Re: [PATCH 1/3] ui/sdl2: reenable the SDL2 Windows keyboard hook procedure

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

Hi

On Mon, Sep 9, 2024 at 10:22 AM Volker Rümelin <vr_qemu@t-online.de> wrote:
>
> Windows only:
>
> The libSDL2 Windows message loop needs the libSDL2 Windows low
> level keyboard hook procedure to grab the left and right Windows
> keys correctly. Reenable the SDL2 Windows keyboard hook procedure.
>
> Because the QEMU Windows keyboard hook procedure is still needed
> to filter out the special left Control key event for every Alt Gr
> key event, it's important to install the two keyboard hook
> procedures in the following order. First the SDL2 procedure, then
> the QEMU procedure.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2139
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2323
> Tested-by: Howard Spoelstra <hsp.cat7@gmail.com>
> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
> ---
>  ui/sdl2.c           | 53 ++++++++++++++++++++++++++++++---------------
>  ui/win32-kbd-hook.c |  3 +++
>  2 files changed, 38 insertions(+), 18 deletions(-)
>
> diff --git a/ui/sdl2.c b/ui/sdl2.c
> index 98ed974371..ac37c173a1 100644
> --- a/ui/sdl2.c
> +++ b/ui/sdl2.c
> @@ -42,6 +42,7 @@ static SDL_Surface *guest_sprite_surface;
>  static int gui_grab; /* if true, all keyboard/mouse events are grabbed */
>  static bool alt_grab;
>  static bool ctrl_grab;
> +static bool win32_kbd_grab;
>
>  static int gui_saved_grab;
>  static int gui_fullscreen;
> @@ -202,6 +203,19 @@ static void sdl_update_caption(struct sdl2_console *scon)
>      }
>  }
>
> +static void *sdl2_win32_get_hwnd(struct sdl2_console *scon)
> +{
> +#ifdef CONFIG_WIN32
> +    SDL_SysWMinfo info;
> +
> +    SDL_VERSION(&info.version);
> +    if (SDL_GetWindowWMInfo(scon->real_window, &info)) {
> +        return info.info.win.window;
> +    }
> +#endif
> +    return NULL;
> +}
> +
>  static void sdl_hide_cursor(struct sdl2_console *scon)
>  {
>      if (scon->opts->has_show_cursor && scon->opts->show_cursor) {
> @@ -259,9 +273,16 @@ static void sdl_grab_start(struct sdl2_console *scon)
>      } else {
>          sdl_hide_cursor(scon);
>      }
> +    /*
> +     * Windows: To ensure that QEMU's low level keyboard hook procedure is
> +     * called before SDL2's, the QEMU procedure must first be removed and
> +     * then the SDL2 and QEMU procedures must be installed in this order.
> +     */
> +    win32_kbd_set_window(NULL);
>      SDL_SetWindowGrab(scon->real_window, SDL_TRUE);
> +    win32_kbd_set_window(sdl2_win32_get_hwnd(scon));
>      gui_grab = 1;
> -    win32_kbd_set_grab(true);
> +    win32_kbd_set_grab(win32_kbd_grab);
>      sdl_update_caption(scon);
>  }
>
> @@ -370,19 +391,6 @@ static int get_mod_state(void)
>      }
>  }
>
> -static void *sdl2_win32_get_hwnd(struct sdl2_console *scon)
> -{
> -#ifdef CONFIG_WIN32
> -    SDL_SysWMinfo info;
> -
> -    SDL_VERSION(&info.version);
> -    if (SDL_GetWindowWMInfo(scon->real_window, &info)) {
> -        return info.info.win.window;
> -    }
> -#endif
> -    return NULL;
> -}
> -
>  static void handle_keydown(SDL_Event *ev)
>  {
>      int win;
> @@ -605,7 +613,7 @@ static void handle_windowevent(SDL_Event *ev)
>          sdl2_redraw(scon);
>          break;
>      case SDL_WINDOWEVENT_FOCUS_GAINED:
> -        win32_kbd_set_grab(gui_grab);
> +        win32_kbd_set_grab(win32_kbd_grab && gui_grab);
>          if (qemu_console_is_graphic(scon->dcl.con)) {
>              win32_kbd_set_window(sdl2_win32_get_hwnd(scon));
>          }
> @@ -849,6 +857,7 @@ static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
>      uint8_t data = 0;
>      int i;
>      SDL_SysWMinfo info;
> +    SDL_version ver;
>      SDL_Surface *icon = NULL;
>      char *dir;
>
> @@ -866,10 +875,7 @@ static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
>  #ifdef SDL_HINT_VIDEO_X11_NET_WM_BYPASS_COMPOSITOR /* only available since SDL 2.0.8 */
>      SDL_SetHint(SDL_HINT_VIDEO_X11_NET_WM_BYPASS_COMPOSITOR, "0");
>  #endif
> -#ifndef CONFIG_WIN32
> -    /* QEMU uses its own low level keyboard hook procedure on Windows */
>      SDL_SetHint(SDL_HINT_GRAB_KEYBOARD, "1");
> -#endif
>  #ifdef SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED
>      SDL_SetHint(SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED, "0");
>  #endif
> @@ -877,6 +883,17 @@ static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
>      SDL_EnableScreenSaver();
>      memset(&info, 0, sizeof(info));
>      SDL_VERSION(&info.version);
> +    /*
> +     * Since version 2.16.0 under Windows, SDL2 has its own low level
> +     * keyboard hook procedure to grab the keyboard. The remaining task of
> +     * QEMU's low level keyboard hook procedure is to filter out the special
> +     * left Control up/down key event for every Alt Gr key event on keyboards
> +     * with an international layout.
> +     */
> +    SDL_GetVersion(&ver);
> +    if (ver.major == 2 && ver.minor < 16) {
> +        win32_kbd_grab = true;
> +    }
>

Note: there is no 2.16 release. They jumped from 2.0.22 to 2.24 (see
https://github.com/libsdl-org/SDL/releases/tag/release-2.24.0)

The windows hook was indeed added in 2.0.16, released on Aug 10, 2021.

Given the distribution nature of the Windows binaries, I think we
could simply depend on a much recent version without worrying about
compatibility with < 2.0.16. This would help reduce the potential
combinations of versions and bugs reports.

>      gui_fullscreen = o->has_full_screen && o->full_screen;
>
> diff --git a/ui/win32-kbd-hook.c b/ui/win32-kbd-hook.c
> index 1ac237db9e..39d42134a2 100644
> --- a/ui/win32-kbd-hook.c
> +++ b/ui/win32-kbd-hook.c
> @@ -91,6 +91,9 @@ void win32_kbd_set_window(void *hwnd)
>              win32_unhook_notifier.notify = keyboard_hook_unhook;
>              qemu_add_exit_notifier(&win32_unhook_notifier);
>          }
> +    } else if (!hwnd && win32_keyboard_hook) {
> +        keyboard_hook_unhook(&win32_unhook_notifier, NULL);
> +        qemu_remove_exit_notifier(&win32_unhook_notifier);
>      }
>
>      win32_window = hwnd;
> --
> 2.35.3
>