PlotSettings::PlotSettings(): minX(-50.), minY(-4.), maxX(50.), maxY(45.)
{
    numXTicks = 8;
    numYTicks = 8;
}

/// Увеличение/уменьшение значения minX, maxX, minY, maxY на интервал между 2-мя отметками
void PlotSettings::scroll(double dx, double dy)
{
    double stepX = spanX() / numXTicks;
    minX += dx * stepX;
    maxX += dx * stepX;

    double stepY = spanY() / numYTicks;
    minY += dy * stepY;
    maxY += dy * stepY;

    adjust();
}

/// Увеличение/уменьшение значения minX, maxX, minY, maxY на интервал между 2-мя отметками
void PlotSettings::scale(double delta_x, double delta_y)
{
    if((minX == maxX || minY == maxY) && delta_x < 0 && delta_y < 0) return;

    double stepX = spanX() / numXTicks;
    minX -= delta_x * stepX;
    maxX += delta_x * stepX;

    double stepY = spanY() / numYTicks;
    minY -= delta_y * stepY;
    maxY += delta_y * stepY;
}

/// Округление значений minX, minY, maxX, maxY
void PlotSettings::adjust()
{
    adjustAxis(minX, maxX, numXTicks);
    adjustAxis(minY, maxY, numYTicks);
}

/// Округление значений заданной точки point
void PlotSettings::adjust(QPointF& point)
{
    double mn_x = minX, mn_y = minY;
    int ticks_x = numXTicks, ticks_y = numYTicks;
    double mx_x = point.x(), mx_y = point.y();

    adjustAxis(mn_x, mx_x, ticks_x);
    adjustAxis(mn_y, mx_y, ticks_y);

    point.setX(mx_x);
    point.setY(mx_y);
}

/// Преобразование параметров в удобные значения
void PlotSettings::adjustAxis(double& min, double&  max, int& numTicks)
{
    const int MinTicks = 5;
    double grossStep = (max - min) / MinTicks;
    double step = pow(10.0, floor(log10(grossStep)));

    if(5 * step < grossStep)
        step *= 5;
    else if(2 * step < grossStep)
        step *= 2;

    numTicks = int(ceil(max / step) - floor(min / step));        
    if(numTicks < MinTicks)
        numTicks = MinTicks;

    min = floor(min / step) * step;
    max = ceil(max / step) * step;
}

#ifndef GRAPHICWIDGET_H
#define GRAPHICWIDGET_H

#include "ui_GraphicWidget.h"
#include "PlotSettings.h"

#include <QtGui/QWidget>

class QPaintEvent;
class QPainter;

/// Виджет, где будет отрисовываться график
class GraphicWidget: public QWidget, public Ui::GraphicWidgetClass
{
    Q_OBJECT

private:
    PlotSettings settings;        ///< настройка для различных масштабов

private:
    void drawGrid(QPainter *painter);

protected:
    void paintEvent(QPaintEvent* event);

public:
    GraphicWidget(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~GraphicWidget();
    void setPlotSettings(const PlotSettings& sts) { settings = sts; settings.adjust(); update(); }
};

#endif // GRAPHICWIDGET_H

#include "GraphicWidget.h"

#include <QPainter>
#include <QRect>
#include <QString>
#include <algorithm>
using namespace std;

GraphicWidget::GraphicWidget(QWidget *parent, Qt::WFlags flags): QWidget(parent, flags)
{
    setupUi(this);

    /// Инициализация необходимых параметров
    setPlotSettings(PlotSettings());
}

GraphicWidget::~GraphicWidget()
{}

/// Отрисовка сетки
void GraphicWidget::drawGrid(QPainter *painter)
{
    QRect rect(graphWidget -> rect());
    if(!rect.isValid()) return;
    
