Correctly translate buffer positions to screen positions when the buffer has tab chars

spec/app/editor-spec.coffee

@@ -1661,6 +1661,11 @@ describe "Editor", ->
           expect(editor.getCursorBufferPosition()).toEqual [0, 1]
           expect(editor.getCursorScreenPosition()).toEqual [0, editor.tabText.length]
 
+          editor.trigger 'tab'
+          expect(buffer.lineForRow(0)).toMatch(/^\t\t/)
+          expect(editor.getCursorBufferPosition()).toEqual [0, 2]
+          expect(editor.getCursorScreenPosition()).toEqual [0, editor.tabText.length * 2]
+
     describe "undo/redo", ->
       it "undoes/redoes the last change", ->
         buffer.insert [0, 0], "foo"

spec/app/screen-line-fragment-spec.coffee

@@ -3,11 +3,12 @@ Buffer = require 'buffer'
 Highlighter = require 'highlighter'
 
 describe "screenLineFragment", ->
-  [screenLine, highlighter] = []
+  [buffer, tabText, screenLine, highlighter] = []
 
   beforeEach ->
+    tabText = '  '
     buffer = new Buffer(require.resolve 'fixtures/sample.js')
-    highlighter = new Highlighter(buffer)
+    highlighter = new Highlighter(buffer, tabText)
     screenLine = highlighter.lineForScreenRow(3)
 
   describe ".splitAt(column)", ->
@@ -75,7 +76,36 @@ describe "screenLineFragment", ->
       expect(concatenated.screenDelta).toEqual [2, 0]
       expect(concatenated.bufferDelta).toEqual [2, 0]
 
+  describe ".translateColumn(sourceDeltaType, targetDeltaType, sourceColumn, skipAtomicTokens: false)", ->
+    beforeEach ->
+      buffer.insert([0, 13], '\t')
+      buffer.insert([0, 0], '\t\t')
+      screenLine = highlighter.lineForScreenRow(0)
 
+    describe "when translating from buffer to screen coordinates", ->
+      it "accounts for tab characters being wider on screen", ->
+        expect(screenLine.translateColumn('bufferDelta', 'screenDelta', 0)).toBe 0
+        expect(screenLine.translateColumn('bufferDelta', 'screenDelta', 1)).toBe 2
+        expect(screenLine.translateColumn('bufferDelta', 'screenDelta', 2)).toBe 4
+        expect(screenLine.translateColumn('bufferDelta', 'screenDelta', 3)).toBe 5
+        expect(screenLine.translateColumn('bufferDelta', 'screenDelta', 15)).toBe 17
+        expect(screenLine.translateColumn('bufferDelta', 'screenDelta', 16)).toBe 19
 
+    describe "when translating from screen coordinates to buffer coordinates", ->
+      describe "when skipAtomicTokens is false (the default)", ->
+        it "clips positions in the middle of tab tokens to the beginning", ->
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 0)).toBe 0
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 1)).toBe 0
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 2)).toBe 1
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 3)).toBe 1
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 4)).toBe 2
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 5)).toBe 3
 
+      describe "when skipAtomicTokens is true", ->
+        it "clips positions in the middle of tab tokens to the end", ->
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 0, skipAtomicTokens: true)).toBe 0
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 1, skipAtomicTokens: true)).toBe 1
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 2, skipAtomicTokens: true)).toBe 1
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 3, skipAtomicTokens: true)).toBe 2
+          expect(screenLine.translateColumn('screenDelta', 'bufferDelta', 5, skipAtomicTokens: true)).toBe 3
 

src/app/line-map.coffee

@@ -136,7 +136,8 @@ class LineMap
       targetDelta.column = 0
     else
       additionalColumns = sourcePosition.column - sourceDelta.column
-      targetDelta.column += lastLineFragment.clipColumn(additionalColumns, { skipAtomicTokens })
+      additionalColumns = lastLineFragment.translateColumn(sourceDeltaType, targetDeltaType, additionalColumns, { skipAtomicTokens })
+      targetDelta.column += additionalColumns
 
     targetDelta
 

src/app/screen-line-fragment.coffee

@@ -44,24 +44,30 @@ class ScreenLineFragment
     bufferDelta = @bufferDelta.add(other.bufferDelta)
     new ScreenLineFragment(tokens, text, screenDelta, bufferDelta, {state: other.state})
 
-  clipColumn: (column, { skipAtomicTokens }) ->
+  translateColumn: (sourceDeltaType, targetDeltaType, sourceColumn, options={}) ->
+    { skipAtomicTokens } = options
     textLength = @text.length
-    column = Math.min(column, textLength)
+    sourceColumn = Math.min(sourceColumn, textLength)
 
-    currentColumn = 0
+    currentSourceColumn = 0
+    currentTargetColumn = 0
     for token in @tokens
-      tokenStartColumn = currentColumn
-      tokenEndColumn = tokenStartColumn + token.value.length
-      break if tokenEndColumn > column
-      currentColumn = tokenEndColumn
+      tokenStartTargetColumn = currentTargetColumn
+      tokenStartSourceColumn = currentSourceColumn
+      tokenEndSourceColumn = currentSourceColumn + token[sourceDeltaType]
+      tokenEndTargetColumn = currentTargetColumn + token[targetDeltaType]
+      break if tokenEndSourceColumn > sourceColumn
+      currentSourceColumn = tokenEndSourceColumn
+      currentTargetColumn = tokenEndTargetColumn
 
     if token?.isAtomic
-      if skipAtomicTokens and column > tokenStartColumn
-        tokenEndColumn
+      if skipAtomicTokens and sourceColumn > tokenStartSourceColumn
+        tokenEndTargetColumn
       else
-        tokenStartColumn
+        tokenStartTargetColumn
     else
-      column
+      remainingColumns = sourceColumn - currentSourceColumn
+      currentTargetColumn + remainingColumns
 
   isSoftWrapped: ->
     @screenDelta.row == 1 and @bufferDelta.row == 0

src/app/token.coffee

@@ -4,7 +4,9 @@ class Token
   type: null
   isAtomic: null
 
-  constructor: ({@value, @type, @isAtomic}) ->
+  constructor: ({@value, @type, @isAtomic, @bufferDelta}) ->
+    @screenDelta = @value.length
+    @bufferDelta ?= @screenDelta
 
   isEqual: (other) ->
     @value == other.value and @type == other.type and !!@isAtomic == !!other.isAtomic
@@ -22,4 +24,4 @@ class Token
         new Token(value: substring, type: @type)
 
   buildTabToken: (tabText) ->
-    new Token(value: tabText, type: @type, isAtomic: true)
+    new Token(value: tabText, type: @type, bufferDelta: 1, isAtomic: true)