如何让GtkToolbar实现水平与垂直方向的扩展？

当前部件树 #

当前UI配置：

• homescreen（GtkFixed）已设置为水平和垂直扩展
• navigationbar（GtkFixed）设置为水平扩展，固定高度120

我尝试让GtkToolbar实现水平和垂直扩展，但始终无法生效。

Toolbar当前状态 #

完整UI XML代码 #

<?xml version="1.0" encoding="UTF-8"?><!-- Generated with glade 3.38.2 --><interface><requires lib="gtk+" version="3.20"/><object class="GtkWindow" id="window"><property name="width-request">1024</property><property name="height-request">600</property><property name="can-focus">False</property><child><object class="GtkBox"><property name="width-request">1024</property><property name="height-request">600</property><property name="visible">True</property><property name="can-focus">False</property><property name="orientation">vertical</property><child><object class="GtkFixed" id="homescreen"><property name="visible">True</property><property name="can-focus">False</property></object><packing><property name="expand">True</property><property name="fill">True</property><property name="position">0</property></packing></child><child><object class="GtkFixed" id="navigationbar"><property name="height-request">120</property><property name="visible">True</property><property name="can-focus">False</property><property name="valign">end</property><child><object class="GtkToolbar"><property name="visible">True</property><property name="can-focus">False</property><property name="hexpand">True</property><property name="vexpand">True</property><child><object class="GtkToolButton"><property name="visible">True</property><property name="can-focus">False</property><property name="label" translatable="yes">__glade_unnamed_4</property><property name="use-underline">True</property></object><packing><property name="expand">False</property><property name="homogeneous">True</property></packing></child></object><packing><property name="x">0</property><property name="y">0</property></packing></child></object><packing><property name="expand">False</property><property name="fill">True</property><property name="position">1</property></packing></child></object></child></object></interface>

内容的提问来源于stack exchange，提问作者Laura