[Spice-devel] [PATCH spice-gtk] widget: handle smooth-scroll events

[Christophe Fergeau]

Hey,

On Thu, Jun 07, 2018 at 07:42:24PM +0200, marcandre.lureau at redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau at redhat.com>
> 
> With touchpads and similar devices, scroll events are not emitted on
> Wayland, but only smooth-scroll events.
> 
> There is some discussion about handling smooth-scroll events in Spice
> (see "Add horizontal mouse wheel support" thread), but it will mean
> support from various components. For compatibility reasons, in the
> meantime, let's synthetize the smooth-scroll events to regular scroll
> buttons to fix scrolling.

Indeed, nice idea.. ;)

> 
> Tested on f28, gnome-shell under X and wayland.
> 
> Related to:
> https://bugzilla.redhat.com/show_bug.cgi?id=1386602
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau at redhat.com>
> ---
>  src/spice-widget-priv.h |  1 +
>  src/spice-widget.c      | 32 ++++++++++++++++++++++++--------
>  2 files changed, 25 insertions(+), 8 deletions(-)
> 
> diff --git a/src/spice-widget-priv.h b/src/spice-widget-priv.h
> index 1189cbb..ac69b5f 100644
> --- a/src/spice-widget-priv.h
> +++ b/src/spice-widget-priv.h
> @@ -151,6 +151,7 @@ struct _SpiceDisplayPrivate {
>          SpiceGlScanout      scanout;
>      } egl;
>  #endif // HAVE_EGL
> +    double scroll_delta_y;
>  };
>  
>  int      spice_cairo_image_create                 (SpiceDisplay *display);
> diff --git a/src/spice-widget.c b/src/spice-widget.c
> index 72f5334..a1a2fcd 100644
> --- a/src/spice-widget.c
> +++ b/src/spice-widget.c
> @@ -682,6 +682,8 @@ G_GNUC_END_IGNORE_DEPRECATIONS
>                            GDK_ENTER_NOTIFY_MASK |
>                            GDK_LEAVE_NOTIFY_MASK |
>                            GDK_KEY_PRESS_MASK |
> +                          /* on Wayland, w get only smooth scroll events */

w -> we

> +                          GDK_SMOOTH_SCROLL_MASK |
>                            GDK_SCROLL_MASK);
>      gtk_widget_set_can_focus(widget, true);
>      gtk_event_box_set_above_child(GTK_EVENT_BOX(widget), true);
> @@ -2005,9 +2007,17 @@ static gboolean motion_event(GtkWidget *widget, GdkEventMotion *motion)
>      return true;
>  }
>  
> +static void press_and_release(SpiceDisplay *display,
> +                              gint button, gint button_state)
> +{
> +    SpiceDisplayPrivate *d = display->priv;
> +
> +    spice_inputs_channel_button_press(d->inputs, button, button_state);
> +    spice_inputs_channel_button_release(d->inputs, button, button_state);
> +}
> +
>  static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *scroll)
>  {
> -    int button;
>      SpiceDisplay *display = SPICE_DISPLAY(widget);
>      SpiceDisplayPrivate *d = display->priv;
>  
> @@ -2019,18 +2029,24 @@ static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *scroll)
>          return true;
>  
>      if (scroll->direction == GDK_SCROLL_UP)
> -        button = SPICE_MOUSE_BUTTON_UP;
> +        press_and_release(display, SPICE_MOUSE_BUTTON_UP,
> +                          button_mask_gdk_to_spice(scroll->state));
>      else if (scroll->direction == GDK_SCROLL_DOWN)
> -        button = SPICE_MOUSE_BUTTON_DOWN;
> -    else {
> +        press_and_release(display, SPICE_MOUSE_BUTTON_DOWN,
> +                          button_mask_gdk_to_spice(scroll->state));
> +    else if (scroll->direction == GDK_SCROLL_SMOOTH) {
> +        d->scroll_delta_y += scroll->delta_y;
> +        while (ABS(d->scroll_delta_y) > 1) {
> +            press_and_release(display,
> +                              d->scroll_delta_y < 0 ? SPICE_MOUSE_BUTTON_UP : SPICE_MOUSE_BUTTON_DOWN,
> +                              button_mask_gdk_to_spice(scroll->state));
> +            d->scroll_delta_y += d->scroll_delta_y < 0 ? 1 : -1;

A regular if () would be better for readibility in my opinion.

> +        }

So a change of 1 on the y axis corresponds to 1 press of the button, is
this arbitrary, or is there some rational for that?

> +    } else {
>          DISPLAY_DEBUG(display, "unsupported scroll direction");

We could try to get there on GDK_SCROLL_SMOOTH when delta_y is 0 in the
event, but it's not really important.

>          return true;

That 'return true' is now redundant with the one just below.

Christophe

>      }
>  
> -    spice_inputs_channel_button_press(d->inputs, button,
> -                                      button_mask_gdk_to_spice(scroll->state));
> -    spice_inputs_channel_button_release(d->inputs, button,
> -                                        button_mask_gdk_to_spice(scroll->state));
>      return true;
>  }
>  
> 
> base-commit: e5ece54aca21ae7c4475a8cfebc74d40b6aea44a
> -- 
> 2.18.0.rc1.1.gae296d1cf5
> 
> _______________________________________________
> Spice-devel mailing list
> Spice-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/spice-devel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/spice-devel/attachments/20180608/3c565c17/attachment-0001.sig>