第11章 GUI Page411~420 步骤五 支持其他图形

运行效果：

源代码

//item_i.hpp 抽象“图形元素”接口定义
#ifndef ITEM_I_HPP_INCLUDED
#define ITEM_I_HPP_INCLUDED

#include <wx/gdicmn.h>
#include <wx/dc.h>

class IItem
{
public:
    //作为接口，记得要有虚析构
    virtual ~IItem()
    {

    }

    //使用DC画出自己
    //注意：“画”的方法不应该修改对象的数据
    virtual void Draw(wxDC& dc) const = 0; //纯虚函数

    //开始在某一点上绘图
    virtual void OnDrawStart(wxPoint const& point) = 0; //纯虚函数
    //结束在某一点
    virtual void OnDrawEnd(wxPoint const& point) = 0; //纯虚函数
};

#endif // ITEM_I_HPP_INCLUDED

//item_line.hpp 修改现有的LineItem类，实现IItem接口

#ifndef ITEM_LINE_HPP_INCLUDED
#define ITEM_LINE_HPP_INCLUDED

#include "item_i.hpp"

class LineItem : public IItem
{
public:
    LineItem()
        : _startPosition(0, 0), _endPosition(0, 0)
    {

    }

    virtual void Draw(wxDC& dc) const;

//    virtual void OnDrawStart(wxPoint const& point) //书上写法
    void OnDrawStart(wxPoint const& point) override //C++11
    {
        _startPosition = point;
    }

    virtual void OnDrawEnd(wxPoint const& point) //写不写virtual不影响
    {
        _endPosition = point;
    }


private:
    //不写Logic后缀，但仍然是存储逻辑坐标
    wxPoint _startPosition, _endPosition;
};

#endif // ITEM_LINE_HPP_INCLUDED

//item_line.cpp
#include "item_line.hpp"

void LineItem::Draw(wxDC& dc) const
{
    dc.DrawLine(_startPosition, _endPosition);//就这一行，画直线
}

/***************************************************************
 * Name:      wxMyPainterApp.h
 * Purpose:   Defines Application Class
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#ifndef WXMYPAINTERAPP_H
#define WXMYPAINTERAPP_H

#include <wx/app.h>

class wxMyPainterApp : public wxApp
{
    public:
        virtual bool OnInit();
};

#endif // WXMYPAINTERAPP_H

/***************************************************************
 * Name:      wxMyPainterApp.cpp
 * Purpose:   Code for Application Class
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#include "wxMyPainterApp.h"

//(*AppHeaders
#include "wxMyPainterMain.h"
#include <wx/image.h>
//*)

IMPLEMENT_APP(wxMyPainterApp);

bool wxMyPainterApp::OnInit()
{
    //(*AppInitialize
    bool wxsOK = true;
    wxInitAllImageHandlers();
    if ( wxsOK )
    {
    	wxMyPainterFrame* Frame = new wxMyPainterFrame(0);
    	Frame->Show();
    	SetTopWindow(Frame);
    }
    //*)
    return wxsOK;

}

/***************************************************************
 * Name:      wxMyPainterMain.h
 * Purpose:   Defines Application Frame
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#ifndef WXMYPAINTERMAIN_H
#define WXMYPAINTERMAIN_H
#include <list>
#include "item_i.hpp"

//(*Headers(wxMyPainterFrame)
#include <wx/scrolwin.h>
#include <wx/sizer.h>
#include <wx/menu.h>
#include <wx/listbox.h>
#include <wx/frame.h>
#include <wx/statusbr.h>
//*)

class wxMyPainterFrame: public wxFrame
{
    public:

        wxMyPainterFrame(wxWindow* parent,wxWindowID id = -1);
        virtual ~wxMyPainterFrame();

    private:

        //(*Handlers(wxMyPainterFrame)
        void OnQuit(wxCommandEvent& event);
        void OnAbout(wxCommandEvent& event);
        void OnScrolledWindow1LeftDown(wxMouseEvent& event);
        void OnScrolledWindow1MouseMove(wxMouseEvent& event);
        void OnScrolledWindow1LeftUp(wxMouseEvent& event);
        void OnScrolledWindow1Paint(wxPaintEvent& event);
        //*)

        //(*Identifiers(wxMyPainterFrame)
        static const long ID_LISTBOX1;
        static const long ID_SCROLLEDWINDOW1;
        static const long idMenuQuit;
        static const long idMenuNone;
        static const long idMenuLine;
        static const long idMenuRectangle;
        static const long idMenuCircle;
        static const long idMenuText;
        static const long idMenuAbout;
        static const long ID_STATUSBAR1;
        //*)

        //(*Declarations(wxMyPainterFrame)
        wxMenuItem* MenuItemLine;
        wxMenuItem* MenuItemNone;
        wxScrolledWindow* ScrolledWindow1;
        wxMenu* Menu3;
        wxMenuItem* MenuItemText;
        wxStatusBar* StatusBar1;
        wxMenuItem* MenuItemRectangle;
        wxMenuItem* MenuItemCircle;
        wxListBox* ListBox1;
        //*)

    private:
        void RemoveAllItems();
        IItem* CreateNewItem();
        /*每当用户鼠标按下，就创建一个新的_newItem,等画完之后（鼠标抬起），
        就将它加入“_items”列表中。这也解释了为什么不需要“_drawing”这个标志，
        因为当“_newItem”不为空，就说明用户正在画新的线。OnPaint事件的思路配套调整
        为：每次都画出“_items”中的所有元素；然后如果“_newItem”不为空，则把用户正在
        拖拽的线也画出来。*/
        IItem* _newItem;
        std::list <IItem*> _items;

        DECLARE_EVENT_TABLE()
};

#endif // WXMYPAINTERMAIN_H

/***************************************************************
 * Name:      wxMyPainterMain.cpp
 * Purpose:   Code for Application Frame
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#include "wxMyPainterMain.h"
#include <wx/msgdlg.h>
#include <wx/dcclient.h>
#include "item_line.hpp"

//(*InternalHeaders(wxMyPainterFrame)
#include <wx/settings.h>
#include <wx/intl.h>
#include <wx/string.h>
//*)

//helper functions
enum wxbuildinfoformat {
    short_f, long_f };

wxString wxbuildinfo(wxbuildinfoformat format)
{
    wxString wxbuild(wxVERSION_STRING);

    if (format == long_f )
    {
#if defined(__WXMSW__)
        wxbuild << _T("-Windows");
#elif defined(__UNIX__)
        wxbuild << _T("-Linux");
#endif

#if wxUSE_UNICODE
        wxbuild << _T("-Unicode build");
#else
        wxbuild << _T("-ANSI build");
#endif // wxUSE_UNICODE
    }

    return wxbuild;
}

//(*IdInit(wxMyPainterFrame)
const long wxMyPainterFrame::ID_LISTBOX1 = wxNewId();
const long wxMyPainterFrame::ID_SCROLLEDWINDOW1 = wxNewId();
const long wxMyPainterFrame::idMenuQuit = wxNewId();
const long wxMyPainterFrame::idMenuNone = wxNewId();
const long wxMyPainterFrame::idMenuLine = wxNewId();
const long wxMyPainterFrame::idMenuRectangle = wxNewId();
const long wxMyPainterFrame::idMenuCircle = wxNewId();
const long wxMyPainterFrame::idMenuText = wxNewId();
const long wxMyPainterFrame::idMenuAbout = wxNewId();
const long wxMyPainterFrame::ID_STATUSBAR1 = wxNewId();
//*)

