ChartCtrl源码剖析之——CChartScrollBar类

CChartScrollBar类用来针对每个轴的数据进行滚动，将那些不在当前区域内的数据通过滚动展示出来。

CChartScrollBar类的头文件。

#pragma once

class CChartAxis;

class CChartScrollBar : public CScrollBar

{

public:

    CChartScrollBar(CChartAxis* pParentAxis);

    ~CChartScrollBar();

    void CreateScrollBar(const CRect& PlottingRect);

    void OnHScroll(UINT nSBCode, UINT nPos);

    void OnVScroll(UINT nSBCode, UINT nPos);

    void Refresh();

    void SetEnabled(bool bEnabled)  { m_bEnabled = bEnabled; }

    bool GetEnabled() const            { return m_bEnabled; }

    void SetAutoHide(bool bAutoHide)  { m_bAutoHide = bAutoHide; }

    bool GetAutoHide() const          { return m_bAutoHide; }

    void OnMouseEnter();

    void OnMouseLeave();

private:

    bool IsScrollInverted() const;

    void MoveAxisToPos(int PreviousPos, int CurPos);

    CChartAxis* m_pParentAxis;

    bool m_bEnabled;

    bool m_bAutoHide;

};

CChartScrollBar类的源文件。

#include "stdafx.h"

#include "ChartScrollBar.h"

#include "ChartAxis.h"

#include "ChartCtrl.h"

#include "math.h"

CChartScrollBar::CChartScrollBar(CChartAxis* pParentAxis)

: CScrollBar(), m_pParentAxis(pParentAxis), m_bEnabled(false),

   m_bAutoHide(true)

{

}

CChartScrollBar::~CChartScrollBar()

{

}

void CChartScrollBar::CreateScrollBar(const CRect& PlottingRect)

{

    CRect Temp = PlottingRect;

    Temp.top++; Temp.left++;

    DWORD dwStyle = SBS_HORZ | WS_CHILD;

    if (m_pParentAxis->IsHorizontal())

    {

        if (m_pParentAxis->m_bIsSecondary)

            dwStyle |= SBS_TOPALIGN;

        else

            dwStyle += SBS_BOTTOMALIGN;

    }

    else

    {

        if (m_pParentAxis->m_bIsSecondary)

            dwStyle |= SBS_VERT | SBS_RIGHTALIGN;

        else

            dwStyle += SBS_VERT | SBS_LEFTALIGN;

    }

    CScrollBar::Create(dwStyle, Temp, m_pParentAxis->m_pParent,);

    SCROLLINFO info;

    info.cbSize = sizeof(SCROLLINFO);

    info.fMask = SIF_ALL;

    info.nMin = ;

    info.nMax = ;

    info.nPage = ;

    info.nPos = ;

    CScrollBar::SetScrollInfo(&info);

}

bool CChartScrollBar::IsScrollInverted() const

{

    bool bInverted = false;

    if (m_pParentAxis->IsInverted() && m_pParentAxis->m_bIsHorizontal)

        bInverted = true;

    if (!m_pParentAxis->IsInverted() && !m_pParentAxis->m_bIsHorizontal)

        bInverted = true;

    return bInverted;

}

void CChartScrollBar::Refresh()

{

    double AxisMin=, AxisMax=;

    double SeriesMin=, SeriesMax=;

    m_pParentAxis->GetMinMax(AxisMin,AxisMax);

    m_pParentAxis->GetSeriesMinMax(SeriesMin,SeriesMax);

    double dStep = ;

    int iTotalSteps = ;

    int iCurrentStep = ;

    if (m_pParentAxis->IsLogarithmic())

    {

        // TODO: do something if the series has 0 in it

        dStep = pow(AxisMax/AxisMin,0.1);

        iTotalSteps = (int)ceil(log(SeriesMax/SeriesMin)/log(dStep));

        iCurrentStep = (int)(log(AxisMin/SeriesMin)/log(dStep));

    }

    else

    {

        dStep = (AxisMax - AxisMin) / 10.0;

        iTotalSteps = (int)ceil((SeriesMax - SeriesMin)/dStep);

        iCurrentStep = (int)(iTotalSteps * ((AxisMin - SeriesMin)/(SeriesMax-SeriesMin)));

    }

    SCROLLINFO info;

    info.cbSize = sizeof(SCROLLINFO);

    info.fMask = SIF_ALL;

    if ( (AxisMax-AxisMin) ==  || (SeriesMax-SeriesMin)== )

    {

        info.nMin = ;

        info.nMax = ;

        info.nPage = ;

        info.nPos = ;

    }

    else

    {

        info.nMin = ;

        info.nMax = iTotalSteps;

        info.nPage = ;

        info.nPos = iCurrentStep;

        if (IsScrollInverted())

            info.nPos = iTotalSteps -  - iCurrentStep;

        else

            info.nPos = iCurrentStep;

    }

    CScrollBar::SetScrollInfo(&info);

