Support one level of dropdown menus in the navbar

A `main` menu entry with child entries (others with `parent:` set) is
now rendered as a Bootstrap dropdown; flat entries are unchanged.
Active-state highlighting is trailing-slash tolerant and marks the
dropdown parent active when one of its children is the current page.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -1,3 +1,77 @@
 # hugo_bootstrap_theme
 
 Simple Bootstrap-based theme for Hugo.
+
+
+## Shortcodes
+
+### `lead`
+
+Wraps its content in a Bootstrap `.lead` paragraph (the Markdown
+attribute syntax `{.lead}` cannot target a paragraph):
+
+```
+{{< lead >}}
+An introductory paragraph that stands out.
+{{< /lead >}}
+```
+
+Pass extra classes with `class`, e.g. `{{< lead class="mb-5" >}}`.
+
+### `banner`
+
+A full-bleed banner / hero image: it spans the entire viewport width
+while the rest of the page stays within `.container`. Put it on the
+first line of a page's content to get a hero flush against the navbar.
+
+```
+{{< banner src="hero.png" alt="…" >}}
+```
+
+`src` is resolved as a page resource first, then a global resource
+(`assets/`), then as a plain link respecting the site's base URL.
+Optional params: `title`, `height` (a CSS length such as `60vh`, which
+crops the image with `object-fit: cover`) and `class`.
+
+
+## Navigation
+
+The navbar renders the `main` menu. A top-level entry that has child
+entries (other entries pointing at it with `parent:`) is rendered as a
+Bootstrap dropdown; entries without children stay as plain links. Only
+one level of nesting is supported (Bootstrap 5 has no nested submenus).
+
+```yaml
+# hugo.yaml / menus.yaml
+menu:
+  main:
+    - name: Home
+      pageRef: /
+      weight: 1
+    - name: Research
+      weight: 2
+    - name: Proposals
+      parent: Research
+      pageRef: /proposals
+      weight: 1
+    - name: History
+      parent: Research
+      pageRef: /history
+      weight: 2
+```
+
+The entry matching the current page (and its parent, for a dropdown
+child) gets Bootstrap's `active` class. A parent entry acts only as the
+dropdown toggle, so it does not need its own `url`/`pageRef`.
+
+
+## Custom error page
+
+The theme has a custom 404 error page.
+
+If the site has an SVG image in `assets/svg/404.svg`,
+this image will be displayed instead of a generic 404
+code. Regardless of whether an SVG assets exists or not,
+English and German explanations of what's going on will
+be included on the page.
+

assets/scss/hugo_bootstrap_theme.scss

@@ -15,6 +15,12 @@
   --bs-body-line-height: 1.5;
 }
 
+// Keep the full-bleed `.banner` from adding a horizontal scrollbar
+// (100vw is wider than the viewport when a vertical scrollbar is shown).
+html {
+  overflow-x: hidden;
+}
+
 body {
   font-family: var(--bs-font-sans-serif);
   line-height: var(--bs-body-line-height);
@@ -61,8 +67,23 @@ h1, h2, h3, h4, h5 {
   }
 }
 
-// Images
+// Full-bleed banner / hero image: spans the viewport width while the
+// surrounding page content stays within `.container`. Works from inside
+// any centred `.container` because the horizontal margins cancel out the
+// container offset (50% of the parent - 50% of the viewport).
 .banner {
+  display: block;
+  width: 100vw;
+  max-width: 100vw;
+  margin-left: calc(50% - 50vw);
+  margin-right: calc(50% - 50vw);
   margin-bottom: 2rem;
 }
 