BEGIN_EVENT_TABLE(wxMyPainterFrame,wxFrame)
    //(*EventTable(wxMyPainterFrame)
    //*)
END_EVENT_TABLE()

wxMyPainterFrame::wxMyPainterFrame(wxWindow* parent,wxWindowID id)
    : _newItem(nullptr)
{
    //(*Initialize(wxMyPainterFrame)
    wxMenuItem* MenuItemAbout;
    wxMenu* Menu1;
    wxMenuItem* MenuItemQuit;
    wxBoxSizer* BoxSizer1;
    wxMenuBar* MenuBar1;
    wxMenu* Menu2;

    Create(parent, id, wxEmptyString, wxDefaultPosition, wxDefaultSize, wxDEFAULT_FRAME_STYLE, _T("id"));
    SetClientSize(wxSize(208,94));
    BoxSizer1 = new wxBoxSizer(wxHORIZONTAL);
    ListBox1 = new wxListBox(this, ID_LISTBOX1, wxDefaultPosition, wxSize(168,68), 0, 0, 0, wxDefaultValidator, _T("ID_LISTBOX1"));
    BoxSizer1->Add(ListBox1, 0, wxALL|wxEXPAND, 5);
    ScrolledWindow1 = new wxScrolledWindow(this, ID_SCROLLEDWINDOW1, wxDefaultPosition, wxDefaultSize, wxVSCROLL|wxHSCROLL, _T("ID_SCROLLEDWINDOW1"));
    ScrolledWindow1->SetBackgroundColour(wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW));
    BoxSizer1->Add(ScrolledWindow1, 1, wxALL|wxEXPAND, 5);
    SetSizer(BoxSizer1);
    MenuBar1 = new wxMenuBar();
    Menu1 = new wxMenu();
    MenuItemQuit = new wxMenuItem(Menu1, idMenuQuit, _("退出\tAlt-F4"), _("Quit the application"), wxITEM_NORMAL);
    Menu1->Append(MenuItemQuit);
    MenuBar1->Append(Menu1, _("文件[&F]"));
    Menu3 = new wxMenu();
    MenuItemNone = new wxMenuItem(Menu3, idMenuNone, _("无"), wxEmptyString, wxITEM_RADIO);
    Menu3->Append(MenuItemNone);
    MenuItemLine = new wxMenuItem(Menu3, idMenuLine, _("直线"), wxEmptyString, wxITEM_RADIO);
    Menu3->Append(MenuItemLine);
    MenuItemRectangle = new wxMenuItem(Menu3, idMenuRectangle, _("矩形"), wxEmptyString, wxITEM_RADIO);
    Menu3->Append(MenuItemRectangle);
    MenuItemCircle = new wxMenuItem(Menu3, idMenuCircle, _("圆形"), wxEmptyString, wxITEM_RADIO);
    Menu3->Append(MenuItemCircle);
    MenuItemText = new wxMenuItem(Menu3, idMenuText, _("文字"), wxEmptyString, wxITEM_RADIO);
    Menu3->Append(MenuItemText);
    MenuBar1->Append(Menu3, _("组件[&I]"));
    Menu2 = new wxMenu();
    MenuItemAbout = new wxMenuItem(Menu2, idMenuAbout, _("关于\tF1"), _("Show info about this application"), wxITEM_NORMAL);
    Menu2->Append(MenuItemAbout);
    MenuBar1->Append(Menu2, _("帮助[&H]"));
    SetMenuBar(MenuBar1);
    StatusBar1 = new wxStatusBar(this, ID_STATUSBAR1, 0, _T("ID_STATUSBAR1"));
    int __wxStatusBarWidths_1[1] = { -1 };
    int __wxStatusBarStyles_1[1] = { wxSB_NORMAL };
    StatusBar1->SetFieldsCount(1,__wxStatusBarWidths_1);
    StatusBar1->SetStatusStyles(1,__wxStatusBarStyles_1);
    SetStatusBar(StatusBar1);
    SetSizer(BoxSizer1);
    Layout();

