implement demolish button

src/ui/GameWorldView.cpp

@@ -901,16 +901,7 @@ void GameWorldView::keyPressEvent(QKeyEvent* event)
         emit escapeMenuRequested();
         break;
     case Qt::Key_Backspace:
-        if (m_demolishMode)
-        {
-            m_demolishMode    = false;
-            m_demolishHoverId = kInvalidEntityId;
-        }
-        else
-        {
-            if (m_builderType.has_value()) { exitBuilderMode(); }
-            m_demolishMode = true;
-        }
+        toggleDemolishMode();
         break;
     default:
         QOpenGLWidget::keyPressEvent(event);
@@ -1090,12 +1081,28 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
 // Slots
 // ---------------------------------------------------------------------------
 
+void GameWorldView::toggleDemolishMode()
+{
+    if (m_demolishMode)
+    {
+        m_demolishMode    = false;
+        m_demolishHoverId = kInvalidEntityId;
+    }
+    else
+    {
+        if (m_builderType.has_value()) { exitBuilderMode(); }
+        m_demolishMode = true;
+    }
+    emit demolishModeChanged(m_demolishMode);
+}
+
 void GameWorldView::enterBuilderMode(BuildingType type)
 {
     m_builderType   = type;
     m_ghostRotation = Rotation::East;
     m_ghostValid    = false;
     m_demolishMode  = false;
+    emit demolishModeChanged(false);
 }
 
 void GameWorldView::exitBuilderMode()
@@ -1128,6 +1135,7 @@ void GameWorldView::resetForNewGame()
     m_ghostValid       = false;
     m_demolishMode     = false;
     m_demolishHoverId  = kInvalidEntityId;
+    emit demolishModeChanged(false);
     m_selectedIds.clear();
     m_boxSelecting     = false;
     m_scrollXTiles     = 0.0f;