[Spice-devel] [PATCH spice-gtk v2] widget: handle smooth-scroll events

[Christophe Fergeau]

On Fri, Jun 08, 2018 at 12:32:27PM +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.
> 
> 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      | 43 ++++++++++++++++++++++++++++++-----------
>  2 files changed, 33 insertions(+), 11 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..f5b7b40 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, only smooth-scroll events are emitted */
> +                          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);
> @@ -2005,11 +2007,20 @@ 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;
> +    gint button_state = button_mask_gdk_to_spice(scroll->state);
>  
>      DISPLAY_DEBUG(display, "%s", __FUNCTION__);
>  
> @@ -2018,19 +2029,29 @@ static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *scroll)
>      if (d->disable_inputs)
>          return true;
>  
> -    if (scroll->direction == GDK_SCROLL_UP)
> -        button = SPICE_MOUSE_BUTTON_UP;
> -    else if (scroll->direction == GDK_SCROLL_DOWN)
> -        button = SPICE_MOUSE_BUTTON_DOWN;
> -    else {
> +    switch (scroll->direction) {
> +    case GDK_SCROLL_UP:
> +        press_and_release(display, SPICE_MOUSE_BUTTON_UP, button_state);
> +        break;
> +    case GDK_SCROLL_DOWN:
> +        press_and_release(display, SPICE_MOUSE_BUTTON_DOWN, button_state);
> +        break;
> +    case GDK_SCROLL_SMOOTH:
> +        d->scroll_delta_y += scroll->delta_y;
> +        while (ABS(d->scroll_delta_y) > 1) {
> +            if (d->scroll_delta_y < 0) {
> +                press_and_release(display, SPICE_MOUSE_BUTTON_UP, button_state);
> +                d->scroll_delta_y += 1;
> +            } else {
> +                press_and_release(display, SPICE_MOUSE_BUTTON_DOWN, button_state);
> +                d->scroll_delta_y += -1;

d->scroll_delta_y -= 1 ? (I'm fine either way).

Acked-by: Christophe Fergeau <cfergeau at redhat.com>

Christophe

> +            }
> +        }
> +        break;
> +    default:
>          DISPLAY_DEBUG(display, "unsupported scroll direction");
> -        return true;
>      }
>  
> -    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
> 
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