Made the input focus grabbing even more aggressive

This fixes keyboard focus not returning when closing dialogs in Melda
plugins. I'll have to do some more testing to see if this does not
introduce any unwanted side effects.

src/wine-host/editor.cpp

@@ -266,13 +266,23 @@ void Editor::fix_local_coordinates() const {
 }
 
 void Editor::grab_input_focus() const {
-    // Explicitely request input focus when the user clicks on the window. This
-    // is needed for Bitwig Studio 3.2, as the parent window now captures all
-    // keyboard events and forwards them to the main Bitwig Studio window
-    // instead of allowing the child window to handle those events. We used to
-    // do this on the X11 FocusIn event, but that's not getting fired for REAPER
-    // so we now do this on `WM_PARENTNOTIFY` which included every time the user
-    // clicks on the Wine window.
+    // Explicitely request input focus when the user clicks on the window.
+    // Without this the parent window will capture all keyboard events in most
+    // hosts. Ideally we would just do this whenever the child window calls
+    // `SetFocus()` (or no handling should be necessary), but as far as I'm
+    // aware there is no way to do this. Right now we're doing grabbing input
+    // focus in one of two situations:
+    //
+    // - On `WM_PARENTNOTIFY`, which include every time the user clicks on the
+    //   Wine window. On most hosts we could get away with using the `FocusIn`
+    //   X11 event instead, but this does not work reliably in REAPER and
+    //   Ardour.
+    // - On `WM_NCACTIVATE` and `WM_CANCELMODE`. This is a small HACK to
+    //   immediatly grab keyboard focus again when the user closes a popup
+    //   window. Again, this is only needed for Ardour and REAPER, but without
+    //   this the F1 help dialog system in Melda plugins does not work like
+    //   you'd expect, instead requiring you to click on the window in between
+    //   F1 presses.
     xcb_set_input_focus(x11_connection.get(), XCB_INPUT_FOCUS_PARENT,
                         wine_window, XCB_CURRENT_TIME);
     xcb_flush(x11_connection.get());
@@ -313,6 +323,10 @@ LRESULT CALLBACK window_proc(HWND handle,
             editor->send_idle_event();
             return 0;
         } break;
+        // See the comment in `Editor::grab_input_focus()` for more details on
+        // what's happening here
+        case WM_NCACTIVATE:
+        case WM_CANCELMODE:
         case WM_PARENTNOTIFY: {
             auto editor = reinterpret_cast<Editor*>(
                 GetWindowLongPtr(handle, GWLP_USERDATA));

src/wine-host/editor.h

@@ -146,7 +146,8 @@ class Editor {
     /**
      * Steal keyboard focus. This is done whenever the user clicks on the window
      * since we don't have a way to detect whether the client window is calling
-     * `SetFocus()`.
+     * `SetFocus()`. See the comment inside of this function for more details on
+     * when this is used.
      */
     void grab_input_focus() const;