nitpicker: remove dirty_rect state from view stack

In the presence of potentially multiple output back ends, this
dirty_rect state must be maintained individually per back end. Instead
of storing the dirty_rect as view-stack member, the view stack now calls
a new 'Damage::mark_as_damaged' interface, which allows nitpicker to
propagate this information to multiple back ends. Unfortunately, the
patch must remove the per-view dirty_rect state.

Issue #3812

repos/os/src/server/nitpicker/main.cc

@@ -22,6 +22,7 @@
 #include <framebuffer_session/connection.h>
 #include <os/session_policy.h>
 #include <nitpicker_gfx/tff_font.h>
+#include <util/dirty_rect.h>
 
 /* local includes */
 #include "types.h"
@@ -195,7 +196,7 @@ class Nitpicker::Gui_root : public Root_component<Gui_session>,
 };
 
 
-struct Nitpicker::Main : Focus_updater
+struct Nitpicker::Main : Focus_updater, View_stack::Damage
 {
 	Env &_env;
 
@@ -225,15 +226,33 @@ struct Nitpicker::Main : Focus_updater
 
 		Area size = screen.size();
 
+		typedef Genode::Dirty_rect<Rect, 3> Dirty_rect;
+
+		Dirty_rect dirty_rect { };
+
 		/**
 		 * Constructor
 		 */
 		Framebuffer_screen(Region_map &rm, Framebuffer::Session &fb)
-		: framebuffer(fb), fb_ds(rm, framebuffer.dataspace()) { }
+		:
+			framebuffer(fb), fb_ds(rm, framebuffer.dataspace())
+		{
+			dirty_rect.mark_as_dirty(Rect(Point(0, 0), size));
+		}
 	};
 
 	Reconstructible<Framebuffer_screen> _fb_screen = { _env.rm(), _framebuffer };
 
+	/**
+	 * View_stack::Damage interface
+	 */
+	void mark_as_damaged(Rect rect) override
+	{
+		if (_fb_screen.constructed()) {
+			_fb_screen->dirty_rect.mark_as_dirty(rect);
+		}
+	}
+
 	Point _initial_pointer_pos()
 	{
 		Area const scr_size = _fb_screen->screen.size();
@@ -266,7 +285,7 @@ struct Nitpicker::Main : Focus_updater
 	Tff_font const _font { _binary_default_tff_start, _glyph_buffer };
 
 	Focus      _focus { };
-	View_stack _view_stack { _fb_screen->screen.size(), _focus, _font };
+	View_stack _view_stack { _fb_screen->screen.size(), _focus, _font, *this };
 	User_state _user_state { _focus, _global_keys, _view_stack, _initial_pointer_pos() };
 
 	View_owner _global_view_owner { };
@@ -361,16 +380,6 @@ struct Nitpicker::Main : Focus_updater
 	 */
 	bool _motion_activity = false;
 
-	/**
-	 * Perform redraw and flush pixels to the framebuffer
-	 */
-	void _draw_and_flush()
-	{
-		_view_stack.draw(_fb_screen->screen).flush([&] (Rect const &rect) {
-			_framebuffer.refresh(rect.x1(), rect.y1(),
-			                     rect.w(),  rect.h()); });
-	}
-
 	Main(Env &env) : _env(env)
 	{
 		_view_stack.default_background(_builtin_background);
@@ -471,13 +480,19 @@ void Nitpicker::Main::_handle_input()
 	if (result.motion_activity)
 		_view_stack.geometry(_pointer_origin, Rect(_user_state.pointer_pos(), Area()));
 
-	/* perform redraw and flush pixels to the framebuffer */
-	_view_stack.draw(_fb_screen->screen).flush([&] (Rect const &rect) {
+	/* perform redraw */
+	{
+		/* call 'Dirty_rect::flush' on a copy to preserve the state */
+		Dirty_rect dirty_rect = _fb_screen->dirty_rect;
+		dirty_rect.flush([&] (Rect const &rect) {
+			_view_stack.draw(_fb_screen->screen, rect); });
+	}
+
+	/* flush pixels to the framebuffer, reset dirty_rect */
+	_fb_screen->dirty_rect.flush([&] (Rect const &rect) {
 		_framebuffer.refresh(rect.x1(), rect.y1(),
 		                     rect.w(),  rect.h()); });
 
-	_view_stack.mark_all_views_as_clean();
-
 	/* deliver framebuffer synchronization events */
 	for (Gui_session *s = _session_list.first(); s; s = s->next())
 		s->submit_sync();

repos/os/src/server/nitpicker/view.h

@@ -17,7 +17,6 @@
 /* Genode includes */
 #include <util/string.h>
 #include <util/list.h>
-#include <util/dirty_rect.h>
 #include <base/weak_ptr.h>
 #include <base/rpc_server.h>
 
@@ -30,8 +29,6 @@ namespace Nitpicker {
 	class Buffer;
 	class Focus;
 
-	typedef Dirty_rect<Rect, 3> Dirty_rect;
-
 	/*
 	 * For each buffer, there is a list of views that belong to this buffer.
 	 */
@@ -104,7 +101,6 @@ class Nitpicker::View : private Same_buffer_list_elem,
 		Point       _buffer_off { };  /* offset to the visible buffer area    */
 		View_owner &_owner;
 		Title       _title      { "" };
-		Dirty_rect  _dirty_rect { };
 
 		List<View_parent_elem> _children { };
 