+// When the banner is the first thing in the page body, pull it flush
+// against the navbar by cancelling the layout's top padding (`py-5`).
+.content-body > .banner:first-child,
+.content-body > p:first-child > .banner:only-child {
+  margin-top: -3rem;
+}
+

layouts/404.html

@@ -0,0 +1,47 @@
+{{ define "main" }}
+<div class="container">
+  <div class="row">
+    <div class="col mt-5 mb-5">
+      {{ with resources.Get "svg/404.svg" }}
+        {{ .Content | safeHTML }}
+      {{ else }}
+        <h1 class="display-1 mx-auto text-center">
+          404
+        </h1>
+      {{ end }}
+    </div>
+  </div>
+  <div class="row">
+    <div class="col-lg-6">
+      <div class="alert alert-danger mb-5" lang="en">
+        <h4 class="alert-heading">
+          Page not found
+        </h4>
+        <p>
+          The page you were trying to navigate to was not found on this
+          server.
+        </p>
+        <hr />
+        <p class="mb-0">
+          <a href="{{ .Site.BaseURL }}" class="alert-link">Back to the home page.</a>
+        </p>
+      </div>
+    </div>
+    <div class="col-lg-6">
+      <div class="alert alert-danger" lang="de">
+        <h4 class="alert-heading">
+          Seite nicht gefunden
+        </h4>
+        <p>
+          Die angeforderte Seite existiert nicht auf diesem Server.
+        </p>
+        <hr />
+        <p class="mb-0">
+          <a href="{{ .Site.BaseURL }}" class="alert-link">Zurück zur Homepage.</a>
+        </p>
+      </div>
+    </div>
+  </div>
+</div>
+{{ end }}
+

layouts/_partials/footer.html

@@ -2,7 +2,7 @@
   <div class="container py-4">
     <div class="row">
       <div class="col-md-6">
-        <p>&copy; {{ now.Year }} {{ .Site.Title }}</p>
+        <p>&copy; {{ now.Year }} {{ or (or .Params.Author .Site.Params.Author) .Site.Title }}</p>
       </div>
       <div class="col-md-6 text-md-end">
         <p>

layouts/_partials/header.html

@@ -1,46 +1,53 @@
 <nav class="navbar navbar-expand-lg navbar-light bg-light sticky-top">
   <div class="container"> <!-- Changed from container-fluid to container -->
     <a class="navbar-brand fw-bold" href="{{ .Site.BaseURL }}">
-      <img src="/img/favicon.svg" alt="{{ .Site.Title }}" title="{{ .Site.Title }}">
+      {{- $logo := "img/favicon.svg" -}}
+      {{- if os.FileExists "static/img/logo.svg" -}}{{- $logo = "img/logo.svg" -}}{{- end -}}
+      <img src="{{ $logo | relURL }}" alt="{{ .Site.Title }}" title="{{ .Site.Title }}">
     </a>
-    
-    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" 
-            data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" 
+
+    <button class="navbar-toggler" type="button" data-bs-toggle="collapse"
+            data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false"
             aria-label="Toggle navigation">
       <span class="navbar-toggler-icon"></span>
     </button>
-    
+
     <div class="collapse navbar-collapse" id="navbarNav">
       <ul class="navbar-nav ms-auto">
-        {{ range .Site.Menus.main }}
-          {{ if .HasChildren }}
-            <!-- Dropdown menu for items with children -->
+        {{- /* Current page, without a trailing slash, for menu-item highlighting. */ -}}
+        {{- $current := strings.TrimSuffix "/" .RelPermalink -}}
+        {{- range .Site.Menus.main -}}
+          {{- $isActive := and .URL (eq (strings.TrimSuffix "/" .URL) $current) -}}
+          {{- if .HasChildren -}}
+            {{- /* A menu entry with sub-entries (set `parent:` on them) becomes a dropdown. */ -}}
+            {{- range .Children -}}
+              {{- if and .URL (eq (strings.TrimSuffix "/" .URL) $current) }}{{ $isActive = true }}{{ end -}}
+            {{- end -}}
+            {{- $id := printf "navbar-%s" (.Identifier | default (.Name | urlize)) -}}
             <li class="nav-item dropdown">
-              <a class="nav-link dropdown-toggle" href="#" id="navbar{{ .Name | urlize }}" 
-                 role="button" data-bs-toggle="dropdown" aria-expanded="false">
+              <a class="nav-link dropdown-toggle{{ if $isActive }} active{{ end }}" href="#"
+                 id="{{ $id }}" role="button" data-bs-toggle="dropdown" aria-expanded="false">
                 {{ .Name }}
               </a>
-              <ul class="dropdown-menu" aria-labelledby="navbar{{ .Name | urlize }}">
-                {{ range .Children }}
+              <ul class="dropdown-menu" aria-labelledby="{{ $id }}">
+                {{- range .Children }}
                   <li>
-                    <a class="dropdown-item {{ if eq .URL ($.RelPermalink) }}active{{ end }}" 
-                       href="{{ .URL | relURL }}">
+                    <a class="dropdown-item{{ if and .URL (eq (strings.TrimSuffix "/" .URL) $current) }} active{{ end }}"
+                       href="{{ .URL }}">
                       {{ .Name }}
                     </a>
                   </li>
-                {{ end }}
+                {{- end }}
               </ul>
             </li>
-          {{ else }}
-            <!-- Regular menu item -->
+          {{- else -}}
             <li class="nav-item">
-              <a class="nav-link {{ if eq .URL ($.RelPermalink) }}active{{ end }}" 
-                 href="{{ .URL | relURL }}">
+              <a class="nav-link{{ if $isActive }} active{{ end }}" href="{{ .URL }}">
                 {{ .Name }}
               </a>
             </li>
-          {{ end }}
-        {{ end }}
+          {{- end -}}
+        {{- end }}
       </ul>
     </div>
   </div>

