Preserve lines in TextEditorPresenter based on ::mouseWheelScreenRow

spec/text-editor-presenter-spec.coffee

@@ -77,41 +77,6 @@ describe "TextEditorPresenter", ->
         expectStateUpdate presenter, -> advanceClock(100)
         expect(presenter.state.scrollingVertically).toBe false
 
-    describe ".mouseWheelScreenRow", ->
-      it "reflects the most recently assigned ::mouseWheelScreenRow while .scrollingVertically is true", ->
-        presenter = new TextEditorPresenter(model: editor, scrollTop: 10, stoppedScrollingDelay: 200)
-        presenter.setMouseWheelScreenRow(3)
-        expect(presenter.state.scrollingVertically).toBe false
-        expect(presenter.state.mouseWheelScreenRow).toBeNull()
-
-        expectStateUpdate presenter, -> presenter.setScrollTop(0)
-        expect(presenter.state.scrollingVertically).toBe true
-        expect(presenter.state.mouseWheelScreenRow).toBe 3
-
-        presenter.setMouseWheelScreenRow(5)
-        expect(presenter.state.scrollingVertically).toBe true
-        expect(presenter.state.mouseWheelScreenRow).toBe 5
-
-        advanceClock(100)
-        expect(presenter.state.scrollingVertically).toBe true
-        expect(presenter.state.mouseWheelScreenRow).toBe 5
-
-        # should wait 200ms after the last scroll to clear
-        presenter.setScrollTop(10)
-
-        advanceClock(100) # so not yet...
-        expect(presenter.state.scrollingVertically).toBe true
-        expect(presenter.state.mouseWheelScreenRow).toBe 5
-
-        expectStateUpdate presenter, -> advanceClock(100) # clear now
-        expect(presenter.state.scrollingVertically).toBe false
-        expect(presenter.state.mouseWheelScreenRow).toBeNull()
-
-        # should be cleared even when we scroll again
-        expectStateUpdate presenter, -> presenter.setScrollTop(20)
-        expect(presenter.state.scrollingVertically).toBe true
-        expect(presenter.state.mouseWheelScreenRow).toBeNull()
-
     describe ".content", ->
       describe ".scrollWidth", ->
         it "is initialized as the max of the clientWidth and the width of the longest line", ->
@@ -399,6 +364,40 @@ describe "TextEditorPresenter", ->
             tokens: line3.tokens
           }
 
+        it "does not remove out-of-view lines corresponding to ::mouseWheelScreenRow until ::stoppedScrollingDelay elapses", ->
+          presenter = new TextEditorPresenter(model: editor, clientHeight: 25, scrollTop: 0, lineHeight: 10, lineOverdrawMargin: 1, stoppedScrollingDelay: 200)
+
+          expect(lineStateForScreenRow(presenter, 0)).toBeDefined()
+          expect(lineStateForScreenRow(presenter, 4)).toBeDefined()
+          expect(lineStateForScreenRow(presenter, 5)).toBeUndefined()
+
+          presenter.setMouseWheelScreenRow(0)
+          expectStateUpdate presenter, -> presenter.setScrollTop(35)
+
+          expect(lineStateForScreenRow(presenter, 0)).toBeDefined()
+          expect(lineStateForScreenRow(presenter, 1)).toBeUndefined()
+          expect(lineStateForScreenRow(presenter, 7)).toBeDefined()
+          expect(lineStateForScreenRow(presenter, 8)).toBeUndefined()
+
+          expectStateUpdate presenter, -> advanceClock(200)
+
+          expect(lineStateForScreenRow(presenter, 0)).toBeUndefined()
+          expect(lineStateForScreenRow(presenter, 1)).toBeUndefined()
+          expect(lineStateForScreenRow(presenter, 7)).toBeDefined()
+          expect(lineStateForScreenRow(presenter, 8)).toBeUndefined()
+
+        it "does not preserve on-screen lines even if they correspond to ::mouseWheelScreenRow", ->
+          presenter = new TextEditorPresenter(model: editor, clientHeight: 25, scrollTop: 0, lineHeight: 10, lineOverdrawMargin: 1, stoppedScrollingDelay: 200)
+          oldLine3 = editor.tokenizedLineForScreenRow(6)
+
+          presenter.setMouseWheelScreenRow(3)
+
+          expectStateUpdate presenter, -> editor.getBuffer().insert([3, Infinity], 'xyz')
+          newLine3 = editor.tokenizedLineForScreenRow(3)
+
+          expect(presenter.state.content.lines[oldLine3.id]).toBeUndefined()
+          expect(presenter.state.content.lines[newLine3.id]).toBeDefined()
+
         describe "[lineId]", -> # line state objects
           it "includes the .endOfLineInvisibles if the editor.showInvisibles config option is true", ->
             editor.setText("hello\nworld\r\n")

src/text-editor-presenter.coffee

@@ -50,7 +50,6 @@ class TextEditorPresenter
   buildState: ->
     @state =
       scrollingVertically: false
-      mouseWheelScreenRow: null
       content:
         blinkCursorsOff: false
         lines: {}
@@ -97,6 +96,11 @@ class TextEditorPresenter
         @buildLineState(row, line)
       row++
 
+    if @getMouseWheelScreenRow()? and not startRow <= @getMouseWheelScreenRow() < endRow
+      preservedLine = @model.tokenizedLineForScreenRow(@getMouseWheelScreenRow())
+      visibleLineIds[preservedLine.id] = true
+      @updateLineState(@getMouseWheelScreenRow(), preservedLine)
+
     for id, line of @state.content.lines
       unless visibleLineIds.hasOwnProperty(id)
         delete @state.content.lines[id]
@@ -361,14 +365,15 @@ class TextEditorPresenter
       @stoppedScrollingTimeoutId = null
     @stoppedScrollingTimeoutId = setTimeout(@didStopScrolling.bind(this), @stoppedScrollingDelay)
     @state.scrollingVertically = true
-    @state.mouseWheelScreenRow = @getMouseWheelScreenRow()
     @emitter.emit 'did-update-state'
 
   didStopScrolling: ->
     @state.scrollingVertically = false
-    @state.mouseWheelScreenRow = null
-    @mouseWheelScreenRow = null
-    @emitter.emit 'did-update-state'
+    if @getMouseWheelScreenRow()?
+      @mouseWheelScreenRow = null
+      @updateLinesState()
+    else
+      @emitter.emit 'did-update-state'
 
   getScrollTop: -> @scrollTop
 
@@ -418,7 +423,6 @@ class TextEditorPresenter
   getLineHeight: -> @lineHeight
 
   setMouseWheelScreenRow: (@mouseWheelScreenRow) ->
-    @state.mouseWheelScreenRow = @mouseWheelScreenRow if @state.scrollingVertically
 
   getMouseWheelScreenRow: -> @mouseWheelScreenRow