Hide loading message in case of fast iframe loading

Previously, in case the iframe was already fully loaded, the callbacks
were not called, and thus the loading message didn't disappear.

Author: pabzm

program/js/app.js

@@ -250,22 +250,17 @@ function rcube_webmail() {
 
         if (this.task === 'mail' && (this.env.action === 'preview' || this.env.action === 'show')) {
             document.querySelectorAll('iframe.framed-message-part').forEach((iframe) => {
-                // Resize twice initially: first time when the iframe's
-                // document was parsed, to already provide roughly the
-                // correct height; second time when all resources have been
-                // loaded, to finally ensure the correct height with all
-                // images etc.
-                iframe.addEventListener('DOMContentLoaded', () => this.resize_preview_iframe(iframe));
-                iframe.addEventListener('load', () => {
-                    this.resize_preview_iframe(iframe);
-                    // Hide "Loading data" message.
-                    $(iframe).siblings('.loading').hide();
-                    // Show notice
-                    if (iframe.contentDocument.body.dataset.extlinks === 'true') {
-                        $(this.gui_objects.remoteobjectsmsg).show();
-                        this.enable_command('load-remote', true);
-                    }
-                });
+                if (iframe.contentDocument.readyState === 'complete') {
+                    this.iframe_actions_after_load(iframe);
+                } else {
+                    // Resize twice initially: first time when the iframe's
+                    // document was parsed, to already provide roughly the
+                    // correct height; second time when all resources have been
+                    // loaded, to finally ensure the correct height with all
+                    // images etc.
+                    iframe.addEventListener('DOMContentLoaded', () => this.resize_preview_iframe(iframe));
+                    iframe.addEventListener('load', () => this.iframe_actions_after_load(iframe));
+                }
                 // Also run on window resizes, because the changed text flow could need more space.
                 window.addEventListener('resize', () => this.resize_preview_iframe(iframe));
             });
@@ -10683,6 +10678,17 @@ function rcube_webmail() {
         setTimeout('window.print()', 10);
     };
 
+    this.iframe_actions_after_load = function (iframe) {
+        this.resize_preview_iframe(iframe);
+        // Hide "Loading data" message.
+        $(iframe).siblings('.loading').hide();
+        // Show notice
+        if (iframe.contentDocument.body.dataset.extlinks === 'true') {
+            $(this.gui_objects.remoteobjectsmsg).show();
+            this.enable_command('load-remote', true);
+        }
+    };
+
     this.resize_preview_iframe = function (iframe) {
         // Cancel runs that we're scheduled ealier but didn't run yet.
         if (iframe.resizePreviewIframeTimer) {