From 3372f4424ea31d88a888908b1200e9e787a72ee6 Mon Sep 17 00:00:00 2001
From: Robbert van der Helm <mail@robbertvanderhelm.nl>
Date: Sat, 10 Jul 2021 16:43:23 +0200
Subject: [PATCH] Create a window for the X11 proxy

---
 src/wine-host/xdnd-proxy.cpp | 46 ++++++++++++++++++++++++++++--------
 src/wine-host/xdnd-proxy.h   | 43 +++++++++++++++++++++++++++++++--
 2 files changed, 77 insertions(+), 12 deletions(-)

diff --git a/src/wine-host/xdnd-proxy.cpp b/src/wine-host/xdnd-proxy.cpp
index 6d0277b8..64346be5 100644
--- a/src/wine-host/xdnd-proxy.cpp
+++ b/src/wine-host/xdnd-proxy.cpp
@@ -57,9 +57,43 @@ void CALLBACK dnd_winevent_callback(HWINEVENTHOOK hWinEventHook,
                                     DWORD idEventThread,
                                     DWORD dwmsEventTime);
 
+ProxyWindow::ProxyWindow(std::shared_ptr<xcb_connection_t> x11_connection)
+    : x11_connection(x11_connection),
+      window(xcb_generate_id(x11_connection.get())) {
+    const xcb_screen_t* screen =
+        xcb_setup_roots_iterator(xcb_get_setup(x11_connection.get())).data;
+
+    xcb_create_window(x11_connection.get(), XCB_COPY_FROM_PARENT, window,
+                      screen->root, 0, 0, 1, 1, 0, XCB_WINDOW_CLASS_INPUT_ONLY,
+                      XCB_COPY_FROM_PARENT, 0, nullptr);
+    xcb_flush(x11_connection.get());
+}
+
+ProxyWindow::~ProxyWindow() noexcept {
+    if (!is_moved) {
+        xcb_destroy_window(x11_connection.get(), window);
+        xcb_flush(x11_connection.get());
+    }
+}
+
+ProxyWindow::ProxyWindow(ProxyWindow&& o) noexcept
+    : x11_connection(std::move(o.x11_connection)), window(std::move(o.window)) {
+    o.is_moved = true;
+}
+ProxyWindow& ProxyWindow::operator=(ProxyWindow&& o) noexcept {
+    if (&o != this) {
+        x11_connection = std::move(o.x11_connection);
+        window = std::move(o.window);
+
+        o.is_moved = true;
+    }
+
+    return *this;
+}
+
 WineXdndProxy::WineXdndProxy()
     : x11_connection(xcb_connect(nullptr, nullptr), xcb_disconnect),
-      proxy_window(xcb_generate_id(x11_connection.get())),
+      proxy_window(x11_connection),
       hook_handle(
           SetWinEventHook(EVENT_OBJECT_CREATE,
                           EVENT_OBJECT_CREATE,
@@ -68,15 +102,7 @@ WineXdndProxy::WineXdndProxy()
                           0,
                           0,
                           WINEVENT_OUTOFCONTEXT | WINEVENT_SKIPOWNPROCESS),
-          UnhookWinEvent) {
-    //
-}
-
-WineXdndProxy::~WineXdndProxy() noexcept {
-    // TODO: Move this to a RAII wrapper
-    xcb_destroy_window(x11_connection.get(), proxy_window);
-    xcb_flush(x11_connection.get());
-}
+          UnhookWinEvent) {}
 
 WineXdndProxy::Handle::Handle(WineXdndProxy* proxy) : proxy(proxy) {}
 
diff --git a/src/wine-host/xdnd-proxy.h b/src/wine-host/xdnd-proxy.h
index 2bd6a41b..1818d8f9 100644
--- a/src/wine-host/xdnd-proxy.h
+++ b/src/wine-host/xdnd-proxy.h
@@ -26,6 +26,35 @@
 
 #include <windows.h>
 
+/**
+ * A simple, unmapped 1x1 proxy window we'll use for our Wine->X11 drag-and-drop
+ * proxy so we can send and receive client messages.
+ */
+class ProxyWindow {
+   public:
+    /**
+     * Create the proxy window.
+     */
+    ProxyWindow(std::shared_ptr<xcb_connection_t> x11_connection);
+
+    /**
+     * Destroy the window again when this object gets dropped.
+     */
+    ~ProxyWindow() noexcept;
+
+    ProxyWindow(const ProxyWindow&) noexcept = delete;
+    ProxyWindow& operator=(const ProxyWindow&) noexcept = delete;
+
+    ProxyWindow(ProxyWindow&&) noexcept;
+    ProxyWindow& operator=(ProxyWindow&&) noexcept;
+
+   private:
+    std::shared_ptr<xcb_connection_t> x11_connection;
+    xcb_window_t window;
+
+    bool is_moved = false;
+};
+
 /**
  * A simple wrapper that registers a WinEvents hook to listen for new windows
  * being created, and handles XDND client messages to achieve the behaviour
@@ -33,6 +62,9 @@
  */
 class WineXdndProxy {
    protected:
+    /**
+     * Initialize the proxy and register all hooks.
+     */
     WineXdndProxy();
 
    public:
@@ -106,13 +138,20 @@ class WineXdndProxy {
     void handle_x11_events() const noexcept;
 
    private:
-    std::unique_ptr<xcb_connection_t, decltype(&xcb_disconnect)> x11_connection;
+    /**
+     * We need a dedicated X11 connection for our proxy because we can have
+     * multiple open editors in a single process (e.g. when using VST3 plugins
+     * or plugin groups), and client messages are sent to the X11 connection
+     * that created the window. So we cannot just reuse the connection from the
+     * editor.
+     */
+    std::shared_ptr<xcb_connection_t> x11_connection;
 
     /**
      * We need an unmapped proxy window to send and receive client messages for
      * the XDND protocol.
      */
-    xcb_window_t proxy_window;
+    ProxyWindow proxy_window;
 
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wignored-attributes"