}

void CChartScrollBar::OnHScroll(UINT nSBCode, UINT nPos)

{

    int MinPos;

    int MaxPos;

    int PreviousPos = CScrollBar::GetScrollPos();

    CScrollBar::GetScrollRange(&MinPos, &MaxPos);

    int CurPos = PreviousPos;

    bool bUpdate = true;

    switch (nSBCode)

    {

    case SB_LEFT:

        CurPos = ;

        break;

    case SB_RIGHT:

        CurPos = MaxPos;

        break;

    case SB_ENDSCROLL:

        bUpdate = false;

        break;

    case SB_LINELEFT:

        if (CurPos > MinPos)

            CurPos--;

        break;

    case SB_LINERIGHT:

        if (CurPos < MaxPos-)

            CurPos++;

        break;

    case SB_PAGELEFT:

        if (CurPos > MinPos)

            CurPos = max(MinPos, CurPos - );

        break;

    case SB_PAGERIGHT:

        if (CurPos < MaxPos-)

            CurPos = min(MaxPos, CurPos + );

        break;

    case SB_THUMBPOSITION:

            CurPos = nPos;

        break;

    case SB_THUMBTRACK:

            CurPos = nPos;

        break;

    }

    if (bUpdate)

    {

        // Set the new position of the thumb (scroll box).

        CScrollBar::SetScrollPos(CurPos);

        MoveAxisToPos(PreviousPos,CurPos);

    }

}

void CChartScrollBar::OnVScroll(UINT nSBCode, UINT nPos)

{

    int MinPos;

    int MaxPos;

    int PreviousPos = CScrollBar::GetScrollPos();

    CScrollBar::GetScrollRange(&MinPos, &MaxPos);

    int CurPos = PreviousPos;

    bool bUpdate = true;

    switch (nSBCode)

    {

    case SB_BOTTOM:

        CurPos = MaxPos;

        break;

    case SB_TOP:

        CurPos = ;

        break;

    case SB_ENDSCROLL:

        bUpdate = false;

        break;

    case SB_LINEDOWN:

        if (CurPos < MaxPos-)

            CurPos++;

        break;

    case SB_LINEUP:

        if (CurPos > MinPos)

            CurPos--;

        break;

    case SB_PAGEUP:

        if (CurPos > MinPos)

            CurPos = max(MinPos, CurPos - );

        break;

    case SB_PAGEDOWN:

        if (CurPos < MaxPos-)

            CurPos = min(MaxPos, CurPos + );

        break;

    case SB_THUMBPOSITION:

        CurPos = nPos;

        break;

    case SB_THUMBTRACK:

        CurPos = nPos;

        break;

    }

    if (bUpdate)

    {

        // Set the new position of the thumb (scroll box).

        CScrollBar::SetScrollPos(CurPos);

        MoveAxisToPos(PreviousPos,CurPos);

    }

}

void CChartScrollBar::MoveAxisToPos(int PreviousPos, int CurPos)

{

    double AxisMin=, AxisMax=;

    double SeriesMin=, SeriesMax=;

    m_pParentAxis->GetMinMax(AxisMin,AxisMax);

    m_pParentAxis->GetSeriesMinMax(SeriesMin,SeriesMax);

    if (m_pParentAxis->IsLogarithmic())

    {

        double dStep = pow(AxisMax/AxisMin,0.1);

        double dFactor = pow(dStep,(CurPos - PreviousPos));

        if (IsScrollInverted())

            m_pParentAxis->SetZoomMinMax(AxisMin/dFactor,AxisMax/dFactor);

        else

            m_pParentAxis->SetZoomMinMax(AxisMin*dFactor,AxisMax*dFactor);

    }

    else

    {

        double dStep = (AxisMax - AxisMin) / 10.0;

        double dOffset = (CurPos - PreviousPos) * dStep;

        if (IsScrollInverted())

            m_pParentAxis->SetZoomMinMax(AxisMin-dOffset,AxisMax-dOffset);

        else

            m_pParentAxis->SetZoomMinMax(AxisMin+dOffset,AxisMax+dOffset);

    }

}

void CChartScrollBar::OnMouseEnter()

{

    if (m_bEnabled && m_bAutoHide)

        ShowWindow(SW_SHOW);

}

void CChartScrollBar::OnMouseLeave()

{

    if (m_bEnabled && m_bAutoHide)

        ShowWindow(SW_HIDE);

}

这份源码一开始读的时候在info.nPage产生了理解偏差，再一次读的时候又在这个地方纠结了很久，现在把这个参数的意义再捋一遍，它的英文解释如下：

nPage

Specifies the page size. A scroll bar uses this value to determine the appropriate size of the proportional scroll box.

该值表示页尺寸，同时表示比例滚动框的大小。将这个理解清楚之后，后面OnHScroll函数和OnVScroll函数里面的加减10与加减9就相对比较好理解。

巴特西

ChartCtrl源码剖析之——CChartScrollBar类

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