Add loading indicator to the test liveview

This PR removes the empty box which was visible in the webui before liveview content is received by the responsible canvas element.
It also adds a loading animation indicating that the liveview is being loaded.
Test cases are also added to confirm the elements are displayed and hidden as expected.

Related Issue: https://progress.opensuse.org/issues/134840

assets/javascripts/running.js

@@ -321,13 +321,16 @@ var last_event;
 function loadCanvas(canvas, dataURL) {
   var context = canvas.getContext('2d');
 
-  // load image from data url
+  // load image from data URL
   var scrn = new Image();
   scrn.onload = function () {
     canvas.width = this.width;
     canvas.height = this.height;
     context.clearRect(0, 0, this.width, this.width);
     context.drawImage(this, 0, 0);
+
+    // hide loading animation after the first image is loaded
+    document.getElementById('liveview-loading').style.display = 'none';
   };
   scrn.src = dataURL;
 }

t/ui/18-tests-details.t

@@ -311,6 +311,40 @@ subtest 'running job' => sub {
     # waiting for the periodic call anyways
     $driver->execute_script('window.enableStatusUpdates = false');
 
+    subtest 'liveview loading animation is displayed' => sub {
+        $driver->find_element_by_link_text('Details')->click();
+        like current_tab, qr/details/i, 'switched to details tab';
+        $driver->find_element_by_link_text('Live View')->click();
+        like current_tab, qr/live/i, 'switched back to live tab';
+        my $loading_element = $driver->find_element('#liveview-loading', 'css');
+        ok $loading_element, 'liveview-loading element exists after tab switch';
+        ok $loading_element->is_displayed(), 'liveview-loading is visible after tab switch';
+    };
+    subtest 'liveview loading animation hides after live view starts' => sub {
+        my $loading_element = $driver->find_element('#liveview-loading');
+        ok $loading_element->is_displayed(), 'liveview-loading is initially visible';
+        # simulate the live view starting
+        $driver->execute_script(
+            q{
+            var canvas = document.getElementById('livestream');
+            var dataURL = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR4nGNgYAAAAAMAAWgmWQ0AAAAASUVORK5CYII=';
+            loadCanvas(canvas, dataURL);
+        }
+        );
+        wait_until sub {
+            my $loading_element = $driver->find_element('#liveview-loading');
+            !$loading_element->is_displayed();
+        }, 'liveview-loading is hidden after live view starts', 5;
+        my $canvas = $driver->find_element('#livestream');
+        ok $canvas->is_displayed(), 'livestream canvas is displayed';
+        $driver->find_element_by_link_text('Details')->click();
+        like current_tab, qr/details/i, 'switched to details tab';
+        $driver->find_element_by_link_text('Live View')->click();
+        like current_tab, qr/live/i, 'switched back to live tab';
+        $loading_element = $driver->find_element('#liveview-loading', 'css');
+        ok $loading_element, 'liveview-loading element exists after tab switch';
+        ok !$loading_element->is_displayed(), 'liveview-loading is still hidden after tab switch';
+    };
     subtest 'info panel contents' => sub {
         like(
             $driver->find_element('#assigned-worker')->get_text,

templates/webapi/test/live.html.ep

@@ -193,6 +193,13 @@
 </div>
 
 <div id="canholder">
+  <div id="liveview-loading">
+    <div class="d-flex justify-content-center">
+      <i class="fa fa-circle-o-notch fa-spin fa-4x" role="status">
+        <span class="sr-only">Loading…</span>
+      </i>
+    </div>
+  </div>
   <canvas id="livestream" data-url="/liveviewhandler/tests/<%= $testid %>/streaming">
   </canvas>
 </div>