Re: [PATCH] display/gtk: get proper refreshrate

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Nikola,

Cc'ing the qemu-devel list.

On 12/31/19 1:38 AM, Nikola Pavlica wrote:
> On Mon, 2019-12-30 at 23:59 +0100, Philippe Mathieu-Daudé wrote:
>> Hi Nikola,
>>
>> Thanks for your patch!
>>
>> On 12/30/19 6:28 PM, Nikola Pavlica wrote:
>>>   From 70c95b18fa056b2dd0ecc202ab517bc775b986da Mon Sep 17 00:00:00
>>> 2001
>>> From: Nikola Pavlica <pavlica.nikola@gmail.com>
>>> Date: Mon, 30 Dec 2019 18:17:35 +0100
>>> Subject: [PATCH] display/gtk: get proper refreshrate
>>
>> Can you describe here the problem you encountered, and how your
>> patch
>> fixes it?
>>
>>> Signed-off-by: Nikola Pavlica <pavlica.nikola@gmail.com>
>>> ---
>>>    ui/gtk.c | 5 +++++
>>>    1 file changed, 5 insertions(+)
>>>
>>> diff --git a/ui/gtk.c b/ui/gtk.c
>>> index 692ccc7bbb..7a041457f2 100644
>>> --- a/ui/gtk.c
>>> +++ b/ui/gtk.c
>>> @@ -2259,6 +2259,11 @@ static void gtk_display_init(DisplayState
>>> *ds,
>>> DisplayOptions *opts)
>>>            opts->u.gtk.grab_on_hover) {
>>>            gtk_menu_item_activate(GTK_MENU_ITEM(s-
>>>> grab_on_hover_item));
>>>        }
>>> +
>>> +    GdkDisplay *display = gdk_display_get_default();
>>
>> Can we use window_display declared earlier instead?
>>
>>       window_display = gtk_widget_get_display(s->window);
>>
>> If you look at the CODING_STYLE.rst file referenced here:
>> https://wiki.qemu.org/Contribute/SubmitAPatch#Use_the_QEMU_coding_style
>> It states:
>>
>>     Declarations
>>     ============
>>
>>     Mixed declarations (interleaving statements and declarations
>>     within blocks) are generally not allowed; declarations should
>>     be at the beginning of blocks.
>>
>> So you should move the declaration of both display/monitor variables
>> earlier, around line 2192.
>>
>>> +    GdkMonitor *monitor =
>>> gdk_display_get_primary_monitor(display);
>>> +    vc->gfx.dcl.update_interval = 1000000 /
>>> +        gdk_monitor_get_refresh_rate(monitor);
>>
>> Now looking at this line, I think this should be done in the
>> gd_vc_gfx_init() function (line 2029, before the
>> register_displaychangelistener() call).
>>
>>>    }
>>>    
>>>    static void early_gtk_display_init(DisplayOptions *opts)
>>>
>>
>> As suggested on IRC, your patch have more chances to get reviewed if
>> you
>> Cc its maintainers. See this help here:
>> https://wiki.qemu.org/Contribute/SubmitAPatch#CC_the_relevant_maintainer
>>
>> In this case we get:
>>
>> $ ./scripts/get_maintainer.pl -f ui/gtk.c
>> Gerd Hoffmann <kraxel@redhat.com> (odd fixer:Graphics)
>> qemu-devel@nongnu.org (open list:All patches CC here)
>>
>> I'm Cc'ing Gerd for you.
>>
>> Regards,
>>
>> Phil.
>>

This patch is hard to review because it follows another patch...
See: 
https://wiki.qemu.org/Contribute/SubmitAPatch#Do_not_send_as_an_attachment

This is v2, next time post a v3 as a new thread please.

>  From f4934509ac2da1bbb747422990587433ecc44a0b Mon Sep 17 00:00:00 2001
> From: Nikola Pavlica <pavlica.nikola@gmail.com>
> Date: Tue, 31 Dec 2019 01:12:42 +0100
> Subject: [PATCH v2] display/gtk: get proper refreshrate

<here goes the description of problem and fix>

> Signed-off-by: Nikola Pavlica <pavlica.nikola@gmail.com>
> ---
>   ui/gtk.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/ui/gtk.c b/ui/gtk.c
> index 692ccc7bbb..2055dcc03d 100644
> --- a/ui/gtk.c
> +++ b/ui/gtk.c
> @@ -1967,6 +1967,10 @@ static GSList *gd_vc_gfx_init(GtkDisplayState
> *s, VirtualConsole *vc,
>   {
>       bool zoom_to_fit = false;
>   
> +    GdkDisplay *dpy = gtk_widget_get_display(s->window);
> +    GdkWindow *win = gtk_widget_get_window(s->window);
> +    GdkMonitor *monitor = gdk_display_get_monitor_at_window(dpy, win);
> +
>       vc->label = qemu_console_get_label(con);
>       vc->s = s;
>       vc->gfx.scale_x = 1.0;
> @@ -2026,6 +2030,8 @@ static GSList *gd_vc_gfx_init(GtkDisplayState *s,
> VirtualConsole *vc,
>   
>       vc->gfx.kbd = qkbd_state_init(con);
>       vc->gfx.dcl.con = con;
> +    vc->gfx.dcl.update_interval = 1000000 /
> +        gdk_monitor_get_refresh_rate(monitor);

 From the documentation of gdk_monitor_get_refresh_rate():

   The value is in milli-Hertz, so a refresh rate of 60Hz is
   returned as 60000.

   Returns

     the refresh rate in milli-Hertz, or 0

Watch out we don't want to crash on division by zero. Maybe we don't 
want to set the update_interval if the refresh rate is null.

Also, I'd try to avoid the magic value and define something more obvious 
to review, such:

   #define MSEC_PER_MILLIHZ 1000000

   ...

   int refresh_rate_millihz;

   ...

   refresh_rate_millihz = gdk_monitor_get_refresh_rate()
   if (refresh_rate_millihz) {
       vc->gfx.dcl.update_interval = MSEC_PER_MILLIHZ / 
refresh_rate_millihz;
   }

>       register_displaychangelistener(&vc->gfx.dcl);
>   
>       gd_connect_vc_gfx_signals(vc);
>