From 7becab88ae5287846299f22d291ccd44740fddbc Mon Sep 17 00:00:00 2001
From: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Date: Fri, 5 Apr 2019 17:36:11 +0200
Subject: Implement standard zoom handling by mouse wheel and keys.

Suggested by Ales Kapica.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
---
 qtmips_gui/graphicsview.cpp | 46 +++++++++++++++++++++++++++++++++++++++++----
 qtmips_gui/graphicsview.h   | 11 ++++++++++-
 2 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/qtmips_gui/graphicsview.cpp b/qtmips_gui/graphicsview.cpp
index 6dc679d..88a8c6e 100644
--- a/qtmips_gui/graphicsview.cpp
+++ b/qtmips_gui/graphicsview.cpp
@@ -35,18 +35,21 @@
 
 #include "graphicsview.h"
 
-GraphicsView::GraphicsView(QWidget *parent) : QGraphicsView(parent) {
+GraphicsView::GraphicsView(QWidget *parent) : Super(parent) {
+    prev_height = 0;
+    prev_width = 0;
     setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
 }
 
 void GraphicsView::setScene(QGraphicsScene *scene) {
-    QGraphicsView::setScene(scene);
+    Super::setScene(scene);
     update_scale();
 }
 
 void GraphicsView::resizeEvent(QResizeEvent *event) {
-    QGraphicsView::resizeEvent(event);
-    update_scale();
+    Super::resizeEvent(event);
+    if ((width() != prev_height) || (height() != prev_width))
+        update_scale();
 }
 
 void GraphicsView::update_scale() {
@@ -56,6 +59,8 @@ void GraphicsView::update_scale() {
     // Note: there is somehow three pixels error when viewing so we have to always compensate
     const int w = scene()->width() + 3;
     const int h = scene()->height() + 3;
+    prev_height = width();
+    prev_width = height();
 
     qreal scale = 1;
     if (height() > h && width() > w) {
@@ -69,3 +74,36 @@ void GraphicsView::update_scale() {
     t.scale(scale, scale);
     setTransform(t, false);
 }
+
+void GraphicsView::wheelEvent(QWheelEvent *event) {
+    if (event->modifiers() & Qt::ControlModifier) {
+        // zoom
+        const ViewportAnchor anchor = transformationAnchor();
+        setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
+        int angle = event->angleDelta().y();
+        qreal factor;
+        if (angle > 0) {
+            factor = 1.1;
+        } else {
+            factor = 0.9;
+        }
+        scale(factor, factor);
+        setTransformationAnchor(anchor);
+    } else {
+        Super::wheelEvent(event);
+    }
+}
+
+void GraphicsView::keyPressEvent(QKeyEvent *event) {
+    qreal factor = 1.1;
+    if (event->matches(QKeySequence::ZoomIn) ||
+        (event->key() == Qt::Key_Equal) ||
+        (event->key() == Qt::Key_Plus)) {
+        scale(factor, factor);
+    } else if (event->matches(QKeySequence::ZoomOut) ||
+               (event->key() == Qt::Key_Minus)) {
+        scale(1 / factor, 1 / factor);
+    } else {
+        Super::keyPressEvent(event);
+    }
+}
diff --git a/qtmips_gui/graphicsview.h b/qtmips_gui/graphicsview.h
index 8b47611..b970e86 100644
--- a/qtmips_gui/graphicsview.h
+++ b/qtmips_gui/graphicsview.h
@@ -38,18 +38,27 @@
 
 #include <QGraphicsView>
 #include <QGraphicsScene>
+#include <QWheelEvent>
+#include <QResizeEvent>
+#include <QKeyEvent>
 
 class GraphicsView : public QGraphicsView {
+    Q_OBJECT
+    using Super = QGraphicsView;
+
 public:
     GraphicsView(QWidget *parent);
-
     void setScene(QGraphicsScene *scene);
 
 protected:
     void resizeEvent(QResizeEvent *event);
+    void wheelEvent(QWheelEvent *event) override;
+    void keyPressEvent(QKeyEvent *event) override;
 
 private:
     void update_scale();
+    int prev_height;
+    int prev_width;
 };
 
 #endif // GRAPHICSVIEW_H
-- 
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