fix: always rotate according to current viewport state

app/graphicsview.cpp

@@ -133,6 +133,19 @@ void GraphicsView::zoomView(qreal scaleFactor)
     emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
 }
 
+// This is always according to user's view.
+// the direction of the rotation will NOT be clockwise because the y-axis points downwards.
+void GraphicsView::rotateView(bool clockwise)
+{
+    resetScale();
+
+    QTransform tf(0,                  clockwise ? 1 : -1, 0,
+                  clockwise ? -1 : 1, 0,                  0,
+                  0,                  0,                  1);
+    tf = transform() * tf;
+    setTransform(tf);
+}
+
 void GraphicsView::flipView(bool horizontal)
 {
     QTransform tf(horizontal ? -1 : 1, 0,                   0,
@@ -151,12 +164,6 @@ void GraphicsView::resetScale()
     emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
 }
 
-void GraphicsView::rotateView(qreal rotateAngel)
-{
-    resetScale();
-    rotate(rotateAngel);
-}
-
 void GraphicsView::fitInView(const QRectF &rect, Qt::AspectRatioMode aspectRadioMode)
 {
     QGraphicsView::fitInView(rect, aspectRadioMode);

app/graphicsview.h

@@ -26,9 +26,9 @@ public:
 
     void resetTransform();
     void zoomView(qreal scaleFactor);
+    void rotateView(bool clockwise = true);
     void flipView(bool horizontal = true);
     void resetScale();
-    void rotateView(qreal rotateAngel);
     void fitInView(const QRectF &rect, Qt::AspectRatioMode aspectRadioMode = Qt::IgnoreAspectRatio);
 
     void checkAndDoFitInView(bool markItOnAnyway = true);

app/mainwindow.cpp

@@ -119,7 +119,7 @@ MainWindow::MainWindow(QWidget *parent)
             this, &MainWindow::toggleCheckerboard);
     connect(m_bottomButtonGroup, &BottomButtonGroup::rotateRightBtnClicked,
             this, [ = ](){
-        m_graphicsView->rotateView(90);
+        m_graphicsView->rotateView();
         m_graphicsView->checkAndDoFitInView();
         m_gv->setVisible(false);
     });