From b3e29ad4a6a21db54c3fb7bb0806b29f1b59b845 Mon Sep 17 00:00:00 2001
From: Gary Wang <wzc782970009@gmail.com>
Date: Sun, 29 Sep 2019 21:22:20 +0800
Subject: [PATCH] feat: resize window policy

---
 graphicsview.cpp | 53 +++++++++++++++++++++++++++++++++++++++++-------
 graphicsview.h   |  6 ++++++
 2 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/graphicsview.cpp b/graphicsview.cpp
index 44e5058..d028303 100644
--- a/graphicsview.cpp
+++ b/graphicsview.cpp
@@ -14,6 +14,7 @@ GraphicsView::GraphicsView(QWidget *parent)
     setDragMode(QGraphicsView::ScrollHandDrag);
     setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
     setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    setResizeAnchor(QGraphicsView::AnchorUnderMouse);
     setStyleSheet("background-color: rgba(0, 0, 0, 180);"
                   "border-radius: 3px;");
     setAcceptDrops(true);
@@ -21,7 +22,12 @@ GraphicsView::GraphicsView(QWidget *parent)
 
 void GraphicsView::showImage(const QPixmap &pixmap)
 {
+    resetTransform();
     scene()->showImage(pixmap);
+    if (!isThingSmallerThanWindowWith(transform())) {
+        m_enableFitInView = true;
+        fitInView(sceneRect(), Qt::KeepAspectRatio);
+    }
 }
 
 void GraphicsView::showText(const QString &text)
@@ -41,23 +47,19 @@ void GraphicsView::setScene(GraphicsScene *scene)
 
 void GraphicsView::mousePressEvent(QMouseEvent *event)
 {
-    QGraphicsItem *item = itemAt(event->pos());
-    if (!item) {
+    if (shouldIgnoreMousePressMoveEvent(event)) {
         event->ignore();
         // blumia: return here, or the QMouseEvent event transparency won't
         //         work if we set a QGraphicsView::ScrollHandDrag drag mode.
         return;
     }
 
-    qDebug() << item;
-
     return QGraphicsView::mousePressEvent(event);
 }
 
 void GraphicsView::mouseMoveEvent(QMouseEvent *event)
 {
-    QGraphicsItem *item = itemAt(event->pos());
-    if (!item) {
+    if (shouldIgnoreMousePressMoveEvent(event)) {
         event->ignore();
     }
 
@@ -76,13 +78,28 @@ void GraphicsView::mouseReleaseEvent(QMouseEvent *event)
 
 void GraphicsView::wheelEvent(QWheelEvent *event)
 {
-    if(event->delta() > 0) {
+    m_enableFitInView = false;
+    if (event->delta() > 0) {
         scale(1.25, 1.25);
     } else {
         scale(0.8, 0.8);
     }
 }
 
+void GraphicsView::resizeEvent(QResizeEvent *event)
+{
+    if (m_enableFitInView) {
+        if (isThingSmallerThanWindowWith(QTransform()) && transform().m11() >= 1) {
+            // no longer need to do fitInView()
+            // but we leave the m_enableFitInView value unchanged in case
+            // user resize down the window again.
+        } else {
+            fitInView(sceneRect(), Qt::KeepAspectRatio);
+        }
+    }
+    return QGraphicsView::resizeEvent(event);
+}
+
 void GraphicsView::dragEnterEvent(QDragEnterEvent *event)
 {
     if (event->mimeData()->hasUrls() || event->mimeData()->hasImage() || event->mimeData()->hasText()) {
@@ -129,5 +146,27 @@ void GraphicsView::dropEvent(QDropEvent *event)
         }
     } else if (mimeData->hasText()) {
         showText(mimeData->text());
+    } else {
+        showText("Not supported mimedata: " + mimeData->formats().first());
     }
 }
+
+bool GraphicsView::isThingSmallerThanWindowWith(const QTransform &transform) const
+{
+    return rect().size().expandedTo(transform.mapRect(sceneRect()).size().toSize())
+            == rect().size();
+}
+
+bool GraphicsView::shouldIgnoreMousePressMoveEvent(const QMouseEvent *event) const
+{
+    if (isThingSmallerThanWindowWith(transform())) {
+        return true;
+    }
+
+    QGraphicsItem *item = itemAt(event->pos());
+    if (!item) {
+        return true;
+    }
+
+    return false;
+}
diff --git a/graphicsview.h b/graphicsview.h
index 956f8ac..9da4260 100644
--- a/graphicsview.h
+++ b/graphicsview.h
@@ -20,10 +20,16 @@ private:
     void mouseMoveEvent(QMouseEvent * event) override;
     void mouseReleaseEvent(QMouseEvent * event) override;
     void wheelEvent(QWheelEvent *event) override;
+    void resizeEvent(QResizeEvent *event) override;
 
     void dragEnterEvent(QDragEnterEvent *event) override;
     void dragMoveEvent(QDragMoveEvent *event) override;
     void dropEvent(QDropEvent *event) override;
+
+    bool isThingSmallerThanWindowWith(const QTransform &transform) const;
+    bool shouldIgnoreMousePressMoveEvent(const QMouseEvent *event) const;
+
+    bool m_enableFitInView = false;
 };
 
 #endif // GRAPHICSVIEW_H