Preemptively unset WAYLAND_DISPLAY

src/common/process.cpp

@@ -174,6 +174,13 @@ void ProcessEnvironment::insert(const std::string& key,
     variables_.push_back(key + "=" + value);
 }
 
+size_t ProcessEnvironment::erase(const std::string& key) {
+    return std::erase_if(variables_, [&key](const std::string& variable) {
+        return variable.starts_with(key) && variable.size() > key.size() &&
+               variable[key.size()] == '=';
+    });
+}
+
 char* const* ProcessEnvironment::make_environ() const {
     recreated_environ_.clear();
 

src/common/process.h

@@ -101,6 +101,14 @@ class ProcessEnvironment {
      */
     void insert(const std::string& key, const std::string& value);
 
+    /**
+     * Remove an environment variable from the environment. Returns the number
+     * of elements erased (to stay consistent with the STL map interface). This
+     * can be higher than 1 if the map contains duplicate or overwritten
+     * environment variables.
+     */
+    size_t erase(const std::string& key);
+
     /**
      * Create an environ-like object from the updated environment that can be
      * passed to the `exec*e()` functions. These pointers will be invalidated

src/plugin/utils.cpp

@@ -70,6 +70,14 @@ ProcessEnvironment PluginInfo::create_host_env() const {
                },
                wine_prefix_);
 
+    // As of writing upstream Wine does not yet have a Wayland driver, but one
+    // is in the process of being merged. If this ever becomes enabled by
+    // default on distros, Wine could suddenly start using using Wayland instead
+    // of X11. This would break yabridge's embedding and drag-and-drop handling.
+    // So we'll preemptively avoid this by unsetting the `WAYLAND_DISPLAY`
+    // environment variable.
+    env.erase("WAYLAND_DISPLAY");
+
     return env;
 }
 

src/plugin/utils.h

@@ -79,6 +79,9 @@ struct PluginInfo {
      * `WINEPREFIX` was already set then nothing will be changed. Otherwise
      * we'll set `WINEPREFIX` to the detected Wine prefix, or it will be left
      * unset if we could not detect a prefix.
+     *
+     * This also unsets `WAYLAND_DISPLAY` so if Wine has been compiled with
+     * Wayland support, it won't suddenly start using that over X11.
      */
     ProcessEnvironment create_host_env() const;