Use renderTo and renderFrom (instead of firstVisible/lastVisible) to adjust visible lines.

Fix specs that had wrong assumptions,

spec/app/editor-spec.coffee

@@ -537,28 +537,28 @@ describe "Editor", ->
             expect(editor.visibleLines.find('.line').length).toBe 8
 
             editor.scrollTop(editor.lineHeight * 1.5)
-            expect(editor.visibleLines.find('.line').length).toBe 8
+            expect(editor.visibleLines.find('.line').length).toBe 9
             expect(editor.visibleLines.find('.line:first').text()).toBe buffer.lineForRow(0)
-            expect(editor.visibleLines.find('.line:last').text()).toBe buffer.lineForRow(7)
+            expect(editor.visibleLines.find('.line:last').text()).toBe buffer.lineForRow(8)
 
-            editor.scrollTop(editor.lineHeight * 3.5) # first visible row will be 3, last will be 8
+            editor.scrollTop(editor.lineHeight * 3.5)
             expect(editor.visibleLines.find('.line').length).toBe 10
             expect(editor.visibleLines.find('.line:first').text()).toBe buffer.lineForRow(1)
             expect(editor.visibleLines.find('.line:last').html()).toBe ' ' # line 10 is blank
             expect(editor.gutter.find('.line-number:first').text()).toBe '2'
             expect(editor.gutter.find('.line-number:last').text()).toBe '11'
 
+            editor.scrollTop(editor.lineHeight * 5.5)
+            expect(editor.visibleLines.find('.line').length).toBe 10
+            expect(editor.visibleLines.find('.line:first').text()).toBe buffer.lineForRow(3)
+            expect(editor.visibleLines.find('.line:last').text()).toBe buffer.lineForRow(12)
+            expect(editor.gutter.find('.line-number:first').text()).toBe '4'
+            expect(editor.gutter.find('.line-number:last').text()).toBe '13'
+
             # here we don't scroll far enough to trigger additional rendering
-            editor.scrollTop(editor.lineHeight * 5.5) # first visible row will be 5, last will be 10
+            editor.scrollTop(editor.lineHeight * 7.5)
             expect(editor.visibleLines.find('.line').length).toBe 10
-            expect(editor.visibleLines.find('.line:first').text()).toBe buffer.lineForRow(1)
-            expect(editor.visibleLines.find('.line:last').html()).toBe ' ' # line 10 is blank
-            expect(editor.gutter.find('.line-number:first').text()).toBe '2'
-            expect(editor.gutter.find('.line-number:last').text()).toBe '11'
-
-            editor.scrollTop(editor.lineHeight * 7.5) # first visible row is 7, last will be 12
-            expect(editor.visibleLines.find('.line').length).toBe 8
-            expect(editor.visibleLines.find('.line:first').text()).toBe buffer.lineForRow(5)
+            expect(editor.visibleLines.find('.line:first').text()).toBe buffer.lineForRow(3)
             expect(editor.visibleLines.find('.line:last').text()).toBe buffer.lineForRow(12)
 
             editor.scrollTop(editor.lineHeight * 3.5) # first visible row will be 3, last will be 8
@@ -690,6 +690,17 @@ describe "Editor", ->
           expect(editor.visibleLines.find(".line:first").text()).toBe buffer.lineForRow(0)
           expect(editor.visibleLines.find(".line:last").text()).toBe buffer.lineForRow(6)
 
+    describe "when folding leaves less then a screen worth of text (regression)", ->
+      it "renders lines properly", ->
+        editor.lineOverdraw = 1
+        editor.clearVisibleLines()
+        editor.attachToDom(heightInLines: 5)
+        editor.renderer.toggleFoldAtBufferRow(4)
+        editor.renderer.toggleFoldAtBufferRow(0)
+
+        expect(editor.visibleLines.find('.line').length).toBe 1
+        expect(editor.visibleLines.find('.line').text()).toBe buffer.lineForRow(0)
+
   describe "gutter rendering", ->
     beforeEach ->
       editor.attachToDom(heightInLines: 5.5)
@@ -701,9 +712,9 @@ describe "Editor", ->
 
       # here we don't scroll far enough to trigger additional rendering
       editor.scrollTop(editor.lineHeight * 1.5)
-      expect(editor.visibleLines.find('.line').length).toBe 8
+      expect(editor.visibleLines.find('.line').length).toBe 9
       expect(editor.gutter.find('.line-number:first').text()).toBe "1"
-      expect(editor.gutter.find('.line-number:last').text()).toBe "8"
+      expect(editor.gutter.find('.line-number:last').text()).toBe "9"
 
       editor.scrollTop(editor.lineHeight * 3.5)
       expect(editor.visibleLines.find('.line').length).toBe 10

src/app/editor.coffee

@@ -233,7 +233,7 @@ class Editor extends View
   afterAttach: (onDom) ->
     return if @attached or not onDom
     @attached = true
-    @clearLines()
+    @clearVisibleLines()
     @subscribeToFontSize()
     @calculateDimensions()
     @setMaxLineLength() if @softWrap
@@ -291,10 +291,10 @@ class Editor extends View
       @scrollTop() + @scrollView.height()
 
   renderVisibleLines: ->
-    @clearLines()
+    @clearVisibleLines()
     @updateVisibleLines()
 
-  clearLines: ->
+  clearVisibleLines: ->
     @lineCache = []
     @visibleLines.find('.line').remove()
 
@@ -307,7 +307,7 @@ class Editor extends View
     renderFrom = Math.max(0, firstVisibleScreenRow - @lineOverdraw)
     renderTo = Math.min(@getLastScreenRow(), lastVisibleScreenRow + @lineOverdraw)
 
-    if firstVisibleScreenRow < @firstRenderedScreenRow
+    if renderFrom < @firstRenderedScreenRow
       @removeLineElements(Math.max(@firstRenderedScreenRow, renderTo + 1), @lastRenderedScreenRow)
       @lastRenderedScreenRow = renderTo
       newLines = @buildLineElements(renderFrom, Math.min(@firstRenderedScreenRow - 1, renderTo))
@@ -315,7 +315,7 @@ class Editor extends View
       @firstRenderedScreenRow = renderFrom
       renderedLines = true
 
-    if lastVisibleScreenRow > @lastRenderedScreenRow
+    if renderTo > @lastRenderedScreenRow
       if 0 <= @firstRenderedScreenRow < renderFrom
         @removeLineElements(@firstRenderedScreenRow, Math.min(@lastRenderedScreenRow, renderFrom - 1))
       @firstRenderedScreenRow = renderFrom