    QRect boundString;    
    double great_max = max(settings.numXTicks, settings.numYTicks) + 1;
    for(register int i=0, j=0, k=0; i<=great_max; ++i, ++j, ++k)
    {
        if(j <= settings.numXTicks)                ///< отрисовка вдоль оси X
        {
            int x = rect.left() + (j * (rect.width() - 1) / settings.numXTicks);
            double label = settings.minX + (j * settings.spanX() / settings.numXTicks);
            QString s_label(QString::number(label, 'f', 3));

            painter -> setPen(Qt::black);
            painter -> drawLine(x, rect.top(), x, rect.bottom());

            int flags = Qt::AlignHCenter | Qt::AlignTop;
            boundString = painter -> boundingRect(boundString, flags, s_label);    
            painter -> drawText(x - (boundString.width() + 5), rect.bottom() - (boundString.height() + 5), 
                            boundString.width(), boundString.height(), flags, s_label);
        }
        if(k <= settings.numYTicks)                ///< отрисовка вдоль оси Y
        {
            int y = rect.bottom() - (k * (rect.height() - 1) / settings.numYTicks);
            double label = settings.minY + (k * settings.spanY() / settings.numYTicks);
            QString s_label(QString::number(label, 'f', 3));

            painter -> setPen(Qt::black);
            painter -> drawLine(rect.left(), y, rect.right(), y);

            int flags = Qt::AlignRight | Qt::AlignTop;
            boundString = painter -> boundingRect(boundString, flags, s_label);    
            painter -> drawText(rect.left() + 7, y - boundString.height(),
                                boundString.width(), boundString.height(), flags, s_label);
        }
    }
    painter -> drawRect(rect.adjusted(0, 0, -1, -1));
}

/// Отрисовка графика
void GraphicWidget::paintEvent(QPaintEvent* event)
{
    QPainter painter(this);
    drawGrid(&painter);

    QWidget::paintEvent(event);
}

#include <QRubberBand>
#include <QKeyEvent>
#include <QWheelEvent>
#include <QMouseEvent>


/// Отрисовка графика
void GraphicWidget::paintEvent(QPaintEvent* events)
{
    QPainter painter(this);
    drawGrid(&painter);

    QWidget::paintEvent(events);
}

/// Нажатие на кнопки клавиатуры
void GraphicWidget::keyPressEvent(QKeyEvent* events)
{
    switch(events -> key())
    {
    case Qt::Key_Plus:
        zoom(-1.0);
    break;
    case Qt::Key_Minus:
        zoom(1.0);
    break;
    case Qt::Key_Left:
        settings.scroll(-1.0, 0.0);
        update();
    break;
    case Qt::Key_Right:
        settings.scroll(1.0, 0.0);
        update();
    break;
    case Qt::Key_Up:
        settings.scroll(0.0, 1.0);
        update();
    break;
    case Qt::Key_Down:
        settings.scroll(0.0, -1.0);
        update();
    break;
    case Qt::Key_X:
        if(events -> modifiers() & Qt::ALT) close();
    break;
    case Qt::Key_Return:
        if(events -> modifiers() & Qt::ALT)
        {
            if(!isMaximized()) showMaximized();
            else showNormal();
        }
    break;
    default:
        QWidget::keyPressEvent(events);
    }
}

/// Изменение масштаба при движении колесика
void GraphicWidget::wheelEvent(QWheelEvent* events)
{
    int numDegrees = events -> delta() / 8;
    double numTicks = numDegrees / 15.0;
    
    zoom(numTicks);
    update();
}

/// Нажатие на кнопку - изменение масштаба
void GraphicWidget::mousePressEvent(QMouseEvent* events)
{
    QWidget::mousePressEvent(events);

    QRect r;
    switch(events -> button())
    {
    case Qt::LeftButton:                ///< если нажата левая кнопка мыши
        origin = events -> pos();
        rubberBandIsShown = true;
        setCursor(Qt::CrossCursor);
        r = QRect(origin, QSize());
        rubber -> setGeometry(r);
        rubber -> show();
    break;
    case Qt::RightButton:                ///< если нажата правая кнопка мыши
    break;
    default:
    break;
    }
}

