st/scrollview: Add ::content-padding property to StScrollView

This will be needed for fine tuning of the visible area for appGrid
navigation purposes. We most nominally can let it happen via CSS as
the size calculations happen on size allocate, so we want to avoid
triggering relayouts while adapting to the given size.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1630>

2 files changed, 29 insertions, 0 deletions

diff --git a/src/st/st-scroll-view-fade.c b/src/st/st-scroll-view-fade.c
index 38d40ed65..3ca731337 100644
--- a/src/st/st-scroll-view-fade.c
+++ b/src/st/st-scroll-view-fade.c
@@ -97,6 +97,7 @@ st_scroll_view_fade_paint_target (ClutterOffscreenEffect *effect,
   gboolean h_scroll_visible, v_scroll_visible;
 
   ClutterActorBox allocation, content_box, paint_box;
+  ClutterMargin *content_padding;
 
   float fade_area_topleft[2];
   float fade_area_bottomright[2];
@@ -108,6 +109,13 @@ st_scroll_view_fade_paint_target (ClutterOffscreenEffect *effect,
   clutter_actor_get_allocation_box (self->actor, &allocation);
   st_theme_node_get_content_box (st_widget_get_theme_node (ST_WIDGET (self->actor)),
                                 (const ClutterActorBox *)&allocation, &content_box);
+  g_object_get (self->actor, "content-padding", &content_padding, NULL);
+
+  content_box.x1 += content_padding->left;
+  content_box.x2 -= content_padding->right;
+  content_box.y1 += content_padding->top;
+  content_box.y2 -= content_padding->bottom;
+  clutter_margin_free (content_padding);
 
   /*
    * The FBO is based on the paint_volume's size which can be larger then the actual
diff --git a/src/st/st-scroll-view.c b/src/st/st-scroll-view.c
index 3b9711ea2..606701565 100644
--- a/src/st/st-scroll-view.c
+++ b/src/st/st-scroll-view.c
@@ -84,6 +84,8 @@ struct _StScrollViewPrivate
   StAdjustment *vadjustment;
   ClutterActor *vscroll;
 
+  ClutterMargin content_padding;
+
   StPolicyType hscrollbar_policy;
   StPolicyType vscrollbar_policy;
 
@@ -116,6 +118,7 @@ enum {
   PROP_VSCROLLBAR_VISIBLE,
   PROP_MOUSE_SCROLL,
   PROP_OVERLAY_SCROLLBARS,
+  PROP_CONTENT_PADDING,
 
   N_PROPS
 };
@@ -156,6 +159,9 @@ st_scroll_view_get_property (GObject    *object,
     case PROP_OVERLAY_SCROLLBARS:
       g_value_set_boolean (value, priv->overlay_scrollbars);
       break;
+    case PROP_CONTENT_PADDING:
+      g_value_set_boxed (value, &priv->content_padding);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
     }
@@ -233,6 +239,9 @@ st_scroll_view_set_property (GObject      *object,
                                  priv->hscrollbar_policy,
                                  g_value_get_enum (value));
       break;
+    case PROP_CONTENT_PADDING:
+      priv->content_padding = * (ClutterMargin *) g_value_get_boxed (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
     }
@@ -545,6 +554,11 @@ st_scroll_view_allocate (ClutterActor          *actor,
 
   st_theme_node_get_content_box (theme_node, box, &content_box);
 
+  content_box.x1 += priv->content_padding.left;
+  content_box.x2 -= priv->content_padding.right;
+  content_box.y1 += priv->content_padding.top;
+  content_box.y2 += priv->content_padding.bottom;
+
   avail_width = content_box.x2 - content_box.x1;
   avail_height = content_box.y2 - content_box.y1;
 
@@ -933,6 +947,13 @@ st_scroll_view_class_init (StScrollViewClass *klass)
                           FALSE,
                           ST_PARAM_READWRITE);
 
+  props[PROP_CONTENT_PADDING] =
+    g_param_spec_boxed ("content-padding",
+                        "Content padding",
+                        "Content padding",
+                        CLUTTER_TYPE_MARGIN,
+                        ST_PARAM_READWRITE);
+
   g_object_class_install_properties (object_class, N_PROPS, props);
 }