Add an ability to avoid track flushing when file formats have sub-track precision.

Storage/Disk/Disk.hpp

@@ -61,6 +61,12 @@ class Disk {
 			@returns whether the disk image is read only. Defaults to @c true if not overridden.
 		*/
 		virtual bool get_is_read_only() = 0;
+
+		/*!
+			@returns @c true if the tracks at the two addresses are different. @c false if they are the same track.
+				This can avoid some degree of work when disk images offer sub-head-position precision.
+		*/
+		virtual bool tracks_differ(Track::Address, Track::Address) = 0;
 };
 
 }

Storage/Disk/DiskImage/DiskImage.hpp

@@ -67,6 +67,12 @@ class DiskImage {
 			@returns whether the disk image is read only. Defaults to @c true if not overridden.
 		*/
 		virtual bool get_is_read_only() { return true; }
+
+		/*!
+			@returns @c true if the tracks at the two addresses are different. @c false if they are the same track.
+				This can avoid some degree of work when disk images offer sub-head-position precision.
+		*/
+		virtual bool tracks_differ(Track::Address lhs, Track::Address rhs) { return lhs == rhs; }
 };
 
 class DiskImageHolderBase: public Disk {
@@ -93,6 +99,7 @@ template <typename T> class DiskImageHolder: public DiskImageHolderBase {
 		void set_track_at_position(Track::Address address, const std::shared_ptr<Track> &track);
 		void flush_tracks();
 		bool get_is_read_only();
+		bool tracks_differ(Track::Address lhs, Track::Address rhs);
 
 	private:
 		T disk_image_;

Storage/Disk/DiskImage/DiskImageImplementation.hpp

@@ -58,3 +58,7 @@ template <typename T> std::shared_ptr<Track> DiskImageHolder<T>::get_track_at_po
 template <typename T> DiskImageHolder<T>::~DiskImageHolder() {
 	if(update_queue_) update_queue_->flush();
 }
+
+template <typename T> bool DiskImageHolder<T>::tracks_differ(Track::Address lhs, Track::Address rhs) {
+	return disk_image_.tracks_differ(lhs, rhs);
+}

Storage/Disk/Track/Track.hpp

@@ -84,6 +84,13 @@ class Track {
 				int rhs_largest_position = rhs.position.as_largest();
 				return std::tie(head, largest_position) < std::tie(rhs.head, rhs_largest_position);
 			}
+			constexpr bool operator == (const Address &rhs) const {
+				return head == rhs.head && position == rhs.position;
+			}
+			constexpr bool operator != (const Address &rhs) const {
+				return head != rhs.head || position != rhs.position;
+			}
+
 			constexpr Address(int head, HeadPosition position) : head(head), position(position) {}
 		};
 
@@ -107,11 +114,11 @@ class Track {
 		virtual Event get_next_event() = 0;
 
 		/*!
-			Jumps to the event latest offset that is less than or equal to the input time.
+			Jumps to the start of the fist event that will occur after @c time_since_index_hole.
 
 			@returns the time jumped to.
 		*/
-		virtual Time seek_to(const Time &time_since_index_hole) = 0;
+		virtual float seek_to(float time_since_index_hole) = 0;
 
 		/*!
 			The virtual copy constructor pattern; returns a copy of the Track.