From e1324d901c35dd38f280b90e7637140cced39bb1 Mon Sep 17 00:00:00 2001
From: Gary Wang <wzc782970009@gmail.com>
Date: Sat, 27 Mar 2021 22:22:04 +0800
Subject: [PATCH] fix: always flip according to current viewport state

---
 app/graphicsview.cpp | 20 ++++++++------------
 app/graphicsview.h   |  2 --
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/app/graphicsview.cpp b/app/graphicsview.cpp
index a2012b9..7be7572 100644
--- a/app/graphicsview.cpp
+++ b/app/graphicsview.cpp
@@ -135,11 +135,12 @@ void GraphicsView::zoomView(qreal scaleFactor)
 
 void GraphicsView::flipView(bool horizontal)
 {
-    if (horizontal) {
-        scale(-1, 1);
-    } else {
-        scale(1, -1);
-    }
+    QTransform tf(horizontal ? -1 : 1, 0,                   0,
+                  0,                   horizontal ? 1 : -1, 0,
+                  0,                   0,                   1);
+    tf = transform() * tf;
+    setTransform(tf);
+
     // Ensure the navigation view is also flipped.
     emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), transform());
 }
@@ -179,6 +180,8 @@ inline double zeroOrOne(double number)
     return qFuzzyIsNull(number) ? 0 : (number > 0 ? 1 : -1);
 }
 
+// Note: this only works if we only have 90 degree based rotation
+//       and no shear/translate.
 QTransform GraphicsView::resetScale(const QTransform & orig)
 {
     return QTransform(zeroOrOne(orig.m11()), zeroOrOne(orig.m12()),
@@ -349,10 +352,3 @@ void GraphicsView::applyTransformationModeByScaleFactor()
         scene()->trySetTransformationMode(Qt::FastTransformation);
     }
 }
-
-void GraphicsView::resetWithScaleAndRotate(qreal scaleFactor, qreal rotateAngle)
-{
-    QGraphicsView::resetTransform();
-    scale(scaleFactor, scaleFactor);
-    rotate(rotateAngle);
-}
diff --git a/app/graphicsview.h b/app/graphicsview.h
index bdeeb4a..eb20a03 100644
--- a/app/graphicsview.h
+++ b/app/graphicsview.h
@@ -59,8 +59,6 @@ private:
     void setCheckerboardEnabled(bool enabled, bool invertColor = false);
     void applyTransformationModeByScaleFactor();
 
-    void resetWithScaleAndRotate(qreal scaleFactor, qreal rotateAngle);
-
     bool m_enableFitInView = false;
     bool m_checkerboardEnabled = false;
     bool m_isLastCheckerboardColorInverted = false;