add ability to edit messages

dialogs/editmessage.cpp

@@ -0,0 +1,39 @@
+#include "editmessage.hpp"
+
+EditMessageDialog::EditMessageDialog(Gtk::Window &parent)
+    : Gtk::Dialog("Edit Message", parent, true)
+    , m_layout(Gtk::ORIENTATION_VERTICAL)
+    , m_bbox(Gtk::ORIENTATION_HORIZONTAL)
+    , m_ok("OK")
+    , m_cancel("Cancel") {
+    set_default_size(300, 50);
+
+    m_ok.signal_clicked().connect([&]() {
+        m_content = m_text.get_buffer()->get_text();
+        response(Gtk::RESPONSE_OK);
+    });
+
+    m_cancel.signal_clicked().connect([&]() {
+        response(Gtk::RESPONSE_CANCEL);
+    });
+
+    m_bbox.pack_start(m_ok, Gtk::PACK_SHRINK);
+    m_bbox.pack_start(m_cancel, Gtk::PACK_SHRINK);
+    m_bbox.set_layout(Gtk::BUTTONBOX_END);
+
+    m_text.set_hexpand(true);
+
+    m_scroll.set_hexpand(true);
+    m_scroll.set_vexpand(true);
+    m_scroll.add(m_text);
+
+    m_layout.add(m_scroll);
+    m_layout.add(m_bbox);
+    get_content_area()->add(m_layout);
+
+    show_all_children();
+}
+
+std::string EditMessageDialog::GetContent() {
+    return m_content;
+}