/// Переопределение функции передвижения мыши
void GraphicWidget::mouseMoveEvent(QMouseEvent* events)
{
    if(rubberBandIsShown)
    {
        rubber -> setWindowOpacity(0.0);
        rubber -> setGeometry(QRect(origin, events -> pos()).normalized());
    }

    update();
}

/// Возвращение прежнего вида курсору и изменение масштаба
void GraphicWidget::mouseReleaseEvent(QMouseEvent* events)
{
    if(events -> button() == Qt::LeftButton && rubberBandIsShown)
    {
        rubberBandIsShown = false;
        unsetCursor();
        
        QRect rect = rubber -> geometry().normalized();
        if(rect.width() < 10 || rect.height() < 10)
        {
            double dx = rect.width() / settings.spanX();
            double dy = rect.height() / settings.spanY();
            settings.scroll(dx, dy);

            update();
            return;
        }
        PlotSettings prevSettings = settings;

        double dx = prevSettings.spanX() / width();
        double dy = prevSettings.spanY() / height();
        settings.minX = prevSettings.minX + dx * rect.left();
        settings.maxX = prevSettings.minX + dx * rect.right();
        settings.minY = prevSettings.maxY - dy * rect.bottom();
        settings.maxY = prevSettings.maxY - dy * rect.top();
        settings.adjust();

        rubber -> hide();
        update();
    }
}

#ifndef PLOTSETTINGS_H
#define PLOTSETTINGS_H

#include <QPointF>
#include <cmath>

/// Àáñòðàêòíûé êëàññ äëÿ çàäàíèÿ äèàïàçîíà çíà÷åíèé ïî îñÿì x è y
class PlotSettings
{
public:
    double minX;                        ///< ìèíèìàëüíîå çíà÷åíèå ïî îñè àáñöèññ
    double maxX;                        ///< ìàêñèìàëüíîå çíà÷åíèå ïî îñè àáñöèññ
    int numXTicks;                        ///< êîëè÷åñòâî äåëåíèé íà îñè àáñöèññ
    double minY;                        ///< ìèíèìàëüíîå çíà÷åíèå ïî îñè îðäèíàò
    double maxY;                        ///< ìàêñèìàëüíîå çíà÷åíèå ïî îñè îðäèíàò
    int numYTicks;                        ///< êîëè÷åñòâî äåëåíèé íà îñè îðäèíàò

protected:
    void adjustAxis(double& min, double& max, int& numTicks);

public:
    PlotSettings();
    void scroll(double dx, double dy);
    void scale(double delta_x, double delta_y);
    void adjust();
    void adjust(QPointF& point);
    double spanX() const { return fabs(maxX - minX); }
    double spanY() const { return fabs(maxY - minY); }
};

#endif


#include "PlotSettings.h"

PlotSettings::PlotSettings(): minX(-50.), minY(-4.), maxX(50.), maxY(45.)
{
    numXTicks = 8;
    numYTicks = 8;
}

/// Óâåëè÷åíèå/óìåíüøåíèå çíà÷åíèÿ minX, maxX, minY, maxY íà èíòåðâàë ìåæäó 2-ìÿ îòìåòêàìè
void PlotSettings::scroll(double dx, double dy)
{
    double stepX = spanX() / numXTicks;
    minX += dx * stepX;
    maxX += dx * stepX;

    double stepY = spanY() / numYTicks;
    minY += dy * stepY;
    maxY += dy * stepY;

    adjust();
}

/// Óâåëè÷åíèå/óìåíüøåíèå çíà÷åíèÿ minX, maxX, minY, maxY íà èíòåðâàë ìåæäó 2-ìÿ îòìåòêàìè
void PlotSettings::scale(double delta_x, double delta_y)
{
    if((minX == maxX || minY == maxY) && delta_x < 0 && delta_y < 0) return;

    double stepX = spanX() / numXTicks;
    minX -= delta_x * stepX;
    maxX += delta_x * stepX;

    double stepY = spanY() / numYTicks;
    minY -= delta_y * stepY;
    maxY += delta_y * stepY;
}

/// Îêðóãëåíèå çíà÷åíèé minX, minY, maxX, maxY
void PlotSettings::adjust()
{
    adjustAxis(minX, maxX, numXTicks);
    adjustAxis(minY, maxY, numYTicks);
}