@@ -274,23 +270,6 @@ class Nitpicker::View : private Same_buffer_list_elem,
 		 * Return true if input at screen position 'p' refers to the view
 		 */
 		bool input_response_at(Point p) const;
-
-		/**
-		 * Mark part of view as dirty
-		 *
-		 * \param rect  dirty rectangle in absolute coordinates
-		 */
-		void mark_as_dirty(Rect rect) { _dirty_rect.mark_as_dirty(rect); }
-
-		/**
-		 * Return dirty-rectangle information
-		 */
-		Dirty_rect dirty_rect() const { return _dirty_rect; }
-
-		/**
-		 * Reset dirty rectangle
-		 */
-		void mark_as_clean() { _dirty_rect = Dirty_rect(); }
 };
 
 #endif /* _VIEW_H_ */

repos/os/src/server/nitpicker/view_stack.cc

@@ -190,9 +190,8 @@ void View_stack::draw_rec(Canvas_base &canvas, Font const &font,
 	if (next && left.valid()) draw_rec(canvas, font, next, left);
 
 	/* draw current view */
-	view->dirty_rect().flush([&] (Rect const &dirty_rect) {
-
-		Clip_guard clip_guard(canvas, Rect::intersect(clipped, dirty_rect));
+	{
+		Clip_guard clip_guard(canvas, clipped);
 
 		/* draw background if view is transparent */
 		if (view->uses_alpha())
@@ -200,7 +199,7 @@ void View_stack::draw_rec(Canvas_base &canvas, Font const &font,
 
 		view->frame(canvas, _focus);
 		view->draw(canvas, font, _focus);
-	});
+	}
 
 	/* draw areas at the bottom/right of the current view */
 	if (next &&  right.valid()) draw_rec(canvas, font, next, right);
@@ -213,8 +212,7 @@ void View_stack::refresh_view(View &view, Rect const rect)
 	/* rectangle constrained to view geometry */
 	Rect const view_rect = Rect::intersect(rect, _outline(view));
 
-	for (View *v = _first_view(); v; v = v->view_stack_next())
-		_mark_view_as_dirty(*v, view_rect);
+	_damage.mark_as_damaged(view_rect);
 
 	view.for_each_child([&] (View &child) { refresh_view(child, rect); });
 }
@@ -286,7 +284,7 @@ void View_stack::title(View &view, const char *title)
 	view.title(_font, title);
 	_place_labels(view.abs_geometry());
 
-	_mark_view_as_dirty(view, _outline(view));
+	_damage.mark_as_damaged(_outline(view));
 }
 
 

repos/os/src/server/nitpicker/view_stack.h

@@ -23,6 +23,13 @@ namespace Nitpicker { class View_stack; }
 
 class Nitpicker::View_stack
 {
+	public:
+
+		struct Damage : Interface, Noncopyable
+		{
+			virtual void mark_as_damaged(Rect) = 0;
+		};
+
 	private:
 
 		Area                   _size;
@@ -30,7 +37,7 @@ class Nitpicker::View_stack
 		Font            const &_font;
 		List<View_stack_elem>  _views { };
 		View                  *_default_background = nullptr;
-		Dirty_rect mutable     _dirty_rect { };
+		Damage                &_damage;
 
 		/**
 		 * Return outline geometry of a view
@@ -79,27 +86,15 @@ class Nitpicker::View_stack
 		template <typename VIEW>
 		VIEW *_next_view(VIEW &view) const;
 
-		/**
-		 * Schedule 'rect' to be redrawn
-		 */
-		void _mark_view_as_dirty(View &view, Rect rect)
-		{
-			_dirty_rect.mark_as_dirty(rect);
-
-			view.mark_as_dirty(rect);
-		}
-
 	public:
 
 		/**
 		 * Constructor
 		 */
-		View_stack(Area size, Focus &focus, Font const &font)
+		View_stack(Area size, Focus &focus, Font const &font, Damage &damage)
 		:
-			_size(size), _focus(focus), _font(font)
-		{
-			_dirty_rect.mark_as_dirty(Rect(Point(0, 0), _size));
-		}
+			_size(size), _focus(focus), _font(font), _damage(damage)
+		{ }
 
 		/**
 		 * Return size
@@ -121,16 +116,11 @@ class Nitpicker::View_stack
 		void draw_rec(Canvas_base &, Font const &, View const *, Rect) const;
 
 		/**
-		 * Draw dirty areas
+		 * Draw specified area
 		 */
-		Dirty_rect draw(Canvas_base &canvas) const
+		void draw(Canvas_base &canvas, Rect rect) const
 		{
-			Dirty_rect result = _dirty_rect;
-
-			_dirty_rect.flush([&] (Rect const &rect) {
-				draw_rec(canvas, _font, _first_view(), rect); });
-
-			return result;
+			draw_rec(canvas, _font, _first_view(), rect);
 		}
 
 		/**
@@ -141,19 +131,7 @@ class Nitpicker::View_stack
 			Rect const whole_screen(Point(), _size);
 
 			_place_labels(whole_screen);
-			_dirty_rect.mark_as_dirty(whole_screen);
-
-			for (View *view = _first_view(); view; view = view->view_stack_next())
-				view->mark_as_dirty(_outline(*view));
-		}
-
-		/**
-		 * mark all view-local dirty rectangles a clean
-		 */
-		void mark_all_views_as_clean()
-		{
-			for (View *view = _first_view(); view; view = view->view_stack_next())
-				view->mark_as_clean();
+			_damage.mark_as_damaged(whole_screen);
 		}
 
 		/**