class TokenizedBuffer extends Model
 
     @updateInvalidRows(start, end, delta)
     previousEndStack = @stackForRow(end) # used in spill detection below
-    newTokenizedLines = @buildTokenizedLinesForRows(start, end + delta, @stackForRow(start - 1), @openScopesForRow(start))
+    if @largeFileMode
+      newTokenizedLines = @buildPlaceholderTokenizedLinesForRows(start, end + delta)
+    else
+      newTokenizedLines = @buildTokenizedLinesForRows(start, end + delta, @stackForRow(start - 1), @openScopesForRow(start))
     _.spliceWithArray(@tokenizedLines, start, end - start + 1, newTokenizedLines)
 
     start = @retokenizeWhitespaceRowsIfIndentLevelChanged(start - 1, -1)
@@ -344,6 +349,10 @@ class TokenizedBuffer extends Model
     if 0 <= bufferRow < @tokenizedLines.length
       @tokenizedLines[bufferRow] ?= @buildPlaceholderTokenizedLineForRow(bufferRow)
 
+  tokenizedLinesForRows: (startRow, endRow) ->
+    for row in [startRow..endRow] by 1
+      @tokenizedLineForRow(row)
+
   stackForRow: (bufferRow) ->
     @tokenizedLines[bufferRow]?.ruleStack