layouts/_partials/scripts_extra.html

@@ -0,0 +1,2 @@
+<!-- extra scripts may go here -->
+

layouts/_shortcodes/banner.html

@@ -1,4 +1,36 @@
-{{ $src := .Get "src" }}
-{{ $alt := .Get "alt" }}
-{{ $title := .Get "title" }}
-<img class="banner img-fluid" src="{{ $src }}" alt="{{ $alt }}" title="{{ $title }}" width="100%">
+{{- /*
+  Full-bleed banner / hero image.
+
+  The image spans the entire viewport width while the surrounding page
+  content stays within `.container` (see the `.banner` rules in
+  hugo_bootstrap_theme.scss). Place the shortcode as the first line of a
+  page's content to get a hero that sits flush against the navbar.
+
+  Params:
+    src     image path - resolved as a page resource first, then a global
+            resource (assets/), then treated as a link/URL respecting the
+            site's base URL
+    alt     alternative text (default: empty)
+    title   optional title attribute
+    height  optional CSS length (e.g. "60vh"); crops the image with
+            object-fit: cover
+    class   optional extra CSS classes
+*/ -}}
+{{- $src := .Get "src" -}}
+{{- $alt := or (.Get "alt") "" -}}
+{{- $title := .Get "title" -}}
+{{- $height := .Get "height" -}}
+{{- $class := .Get "class" -}}
+{{- $url := $src -}}
+{{- with $.Page.Resources.GetMatch $src -}}
+  {{- $url = .RelPermalink -}}
+{{- else -}}
+  {{- with resources.Get $src -}}
+    {{- $url = .RelPermalink -}}
+  {{- else -}}
+    {{- $url = $src | relURL -}}
+  {{- end -}}
+{{- end -}}
+<img class="banner{{ with $class }} {{ . }}{{ end }}" src="{{ $url }}" alt="{{ $alt }}"
+  {{- with $title }} title="{{ . }}"{{ end }}
+  {{- with $height }} style="height:{{ . }};object-fit:cover"{{ end }}>

layouts/_shortcodes/lead.html

@@ -0,0 +1,2 @@
+{{ $additional_classes := .Get "class" }}
+<p class="lead {{ $additional_classes }}">{{ .Inner | safeHTML }}</p>