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

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)