From 5b57e69da256a9bdd2337d37188b8ba7cda7e24f Mon Sep 17 00:00:00 2001
From: Tim van der Meij <timvandermeij@gmail.com>
Date: Sun, 30 Dec 2018 14:57:45 +0100
Subject: [PATCH] Optimize `CanvasGraphics.setFont` to avoid intermediate
 string creation

This method creates quite a few intermediate strings on each call and
it's called often, even for smaller documents like the Tracemonkey
document. Scrolling from top to bottom in that document resulted in
14126 strings being created in this method. With this commit applied,
this is reduced to 2018 strings.
---
 src/display/canvas.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/display/canvas.js b/src/display/canvas.js
index 99c97e13f..4aadb70a3 100644
--- a/src/display/canvas.js
+++ b/src/display/canvas.js
@@ -1317,7 +1317,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
       var name = fontObj.loadedName || 'sans-serif';
       var bold = fontObj.black ? '900' : (fontObj.bold ? 'bold' : 'normal');
       var italic = fontObj.italic ? 'italic' : 'normal';
-      var typeface = '"' + name + '", ' + fontObj.fallbackName;
+      var typeface = `"${name}", ${fontObj.fallbackName}`;
 
       // Some font backends cannot handle fonts below certain size.
       // Keeping the font at minimal size and using the fontSizeScale to change
@@ -1327,8 +1327,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
                             size > MAX_FONT_SIZE ? MAX_FONT_SIZE : size;
       this.current.fontSizeScale = size / browserFontSize;
 
-      var rule = italic + ' ' + bold + ' ' + browserFontSize + 'px ' + typeface;
-      this.ctx.font = rule;
+      this.ctx.font = `${italic} ${bold} ${browserFontSize}px ${typeface}`;
     },
     setTextRenderingMode: function CanvasGraphics_setTextRenderingMode(mode) {
       this.current.textRenderingMode = mode;