From 162a85a0e108e575cf118ff25283cb8ebaca573f Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Fri, 10 Feb 2017 16:03:16 -0800
Subject: [PATCH] Add assertion to debug NaN startRow on TextEditorPresenter

Signed-off-by: Nathan Sobo <nathan@github.com>
---
 src/text-editor-presenter.coffee | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/text-editor-presenter.coffee b/src/text-editor-presenter.coffee
index 3c4739ca5..1106cee09 100644
--- a/src/text-editor-presenter.coffee
+++ b/src/text-editor-presenter.coffee
@@ -622,6 +622,18 @@ class TextEditorPresenter
     return unless @scrollTop? and @lineHeight?
 
     @startRow = Math.max(0, @lineTopIndex.rowForPixelPosition(@scrollTop))
+    atom.assert(
+      Number.isFinite(@startRow),
+      'Invalid start row',
+      (error) =>
+        error.metadata = {
+          startRow: @startRow?.toString(),
+          scrollTop: @scrollTop?.toString(),
+          scrollHeight: @scrollHeight?.toString(),
+          clientHeight: @clientHeight?.toString(),
+          lineHeight: @lineHeight?.toString()
+        }
+    )
 
   updateEndRow: ->
     return unless @scrollTop? and @lineHeight? and @height?