From 4555c4ee9625c4d77f3d7e8c904e25cb6f34d615 Mon Sep 17 00:00:00 2001
From: Raman Gupta <rocketraman@gmail.com>
Date: Mon, 24 Aug 2015 18:37:22 -0400
Subject: [PATCH] Fallback to canvas measurement when font glyph not available

If characters are inserted for which the configured font has no glyph,
the code assigns a default width of 0 to the character. This causes the
line wrapping and cursor positioning logic to be incorrect.

Instead of assigning a default width of 0, fallback to a canvas-based
measurement to determine the width the browser will use when rendering the
character.

Fixes #11.
---
 src/core/TextFontMetrics.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/core/TextFontMetrics.js b/src/core/TextFontMetrics.js
index 7216fe4..425c5f6 100644
--- a/src/core/TextFontMetrics.js
+++ b/src/core/TextFontMetrics.js
@@ -49,7 +49,8 @@ function calcCharAdvanceOpenType(char, fontSize, font, unitsPerEm) {
   let glyph = font.charToGlyph(char)
   return glyph.unicode ?
     glyph.advanceWidth * calcFontScale(fontSize, unitsPerEm) :
-    0
+    // font doesn't contain a glyph for this char, fallback to canvas measurement
+    calcTextAdvanceCanvas(char, fontSize, font)
 }
 
 let canvas = _.memoize(function() {