menu view: cleanly separate update, layout phases

This patch improves the separation of the update and layout phases to
avoid superfluous geometry animations of its child widgets. Prior this
patch, 'Widget::geometry' was called in both phases, potentially
triggering geometry animations with intermediate values at the update
phase.

Related to issue #3221

repos/gems/src/app/menu_view/button_widget.h

@@ -101,11 +101,6 @@ struct Menu_view::Button_widget : Widget, Animator::Item
 		_selected = new_selected;
 
 		_update_children(node);
-
-		_children.for_each([&] (Widget &child) {
-			child.geometry(Rect(Point(margin.left + _padding.left,
-			                          margin.top  + _padding.top),
-			                    child.min_size())); });
 	}
 
 	Area min_size() const override
@@ -176,9 +171,20 @@ struct Menu_view::Button_widget : Widget, Animator::Item
 
 	void _layout() override
 	{
-		_children.for_each([&] (Widget &w) {
+		_children.for_each([&] (Widget &child) {
-			w.size(Area(geometry().w() - _space().w(),
+
-			            geometry().h() - _space().h())); });
+			child.position(Point(margin.left + _padding.left,
+			                     margin.top  + _padding.top));
+
+			Area const avail = geometry().area();
+
+			unsigned const
+				w = avail.w() >= _space().w() ? avail.w() - _space().w() : 0,
+				h = avail.h() >= _space().h() ? avail.h() - _space().w() : 0;
+
+			child.size(Area(max(w, child.min_size().w()),
+			                max(h, child.min_size().h())));
+		});
 	}
 
 

repos/gems/src/app/menu_view/depgraph_widget.h

@@ -28,8 +28,6 @@ namespace Menu_view { struct Depgraph_widget; }
 
 struct Menu_view::Depgraph_widget : Widget
 {
-	Area _min_size { }; /* value cached from layout computation */
-
 	struct Depth_direction
 	{
 		enum Value { EAST, WEST, NORTH, SOUTH };
@@ -78,6 +76,24 @@ struct Menu_view::Depgraph_widget : Widget
 		Registry<Registered<Anchor> > _server_anchors { };
 		Registry<Registered<Anchor> > _client_anchors { };
 
+		Rect _widget_geometry { Point(0, 0), Area(0, 0) };
+
+		/**
+		 * Set cached widget geometry, calculated during 'update'
+		 */
+		void widget_geometry(Rect geometry) { _widget_geometry = geometry; }
+
+		/**
+		 * Propagate cached geometry to widget, called during '_layout'
+		 *
+		 * Calling this method may trigger the widget's geometry animation.
+		 */
+		void apply_layout_to_widget()
+		{
+			_widget.position(_widget_geometry.p1());
+			_widget.size(_widget_geometry.area());
+		}
+
 		struct Dependency : Animator::Item
 		{
 			Anchor::Type const _type;
@@ -556,7 +572,8 @@ struct Menu_view::Depgraph_widget : Widget
 			if (client && !server) {
 				warning("node '", client_name, "' depends on "
 				        "non-existing node '", server_name, "'");
-				client->_widget.geometry(Rect(Point(0, 0), Area(0, 0)));
+				client->_widget.position(Point(0, 0));
+				client->_widget.size(Area(0, 0));
 			}
 		});
 
@@ -588,9 +605,17 @@ struct Menu_view::Depgraph_widget : Widget
 		});
 
 		/*
-		 * Apply layout to the children, determine _min_size
+		 * Calculate the bounding box and the designated geometries of all
+		 * widgets.
+		 *
+		 * The bounding box dictates the 'min_size' of the depgraph widget.
+		 *
+		 * The computed widget geometries are stored in their corresponding
+		 * 'Node' objects but are not immediately propagated to the widgets.
+		 * The computed geometries are applied to the widgets in '_layout'
+		 * phase.
 		 */
-		Rect bounding_box(Point(0, 0), Area(0, 0));
+		_bounding_box = Rect(Point(0, 0), Area(0, 0));
 		_children.for_each([&] (Widget &w) {
 			_nodes.for_each([&] (Registered_node &node) {
 				if (!node.belongs_to(w))
@@ -607,35 +632,16 @@ struct Menu_view::Depgraph_widget : Widget
 				                     : Rect(Point(breadth_pos, depth_pos),
 				                            Area(breadth_size, depth_size));
 
-				w.geometry(Rect(node_rect.center(w.min_size()), w.min_size()));
+				Rect geometry(node_rect.center(w.min_size()), w.min_size());
 
