Description of problem:

See Eclipse bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=564910

Version-Release number of selected component (if applicable):

GTK 3.22.30-5 (gtk3-3.22.30-5.el7.x86_64)

How reproducible:

In Eclipse, reproducible with steps listed here: https://bugs.eclipse.org/bugs/show_bug.cgi?id=564910#c1

See video attached to the Eclipse bug: https://bugs.eclipse.org/bugs/attachment.cgi?id=287854

So far we have no GTK+ snippet (or Eclipse SWT only snippet) to reproduce the problem with.

Actual results:

Context menu shows ever-growing blank area when scrolling down.

Expected results:

Context menu has no blank area when scrolling down.

Additional info:

After adding prints, it seems that scroll_offset has very high values while this method runs (when the bug occurs):

static void
gtk_menu_scroll_by (GtkMenu *menu,
gint step)
{
GtkMenuPrivate *priv = menu->priv;
GtkBorder arrow_border;
GtkWidget *widget;
gint offset;
gint view_height;

widget = GTK_WIDGET (menu);
offset = priv->scroll_offset + step;

get_arrows_border (menu, &arrow_border);

/* Don't scroll over the top if we weren't before: */
if ((priv->scroll_offset >= 0) && (offset < 0))
offset = 0;

view_height = gdk_window_get_height (gtk_widget_get_window (widget));

if (priv->scroll_offset == 0 &&
view_height >= priv->requested_height)
return;

/* Don't scroll past the bottom if we weren't before: */
if (priv->scroll_offset > 0)
view_height -= arrow_border.top;

/* Since arrows are shown, reduce view height even more */
view_height -= arrow_border.bottom;

if ((priv->scroll_offset + view_height <= priv->requested_height) &&
(offset + view_height > priv->requested_height))
offset = priv->requested_height - view_height;

if (offset != priv->scroll_offset)
gtk_menu_scroll_to (menu, offset);
}

While checking the GTK+ code in gtkmenu.c, I noticed this bug and patch:

https://bugzilla.gnome.org/show_bug.cgi?id=678113
https://github.com/GNOME/gtk/commit/bd3ca2b30efc534f8b7c18dfd8a9f072592044c7

After adding clamping to the method above, the blank area of the menu was reduced to only 1 blank item at most (while not ideal, still a lot better than before, see attached video "bug564910_gtkmenu_offset_clamp.mp4"):

diff --git a/gtk/gtkmenu.c b/gtk/gtkmenu.c
index 8f7715022f..09cbec26ab 100644
— a/gtk/gtkmenu.c
+++ b/gtk/gtkmenu.c
@@ -4175,7 +4175,12 @@ gtk_menu_scroll_by (GtkMenu *menu,
offset = priv->requested_height - view_height;

if (offset != priv->scroll_offset)
+

{ + offset = CLAMP (offset, + MIN (priv->scroll_offset, 0), + MAX (priv->scroll_offset, priv->requested_height - view_height)); gtk_menu_scroll_to (menu, offset); + }

}

static gboolean