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display/gtk: get proper refreshrate

Because some VMs in QEMU can get GPU virtualization (using technologies
such as iGVT-g, as mentioned previously), they could produce a video
output that had a higher display refresh rate than of what the GTK
display was displaying. (fxp. Playing a video game inside of a Windows
VM at 60 Hz, while the output stood locked at 33 Hz because of defaults
set in include/ui/console.h)

Since QEMU does indeed have internal systems for determining frame
times as defined in ui/console.c.
The code checks for a variable called update_interval that it later
uses for time calculation. This variable, however, isn't defined
anywhere in ui/gtk.c and instead ui/console.c just sets it to
GUI_REFRESH_INTERVAL_DEFAULT which is 30

update_interval represents the number of milliseconds per display
refresh, and by doing some math we get that 1000/30 = 33.33... Hz

This creates the mentioned problem and what this patch does is that it
checks for the display refresh rate reported by GTK itself (we can take
this as a safe value) and just converts it back to a number of
milliseconds per display refresh.

Signed-off-by: Nikola Pavlica <pavlica.nikola@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200108121342.29597-1-pavlica.nikola@gmail.com

[ kraxel: style tweak: add blank line between vars and code ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

authored by

Nikola Pavlica and committed by
Gerd Hoffmann c4c00922 c388f408

+13
+2
include/ui/gtk.h
··· 28 28 #include "ui/egl-context.h" 29 29 #endif 30 30 31 + #define MILLISEC_PER_SEC 1000000 32 + 31 33 typedef struct GtkDisplayState GtkDisplayState; 32 34 33 35 typedef struct VirtualGfxConsole {
+11
ui/gtk.c
··· 1966 1966 GSList *group, GtkWidget *view_menu) 1967 1967 { 1968 1968 bool zoom_to_fit = false; 1969 + int refresh_rate_millihz; 1970 + 1971 + GdkDisplay *dpy = gtk_widget_get_display(s->window); 1972 + GdkWindow *win = gtk_widget_get_window(s->window); 1973 + GdkMonitor *monitor = gdk_display_get_monitor_at_window(dpy, win); 1969 1974 1970 1975 vc->label = qemu_console_get_label(con); 1971 1976 vc->s = s; ··· 2026 2031 2027 2032 vc->gfx.kbd = qkbd_state_init(con); 2028 2033 vc->gfx.dcl.con = con; 2034 + 2035 + refresh_rate_millihz = gdk_monitor_get_refresh_rate(monitor); 2036 + if (refresh_rate_millihz) { 2037 + vc->gfx.dcl.update_interval = MILLISEC_PER_SEC / refresh_rate_millihz; 2038 + } 2039 + 2029 2040 register_displaychangelistener(&vc->gfx.dcl); 2030 2041 2031 2042 gd_connect_vc_gfx_signals(vc);