Add gtk examples, Update docs

docs/cn/php/core.md

@@ -87,3 +87,22 @@ foreach($_ENV as $k => $v) {
     $os->environ->__setitem__($k, $v);
 }
 ```
+
+## undefined symbol:ffi_type_uint32, version LIBFFI_BASE_7.0
+动态连接库路径存在冲突问题，可以尝试使用下面的方法解决。
+若依然有问题，建议使用系统自带的 `Python` 环境代替 `conda` 创建的环境。
+
+```shell
+export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libffi.so.7
+```
+
+## Import 失败
+大部分情况下，`from a import b` 是等价于 `PyCore::import('a')->b` ，
+但有些特殊的库无法通过以上方法正确加载，可替换为以下方法：
+
+```php
+# 无法加载
+$b = PyCore::import('a')->b;
+# 替换为以下代码
+$b = PyCore::import('a.b');
+```

examples/gtk/build.php

@@ -0,0 +1,20 @@
+<?php
+
+$operator = PyCore::import("operator");
+$builtins = PyCore::import("builtins");
+$gi = PyCore::import('gi');
+$gi->require_version("Gtk", "3.0");
+$Gtk = PyCore::import('gi.repository.Gtk');
+$builder = $Gtk->Builder();
+$builder->add_from_file(__DIR__ . '/test.glade');
+$window = $builder->get_object('window1');
+$window->set_title("hello world");
+$window->show_all();
+$handlers = new PyDict([
+    "onDestroy" => $Gtk->main_quit,
+    "onButtonPressed" => function () {
+        echo "hello\n";
+    }
+]);
+$builder->connect_signals($handlers);
+$Gtk->main();

examples/gtk/gtk.php

@@ -0,0 +1,10 @@
+<?php
+$operator = PyCore::import("operator");
+$builtins = PyCore::import("builtins");
+$gi = PyCore::import('gi');
+$gi->require_version("Gtk", "3.0");
+$Gtk = PyCore::import('gi.repository.Gtk');
+$win = $Gtk->Window(title: "Hello World");
+$win->connect("destroy", $Gtk->main_quit);
+$win->show_all();
+$Gtk->main();

examples/gtk/test.glade

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <!-- interface-requires gtk+ 3.0 -->
+  <object class="GtkWindow" id="window1">
+    <property name="can-focus">False</property>
+    <signal name="destroy" handler="onDestroy" swapped="no"/>
+    <child>
+      <object class="GtkButton" id="button1">
+        <property name="label" translatable="yes">button</property>
+        <property name="use-action-appearance">False</property>
+        <property name="visible">True</property>
+        <property name="can-focus">True</property>
+        <property name="receives-default">True</property>
+        <property name="use-action-appearance">False</property>
+        <signal name="pressed" handler="onButtonPressed" swapped="no"/>
+      </object>
+    </child>
+  </object>
+</interface>