macOS Ventura 13.2.1下Gtkmm4的Gtk::ComboBoxText鼠标选值失效求助

我在程序中添加了一个简单的Gtk::ComboBoxText组件，但无法通过鼠标点击下拉选项来选中对应值，仅能通过键盘方向键和回车键切换选中项。以下是相关代码示例（examplewindow.cc）：

#include <list>
#include <utility>
#include <cstdio>
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <sstream>
#include <gtkmm.h>
#include <soci.h>
#include <soci-sqlite3.h>
#include "examplewindow.h"

ExampleWindow::ExampleWindow()
: m_VBox(Gtk::Orientation::VERTICAL),
  m_Button_Quit("Quit"),
  m_Button_File("Choose File"),
  m_Button_Accept("Accept")
{
  set_title("Gtk::TreeView (ListStore) example");
  set_default_size(400, 200);

  m_VBox.set_margin(5);
  set_child(m_VBox);

  //Add the TreeView, inside a ScrolledWindow, with the button underneath:
  m_ScrolledWindow.set_child(m_TreeView);

  //Only show the scrollbars when they are necessary:
  m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
  m_ScrolledWindow.set_expand();

  m_ComboBoxText.append("Option 1");
  m_ComboBoxText.append("Option 2");
  m_ComboBoxText.append("Option 3");
  m_ComboBoxText.set_active_text("Option 1");

  m_ComboBoxText.signal_changed().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_combo_changed) );

  m_VBox.append(m_ComboBoxText);
  m_VBox.append(m_ScrolledWindow);
  m_VBox.append(m_ButtonBox);

  m_ButtonBox.append(m_Button_File);
  m_ButtonBox.set_margin(5);
  m_Button_File.set_hexpand(true);
  m_Button_File.set_halign(Gtk::Align::BASELINE);
  m_Button_File.signal_clicked().connect( sigc::mem_fun(*this,
              &ExampleWindow::on_file_dialog) );

  m_ButtonBox.append(m_Entry);
  m_Entry.set_width_chars(20);
  m_Entry.set_hexpand(true);
  m_Entry.set_halign(Gtk::Align::FILL);
  m_Entry.signal_changed().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_entry_changed));

  m_ButtonBox.append(m_Button_Accept);
  m_Button_Accept.set_hexpand(true);
  m_Button_Accept.set_halign(Gtk::Align::BASELINE);
  m_Button_Accept.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_accept) );

  m_ButtonBox.append(m_Button_Quit);
  m_ButtonBox.set_margin(5);
  m_Button_Quit.set_hexpand(true);
  m_Button_Quit.set_halign(Gtk::Align::BASELINE);
  m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
              &ExampleWindow::on_button_quit) );

}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_button_quit()
{
  set_visible(false);
}

void ExampleWindow::on_file_dialog()
{
  m_fileChooser = Gtk::FileChooserNative::create("Please choose a folder",  
                                                 *this,    
                                                 Gtk::FileChooser::Action::OPEN,
                                                 "Choose",
                                                 "Cancel");

  m_fileChooser->signal_response().connect(
            [this](int p_responseID)
            {
              this->on_browse_button_clicked(p_responseID);
            }
        );

  m_fileChooser->show();
}

void ExampleWindow::on_button_accept()
{
  std::vector<std::vector<std::string>> content;

  std::string db_name = m_path;
    //std::remove(db_name.c_str());

  if (db_name.empty())
  {
    return;
  }

  std::cout << db_name << std::endl;

  soci::session sql(soci::sqlite3, db_name);

  soci::rowset<soci::row> rs = (sql.prepare << "SELECT * FROM users");

  // iteration through the resultset:
  int i = 0;
  for (soci::rowset<soci::row>::const_iterator it = rs.begin(); it != rs.end(); ++it)
  {

    soci::row const& row = *it;

    std::vector<std::string> row_content;

    for(std::size_t j = 0; j != row.size(); ++j) {

      const soci::column_properties & props = row.get_properties(j);

      switch(props.get_data_type())
      {
        case soci::dt_string:
            row_content.push_back(row.get<std::string>(j));
            break;
        case soci::dt_double:
            row_content.push_back(std::to_string(row.get<double>(j)));
            break;
        case soci::dt_integer:
            row_content.push_back(std::to_string(row.get<int>(j)));
            break;
        case soci::dt_long_long:
            row_content.push_back(std::to_string(row.get<long long>(j)));
            break;
        case soci::dt_unsigned_long_long:
            row_content.push_back(std::to_string(row.get<unsigned long long>(j)));
            break;
        case soci::dt_date:
            break;
        case soci::dt_xml:
            break;
        case soci::dt_blob:
            break;
      }
    }

    content.push_back(row_content);

    i++;
  }

  if (m_refTreeModel) {
    m_TreeView.remove_all_columns();
  }

  m_Columns = new ModelColumns(content.at(0).size());

  //Create the Tree model:
  m_refTreeModel = Gtk::ListStore::create(*m_Columns);
  m_TreeView.set_model(m_refTreeModel);
 
    for(int i=0;i<content.size();i++)
    {
    auto row = *(m_refTreeModel->append());
        for(int j=0;j<content[i].size();j++)
        {
      row[*(m_Columns->col_vect.at(j))] = content[i][j];
        }
    }

  for (int k = 0; k < content.at(0).size(); k++) {
      m_TreeView.append_column("Column " + std::to_string(k), *(m_Columns->col_vect.at(k)));
  }

}

void ExampleWindow::on_entry_changed()
{
  m_path = m_Entry.get_text();
}

void ExampleWindow::on_combo_changed()
{
  std::string m_ComboText= m_ComboBoxText.get_active_text();
  std::cout << "Hola" << std::endl;
  m_ComboBoxText.set_active_text(m_ComboText);
}

void ExampleWindow::on_browse_button_clicked(int p_responseID)
{
  switch(p_responseID)
  {
      case GTK_RESPONSE_ACCEPT:
      {
          m_path = m_fileChooser->get_file()->get_path();
          m_Entry.set_text(m_path);
          break;
      }
      case GTK_RESPONSE_CANCEL:
      {
          std::cout << "Cancel clicked : " << p_responseID  << std::endl;
          break;
      } 
      default:
      {
          std::cout << "Unexpected button clicked: " << p_responseID << std::endl;
          break;
      }
  }
}

问题出在on_combo_changed回调函数里：你在获取当前选中文本后，又调用了m_ComboBoxText.set_active_text(m_ComboText);。这行代码会触发新一轮的signal_changed信号，同时强制重置组件的选中状态——鼠标刚选中新选项，就被这行代码强行覆盖，导致看起来点击操作没有生效。

只需删除这行多余的代码即可解决问题，修改后的回调函数如下：

void ExampleWindow::on_combo_changed()
{
  std::string m_ComboText= m_ComboBoxText.get_active_text();
  std::cout << "Hola" << std::endl;
  // 移除这行不必要的调用，避免干扰选中状态
  // m_ComboBoxText.set_active_text(m_ComboText);
}

当你通过鼠标点击选中下拉项时，Gtk框架已经自动完成了选中状态的更新，signal_changed信号只是通知你状态发生了变化，此时你只需要在回调中处理选中后的业务逻辑（比如打印日志、更新其他组件等），不需要手动再次设置选中文本。

内容的提问来源于stack exchange，提问作者Alberto García