/// Îêðóãëåíèå çíà÷åíèé çàäàííîé òî÷êè point
void PlotSettings::adjust(QPointF& point)
{
    double mn_x = minX, mn_y = minY;
    int ticks_x = numXTicks, ticks_y = numYTicks;
    double mx_x = point.x(), mx_y = point.y();

    adjustAxis(mn_x, mx_x, ticks_x);
    adjustAxis(mn_y, mx_y, ticks_y);

    point.setX(mx_x);
    point.setY(mx_y);
}

/// Ïðåîáðàçîâàíèå ïàðàìåòðîâ â óäîáíûå çíà÷åíèÿ
void PlotSettings::adjustAxis(double& min, double&  max, int& numTicks)
{
    const int MinTicks = 5;
    double grossStep = (max - min) / MinTicks;
    double step = pow(10.0, floor(log10(grossStep)));

    if(5 * step < grossStep)
        step *= 5;
    else if(2 * step < grossStep)
        step *= 2;

    numTicks = int(ceil(max / step) - floor(min / step));        
    if(numTicks < MinTicks)
        numTicks = MinTicks;

    min = floor(min / step) * step;
    max = ceil(max / step) * step;
}


#ifndef GRAPHICWIDGET_H
#define GRAPHICWIDGET_H

#include "ui_GraphicWidget.h"
#include "PlotSettings.h"

#include <QtGui/QWidget>
#include <QPoint>

class QPaintEvent;
class QPainter;
class QRubberBand;
class QKeyEvent;
class QResizeEvent;
class QCloseEvent;
class QShowEvent;
class QWheelEvent;
class QMouseEvent;

/// Âèäæåò, ãäå áóäåò îòðèñîâûâàòüñÿ ãðàôèê
class GraphicWidget: public QWidget, public Ui::GraphicWidgetClass
{
    Q_OBJECT

private:
    PlotSettings settings;        ///< íàñòðîéêà äëÿ ðàçëè÷íûõ ìàñøòàáîâ
    QRubberBand* rubber;        ///< "ðåçèíîâàÿ ëåíòà"
    bool rubberBandIsShown;        ///< ôëàæîê ïîïàäàíèÿ êóðñîðà â "ðåçèíîâóþ ëåíòó"
    QPoint origin;                ///< íà÷àëüíûå êîîðäèíàòû âûäåëÿåìîé îáëàñòè
    QVector<QPointF> curve_vec;    ///< âåêòîð òî÷åê êðèâîé

private:
    void drawGrid(QPainter *painter);
    void drawCurves(QPainter* painter);
    QPointF initXY(double sx, double sy);
    void initCurves();

protected:
    void paintEvent(QPaintEvent* events);
    void keyPressEvent(QKeyEvent* events);
    void wheelEvent(QWheelEvent* events);
    void mousePressEvent(QMouseEvent* events);
    void mouseMoveEvent(QMouseEvent* events);
    void mouseReleaseEvent(QMouseEvent* events);
    void resizeEvent(QResizeEvent* events) { QWidget::resizeEvent(events); update(); }
    void closeEvent(QCloseEvent* events) { QWidget::closeEvent(events); }
    void showEvent(QShowEvent* events) { QWidget::showEvent(events); }

public:
    GraphicWidget(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~GraphicWidget();
    void setPlotSettings(const PlotSettings& sts) { settings = sts; settings.adjust(); update(); }
    void zoom(double delta) { settings.scale(delta, delta); settings.adjust(); update(); }
};

#endif // GRAPHICWIDGET_H


#include "GraphicWidget.h"

#include <QPainter>
#include <QRect>
#include <QString>
#include <QRubberBand>
#include <QKeyEvent>
#include <QWheelEvent>
#include <QMouseEvent>
#include <algorithm>
using namespace std;

GraphicWidget::GraphicWidget(QWidget *parent, Qt::WFlags flags): QWidget(parent, flags), rubberBandIsShown(false),
                rubber(new QRubberBand(QRubberBand::Rectangle, this))
{
    setupUi(this);

