Re: [PULL 17/19] ui/gtk: Consider scaling when propagating ui info

[Michael Tokarev <mjt@tls.msk.ru>]

On 5/24/25 20:35, marcandre.lureau@redhat.com wrote:
> From: Weifeng Liu <weifeng.liu.z@gmail.com>
> 
> The ui width and height sent to guest is supposed to be in buffer
> coordinate. Hence conversion is required.
> 
> If scaling (global window scale and zooming scale) is not respected in
> non-free-scale mode, window size could keep changing because of the
> existence of the iteration of the following steps:
> 
> 1. In resize event or configure event, a size larger (or smaller) than
>     the currently used one might be calculated due to not considering
>     scaling.
> 2. On reception of the display size change event in guest, the guest
>     might decide to do a mode setting and use the larger (or smaller)
>     mode.
> 3. When the new guest scan-out command arrives, QEMU would request the
>     window size to change to fit the new buffer size. This will trigger a
>     resize event or a configure event, making us go back to step 1.
> 
> Signed-off-by: Weifeng Liu <weifeng.liu.z@gmail.com>
> Message-ID: <20250511073337.876650-8-weifeng.liu.z@gmail.com>
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   ui/gtk.c | 25 +++++++++++++++++++++++--
>   1 file changed, 23 insertions(+), 2 deletions(-)

Hi!

I just stumbled upon this change, which looks like a good candidate
for qemu-stable 10.0.x series (lts), what do you think?

Thanks,

/mjt

> diff --git a/ui/gtk.c b/ui/gtk.c
> index 47af49e387..8c4a94c8f6 100644
> --- a/ui/gtk.c
> +++ b/ui/gtk.c
> @@ -772,8 +772,21 @@ static void gd_resize_event(GtkGLArea *area,
>                               gint width, gint height, gpointer *opaque)
>   {
>       VirtualConsole *vc = (void *)opaque;
> +    double pw = width, ph = height;
> +    double sx = vc->gfx.scale_x, sy = vc->gfx.scale_y;
> +    GdkWindow *window = gtk_widget_get_window(GTK_WIDGET(area));
> +    const int gs = gdk_window_get_scale_factor(window);
>   
> -    gd_set_ui_size(vc, width, height);
> +    if (!vc->s->free_scale && !vc->s->full_screen) {
> +        pw /= sx;
> +        ph /= sy;
> +    }
> +
> +    /**
> +     * width and height here are in pixel coordinate, so we must divide it
> +     * by global window scale (gs)
> +     */
> +    gd_set_ui_size(vc, pw / gs, ph / gs);
>   }
>   
>   #endif
> @@ -1836,8 +1849,16 @@ static gboolean gd_configure(GtkWidget *widget,
>                                GdkEventConfigure *cfg, gpointer opaque)
>   {
>       VirtualConsole *vc = opaque;
> +    const double sx = vc->gfx.scale_x, sy = vc->gfx.scale_y;
> +    double width = cfg->width, height = cfg->height;
> +
> +    if (!vc->s->free_scale && !vc->s->full_screen) {
> +        width /= sx;
> +        height /= sy;
> +    }
> +
> +    gd_set_ui_size(vc, width, height);
>   
> -    gd_set_ui_size(vc, cfg->width, cfg->height);
>       return FALSE;
>   }
>