Implement ui element hinting support

libs/ui/include/psemek/ui/controller.hpp

@@ -4,6 +4,7 @@
 #include <psemek/ui/font.hpp>
 #include <psemek/gfx/render_target.hpp>
 #include <psemek/util/pimpl.hpp>
+#include <psemek/util/function.hpp>
 
 namespace psemek::ui
 {
@@ -18,6 +19,9 @@ namespace psemek::ui
 		std::shared_ptr<element> set_root(std::shared_ptr<element> r);
 		element * root();
 
+		void set_hint_delay(float seconds);
+		void on_hint(util::function<void(element *)> callback);
+
 		void reshape(geom::box<float, 2> const & shape);
 
 		bool event(mouse_move const & e);

libs/ui/include/psemek/ui/element.hpp

@@ -11,6 +11,8 @@
 #include <psemek/util/function.hpp>
 
 #include <memory>
+#include <optional>
+#include <string>
 
 namespace psemek::ui
 {
@@ -59,6 +61,9 @@ namespace psemek::ui
 		virtual void style_updated();
 		virtual void own_style_updated();
 
+		virtual std::optional<std::string> const & hint() const { return hint_; }
+		virtual std::optional<std::string> set_hint(std::optional<std::string> hint);
+
 		virtual void update(float /* dt */) {}
 
 		virtual void draw(painter & p) const = 0;
@@ -88,6 +93,8 @@ namespace psemek::ui
 
 		mutable std::vector<util::function<void()>> delayed_callbacks_;
 
+		std::optional<std::string> hint_;
+
 		void post_delayed_callbacks() const;
 	};
 

libs/ui/source/controller.cpp

@@ -57,12 +57,21 @@ namespace psemek::ui
 		painter_impl painter;
 		std::shared_ptr<root_proxy> root;
 		std::optional<geom::point<int, 2>> mouse;
+		float hint_delay = 0.f;
+		float hint_timer = 0.f;
+		util::function<void(element *)> on_hint;
+		element * hinted_element = nullptr;
+		bool hint_called = false;
 
 		impl(async::event_loop * loop);
 
 		template <typename E>
 		bool event(E const & e);
 
+		std::pair<bool, element *> event(mouse_move const & e);
+
+		element * hint() const;
+
 		void update(float dt);
 	};
 
@@ -96,6 +105,33 @@ namespace psemek::ui
 		return false;
 	}
 
+	std::pair<bool, element *> controller::impl::event(mouse_move const & e)
+	{
+		element * hinted = nullptr;
+		auto m = geom::cast<float>(e.position);
+		auto visitor = util::recursive([&](auto && self, element * elem) -> bool {
+			if (elem->hidden()) return false;
+
+			auto cs = elem->children();
+			for (auto it = cs.rbegin(); it != cs.rend(); ++it)
+				if (*it && self(*it)) return true;
+
+			if (elem->enabled())
+			{
+				if (elem->hint() && elem->shape().contains(m) && !hinted)
+					hinted = elem;
+				if (elem->on_event(e))
+					return true;
+			}
+			return false;
+		});
+
+		bool result = false;
+		if (root)
+			result = visitor(root.get());
+		return {result, hinted};
+	}
+
 	void controller::impl::update(float dt)
 	{
 		auto visitor = util::recursive([dt](auto && self, element * elem) -> void {
@@ -140,6 +176,16 @@ namespace psemek::ui
 		return impl().root->root.get();
 	}
 
+	void controller::set_hint_delay(float seconds)
+	{
+		impl().hint_delay = seconds;
+	}
+
+	void controller::on_hint(util::function<void(element *)> callback)
+	{
+		impl().on_hint = std::move(callback);
+	}
+
 	void controller::reshape(geom::box<float, 2> const & shape)
 	{
 		impl().root->reshape(shape);
@@ -148,7 +194,18 @@ namespace psemek::ui
 	bool controller::event(mouse_move const & e)
 	{
 		impl().mouse = e.position;
-		return impl().event(e);
+		auto [ result, new_hinted_element ] = impl().event(e);
+
+		if (new_hinted_element != impl().hinted_element)
+		{
+			if (impl().hint_called && impl().on_hint)
+				impl().on_hint(nullptr);
+			impl().hint_timer = 0.f;
+			impl().hint_called = false;
+		}
+		impl().hinted_element = new_hinted_element;
+
+		return result;
 	}
 
 	bool controller::event(mouse_click const & e)
@@ -169,6 +226,17 @@ namespace psemek::ui
 	void controller::update(float dt)
 	{
 		impl().update(dt);
+
+		if (impl().hinted_element && !impl().hint_called)
+		{
+			impl().hint_timer += dt;
+			if (impl().hint_timer >= impl().hint_delay)
+			{
+				if (impl().on_hint)
+					impl().on_hint(impl().hinted_element);
+				impl().hint_called = true;
+			}
+		}
 	}
 
 	void controller::render(gfx::render_target const & rt)

libs/ui/source/element.cpp

@@ -137,6 +137,12 @@ namespace psemek::ui
 		return merged_own_style_;
 	}
 
+	std::optional<std::string> element::set_hint(std::optional<std::string> hint)
+	{
+		std::swap(hint_, hint);
+		return hint;
+	}
+
 	element::~element()
 	{
 		set_style(nullptr);