Reduce redundant work in metatile selector

include/ui/metatileselector.h

@@ -39,6 +39,7 @@ class MetatileSelector: public SelectablePixmapItem {
         this->primaryTileset = map->layout->tileset_primary;
         this->secondaryTileset = map->layout->tileset_secondary;
         this->selection = MetatileSelection{};
+        this->cellPos = QPoint(-1, -1);
         setAcceptHoverEvents(true);
     }
     QPoint getSelectionDimensions();
@@ -68,13 +69,15 @@ class MetatileSelector: public SelectablePixmapItem {
     int externalSelectionHeight;
     QList<uint16_t> externalSelectedMetatiles;
     MetatileSelection selection;
+    QPoint cellPos;
 
     void updateSelectedMetatiles();
     void updateExternalSelectedMetatiles();
-    uint16_t getMetatileId(int x, int y);
+    uint16_t getMetatileId(int x, int y) const;
     QPoint getMetatileIdCoords(uint16_t);
-    bool shouldAcceptEvent(QGraphicsSceneMouseEvent*);
+    bool positionIsValid(const QPoint &pos) const;
     bool selectionIsValid();
+    void hoverChanged();
 
 signals:
     void hoveredMetatileSelectionChanged(uint16_t);

src/ui/metatileselector.cpp

@@ -114,41 +114,55 @@ void MetatileSelector::setPrefabSelection(MetatileSelection selection) {
     emit selectedMetatilesChanged();
 }
 
-bool MetatileSelector::shouldAcceptEvent(QGraphicsSceneMouseEvent *event) {
-    QPoint pos = this->getCellPos(event->pos());
+bool MetatileSelector::positionIsValid(const QPoint &pos) const {
     return Tileset::metatileIsValid(getMetatileId(pos.x(), pos.y()), this->primaryTileset, this->secondaryTileset);
 }
 
 void MetatileSelector::mousePressEvent(QGraphicsSceneMouseEvent *event) {
-    if (!shouldAcceptEvent(event)) return;
+    QPoint pos = this->getCellPos(event->pos());
+    if (!positionIsValid(pos))
+        return;
+
+    this->cellPos = pos;
     SelectablePixmapItem::mousePressEvent(event);
     this->updateSelectedMetatiles();
 }
 
 void MetatileSelector::mouseMoveEvent(QGraphicsSceneMouseEvent *event) {
-    if (!shouldAcceptEvent(event)) return;
+    QPoint pos = this->getCellPos(event->pos());
+    if (!positionIsValid(pos) || this->cellPos == pos)
+        return;
+
+    this->cellPos = pos;
     SelectablePixmapItem::mouseMoveEvent(event);
     this->updateSelectedMetatiles();
-
-    QPoint pos = this->getCellPos(event->pos());
-    uint16_t metatileId = this->getMetatileId(pos.x(), pos.y());
-    emit this->hoveredMetatileSelectionChanged(metatileId);
+    this->hoverChanged();
 }
 
 void MetatileSelector::mouseReleaseEvent(QGraphicsSceneMouseEvent *event) {
-    if (!shouldAcceptEvent(event)) return;
+    QPoint pos = this->getCellPos(event->pos());
+    if (!positionIsValid(pos))
+        return;
     SelectablePixmapItem::mouseReleaseEvent(event);
-    this->updateSelectedMetatiles();
 }
 
 void MetatileSelector::hoverMoveEvent(QGraphicsSceneHoverEvent *event) {
     QPoint pos = this->getCellPos(event->pos());
-    uint16_t metatileId = this->getMetatileId(pos.x(), pos.y());
+    if (!positionIsValid(pos) || this->cellPos == pos)
+        return;
+
+    this->cellPos = pos;
+    this->hoverChanged();
+}
+
+void MetatileSelector::hoverChanged() {
+    uint16_t metatileId = this->getMetatileId(this->cellPos.x(), this->cellPos.y());
     emit this->hoveredMetatileSelectionChanged(metatileId);
 }
 
 void MetatileSelector::hoverLeaveEvent(QGraphicsSceneHoverEvent*) {
     emit this->hoveredMetatileSelectionCleared();
+    this->cellPos = QPoint(-1, -1);
 }
 
 void MetatileSelector::updateSelectedMetatiles() {
@@ -182,7 +196,7 @@ void MetatileSelector::updateExternalSelectedMetatiles() {
     emit selectedMetatilesChanged();
 }
 
-uint16_t MetatileSelector::getMetatileId(int x, int y) {
+uint16_t MetatileSelector::getMetatileId(int x, int y) const {
     int index = y * this->numMetatilesWide + x;
     if (index < this->primaryTileset->metatiles.length()) {
         return static_cast<uint16_t>(index);