    ScrolledWindow1->Connect(wxEVT_PAINT,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1Paint,0,this);
    ScrolledWindow1->Connect(wxEVT_LEFT_DOWN,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1LeftDown,0,this);
    ScrolledWindow1->Connect(wxEVT_LEFT_UP,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1LeftUp,0,this);
    ScrolledWindow1->Connect(wxEVT_MOTION,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1MouseMove,0,this);
    Connect(idMenuQuit,wxEVT_COMMAND_MENU_SELECTED,(wxObjectEventFunction)&wxMyPainterFrame::OnQuit);
    Connect(idMenuAbout,wxEVT_COMMAND_MENU_SELECTED,(wxObjectEventFunction)&wxMyPainterFrame::OnAbout);
    //*)


    //设置滚动选项
    ScrolledWindow1->SetScrollRate(10, 10);
    ScrolledWindow1->SetVirtualSize(500, 480);
}

wxMyPainterFrame::~wxMyPainterFrame()
{
    RemoveAllItems();
    //(*Destroy(wxMyPainterFrame)
    //*)
}

void wxMyPainterFrame::OnQuit(wxCommandEvent& event)
{
    Close();
}

void wxMyPainterFrame::OnAbout(wxCommandEvent& event)
{
    wxString msg = wxbuildinfo(long_f);
    wxMessageBox(msg, _("Welcome to..."));
}

IItem* wxMyPainterFrame::CreateNewItem()
{
    if(this->MenuItemLine->IsChecked())//小心，别写成IsCheckable()
    {
        return new LineItem();
    }

    return nullptr;
}

void wxMyPainterFrame::RemoveAllItems()
{
    for(std::list<IItem*>::iterator it = _items.begin()
                        ; it != _items.end(); ++it)
    {
        delete *it; //释放每个_newItem占据的内存
    }

    _items.clear(); //释放_items中元素(指向_newItem的指针)占据的内存
}

void wxMyPainterFrame::OnScrolledWindow1LeftDown(wxMouseEvent& event)
{
    if(_newItem) return; //正在划线，返回

    _newItem = this->CreateNewItem();
    if(!_newItem) return;

    _newItem->OnDrawStart(
        ScrolledWindow1->CalcUnscrolledPosition(event.GetPosition()));
}

void wxMyPainterFrame::OnScrolledWindow1MouseMove(wxMouseEvent& event)
{
    if(!_newItem) //不在绘画状态
    {
        return;//直接退出
    }

    _newItem->OnDrawEnd(//物理坐标转为逻辑坐标
        ScrolledWindow1->CalcUnscrolledPosition(event.GetPosition()));
    ScrolledWindow1->Refresh();
}

void wxMyPainterFrame::OnScrolledWindow1LeftUp(wxMouseEvent& event)
{
    if(!_newItem) //不在绘画状态？
    {
        return;//直接退出
    }

    _newItem->OnDrawEnd(//物理坐标转为逻辑坐标
        ScrolledWindow1->CalcUnscrolledPosition(event.GetPosition()));
    _items.push_back(_newItem); //记录到列表中
    _newItem = nullptr; //结束绘画状态

    ScrolledWindow1->Refresh();
}
//将_items中的所有线都画出来
void wxMyPainterFrame::OnScrolledWindow1Paint(wxPaintEvent& event)
{
    wxPaintDC dc(ScrolledWindow1);

    //DoPrepareDC会自行调校
    ScrolledWindow1->DoPrepareDC(dc);

    //先画出list中的每一项
    for(std::list <IItem*> :: const_iterator it = _items.begin()
                ; it != _items.end(); ++it)
    {
        IItem const* item = *it;
        item->Draw(dc);
    }

    //如果刚巧用户正在画新项，把它也显示出来
    //否则用户只能“盲画”了
    if(_newItem)
    {
        _newItem->Draw(dc);
    }
}

关键代码:

抽象出“图形元素”接口类

改造LineItem

改造外部使用环境

实现CreateNewItem()和RemoveAllItems()

实现鼠标按下，移动，抬起函数

实现作画函数