From 9b0c9fa68de363bdd6d1e821eb57e50eaa76fc3c Mon Sep 17 00:00:00 2001
From: Samuel Fadel <samuelfadel@gmail.com>
Date: Tue, 6 Oct 2015 15:51:41 -0300
Subject: Solved issue #1 (history autoscroll).

---
 historygraph.cpp | 30 ++++++++++++++++++++++++++++--
 historygraph.h   |  4 ++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/historygraph.cpp b/historygraph.cpp
index 0aeec20..66249e5 100644
--- a/historygraph.cpp
+++ b/historygraph.cpp
@@ -126,11 +126,13 @@ HistoryGraph::HistoryGraph(QQuickItem *parent)
     : QQuickItem(parent)
     , m_firstNode(0)
     , m_currentNode(0)
+    , m_currentWidth(0.0f)
     , m_needsUpdate(false)
 {
     setClip(true);
     setFlag(QQuickItem::ItemHasContents);
     setAcceptedMouseButtons(Qt::LeftButton);
+    setAcceptHoverEvents(true);
 }
 
 HistoryGraph::~HistoryGraph()
@@ -193,7 +195,7 @@ QSGNode *HistoryGraph::createNodeTree()
     //int breadth = m_firstNode->breadth();
     //int depth   = m_firstNode->depth();
 
-    QSGNode *sceneGraphRoot = new QSGNode;
+    QSGTransformNode *sceneGraphRoot = new QSGTransformNode;
     HistoryItemNode *histNode = m_firstNode;
     float margin = height()*MARGIN;
     float padding = height()*PADDING;
@@ -234,7 +236,12 @@ QSGNode *HistoryGraph::createNodeTree()
         histNode = children[0];
     } while (true);
 
-    // setWidth(xPos + radius + margin);
+    m_currentWidth = x - 2.0f*margin;
+
+    if (m_currentWidth > width()) {
+        m_viewportTransform.setToIdentity();
+        m_viewportTransform.translate(-(m_currentWidth - width() + margin), 0);
+    }
 
     return sceneGraphRoot;
 }
@@ -274,6 +281,8 @@ QSGNode *HistoryGraph::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
         updateNodeTree(root);
     }
 
+    static_cast<QSGTransformNode *>(root->firstChild())->setMatrix(m_viewportTransform);
+
     return root;
 }
 
@@ -309,6 +318,23 @@ HistoryGraph::HistoryItemNode *HistoryGraph::nodeAt(const QPointF &pos, HistoryG
     return 0;
 }
 
+void HistoryGraph::hoverMoveEvent(QHoverEvent *event)
+{
+    if (m_currentWidth < width()) {
+        return;
+    }
+
+    const QPointF &pos = event->posF();
+    float margin = MARGIN * height();
+    float prop = (pos.x() - margin) / (width() - 2*margin);
+    float displ = m_currentWidth - width() + margin;
+
+    m_viewportTransform.setToIdentity();
+    m_viewportTransform.translate(-displ * prop, 0);
+
+    update();
+}
+
 void HistoryGraph::mousePressEvent(QMouseEvent *event)
 {
     HistoryGraph::HistoryItemNode *node = nodeAt(event->localPos());
diff --git a/historygraph.h b/historygraph.h
index 60cce94..6c5bd9a 100644
--- a/historygraph.h
+++ b/historygraph.h
@@ -2,6 +2,7 @@
 #define HISTORYGRAPH_H
 
 #include <QtQuick>
+#include <QMatrix4x4>
 #include <armadillo>
 
 class HistoryGraph : public QQuickItem
@@ -19,6 +20,7 @@ public slots:
 
 protected:
     QSGNode *updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *);
+    void hoverMoveEvent(QHoverEvent *event);
     void mousePressEvent(QMouseEvent *event);
 
 private:
@@ -32,6 +34,8 @@ private:
     void addScatterplot(QSGNode *node, const HistoryItemNode *historyItemNode, float x, float y, float w, float h);
 
     HistoryItemNode *m_firstNode, *m_currentNode;
+    QMatrix4x4 m_viewportTransform;
+    float m_currentWidth;
     bool m_needsUpdate;
 };
 
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