[vte] widget: Implement GtkScrollableInterface::get_border

[Christian Persch <chpe src gnome org>]

commit a7b863a6fcfc7f3bf4f96ce6baffaa240c5830f2
Author: Christian Persch <chpe src gnome org>
Date:   Thu Sep 24 21:39:43 2020 +0200

    widget: Implement GtkScrollableInterface::get_border
    
    https://gitlab.gnome.org/GNOME/vte/-/issues/283

 src/vtegtk.cc      | 26 ++++++++++++++++++++++++--
 src/vteinternal.hh |  1 +
 src/widget.hh      |  1 +
 3 files changed, 26 insertions(+), 2 deletions(-)
---
diff --git a/src/vtegtk.cc b/src/vtegtk.cc
index 936b38b9..bde7f976 100644
--- a/src/vtegtk.cc
+++ b/src/vtegtk.cc
@@ -78,6 +78,8 @@ struct _VteTerminalClassPrivate {
         GtkStyleProvider *style_provider;
 };
 
+static void vte_terminal_scrollable_iface_init(GtkScrollableInterface* iface) noexcept;
+
 #ifdef VTE_DEBUG
 G_DEFINE_TYPE_WITH_CODE(VteTerminal, vte_terminal, GTK_TYPE_WIDGET,
                         {
@@ -85,7 +87,7 @@ G_DEFINE_TYPE_WITH_CODE(VteTerminal, vte_terminal, GTK_TYPE_WIDGET,
                                         g_type_add_instance_private(g_define_type_id, 
sizeof(vte::platform::Widget));
                         }
                         g_type_add_class_private (g_define_type_id, sizeof (VteTerminalClassPrivate));
-                        G_IMPLEMENT_INTERFACE(GTK_TYPE_SCROLLABLE, NULL)
+                        G_IMPLEMENT_INTERFACE(GTK_TYPE_SCROLLABLE, vte_terminal_scrollable_iface_init)
                         if (_vte_debug_on(VTE_DEBUG_LIFECYCLE)) {
                                 g_printerr("vte_terminal_get_type()\n");
                         })
@@ -96,7 +98,7 @@ G_DEFINE_TYPE_WITH_CODE(VteTerminal, vte_terminal, GTK_TYPE_WIDGET,
                                         g_type_add_instance_private(g_define_type_id, 
sizeof(vte::platform::Widget));
                         }
                         g_type_add_class_private (g_define_type_id, sizeof (VteTerminalClassPrivate));
-                        G_IMPLEMENT_INTERFACE(GTK_TYPE_SCROLLABLE, NULL))
+                        G_IMPLEMENT_INTERFACE(GTK_TYPE_SCROLLABLE, vte_terminal_scrollable_iface_init))
 #endif
 
 static inline
@@ -2038,6 +2040,26 @@ vte_terminal_class_init(VteTerminalClass *klass)
 #endif
 }
 
+static gboolean
+vte_terminal_scrollable_get_border(GtkScrollable* scrollable,
+                                   GtkBorder* border) noexcept
+try
+{
+        *border = *WIDGET(VTE_TERMINAL(scrollable))->padding();
+        return true;
+}
+catch (...)
+{
+        vte::log_exception();
+        return false;
+}
+
+static void
+vte_terminal_scrollable_iface_init(GtkScrollableInterface* iface) noexcept
+{
+        iface->get_border = vte_terminal_scrollable_get_border;
+}
+
 /* public API */
 
 /**
diff --git a/src/vteinternal.hh b/src/vteinternal.hh
index 8c510912..065c19d8 100644
--- a/src/vteinternal.hh
+++ b/src/vteinternal.hh
@@ -975,6 +975,7 @@ public:
 
         /* Style stuff */
         GtkBorder m_padding{1, 1, 1, 1};
+        auto padding() const noexcept { return &m_padding; }
 
         vte::glib::RefPtr<GtkAdjustment> m_vadjustment{};
         auto vadjustment() noexcept { return m_vadjustment.get(); }
diff --git a/src/widget.hh b/src/widget.hh
index d870135c..ed9837a3 100644
--- a/src/widget.hh
+++ b/src/widget.hh
@@ -108,6 +108,7 @@ public:
         void set_vscroll_policy(GtkScrollablePolicy policy) noexcept { m_vscroll_policy = policy; }
         auto hscroll_policy() const noexcept { return m_hscroll_policy; }
         auto vscroll_policy() const noexcept { return m_vscroll_policy; }
+        auto padding() const noexcept { return terminal()->padding(); }
 
         bool set_cursor_blink_mode(VteCursorBlinkMode mode) { return 
terminal()->set_cursor_blink_mode(vte::terminal::Terminal::CursorBlinkMode(mode)); }
         auto cursor_blink_mode() const noexcept { return 
VteCursorBlinkMode(terminal()->cursor_blink_mode()); }