From 754d01b3c27d78f4cf8b4563d2eb77544a739543 Mon Sep 17 00:00:00 2001
From: laserpants <johannes@isomorphic.co>
Date: Sat, 19 Mar 2016 13:52:53 +0300
Subject: [PATCH] implement Tabs

---
 tabs.cpp | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tabs.h   | 47 +++++++++++++++++++++++++++++++
 2 files changed, 132 insertions(+)

diff --git a/tabs.cpp b/tabs.cpp
index 4aec7af..a5073d8 100644
--- a/tabs.cpp
+++ b/tabs.cpp
@@ -1 +1,86 @@
+#include <QHBoxLayout>
+#include <QPainter>
+#include <QPropertyAnimation>
 #include "tabs.h"
+#include "tab.h"
+
+Tabs::Tabs(QWidget *parent)
+    : QWidget(parent),
+      _tabLayout(new QHBoxLayout),
+      _animation(new QPropertyAnimation(this)),
+      _tab(0),
+      _tween(1)
+{
+    _animation->setPropertyName("tween");
+    _animation->setEasingCurve(QEasingCurve::OutCirc);
+    _animation->setTargetObject(this);
+    _animation->setDuration(700);
+
+    setLayout(_tabLayout);
+    _tabLayout->setSpacing(0);
+    _tabLayout->setMargin(0);
+}
+
+Tabs::~Tabs()
+{
+}
+
+void Tabs::addTab(Tab *tab)
+{
+    _tabLayout->addWidget(tab);
+    connect(tab, SIGNAL(clicked()), this, SLOT(switchActiveTab()));
+}
+
+void Tabs::paintEvent(QPaintEvent *event)
+{
+    Q_UNUSED(event)
+
+    QPainter painter(this);
+    painter.fillRect(_inkBarGeometry, Qt::black);
+}
+
+void Tabs::switchActiveTab()
+{
+    Tab *tab = static_cast<Tab *>(sender());
+    if (tab) {
+        _previousGeometry = _inkBarGeometry;
+        _tab = _tabLayout->indexOf(tab);
+        _inkBarGeometry = _tabLayout->itemAt(_tab)->geometry();
+        _animation->stop();
+        _animation->setStartValue(0);
+        _animation->setEndValue(1);
+        _animation->start();
+        emit currentChanged(_tab);
+    }
+}
+
+void Tabs::moveEvent(QMoveEvent *event)
+{
+    Q_UNUSED(event)
+
+    updateInkBar();
+}
+
+void Tabs::resizeEvent(QResizeEvent *event)
+{
+    Q_UNUSED(event)
+
+    updateInkBar();
+}
+
+void Tabs::updateInkBar()
+{
+    QLayoutItem *item = _tabLayout->itemAt(_tab);
+    if (item) {
+        const QRect &r = item->geometry();
+        const qreal s = 1-_tween;
+        if (QAbstractAnimation::Running != _animation->state()) {
+            _inkBarGeometry = QRect(r.left(), r.bottom()-3, r.width(), 4);
+        } else {
+            const qreal left = _previousGeometry.left()*s + r.left()*_tween;
+            const qreal width = _previousGeometry.width()*s + r.width()*_tween;
+            _inkBarGeometry = QRect(left, r.bottom()-3, width, 4);
+        }
+        update();
+    }
+}
diff --git a/tabs.h b/tabs.h
index e69de29..6213074 100644
--- a/tabs.h
+++ b/tabs.h
@@ -0,0 +1,47 @@
+#ifndef TABS_H
+#define TABS_H
+
+#include <QWidget>
+
+class QHBoxLayout;
+class QPropertyAnimation;
+class Tab;
+
+class Tabs : public QWidget
+{
+    Q_OBJECT
+
+    Q_PROPERTY(qreal tween WRITE setTween READ tween)
+
+public:
+    explicit Tabs(QWidget *parent = 0);
+    ~Tabs();
+
+    inline void setTween(qreal tween) { _tween = tween; updateInkBar(); }
+    inline qreal tween() const { return _tween; }
+
+    void addTab(Tab *tab);
+
+protected:
+    void paintEvent(QPaintEvent *event) Q_DECL_OVERRIDE;
+    void moveEvent(QMoveEvent *event) Q_DECL_OVERRIDE;
+    void resizeEvent(QResizeEvent *event) Q_DECL_OVERRIDE;
+
+protected slots:
+    void switchActiveTab();
+
+signals:
+    void currentChanged(int);
+
+private:
+    void updateInkBar();
+
+    QHBoxLayout        *const _tabLayout;
+    QPropertyAnimation *const _animation;
+    QRect                     _inkBarGeometry;
+    QRect                     _previousGeometry;
+    int                       _tab;
+    qreal                     _tween;
+};
+
+#endif // TABS_H