From b3d598f551a874b34ff4fb51a0a65631fc3ad070 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Thu, 10 Oct 2013 15:00:41 +0100
Subject: [PATCH] Basic snapping in the timeline.

---
 ChangeLog                 |  2 ++
 src/wx/timeline.cc        | 57 +++++++++++++++++++++++++++++++++++++--
 src/wx/timeline.h         |  9 +++++++
 src/wx/timeline_dialog.cc | 16 ++++++++++-
 src/wx/timeline_dialog.h  |  3 +++
 5 files changed, 84 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 2599b9b97..d741a3a2e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2013-10-10  Carl Hetherington  <cth@carlh.net>
 
+	* Basic snapping in the timeline.
+
 	* Various improvements to dcpomatic_kdm.
 
 2013-10-10  Carl Hetherington  <cth@carlh.net>
diff --git a/src/wx/timeline.cc b/src/wx/timeline.cc
index 87070b35e..1f0aee4e8 100644
--- a/src/wx/timeline.cc
+++ b/src/wx/timeline.cc
@@ -33,7 +33,9 @@ using boost::shared_ptr;
 using boost::weak_ptr;
 using boost::dynamic_pointer_cast;
 using boost::bind;
+using boost::optional;
 
+/** Parent class for components of the timeline (e.g. a piece of content or an axis) */
 class View : public boost::noncopyable
 {
 public:
@@ -332,6 +334,7 @@ Timeline::Timeline (wxWindow* parent, FilmEditor* ed, shared_ptr<Film> film)
 	, _down_view_position (0)
 	, _first_move (false)
 	, _menu (film, this)
+	, _snap (true)
 {
 #ifndef __WXOSX__
 	SetDoubleBuffered (true);
@@ -577,6 +580,9 @@ Timeline::set_position_from_event (wxMouseEvent& ev)
 	wxPoint const p = ev.GetPosition();
 
 	if (!_first_move) {
+		/* We haven't moved yet; in that case, we must move the mouse some reasonable distance
+		   before the drag is considered to have started.
+		*/
 		int const dist = sqrt (pow (p.x - _down_point.x, 2) + pow (p.y - _down_point.y, 2));
 		if (dist < 8) {
 			return;
@@ -584,9 +590,56 @@ Timeline::set_position_from_event (wxMouseEvent& ev)
 		_first_move = true;
 	}
 
-	Time const time_diff = (p.x - _down_point.x) / _pixels_per_time_unit;
 	if (_down_view) {
-		_down_view->content()->set_position (max (static_cast<Time> (0), _down_view_position + time_diff));
+		Time new_position = _down_view_position + (p.x - _down_point.x) / _pixels_per_time_unit;
+		
+		if (_snap) {
+
+			bool first = true;
+			Time nearest_distance = TIME_MAX;
+			Time nearest_new_position = TIME_MAX;
+			
+			/* Find the nearest content edge; this is inefficient */
+			for (ViewList::iterator i = _views.begin(); i != _views.end(); ++i) {
+				shared_ptr<ContentView> cv = dynamic_pointer_cast<ContentView> (*i);
+				if (!cv || cv == _down_view) {
+					continue;
+				}
+
+				{
+					/* Snap starts to ends */
+					Time const d = abs (cv->content()->end() - new_position);
+					if (first || d < nearest_distance) {
+						nearest_distance = d;
+						nearest_new_position = cv->content()->end();
+					}
+				}
+
+				{
+					/* Snap ends to starts */
+					Time const d = abs (cv->content()->position() - (new_position + _down_view->content()->length_after_trim()));
+					if (d < nearest_distance) {
+						nearest_distance = d;
+						nearest_new_position = cv->content()->position() - _down_view->content()->length_after_trim ();
+					}
+				}
+
+				first = false;
+			}
+
+			if (!first) {
+				/* Snap if it's close; `close' means within a proportion of the time on the timeline */
+				if (nearest_distance < (width() / pixels_per_time_unit()) / 32) {
+					new_position = nearest_new_position;
+				}
+			}
+		}
+		
+		if (new_position < 0) {
+			new_position = 0;
+		}
+	
+		_down_view->content()->set_position (new_position);
 
 		shared_ptr<Film> film = _film.lock ();
 		assert (film);
diff --git a/src/wx/timeline.h b/src/wx/timeline.h
index 0217373b9..ef1d10797 100644
--- a/src/wx/timeline.h
+++ b/src/wx/timeline.h
@@ -64,6 +64,14 @@ public:
 
 	void setup_pixels_per_time_unit ();
 
+	void set_snap (bool s) {
+		_snap = s;
+	}
+
+	bool snap () const {
+		return _snap;
+	}
+
 private:
 	void paint ();
 	void left_down (wxMouseEvent &);
@@ -95,6 +103,7 @@ private:
 	Time _down_view_position;
 	bool _first_move;
 	ContentMenu _menu;
+	bool _snap;
 
 	boost::signals2::scoped_connection _playlist_connection;
 };
diff --git a/src/wx/timeline_dialog.cc b/src/wx/timeline_dialog.cc
index 9493d0acb..dbf7ae232 100644
--- a/src/wx/timeline_dialog.cc
+++ b/src/wx/timeline_dialog.cc
@@ -33,10 +33,24 @@ TimelineDialog::TimelineDialog (FilmEditor* ed, shared_ptr<Film> film)
 	, _timeline (this, ed, film)
 {
 	wxBoxSizer* sizer = new wxBoxSizer (wxVERTICAL);
-	
+
+	wxBoxSizer* controls = new wxBoxSizer (wxHORIZONTAL);
+	_snap = new wxCheckBox (this, wxID_ANY, _("Snap"));
+	controls->Add (_snap);
+
+	sizer->Add (controls, 0, wxALL, 12);
 	sizer->Add (&_timeline, 1, wxEXPAND | wxALL, 12);
 
 	SetSizer (sizer);
 	sizer->Layout ();
 	sizer->SetSizeHints (this);
+
+	_snap->SetValue (_timeline.snap ());
+	_snap->Bind (wxEVT_COMMAND_CHECKBOX_CLICKED, boost::bind (&TimelineDialog::snap_toggled, this));
+}
+
+void
+TimelineDialog::snap_toggled ()
+{
+	_timeline.set_snap (_snap->GetValue ());
 }
diff --git a/src/wx/timeline_dialog.h b/src/wx/timeline_dialog.h
index 17ca22c49..1e5955003 100644
--- a/src/wx/timeline_dialog.h
+++ b/src/wx/timeline_dialog.h
@@ -30,5 +30,8 @@ public:
 	TimelineDialog (FilmEditor *, boost::shared_ptr<Film>);
 
 private:
+	void snap_toggled ();
+	
 	Timeline _timeline;
+	wxCheckBox* _snap;
 };
-- 
2.30.2