Optional PC key blocks: function row, navigation, numeric keypad

- Template sections placed above or to the right of the typing keys;
  the user picks any mix in settings, typing keys included
- keysym keys send XKB keysyms on press, optionally repeating
- Geometry lays blocks side by side with one key unit; stretch keys are
  resolved at layout time so composed blocks line up
- Toggling a block resizes the window so keys keep their size

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/layout/LayoutModel.cpp

@@ -16,6 +16,7 @@ QString keyTypeName(KeyType type)
     case KeyType::Globe: return QStringLiteral("globe");
     case KeyType::Dismiss: return QStringLiteral("dismiss");
     case KeyType::Spacer: return QStringLiteral("spacer");
+    case KeyType::Keysym: return QStringLiteral("keysym");
     case KeyType::Letters: break; // expanded before it reaches the model
     }
     return {};
@@ -89,6 +90,27 @@ void LayoutModel::setLayer(const QString &layerName)
     Q_EMIT layerChanged();
 }
 
+void LayoutModel::setVisibleSections(const QStringList &ids)
+{
+    if (ids == m_visibleSections)
+        return;
+    m_visibleSections = ids;
+    rebuild();
+}
+
+QVariantList LayoutModel::sections() const
+{
+    QVariantList list;
+    for (const Section &section : m_layout.sections)
+        list.append(QVariantMap{{QStringLiteral("id"), section.id}, {QStringLiteral("name"), section.name}});
+    return list;
+}
+
+qreal LayoutModel::totalUnits() const
+{
+    return ::totalUnits(m_blocks);
+}
+
 void LayoutModel::setSize(QSizeF size)
 {
     if (size == m_size)
@@ -140,12 +162,39 @@ int LayoutModel::keyAt(QPointF pos) const
     return nearest;
 }
 
+QList<Block> LayoutModel::composeBlocks() const
+{
+    const auto shown = [this](const QString &id) { return m_visibleSections.contains(id); };
+    const Layer *layer = m_layout.layer(m_layerName);
+
+    Block main;
+    for (const Section &section : m_layout.sections) {
+        if (section.placement == Section::Placement::Above && shown(section.id))
+            main += section.rows;
+    }
+    if (layer && shown(MainSectionId))
+        main += layer->rows;
+
+    QList<Block> blocks;
+    if (!main.isEmpty())
+        blocks.append(main);
+    for (const Section &section : m_layout.sections) {
+        if (section.placement == Section::Placement::Right && shown(section.id))
+            blocks.append(section.rows);
+    }
+    // Never show nothing.
+    if (blocks.isEmpty() && layer)
+        blocks.append(layer->rows);
+    return blocks;
+}
+
 void LayoutModel::rebuild()
 {
     beginResetModel();
+    m_blocks = composeBlocks();
     m_keys.clear();
-    if (const Layer *layer = m_layout.layer(m_layerName)) {
-        for (const Row &row : layer->rows) {
+    for (const Block &block : std::as_const(m_blocks)) {
+        for (const Row &row : block) {
             for (const KeyDef &key : row) {
                 if (key.type != KeyType::Spacer)
                     m_keys.append(key);
@@ -161,17 +210,18 @@ void LayoutModel::rebuild()
 void LayoutModel::relayout()
 {
     m_rects.clear();
-    const Layer *layer = m_layout.layer(m_layerName);
-    if (!layer || m_size.isEmpty())
+    if (m_size.isEmpty())
         return;
 
-    const QList<QRectF> all = computeKeyRects(*layer, m_size);
+    const QList<QRectF> all = computeKeyRects(m_blocks, m_size);
     qsizetype i = 0;
-    for (const Row &row : layer->rows) {
-        for (const KeyDef &key : row) {
-            if (key.type != KeyType::Spacer)
-                m_rects.append(all[i]);
-            ++i;
+    for (const Block &block : std::as_const(m_blocks)) {
+        for (const Row &row : block) {
+            for (const KeyDef &key : row) {
+                if (key.type != KeyType::Spacer)
+                    m_rects.append(all[i]);
+                ++i;
+            }
         }
     }
 }