    /// Èíèöèàëèçàöèÿ íåîáõîäèìûõ ïàðàìåòðîâ
    setPlotSettings(PlotSettings());

    initCurves();
}

GraphicWidget::~GraphicWidget()
{}

/// Çàïîëíåíèÿ âåêòîðà ñ êðèâîé (êðèâàÿ y(x) = x)
void GraphicWidget::initCurves()
{
    curve_vec.append(QPointF(-100., -100.));
    curve_vec.append(QPointF(-10., -10.));
    curve_vec.append(QPointF(-1., -1.));
    curve_vec.append(QPointF(0., 0.));
    curve_vec.append(QPointF(1., 1.));
    curve_vec.append(QPointF(1.5, 1.5));
    curve_vec.append(QPointF(5., 5.));
    curve_vec.append(QPointF(10., 10.));
    curve_vec.append(QPointF(100., 100.));
}

/// Îòðèñîâêà ñåòêè
void GraphicWidget::drawGrid(QPainter *painter)
{
    QRect rect(graphWidget -> rect());
    if(!rect.isValid()) return;
    
    QRect boundString;    
    double great_max = max(settings.numXTicks, settings.numYTicks) + 1;
    for(register int i=0, j=0, k=0; i<=great_max; ++i, ++j, ++k)
    {
        if(j <= settings.numXTicks)                ///< îòðèñîâêà âäîëü îñè X
        {
            int x = rect.left() + (j * (rect.width() - 1) / settings.numXTicks);
            double label = settings.minX + (j * settings.spanX() / settings.numXTicks);
            QString s_label(QString::number(label, 'f', 3));

            painter -> setPen(Qt::black);
            painter -> drawLine(x, rect.top(), x, rect.bottom());

            int flags = Qt::AlignHCenter | Qt::AlignTop;
            boundString = painter -> boundingRect(boundString, flags, s_label);    
            painter -> drawText(x - (boundString.width() + 5), rect.bottom() - (boundString.height() + 5), 
                            boundString.width(), boundString.height(), flags, s_label);
        }
        if(k <= settings.numYTicks)                ///< îòðèñîâêà âäîëü îñè Y
        {
            int y = rect.bottom() - (k * (rect.height() - 1) / settings.numYTicks);
            double label = settings.minY + (k * settings.spanY() / settings.numYTicks);
            QString s_label(QString::number(label, 'f', 3));

            painter -> setPen(Qt::black);
            painter -> drawLine(rect.left(), y, rect.right(), y);

            int flags = Qt::AlignRight | Qt::AlignTop;
            boundString = painter -> boundingRect(boundString, flags, s_label);    
            painter -> drawText(rect.left() + 7, y - boundString.height(),
                                boundString.width(), boundString.height(), flags, s_label);
        }
    }
    painter -> drawRect(rect.adjusted(0, 0, -1, -1));
}

/// Èíèöèàëèçàöèÿ êîîðäèíàò - ïðåîáðàçîâàíèå èç êîîðäèíàò ãðàôèêà (sx,sy) â ýêðàííûå (x,y)
QPointF GraphicWidget::initXY(double sx, double sy)
{
    QRect rect(graphWidget -> rect());
    double dx, dy;

    /// Âû÷èñëåíèå ñìåùåíèé âäîëü îñåé
    dx = sx - settings.maxX;
    dy = sy - settings.minY;

    /// Âû÷èñëåíèå ýêðàííûõ êîîðäèíàò
    double x = rect.right() + (dx * (rect.width() - 1) / settings.spanX());
    double y = rect.bottom() - (dy * (rect.height() - 1) / settings.spanY());

    return QPointF(x, y);
}

/// Îòðèñîâêà ãðàôèêà
void GraphicWidget::drawCurves(QPainter* painter)
{
    painter -> setPen(Qt::blue);
    QPolygonF polyline(curve_vec.size());
    for(register int i=0; i<curve_vec.size(); ++i)
        polyline[i] = initXY(curve_vec[i].x(), curve_vec[i].y());
    painter -> drawPolyline(polyline);
}

