Bug 1709062 - Make printpreview_helper use a fixed viewport width. r=dholbert

Recently (due to probably a system upgrade) this test fails locally for
me with an exception in compareCanvases(), because the two preview
windows aren't always the same size.

This is more reliable, faster, more similar to what we actually do
in print preview, and more easily debuggable.

Differential Revision: https://phabricator.services.mozilla.com/D114078

layout/base/tests/chrome/printpreview_helper.xhtml

@@ -20,6 +20,7 @@ var info = window.arguments[0].info;
 var SimpleTest = window.arguments[0].SimpleTest;
 var gWbp;
 var gPrintPreviewWindow;
+var gPrintPreviewBrowser;
 var ctx1;
 var ctx2;
 var counter = 0;
@@ -82,7 +83,24 @@ function printpreview(options = {}) {
   function afterprint() { ++after; }
   frameElts[0].contentWindow.addEventListener("beforeprint", beforeprint, true);
   frameElts[0].contentWindow.addEventListener("afterprint", afterprint, true);
-  gPrintPreviewWindow = frameElts[0].contentWindow.printPreview(settings, listener);
+  {
+    let bc = frameElts[0].contentWindow.browsingContext;
+    let browser = document.createXULElement("browser");
+    browser.setAttribute("type", "content");
+    browser.setAttribute("width", "800");
+    browser.setAttribute("height", "800");
+    browser.style.maxWidth = "800px"; // Deal with XUL silliness.
+    browser.setAttribute("initialBrowsingContextGroupId", bc.group.id);
+    browser.setAttribute("nodefaultsrc", "true");
+    document.documentElement.appendChild(browser);
+    gPrintPreviewBrowser = browser;
+
+    // Force contentViewer creation and layout.
+    browser.browsingContext.docShell.document;
+    browser.getBoundingClientRect();
+
+    gPrintPreviewWindow = frameElts[0].contentWindow.printPreview(settings, listener, browser.browsingContext.docShell);
+  }
   gWbp = gPrintPreviewWindow.docShell.contentViewer;
   gWbp.QueryInterface(Ci.nsIWebBrowserPrint);
   is(before, 1, "Should have called beforeprint listener!");
@@ -98,7 +116,7 @@ function printpreview(options = {}) {
 
 function exitprintpreview() {
   gPrintPreviewWindow.docShell.exitPrintPreview();
-  gPrintPreviewWindow.close();
+  gPrintPreviewBrowser.remove();
 }
 
 function finish() {
@@ -148,7 +166,7 @@ function addHTMLContent(parent) {
   n.innerHTML = s;
 }
 
-function startTest1() {
+async function startTest1() {
   ctx1 = document.getElementsByTagName("canvas")[0].getContext("2d");
   ctx2 = document.getElementsByTagName("canvas")[1].getContext("2d");
   frameElts[0].contentDocument.body.innerHTML = "<div> </div><div>" + counter + " timers</div><div> </div>";
@@ -161,7 +179,7 @@ function startTest1() {
   frameElts[0].contentWindow.setTimeout(frameElts[0].contentWindow.counterTimeout, 0);
   frameElts[0].contentDocument.body.firstChild.innerHTML = "Print preview";
 
-  let ppfinished = printpreview();
+  await printpreview();
   drawPrintPreviewWindow(ctx1);
   frameElts[0].contentDocument.body.firstChild.innerHTML = "Galley presentation";
 
@@ -172,13 +190,10 @@ function startTest1() {
   // And readd.
   addHTMLContent(frameElts[0].contentDocument.body.lastChild);
 
-  setTimeout(function() {
-    finalizeTest1(ppfinished)
-  }, 1000);
+  setTimeout(finalizeTest1, 1000);
 }
 
-async function finalizeTest1(ppfinished) {
-  await ppfinished;
+function finalizeTest1() {
   drawPrintPreviewWindow(ctx2);
   exitprintpreview();
   ok(compareCanvases(), "Canvas should be the same!");
@@ -390,9 +405,11 @@ async function runTest9() {
 }
 
 function drawPrintPreviewWindow(ctx) {
-  ctx.canvas.width = gPrintPreviewWindow.innerWidth;
-  ctx.canvas.height = gPrintPreviewWindow.innerHeight;
-  ctx.drawWindow(gPrintPreviewWindow, 0, 0, gPrintPreviewWindow.innerWidth, gPrintPreviewWindow.innerHeight, "rgb(255, 255, 255)");
+  let width = gPrintPreviewWindow.innerWidth;
+  let height = gPrintPreviewWindow.innerHeight;
+  ctx.canvas.width = width;
+  ctx.canvas.height = height;
+  ctx.drawWindow(gPrintPreviewWindow, 0, 0, width, height, "rgb(255, 255, 255)");
 }
 
 // Test for bug 1524640
@@ -1141,7 +1158,7 @@ async function runTest40() {
 <table style="border: 1px solid black;" xmlns="http://www.w3.org/1999/xhtml">
 <tr><th>Print preview canvas 1</th><th>Print preview canvas 2</th></tr>
 <tr>
-<td><canvas height="400" width="400"></canvas></td>
-<td><canvas height="400" width="400"></canvas></td>
+<td><canvas height="800" width="800"></canvas></td>
+<td><canvas height="800" width="800"></canvas></td>
 </tr></table>
 </window>