Allow grouping by a separate criterion

Add an explicit group role to Dolphin views so items can be grouped independently from the active sort role.
Previously, Dolphin's grouped view always used the current sort role as the grouping criterion. This meant that grouping and sorting were tied together, for example grouping by type also required sorting by type.
This change adds a separate Group By menu. It replaces the previous Show in Groups toggle and allows the user to disable grouping, keep the old Same as Sort behavior, or explicitly group by a selected criterion.
When an explicit group role is set, the model keeps groups stable and uses the normal sort role as a secondary key inside each group. The roles
updater also receives the active group role, so roles used only for grouping are still updated correctly.

BUG: 416134
CCBUG: 510670
CCBUG: 513235
CCBUG: 46393

1 files changed, 38 insertions, 3 deletions

diff --git a/src/kitemviews/kitemmodelbase.cpp b/src/kitemviews/kitemmodelbase.cpp
index 82e491220..a4f7b0890 100644
--- a/src/kitemviews/kitemmodelbase.cpp
+++ b/src/kitemviews/kitemmodelbase.cpp
@@ -50,13 +50,41 @@ bool KItemModelBase::groupedSorting() const
 void KItemModelBase::setSortRole(const QByteArray &role, bool resortItems)
 {
     if (role != m_sortRole) {
-        const QByteArray previous = m_sortRole;
+        const QByteArray previousSortRole = m_sortRole;
         m_sortRole = role;
-        onSortRoleChanged(role, previous, resortItems);
-        Q_EMIT sortRoleChanged(role, previous);
+        onSortRoleChanged(role, previousSortRole, resortItems);
+        Q_EMIT sortRoleChanged(role, previousSortRole);
+
+        if (m_groupRole.isEmpty()) {
+            onGroupRoleChanged(role, previousSortRole, false);
+            Q_EMIT groupRoleChanged(role, previousSortRole);
+        }
+    }
+}
+
+void KItemModelBase::setGroupRole(const QByteArray &role)
+{
+    if (role != m_groupRole) {
+        const QByteArray previousEffective = groupRole();
+        m_groupRole = role;
+        const QByteArray currentEffective = groupRole();
+        if (currentEffective != previousEffective) {
+            onGroupRoleChanged(currentEffective, previousEffective);
+            Q_EMIT groupRoleChanged(currentEffective, previousEffective);
+        }
     }
 }
 
+QByteArray KItemModelBase::groupRole() const
+{
+    return m_groupRole.isEmpty() ? m_sortRole : m_groupRole;
+}
+
+QByteArray KItemModelBase::rawGroupRole() const
+{
+    return m_groupRole;
+}
+
 QByteArray KItemModelBase::sortRole() const
 {
     return m_sortRole;
@@ -149,6 +177,13 @@ void KItemModelBase::onSortRoleChanged(const QByteArray &current, const QByteArr
     Q_UNUSED(resortItems)
 }
 
+void KItemModelBase::onGroupRoleChanged(const QByteArray &current, const QByteArray &previous, bool resortItems)
+{
+    Q_UNUSED(current)
+    Q_UNUSED(previous)
+    Q_UNUSED(resortItems)
+}
+
 void KItemModelBase::onSortOrderChanged(Qt::SortOrder current, Qt::SortOrder previous)
 {
     Q_UNUSED(current)