feat: remove checkerboard icon and change bottom toolbar

app/actionmanager.cpp

@@ -74,7 +74,7 @@ void ActionManager::setupAction(MainWindow *mainWindow)
     CREATE_NEW_ICON_ACTION(mainWindow, actionRotateCounterClockwise, app-icon);
 
     CREATE_NEW_ACTION(mainWindow, actionToggleAvoidResetTransform);
-    CREATE_NEW_ICON_ACTION(mainWindow, actionToggleCheckerboard, view-background-checkerboard);
+    CREATE_NEW_ACTION(mainWindow, actionToggleCheckerboard);
     CREATE_NEW_ACTION(mainWindow, actionTogglePauseAnimation);
     CREATE_NEW_ACTION(mainWindow, actionAnimationNextFrame);
 

app/graphicsview.cpp

@@ -224,7 +224,18 @@ void GraphicsView::fitByOrientation(Qt::Orientation ori, bool scaleDownOnly)
     QRectF originalScene = sceneRect();
     QTransform currentTransform = transform();
     
-    // TODO: May be optimized by matrix arithmetic operation?
+    // TODO: 
+    // I guess following code may be optimized by matrix arithmetic operation.
+    // There is an AI given solution. But I didn't use it.
+    // Because I want to keep the same behavior of upstream.
+
+    // // Horizontal fit: Let the position of top center of viewport, (cx, 0), be inversely mapped to scene.
+    // // And compensate the behavior of `centerOn` which put given point to the center of viewport.
+    // QTransform inv = currentTransform.inverted();
+    // QPointF viewCx = viewport()->rect().center().x();
+    // QPointF viewCy = viewport()->rect().center().y();
+    // // The target is viewport top center. Its y=0, so `centerOn` required scene point is (viewCx, -viewCy).
+    // centerOn(inv.map(QPointF(viewCx, -viewCy)));
 
     if (ori == Qt::Horizontal) {
         // For horizontal fit (fit by width), position at top (for tall images)

app/mainwindow.cpp

@@ -101,7 +101,7 @@ MainWindow::MainWindow(QWidget *parent)
         m_am->actionRotateCounterClockwise,
         m_am->actionRotateClockwise,
         m_am->actionFlipHorizontal,
-        m_am->actionToggleCheckerboard,
+        m_am->actionFlipVertical,
     });
     // Setup right click menus
     {