view::refresh(element) optimization by caching the latest element bounds.

Author: djowel

lib/include/elements/support/context.hpp

@@ -75,17 +75,23 @@ namespace cycfi::elements
       context(context const& rhs, artist::rect bounds_)
        : basic_context(rhs.view, rhs.canvas), element(rhs.element)
        , parent(rhs.parent), bounds(bounds_)
-      {}
+      {
+         update_bounds();
+      }
 
       context(context const& parent_, element* element_, artist::rect bounds_)
        : basic_context(parent_.view, parent_.canvas), element(element_)
        , parent(&parent_), bounds(bounds_)
-      {}
+      {
+         update_bounds();
+      }
 
       context(class view& view_, class canvas& canvas_, element* element_, artist::rect bounds_)
        : basic_context(view_, canvas_), element(element_)
        , parent(nullptr), bounds(bounds_)
-      {}
+      {
+         update_bounds();
+      }
 
       context(context const&) = default;
       context& operator=(context const&) = delete;
@@ -122,6 +128,8 @@ namespace cycfi::elements
 
    private:
 
+      void update_bounds();
+
       using listener_function =
          std::function<
             void(context const& ctx, elements::element*, string_view what)

lib/include/elements/view.hpp

@@ -120,6 +120,8 @@ namespace cycfi { namespace elements
 
    private:
 
+      friend class context;
+
       scaled_content          make_scaled_content() { return elements::scale(1.0, link(_content)); }
 
       layer_composite         _content;
@@ -144,6 +146,10 @@ namespace cycfi { namespace elements
       using tracking_map = std::map<element*, time_point>;
 
       tracking_map            _tracking;
+
+      using bounds_map = std::unordered_map<element*, rect>;
+
+      bounds_map              _bounds_map;
    };
 
    ////////////////////////////////////////////////////////////////////////////
@@ -352,6 +358,14 @@ namespace cycfi { namespace elements
    {
       _io.post(f);
    }
+
+   // Declared in context.hpp. We define this here because view is forward declared in
+   // the header file and thus does not have access to the actual view class.
+   inline void context::update_bounds()
+   {
+      if (auto i = view._bounds_map.find(element); i != view._bounds_map.end())
+         i->second = bounds;
+   }
 }}
 
 #endif

lib/src/view.cpp

@@ -181,6 +181,12 @@ namespace cycfi { namespace elements
 
    void view::refresh(context const& ctx, int outward)
    {
+      if (auto i = _bounds_map.find(ctx.element); i != _bounds_map.end())
+      {
+         refresh(i->second);
+         return;
+      }
+
       context const* ctx_ptr = &ctx;
       while (outward > 0 && ctx_ptr)
       {
@@ -192,6 +198,7 @@ namespace cycfi { namespace elements
          auto tl = ctx.canvas.user_to_device(ctx_ptr->bounds.top_left());
          auto br = ctx.canvas.user_to_device(ctx_ptr->bounds.bottom_right());
          refresh({tl.x, tl.y, br.x, br.y});
+         _bounds_map[ctx_ptr->element] = rect{tl, br};
       }
    }