Re: [PATCH 0/3] SDL2 usability fixes

[Bernhard Beschow]

Am 14. April 2023 19:09:47 UTC schrieb "Volker Rümelin" <vr_qemu@t-online.de>:
>> Am 13.04.23 um 22:43 schrieb Bernhard Beschow:
>>> 
>>> Am 13. April 2023 17:54:34 UTC schrieb "Volker Rümelin" 
>>> <vr_qemu@t-online.de>:
>>>>> I'm trying to use QEMU on Windows hosts for fun and for profit. While the 
>>>>> GTK
>>>>> GUI doesn't seem to support OpenGL under Windows the SDL2 GUI does. Hence 
>>>>> I
>>>>> used the SDL2 GUI where I ran into several issues of which three are 
>>>>> fixed in
>>>>> this series, which are:
>>>>> 
>>>>> * Alt+Tab switches tasks on the host rather than in the guest in 
>>>>> fullscreen mode
>>>>> * Alt+F4 closes QEMU rather than a graphical task in the guest
>>>>> * AltGr keyboard modifier isn't recognized by a Linux guest
>>>>> 
>>>>> More information about each issue is provided in the patches.
>>>>> 
>>>>> Bernhard Beschow (3):
>>>>>     ui/sdl2: Grab Alt+Tab also in fullscreen mode
>>>>>     ui/sdl2: Grab Alt+F4 also under Windows
>>>>>     ui/sdl2-input: Fix AltGr modifier on Windows hosts
>>>>> 
>>>>>    ui/sdl2-input.c | 13 +++++++++++++
>>>>>    ui/sdl2.c       |  2 ++
>>>>>    2 files changed, 15 insertions(+)
>>>>> 
>>>> Hi Bernhard,
>>> Hi Volker,
>>> 
>>>> I don't think these patches are necessary. The AltGr key and the keyboard 
>>>> grab was fixed in 2020 with commit 830473455f ("ui/sdl2: fix handling of 
>>>> AltGr key on Windows") and a few commits before.
>>> Indeed, this patch addresses the AltGr issue. What I noticed in my case is 
>>> that the AltGr behavior is different, depending on whether the *guest* is 
>>> in graphics mode or not. Pressing AltGr in graphics mode issues two key 
>>> modifiers while only one is issued when the guest is in text mode. I'll 
>>> recheck tomorrow when I have access to a Windows host.
>> 
>> Hi Bernhard,
>> 
>> the AltGr behavior depends on the keyboard grab. The AltGr key works without 
>> keyboard grabbed and it doesn't with keyboard grabbed. That's a bug.
>
>Hi Bernhard,
>
>this used to work before SDL2-2.0.16. There was no code for Windows in SDL2 to 
>handle keyboard grabs. Version 2.0.16 introduced a Windows low level keyboard 
>hook procedure to grab the keyboard. Windows calls this callback before the 
>QEMU keyboard hook procedure. This explains the observed behavior.
>
>The fix is to disable SDL_SetHint(SDL_HINT_GRAB_KEYBOARD, "1"); for Windows. 
>This restores the QEMU keyboard grab for all Windows SDL2 versions.

As you wrote below I'll let you take care of it. Thanks!

> Your first two patches are also necessary. But I think you will need a #ifdef 
> SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED for older SDL2 versions.

[x] Done

v2 is out!

Best regards,
Bernhard

>
>I'll write a patch similar to this one after more tests.
>
>diff --git a/ui/sdl2.c b/ui/sdl2.c
>index b011e8d759..9f6b959464 100644
>--- a/ui/sdl2.c
>+++ b/ui/sdl2.c
>@@ -855,7 +855,9 @@ 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
>     SDL_SetHint(SDL_HINT_GRAB_KEYBOARD, "1");
>+#endif
> #ifdef SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED
>     /* available since SDL 2.0.16 */
>     SDL_SetHint(SDL_HINT_ALLOW_ALT_TAB_WHILE_GRABBED, "0");