-				bounding_box = Rect::compound(bounding_box, w.geometry());
+				node.widget_geometry(geometry);
+
+				_bounding_box = Rect::compound(_bounding_box, geometry);
 			});
 		});
-
-		/*
-		 * Mirror coordinates if graph grows towards north or west
-		 */
-		if (_depth_direction.value == Depth_direction::NORTH
-		 || _depth_direction.value == Depth_direction::WEST) {
-
-			_children.for_each([&] (Widget &w) {
-
-				int x = w.geometry().x1(), y = w.geometry().y1();
-
-				if (_depth_direction.value == Depth_direction::NORTH)
-					y = (int)bounding_box.h() - y - w.geometry().h();
-
-				if (_depth_direction.value == Depth_direction::WEST)
-					x = (int)bounding_box.w() - x - w.geometry().w();
-
-				w.geometry(Rect(Point(x, y), w.geometry().area()));
-			});
-		}
-		_min_size = bounding_box.area();
 	}
 
-	Area min_size() const override { return _min_size; }
+	Area min_size() const override { return _bounding_box.area(); }
 
 	void _draw_connect(Surface<Pixel_rgb888> &pixel_surface,
 	                   Surface<Pixel_alpha8> &alpha_surface,
@@ -720,6 +726,36 @@ struct Menu_view::Depgraph_widget : Widget
 
 	void _layout() override
 	{
+		/*
+		 * Apply layout to the children
+		 */
+		_nodes.for_each([&] (Registered_node &node) {
+			if (&node != &_root_node)
+				node.apply_layout_to_widget(); });
+
+		/*
+		 * Mirror coordinates if graph grows towards north or west
+		 */
+		if (_depth_direction.value == Depth_direction::NORTH
+		 || _depth_direction.value == Depth_direction::WEST) {
+
+			_children.for_each([&] (Widget &w) {
+
+				int x = w.geometry().x1(), y = w.geometry().y1();
+
+				if (_depth_direction.value == Depth_direction::NORTH)
+					y = (int)_bounding_box.h() - y - w.geometry().h();
+
+				if (_depth_direction.value == Depth_direction::WEST)
+					x = (int)_bounding_box.w() - x - w.geometry().w();
+
+				w.position(Point(x, y));
+			});
+		}
+
+		/*
+		 * Prompt each child to update its layout
+		 */
 		_children.for_each([&] (Widget &w) {
 			w.size(w.geometry().area()); });
 	}

repos/gems/src/app/menu_view/float_widget.h

@@ -43,7 +43,8 @@ struct Menu_view::Float_widget : Widget
 		int const x = _west  ? 0 : _east  ? w_space : w_space / 2;
 		int const y = _north ? 0 : _south ? h_space : h_space / 2;
 
-		child.geometry(Rect(Point(x, y), Area(w, h)));
+		child.position(Point(x, y));
+		child.size(Area(w, h));
 	}
 
 	void update(Xml_node node) override

repos/gems/src/app/menu_view/frame_widget.h

@@ -44,13 +44,6 @@ struct Menu_view::Frame_widget : Widget
 
 		_update_children(node);
 
-		/*
-		 * layout
-		 */
-		_children.for_each([&] (Widget &child) {
-			child.geometry(Rect(Point(margin.left + padding.left,
-			                          margin.top  + padding.top),
-			                    child.min_size())); });
 	}
 
 	Area min_size() const override
@@ -83,8 +76,19 @@ struct Menu_view::Frame_widget : Widget
 	void _layout() override
 	{
 		_children.for_each([&] (Widget &child) {
-			child.size(Area(geometry().w() - _space().w(),
+
-			                geometry().h() - _space().h())); });
+			child.position(Point(margin.left + padding.left,
+			                     margin.top  + padding.top));
+
+			Area const avail = geometry().area();
+
+			unsigned const
+				w = avail.w() >= _space().w() ? avail.w() - _space().w() : 0,
+				h = avail.h() >= _space().h() ? avail.h() - _space().w() : 0;
+
+			child.size(Area(max(w, child.min_size().w()),
+			                max(h, child.min_size().h())));
+		});
 	}
 
 	private:

repos/gems/src/app/menu_view/root_widget.h

@@ -74,8 +74,8 @@ struct Menu_view::Root_widget : Widget
 	void _layout() override
 	{
 		_children.for_each([&] (Widget &child) {
-			child.size(geometry().area());
 			child.position(Point(0, 0));
+			child.size(_geometry.area());
 		});
 	}
 };

repos/gems/src/app/menu_view/widget.h

@@ -176,12 +176,6 @@ class Menu_view::Widget : List_model<Widget>::Element
 
 		Margin margin { 0, 0, 0, 0 };
 
-		void geometry(Rect geometry)
-		{
-			_geometry = geometry;
-			_trigger_geometry_animation();
-		}
-
 		Rect geometry() const { return _geometry; }
 
 		Rect animated_geometry() const { return _animated_geometry.rect(); }
@@ -220,6 +214,9 @@ class Menu_view::Widget : List_model<Widget>::Element
 		                  Surface<Pixel_alpha8> &alpha_surface,
 		                  Point at) const = 0;
 
+		/**
+		 * Set widget size and update the widget tree's layout accordingly
+		 */
 		void size(Area size)
 		{
 			_geometry = Rect(_geometry.p1(), size);