From 0fee384bd449f3d35d0d5e93553229310f8992a1 Mon Sep 17 00:00:00 2001
From: Mick Ryan <mick@xhr.dev>
Date: Mon, 1 Jul 2019 14:24:26 -0700
Subject: [PATCH] Fix: Chrome Print Preview Fix (#1030)

Add listener that is fired once the iframe has loaded it's content for printing. This enables chrome to show an accurate print preview.
---
 src/lib/viewers/image/ImageViewer.js          | 28 ++++++++++++-----
 .../image/__tests__/ImageViewer-test.js       | 31 ++++++++++++++-----
 2 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/src/lib/viewers/image/ImageViewer.js b/src/lib/viewers/image/ImageViewer.js
index 9da815cb1..0bc698a74 100644
--- a/src/lib/viewers/image/ImageViewer.js
+++ b/src/lib/viewers/image/ImageViewer.js
@@ -291,20 +291,32 @@ class ImageViewer extends ImageBaseViewer {
      * @return {void}
      */
     print() {
+        const browserName = Browser.getName();
+
+        /**
+         * Called async to ensure resource is loaded for print preview. Then removes listener to prevent
+         * multiple handlers.
+         *
+         * @return {void}
+         */
+        const defaultPrintHandler = () => {
+            if (browserName === 'Explorer' || browserName === 'Edge') {
+                this.printframe.contentWindow.document.execCommand('print', false, null);
+            } else {
+                this.printframe.contentWindow.print();
+            }
+
+            this.printframe.removeEventListener('load', defaultPrintHandler);
+            this.emit('printsuccess');
+        };
+
         this.printframe = util.openContentInsideIframe(this.imageEl.outerHTML);
+        this.printframe.addEventListener('load', defaultPrintHandler);
         this.printframe.contentWindow.focus();
 
         this.printImage = this.printframe.contentDocument.querySelector('img');
         this.printImage.style.display = 'block';
         this.printImage.style.margin = '0 auto';
-
-        if (Browser.getName() === 'Explorer' || Browser.getName() === 'Edge') {
-            this.printframe.contentWindow.document.execCommand('print', false, null);
-        } else {
-            this.printframe.contentWindow.print();
-        }
-
-        this.emit('printsuccess');
     }
 
     /**
diff --git a/src/lib/viewers/image/__tests__/ImageViewer-test.js b/src/lib/viewers/image/__tests__/ImageViewer-test.js
index 81217cf62..3750137be 100644
--- a/src/lib/viewers/image/__tests__/ImageViewer-test.js
+++ b/src/lib/viewers/image/__tests__/ImageViewer-test.js
@@ -353,6 +353,7 @@ describe('lib/viewers/image/ImageViewer', () => {
             stubs.focus = sandbox.stub();
             stubs.print = sandbox.stub();
             stubs.mockIframe = {
+                addEventListener() {},
                 contentWindow: {
                     document: {
                         execCommand: stubs.execCommand
@@ -362,7 +363,8 @@ describe('lib/viewers/image/ImageViewer', () => {
                 },
                 contentDocument: {
                     querySelector: sandbox.stub().returns(containerEl.querySelector('img'))
-                }
+                },
+                removeEventListener() {}
             };
 
             stubs.openContentInsideIframe = sandbox.stub(util, 'openContentInsideIframe').returns(stubs.mockIframe);
@@ -377,25 +379,40 @@ describe('lib/viewers/image/ImageViewer', () => {
             expect(stubs.focus).to.be.called;
         });
 
-        it('should execute the print command if the browser is Explorer', () => {
+        it('should execute the print command if the browser is Explorer', (done) => {
             stubs.getName.returns('Explorer');
+            stubs.mockIframe.addEventListener = (type, callback) => {
+                callback();
+                expect(stubs.execCommand).to.be.calledWith('print', false, null);
+
+                done();
+            };
 
             image.print();
-            expect(stubs.execCommand).to.be.calledWith('print', false, null);
         });
 
-        it('should execute the print command if the browser is Edge', () => {
+        it('should execute the print command if the browser is Edge', (done) => {
             stubs.getName.returns('Edge');
+            stubs.mockIframe.addEventListener = (type, callback) => {
+                callback();
+                expect(stubs.execCommand).to.be.calledWith('print', false, null);
+
+                done();
+            };
 
             image.print();
-            expect(stubs.execCommand).to.be.calledWith('print', false, null);
         });
 
-        it('should call the contentWindow print for other browsers', () => {
+        it('should call the contentWindow print for other browsers', (done) => {
             stubs.getName.returns('Chrome');
+            stubs.mockIframe.addEventListener = (type, callback) => {
+                callback();
+                expect(stubs.print).to.be.called;
+
+                done();
+            };
 
             image.print();
-            expect(stubs.print).to.be.called;
         });
     });