Better rows per page calculation

spec/text-editor-presenter-spec.coffee

@@ -2040,6 +2040,10 @@ describe "TextEditorPresenter", ->
         presenter.getState() # trigger state update
         expect(editor.getRowsPerPage()).toBe(10)
 
+        presenter.setLineHeight(5)
+        presenter.getState() # trigger state update
+        expect(editor.getRowsPerPage()).toBe(20)
+
       it "tracks the computed content height if ::autoHeight is true so the editor auto-expands vertically", ->
         presenter = buildPresenter(explicitHeight: null, autoHeight: true)
         expect(presenter.getState().height).toBe editor.getScreenLineCount() * 10

src/text-editor-presenter.coffee

@@ -72,6 +72,7 @@ class TextEditorPresenter
     @updateScrollPosition()
     @updateStartRow()
     @updateEndRow()
+    @updateRowsPerPage()
     @updateCommonGutterState()
     @updateReflowState()
 
@@ -641,6 +642,12 @@ class TextEditorPresenter
     endRow = startRow + visibleLinesCount
     @endRow = Math.min(@model.getScreenLineCount(), endRow)
 
+  updateRowsPerPage: ->
+    rowsPerPage = Math.floor(@getClientHeight() / @lineHeight)
+    if rowsPerPage isnt @rowsPerPage
+      @rowsPerPage = rowsPerPage
+      @model.setRowsPerPage(@rowsPerPage)
+
   updateScrollWidth: ->
     return unless @contentWidth? and @clientWidth?
 
@@ -688,7 +695,6 @@ class TextEditorPresenter
 
     clientHeight = @height - @horizontalScrollbarHeight
     @model.setHeight(clientHeight, true)
-    @model.setRowsPerPage(Math.floor(clientHeight / @lineHeight))
 
     unless @clientHeight is clientHeight
       @clientHeight = clientHeight