Fixed handling of Shift modifiers in Bucket and Shape Fill tools

While handling the key press event, QApplication::keyboardModifiers()
does not appear to be updated yet.

It may be related to catching the key event in an event filter, but the
behavior appears to have changed in some Qt version since I'm sure this
has worked before.

Closes #2883

src/tiled/bucketfilltool.cpp

@@ -71,7 +71,7 @@ void BucketFillTool::tilePositionChanged(QPoint tilePos)
     if (!tileLayer)
         return;
 
-    bool shiftPressed = QApplication::keyboardModifiers() & Qt::ShiftModifier;
+    bool shiftPressed = mModifiers & Qt::ShiftModifier;
     bool fillRegionChanged = false;
 
     TilePainter regionComputer(mapDocument(), tileLayer);
@@ -165,8 +165,10 @@ void BucketFillTool::mousePressed(QGraphicsSceneMouseEvent *event)
     mapDocument()->undoStack()->endMacro();
 }
 
-void BucketFillTool::modifiersChanged(Qt::KeyboardModifiers)
+void BucketFillTool::modifiersChanged(Qt::KeyboardModifiers modifiers)
 {
+    mModifiers = modifiers;
+
     // Don't need to recalculate fill region if there was no fill region
     if (!mPreviewMap)
         return;

src/tiled/bucketfilltool.h

@@ -58,6 +58,7 @@ class BucketFillTool : public AbstractTileFillTool
 private:
     void clearOverlay();
 
+    Qt::KeyboardModifiers mModifiers;
     bool mLastShiftStatus;
 
     /**

src/tiled/shapefilltool.cpp

@@ -119,8 +119,10 @@ void ShapeFillTool::mouseReleased(QGraphicsSceneMouseEvent *event)
     }
 }
 
-void ShapeFillTool::modifiersChanged(Qt::KeyboardModifiers)
+void ShapeFillTool::modifiersChanged(Qt::KeyboardModifiers modifiers)
 {
+    mModifiers = modifiers;
+
     if (mToolBehavior == MakingShape)
         updateFillOverlay();
 }
@@ -179,7 +181,7 @@ void ShapeFillTool::updateFillOverlay()
     int dx = tilePosition().x() - mStartCorner.x();
     int dy = tilePosition().y() - mStartCorner.y();
 
-    if (QApplication::keyboardModifiers() & Qt::ShiftModifier) {
+    if (mModifiers & Qt::ShiftModifier) {
         const int min = std::min(std::abs(dx), std::abs(dy));
         dx = ((dx > 0) - (dx < 0)) * min;
         dy = ((dy > 0) - (dy < 0)) * min;

src/tiled/shapefilltool.h

@@ -59,6 +59,7 @@ class ShapeFillTool : public AbstractTileFillTool
         Circle  // making a circle
     };
 
+    Qt::KeyboardModifiers mModifiers;
     ToolBehavior mToolBehavior;
     Shape mCurrentShape;
     QPoint mStartCorner;