/// Îòðèñîâêà ãðàôèêà
void GraphicWidget::paintEvent(QPaintEvent* events)
{
    QPainter painter(this);
    drawGrid(&painter);
    drawCurves(&painter);

    QWidget::paintEvent(events);
}

/// Íàæàòèå íà êíîïêè êëàâèàòóðû
void GraphicWidget::keyPressEvent(QKeyEvent* events)
{
    switch(events -> key())
    {
    case Qt::Key_Plus:
        zoom(-1.0);
    break;
    case Qt::Key_Minus:
        zoom(1.0);
    break;
    case Qt::Key_Left:
        settings.scroll(-1.0, 0.0);
        update();
    break;
    case Qt::Key_Right:
        settings.scroll(1.0, 0.0);
        update();
    break;
    case Qt::Key_Up:
        settings.scroll(0.0, 1.0);
        update();
    break;
    case Qt::Key_Down:
        settings.scroll(0.0, -1.0);
        update();
    break;
    case Qt::Key_X:
        if(events -> modifiers() & Qt::ALT) close();
    break;
    case Qt::Key_Return:
        if(events -> modifiers() & Qt::ALT)
        {
            if(!isMaximized()) showMaximized();
            else showNormal();
        }
    break;
    default:
        QWidget::keyPressEvent(events);
    }
}

/// Èçìåíåíèå ìàñøòàáà ïðè äâèæåíèè êîëåñèêà
void GraphicWidget::wheelEvent(QWheelEvent* events)
{
    int numDegrees = events -> delta() / 8;
    double numTicks = numDegrees / 15.0;
    
    zoom(numTicks);
    update();
}

/// Íàæàòèå íà êíîïêó - èçìåíåíèå ìàñøòàáà
void GraphicWidget::mousePressEvent(QMouseEvent* events)
{
    QWidget::mousePressEvent(events);

    QRect r;
    switch(events -> button())
    {
    case Qt::LeftButton:                ///< åñëè íàæàòà ëåâàÿ êíîïêà ìûøè
        origin = events -> pos();
        rubberBandIsShown = true;
        setCursor(Qt::CrossCursor);
        r = QRect(origin, QSize());
        rubber -> setGeometry(r);
        rubber -> show();
    break;
    case Qt::RightButton:                ///< åñëè íàæàòà ïðàâàÿ êíîïêà ìûøè
    break;
    default:
    break;
    }
}

/// Ïåðåîïðåäåëåíèå ôóíêöèè ïåðåäâèæåíèÿ ìûøè
void GraphicWidget::mouseMoveEvent(QMouseEvent* events)
{
    if(rubberBandIsShown)
    {
        rubber -> setWindowOpacity(0.0);
        rubber -> setGeometry(QRect(origin, events -> pos()).normalized());
    }

    update();
}

/// Âîçâðàùåíèå ïðåæíåãî âèäà êóðñîðó è èçìåíåíèå ìàñøòàáà
void GraphicWidget::mouseReleaseEvent(QMouseEvent* events)
{
    if(events -> button() == Qt::LeftButton && rubberBandIsShown)
    {
        rubberBandIsShown = false;
        unsetCursor();
        
        QRect rect = rubber -> geometry().normalized();
        if(rect.width() < 10 || rect.height() < 10)
        {
            double dx = rect.width() / settings.spanX();
            double dy = rect.height() / settings.spanY();
            settings.scroll(dx, dy);

            update();
            return;
        }
        PlotSettings prevSettings = settings;

        double dx = prevSettings.spanX() / width();
        double dy = prevSettings.spanY() / height();
        settings.minX = prevSettings.minX + dx * rect.left();
        settings.maxX = prevSettings.minX + dx * rect.right();
        settings.minY = prevSettings.maxY - dy * rect.bottom();
        settings.maxY = prevSettings.maxY - dy * rect.top();
        settings.adjust();

        rubber -> hide();
        update();
    }
}