Disallow empty prefabs

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project somewhat adheres to [Semantic Versioning](https://semver.org/sp
 - Fix not being able to minimize/maximize some windows.
 - Fix some menu items under `Tools` not being disabled when their corresponding button is disabled.
 - Fix the map list search bar stealing keyboard focus whenever a map layout was opened.
+- Disallow creating prefabs with no metatiles.
 
 ## [6.3.1] - 2026-04-12
 ### Added

include/ui/metatileselector.h

@@ -34,6 +34,18 @@ struct MetatileSelection
     bool hasCollision;
     QList<MetatileSelectionItem> metatileItems;
     QList<CollisionSelectionItem> collisionItems;
+
+    bool isEmpty() const {
+        for (const auto& metatileItem : metatileItems) {
+            if (metatileItem.enabled) return false;
+        }
+        if (hasCollision) {
+            for (const auto& collisionItem : collisionItems) {
+                if (collisionItem.enabled) return false;
+            }
+        }
+        return true;
+    };
 };
 
 class MetatileSelector: public SelectablePixmapItem {

include/ui/prefabcreationdialog.h

@@ -24,6 +24,8 @@ private:
     Layout *layout = nullptr;
     Ui::PrefabCreationDialog *ui;
     MetatileSelection selection;
+
+    void validate();
 };
 
 #endif // PREFABCREATIONDIALOG_H

src/ui/prefab.cpp

@@ -82,6 +82,7 @@ void Prefab::loadPrefabs() {
             selection.metatileItems[index].enabled = true;
             selection.collisionItems[index].enabled = true;
         }
+        if (selection.isEmpty()) continue;
 
         this->items.append(PrefabItem{QUuid::createUuid(), name, primaryTileset, secondaryTileset, selection});
     }

src/ui/prefabcreationdialog.cpp

@@ -5,6 +5,7 @@
 #include "prefab.h"
 
 #include <QObject>
+#include <QPushButton>
 
 PrefabCreationDialog::PrefabCreationDialog(QWidget *parent, MetatileSelector *metatileSelector, Layout *layout) :
     QDialog(parent),
@@ -36,9 +37,12 @@ PrefabCreationDialog::PrefabCreationDialog(QWidget *parent, MetatileSelector *me
             this->selection.collisionItems[index].enabled = toggledState;
         }
         pixmapItem->setPixmap(drawMetatileSelection(this->selection, layout));
+        validate();
     });
 
     connect(this, &PrefabCreationDialog::accepted, this, &PrefabCreationDialog::savePrefab);
+
+    validate();
 }
 
 PrefabCreationDialog::~PrefabCreationDialog()
@@ -46,6 +50,13 @@ PrefabCreationDialog::~PrefabCreationDialog()
     delete ui;
 }
 
+void PrefabCreationDialog::validate() {
+    bool valid = !this->selection.isEmpty();
+
+    QPushButton* okButton = ui->buttonBox->button(QDialogButtonBox::Ok);
+    if (okButton) okButton->setEnabled(valid);
+}
+
 void PrefabCreationDialog::savePrefab() {
     prefab.addPrefab(this->selection, this->layout, this->ui->lineEdit_PrefabName->text());
 }