From fb39b47861a69a774a5f9f2029e7644811af7339 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <carl@carlh.net>
Date: Wed, 25 May 2011 16:38:49 +0000
Subject: [PATCH] Zoom session when the mouse pointer is moved up and down
 during a playhead drag.

git-svn-id: svn://localhost/ardour2/branches/3.0@9586 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 gtk2_ardour/editor_drag.cc | 45 ++++++++++++++++++++++++++++++++------
 gtk2_ardour/editor_drag.h  |  3 ++-
 2 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/gtk2_ardour/editor_drag.cc b/gtk2_ardour/editor_drag.cc
index 1784e59944..f8078475d3 100644
--- a/gtk2_ardour/editor_drag.cc
+++ b/gtk2_ardour/editor_drag.cc
@@ -2082,6 +2082,8 @@ CursorDrag::start_grab (GdkEvent* event, Gdk::Cursor* c)
 {
 	Drag::start_grab (event, c);
 
+	_grab_zoom = _editor->frames_per_unit;
+
 	framepos_t where = _editor->event_frame (event, 0, 0);
 	_editor->snap_to_with_modifier (where, event);
 
@@ -2110,17 +2112,46 @@ CursorDrag::start_grab (GdkEvent* event, Gdk::Cursor* c)
 void
 CursorDrag::motion (GdkEvent* event, bool)
 {
-	framepos_t const adjusted_frame = adjusted_current_frame (event);
+	if (_drags->current_pointer_y() != last_pointer_y()) {
 
-	if (adjusted_frame == last_pointer_frame()) {
-		return;
+		/* zoom when we move the pointer up and down */
+
+		/* y range to operate over (pixels) */
+		double const y_range = 256;
+		/* we will multiply the grab zoom by a factor between scale_range and scale_range^-1 */
+		double const scale_range = 4;
+		/* dead zone around the grab point in which to do no zooming (pixels) */
+		double const dead_zone = 16;
+		
+		/* current dy */
+		double dy = _drags->current_pointer_y() - grab_y();
+
+		if (dy < -dead_zone || dy > dead_zone) {
+			/* we are outside the dead zone; remove it from our calculation */
+			if (dy < 0) {
+				dy += dead_zone;
+			} else {
+				dy -= dead_zone;
+			}
+			
+			/* get a number from -1 to 1 as dy ranges from -y_range to y_range */
+			double udy = max (min (dy / y_range, 1.0), -1.0);
+
+			/* and zoom, using playhead focus temporarily */
+			Editing::ZoomFocus const zf = _editor->get_zoom_focus ();
+			_editor->set_zoom_focus (Editing::ZoomFocusPlayhead);
+			_editor->temporal_zoom (_grab_zoom * pow (scale_range, -udy));
+			_editor->set_zoom_focus (zf);
+		}
 	}
-
-	fake_locate (adjusted_frame);
-	
+		
+	framepos_t const adjusted_frame = adjusted_current_frame (event);
+	if (adjusted_frame != last_pointer_frame()) {
+		fake_locate (adjusted_frame);
 #ifdef GTKOSX
-	_editor->update_canvas_now ();
+		_editor->update_canvas_now ();
 #endif
+	}
 }
 
 void
diff --git a/gtk2_ardour/editor_drag.h b/gtk2_ardour/editor_drag.h
index b1e99890e7..3277f0334c 100644
--- a/gtk2_ardour/editor_drag.h
+++ b/gtk2_ardour/editor_drag.h
@@ -594,13 +594,14 @@ public:
 	}
 
 	bool y_movement_matters () const {
-		return false;
+		return true;
 	}
 	
 private:
 	void fake_locate (framepos_t);
 	
 	bool _stop; ///< true to stop the transport on starting the drag, otherwise false
+	double _grab_zoom; ///< editor frames per unit when our grab started
 };
 
 /** Region fade-in drag */