4 files changed, 99 insertions, 2 deletions
diff --git a/include/cru/platform/gui/UiApplication.h b/include/cru/platform/gui/UiApplication.h
index 88aa3e20..3f36c26c 100644
--- a/include/cru/platform/gui/UiApplication.h
+++ b/include/cru/platform/gui/UiApplication.h
@@ -64,12 +64,12 @@ struct CRU_PLATFORM_GUI_API IUiApplication : public virtual IPlatformResource {
   virtual IMenu* GetApplicationMenu();
 
   /**
-   * \todo Implement on Windows.
+   * \todo Implement on Windows/X11.
    */
   virtual std::optional<String> ShowSaveDialog(SaveDialogOptions options);
 
   /**
-   * \todo Implement on Windows.
+   * \todo Implement on Windows/X11.
    */
   virtual std::optional<std::vector<String>> ShowOpenDialog(
       OpenDialogOptions options);
diff --git a/include/cru/platform/gui/xcb/Base.h b/include/cru/platform/gui/xcb/Base.h
new file mode 100644
index 00000000..f3bcfd01
--- /dev/null
+++ b/include/cru/platform/gui/xcb/Base.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <cru/base/Exception.h>
+
+#include "../../Resource.h"
+
+namespace cru::platform::gui::xcb {
+class XcbResource : public Object, public virtual IPlatformResource {
+ public:
+  static String kPlatformId;
+
+ protected:
+  XcbResource() = default;
+
+ public:
+  String GetPlatformId() const final { return kPlatformId; }
+};
+
+class XcbException : public PlatformException {
+ public:
+  using PlatformException::PlatformException;
+};
+}  // namespace cru::platform::gui::xcb
diff --git a/include/cru/platform/gui/xcb/UiApplication.h b/include/cru/platform/gui/xcb/UiApplication.h
new file mode 100644
index 00000000..a58a538f
--- /dev/null
+++ b/include/cru/platform/gui/xcb/UiApplication.h
@@ -0,0 +1,64 @@
+#pragma once
+#include "../UiApplication.h"
+#include "Base.h"
+
+#include <xcb/xcb.h>
+
+namespace cru::platform::gui::xcb {
+class XcbUiApplication : public XcbResource, public virtual IUiApplication {
+ public:
+  XcbUiApplication();
+  ~XcbUiApplication();
+
+  void CheckXcbConnectionError();
+
+  virtual int Run() = 0;
+
+  // Post a quit message with given quit code.
+  virtual void RequestQuit(int quit_code) = 0;
+
+  virtual void AddOnQuitHandler(std::function<void()> handler) = 0;
+
+  virtual bool IsQuitOnAllWindowClosed() = 0;
+  virtual void SetQuitOnAllWindowClosed(bool quit_on_all_window_closed) = 0;
+
+  // Timer id should always be positive (not 0) and never the same. So it's ok
+  // to use negative value (or 0) to represent no timer.
+  virtual long long SetImmediate(std::function<void()> action) = 0;
+  virtual long long SetTimeout(std::chrono::milliseconds milliseconds,
+                               std::function<void()> action) = 0;
+  virtual long long SetInterval(std::chrono::milliseconds milliseconds,
+                                std::function<void()> action) = 0;
+  // Implementation should guarantee calls on timer id already canceled have no
+  // effects and do not crash. Also canceling negative id or 0 should always
+  // result in no-op.
+  virtual void CancelTimer(long long id) = 0;
+
+  virtual std::vector<INativeWindow*> GetAllWindow() = 0;
+
+  virtual INativeWindow* CreateWindow() = 0;
+
+  virtual cru::platform::graphics::IGraphicsFactory* GetGraphicsFactory() = 0;
+
+  virtual ICursorManager* GetCursorManager() = 0;
+
+  virtual IClipboard* GetClipboard() = 0;
+
+  // If return nullptr, it means the menu is not supported.
+  virtual IMenu* GetApplicationMenu();
+
+  /**
+   * \todo Implement on Windows.
+   */
+  virtual std::optional<String> ShowSaveDialog(SaveDialogOptions options);
+
+  /**
+   * \todo Implement on Windows.
+   */
+  virtual std::optional<std::vector<String>> ShowOpenDialog(
+      OpenDialogOptions options);
+
+ private:
+  xcb_connection_t* xcb_;
+};
+}  // namespace cru::platform::gui::xcb
diff --git a/include/cru/platform/gui/xcb/Window.h b/include/cru/platform/gui/xcb/Window.h
new file mode 100644
index 00000000..94f5d350
--- /dev/null
+++ b/include/cru/platform/gui/xcb/Window.h
@@ -0,0 +1,10 @@
+
+#pragma once
+#include "../Window.h"
+#include "Base.h"
+
+namespace cru::platform::gui::xcb {
+class XcbWindow : public XcbResource, public virtual INativeWindow {
+
+};
+}  // namespace cru::platform::gui::x11