c++ - GTKMM/C++11 : How to create a custom composite widget out of other widgets?

Question

我想派生我自己的小部件类并向此类添加标准小部件以创建复合小部件。有没有人有关于如何做到这一点的例子或建议？例如，假设我想创建 4 个按钮的自定义复合小部件。我猜它类似于下面的代码:

//First Question:  Is this the best way to create composite widget? (see below)

//Second Question:  How do you make a widget container expand in 
// the horizontal direction while at the same time shrink in 
// the vertical direction?  because i wanted the boxes to expand horizontally
// to fill the window, and at the same time shrink to minimum width in the vertical
// direction


#include <iostream>

using namespace std;
#include <gtkmm.h>

class MyWidget : public Gtk::Frame {
  public:
    MyWidget() {
        add(m_hbox1);
        m_hbox1.pack_start  (m_vbox1,    Gtk::PackOptions::PACK_SHRINK);
        m_vbox1.pack_start  (m_hbox2,    Gtk::PackOptions::PACK_EXPAND_WIDGET);
        m_hbox2.pack_start  (m_btn_fwd,  Gtk::PackOptions::PACK_EXPAND_WIDGET);
        m_hbox2.pack_start  (m_btn_play, Gtk::PackOptions::PACK_EXPAND_WIDGET);
        m_hbox2.pack_start  (m_btn_stop, Gtk::PackOptions::PACK_EXPAND_WIDGET);
        m_hbox2.pack_start  (m_btn_back, Gtk::PackOptions::PACK_EXPAND_WIDGET);

        show_all_children();
    }
    ~MyWidget() {
    }

  private:

    Gtk::Box    m_vbox1    {Gtk::ORIENTATION_VERTICAL};
    Gtk::Box    m_hbox1    {Gtk::ORIENTATION_HORIZONTAL};
    Gtk::Box    m_hbox2    {Gtk::ORIENTATION_HORIZONTAL};
    Gtk::Button m_btn_fwd  {"Fwd"};
    Gtk::Button m_btn_back {"Back"};
    Gtk::Button m_btn_play {"Play"};
    Gtk::Button m_btn_stop {"Stop"};
};

class MyWindow : public Gtk::Window {
  public:
    MyWindow(string name) {
       set_title(name);
       add(m_vbox);

       // Shrink in Vertical Direction
       m_vbox.pack_start(m_mywidget, Gtk::PackOptions::PACK_SHRINK);

       show_all_children();
    }

  private:
    Gtk::Box    m_vbox      {Gtk::ORIENTATION_VERTICAL};
    MyWidget    m_mywidget;
};

int main(int argc, char *argv[])
{
  auto app = Gtk::Application::create(argc, argv,
     "org.gtkmm.example.actionbar");

  MyWindow window {"Testing Custom Composite Widget"};

  // Shows the window and returns when it is closed.
  return app->run(window);
}

Answer 1

经过几周的实验，我的结论是最好避免使用 C++ 从 Gtk::Widget 继承来创建复合小部件。相反，最好将 gktmm 中的复合小部件作为纯容器类，即。不派生自任何类，并重载 C++11 Functor 运算符以返回一个 Gtk::Box Widget，该 Widget 由对象的构造函数预先打包，其中包含制作复合组件所需的所有小部件。示例:

using namespace std;
#include <gtkmm.h>
#include <iostream>

//======================================================
// SearchBar: An Example GTKMM Composite Widget / wmoore
//======================================================
class SearchBar {
  public:
     SearchBar();
     Gtk::Widget& operator()();

  public:
     Gtk::Box    box {Gtk::ORIENTATION_HORIZONTAL};
     Gtk::Label  label {"search: "};
     Gtk::Entry  entry;
     Gtk::Button BtnOk{"find"};
     Gtk::Button BtnNext{">"};
     Gtk::Button BtnPrev{"<"};
};

inline SearchBar::SearchBar() {
  box.pack_start(label);
  box.pack_start(entry, Gtk::PACK_EXPAND_WIDGET);
  box.pack_end(BtnNext);
  box.pack_end(BtnPrev);
  box.pack_end(BtnOk);
}

inline Gtk::Widget& SearchBar::operator()() {
  return box;
}

class MyWindow : public Gtk::Window {
  public:
    MyWindow(string name) {
       set_title(name);
       add(m_vbox);

       // Shrink in Vertical Direction
       m_vbox.pack_start(m_searchbar(), Gtk::PackOptions::PACK_SHRINK);  
                        // ^^^ NOTE use of C++11 functor operator "()"
                        // added to end of object name
                        // that makes it easy to tell difference between 
                        // Gtk::Widget and Composite widget's built 
                       // from many Gtk::Widget's

      ////Example Connecting of Signals to composite widget:
      // m_searchbar.BtnOk.signal_clicked.connect([]() {
      //     cout << "clicked button!\n";})

       show_all_children();
    }

  private:
    Gtk::Box    m_vbox      {Gtk::ORIENTATION_VERTICAL};
    SearchBar   m_searchbar;
};

int main(int argc, char *argv[])
{
  auto app = Gtk::Application::create(argc, argv,
     "org.gtkmm.example.actionbar");

  MyWindow window {"Testing Custom Composite Widget"};

  // Shows the window and returns when it is closed.
  return app->run(window);
}

使用纯容器类而不是从 Gtk::Widget 继承来创建复合小部件的原因如下:

(1) gtkmm 的 Widget api 非常多，并且倾向于将您添加到复合小部件的任何新公共(public)方法隐藏在一堆您可能不会使用的 gtkmm 小部件方法中。为此原因。最好将所有容器小部件对象添加到类的公共(public)部分，包括顶层框小部件。您仍然可以访问每个对象小部件的所有方法，而不会出现 gtkmm api 困惑。

(2) 从 Gtk::Widget 继承你的类在多态行为方面并没有真正给你带来任何有用的东西，因为复合小部件的小部件已经是从 Gtk::Widget 派生的多态对象。当您将顶级小部件框添加到父小部件时，您的复合小部件的所有子小部件，在框下，都被添加到父小部件的子列表中。因此，复合小部件容器实际上没有必要具有多态行为。

(3) 如果您需要从 Gtk:Widget 派生的复合小部件，很容易在其周围放置一个类包装器，将其转换回从 Gtk::Widget 派生的类。事实上，这一步很容易通过模板类包装器的单行实例化来完成。我能想到这样做的唯一原因是将组件插入回空地(Glade Gui 将 C++11 仿函数运算符识别为返回复合小部件的顶层小部件的标准方法(空地可能支持 future ？愿望 list ...))