Timeline: Visualize future rotations

library/Notifications/Widget/TimeGrid/DynamicGrid.php

@@ -129,7 +129,7 @@ protected function assemble()
         ]);
 
         $overlay = $this->createGridOverlay();
-        if ($overlay->isEmpty()) {
+        if ($overlay->isEmpty() || count($overlay) < count($this->sideBar())) {
             $this->style->addFor($this, [
                 '--primaryRows' => count($this->sideBar())
             ]);

library/Notifications/Widget/Timeline.php

@@ -14,6 +14,7 @@
 use Icinga\Module\Notifications\Widget\TimeGrid\Timescale;
 use Icinga\Module\Notifications\Widget\TimeGrid\Util;
 use Icinga\Module\Notifications\Widget\Timeline\Entry;
+use Icinga\Module\Notifications\Widget\Timeline\FutureEntry;
 use Icinga\Module\Notifications\Widget\Timeline\MinimalGrid;
 use Icinga\Module\Notifications\Widget\Timeline\Rotation;
 use IntlDateFormatter;
@@ -173,7 +174,9 @@ public function getEntries(): Traversable
 
         $occupiedCells = [];
         foreach ($rotations as $rotation) {
+            $entryFound = false;
             foreach ($rotation->fetchTimeperiodEntries($this->start, $this->getGrid()->getGridEnd()) as $entry) {
+                $entryFound = true;
                 if (! $this->minimalLayout) {
                     $entry->setPosition($maxPriority - $rotation->getPriority());
 
@@ -182,6 +185,13 @@ public function getEntries(): Traversable
 
                 $occupiedCells += $getDesiredCells($entry);
             }
+
+            if (! $entryFound && ! $this->minimalLayout) {
+                yield (new FutureEntry())
+                    ->setStart($this->getGrid()->getGridStart())
+                    ->setEnd($this->getGrid()->getGridEnd())
+                    ->setPosition($maxPriority - $rotation->getPriority());
+            }
         }
 
         $entryToCellsMap = new SplObjectStorage();

library/Notifications/Widget/Timeline/FutureEntry.php

@@ -0,0 +1,47 @@
+<?php
+
+/* Icinga Notifications Web | (c) 2025 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Notifications\Widget\Timeline;
+
+use Icinga\Module\Notifications\Widget\TimeGrid\Entry;
+use ipl\Html\Attributes;
+use ipl\Html\BaseHtmlElement;
+use ipl\Html\HtmlElement;
+use ipl\Web\Widget\Icon;
+
+/**
+ * FutureEntry
+ *
+ * Visualize a future entry of the rotation
+ */
+class FutureEntry extends Entry
+{
+    protected $defaultAttributes = ['class' => 'future-entry'];
+
+    protected $continuationType = Entry::TO_NEXT_GRID;
+
+    public function __construct()
+    {
+        parent::__construct(0);
+    }
+
+    public function getColor(int $transparency): string
+    {
+        return ''; // No user, no color, CSS will handle it
+    }
+
+    protected function assembleContainer(BaseHtmlElement $container): void
+    {
+        $container->addHtml(new HtmlElement(
+            'div',
+            new Attributes([
+                'title' => $this->translate('Rotation starts in the future')
+            ]),
+            new Icon('angle-right'),
+            new HtmlElement('span', new Attributes(['class' => 'outline'])),
+            new HtmlElement('span', new Attributes(['class' => 'outline'])),
+            new HtmlElement('span', new Attributes(['class' => 'outline']))
+        ));
+    }
+}

public/css/timeline.less

@@ -44,19 +44,66 @@
       }
     }
 
-    .overlay .entry {
-      margin-top: 1em;
-      margin-bottom: 1em;
-      z-index: 2; // overlap the .clock .time-hand
+    .overlay {
+      .entry {
+        margin-top: 1em;
+        margin-bottom: 1em;
+        z-index: 2; // overlap the .clock .time-hand
+
+        .title {
+          height: 100%;
+          flex-wrap: nowrap;
+          align-items: baseline;
+          padding: .15em .5em;
+
+          .name {
+            .text-ellipsis();
+          }
+        }
+      }
 
-      .title {
-        height: 100%;
-        flex-wrap: nowrap;
-        align-items: baseline;
-        padding: .15em .5em;
+      .future-entry {
+        display: flex;
+        justify-content: end;
+        z-index: 2; // overlap the .clock .time-hand
+        pointer-events: all;
 
-        .name {
-          .text-ellipsis();
+        > div {
+          margin-top: 1em;
+          margin-bottom: 1em;
+          display: flex;
+          align-items: center;
+          justify-content: end;
+          position: relative;
+          width: 3em;
+
+          .outline {
+            content: '';
+            display: block;
+            position: absolute;
+            border: 1px solid @gray-light;
+            border-right-width: 0;
+            top: -1px;
+            bottom: -1px;
+            width: 100%;
+            .rounded-corners(0.25em 0 0 0.25em);
+          }
+
+          .icon {
+            color: @gray;
+          }
+
+          .outline:nth-of-type(1) {
+            left: -1px; // Dock at the grid border
+          }
+
+          .outline:nth-of-type(2) {
+            left: 3px; // 4px gap
+          }
+
+          .outline:nth-of-type(3) {
+            left: 7px; // Same gap
+          }
         }
       }
     }