From 6d0ad48224390eabc59deafeb0953c2b12eb9f5e Mon Sep 17 00:00:00 2001
From: Andrea Bogazzi <andreabogazzi79@gmail.com>
Date: Sun, 28 Jan 2018 12:51:51 +0100
Subject: [PATCH] safeguard canvas (#4650)

---
 src/mixins/itext_click_behavior.mixin.js | 48 ++++++++++++++----------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/src/mixins/itext_click_behavior.mixin.js b/src/mixins/itext_click_behavior.mixin.js
index 739e091253e..cad56c43338 100644
--- a/src/mixins/itext_click_behavior.mixin.js
+++ b/src/mixins/itext_click_behavior.mixin.js
@@ -68,31 +68,39 @@ fabric.util.object.extend(fabric.IText.prototype, /** @lends fabric.IText.protot
   },
 
   /**
-   * Initializes "mousedown" event handler
+   * Default event handler for the basic functionalities needed on _mouseDown
+   * can be overridden to do something different.
+   * Scope of this implementation is: find the click position, set selectionStart
+   * find selectionEnd, initialize the drawing of either cursor or selection area
    */
-  initMousedownHandler: function() {
-    this.on('mousedown', function(options) {
-      if (!this.editable || (options.e.button && options.e.button !== 1)) {
-        return;
-      }
-      var pointer = this.canvas.getPointer(options.e);
+  _mouseDownHandler: function(options) {
+    if (!this.canvas || !this.editable || (options.e.button && options.e.button !== 1)) {
+      return;
+    }
+    var pointer = this.canvas.getPointer(options.e);
 
-      this.__mousedownX = pointer.x;
-      this.__mousedownY = pointer.y;
-      this.__isMousedown = true;
+    this.__mousedownX = pointer.x;
+    this.__mousedownY = pointer.y;
+    this.__isMousedown = true;
 
-      if (this.selected) {
-        this.setCursorByClick(options.e);
-      }
+    if (this.selected) {
+      this.setCursorByClick(options.e);
+    }
 
-      if (this.isEditing) {
-        this.__selectionStartOnMouseDown = this.selectionStart;
-        if (this.selectionStart === this.selectionEnd) {
-          this.abortCursorAnimation();
-        }
-        this.renderCursorOrSelection();
+    if (this.isEditing) {
+      this.__selectionStartOnMouseDown = this.selectionStart;
+      if (this.selectionStart === this.selectionEnd) {
+        this.abortCursorAnimation();
       }
-    });
+      this.renderCursorOrSelection();
+    }
+  },
+
+  /**
+   * Initializes "mousedown" event handler
+   */
+  initMousedownHandler: function() {
+    this.on('mousedown', this._mouseDownHandler);
   },
 
   /**