Better document new loadstate logic and fix up changelogs

[[Split portion of a mixed commit.]]

src/movie.cpp

@@ -1278,27 +1278,55 @@ bool FCEUMOV_ReadState(EMUFILE* is, uint32 size)
 		return false;
 	}
 
-	//complex TAS logic for when a savestate is loaded:
 	//----------------
-	//if we are playing or recording and toggled read-only:
-	//  then, the movie we are playing must match the guid of the one stored in the savestate or else error.
-	//  ---the savestate is assumed to be in the same timeline as the current movie.---
-	//		adelikat: correction: the savestate timeline should not be assumed, because a read-only desync is still potentially destructive
-	//			playing from a desynced state, making a new savestate, and loading it in write mode will destroy a movie, and it isn't always obvious that there is a desync
-	//  if the current movie is not long enough to get to the savestate's frame#, then it is an error. 
-	//  the movie contained in the savestate will be discarded.
-	//  the emulator will be put into play mode.
-	//if we are playing or recording and toggled read+write
-	//  then, the movie we are playing must match the guid of the one stored in the savestate or else error, give the option to load it anyway.
-	//  the movie contained in the savestate will be loaded into memory
-	//  the frames in the movie after the savestate frame will be discarded
-	//  the in-memory movie will have its rerecord count incremented
-	//  the in-memory movie will be dumped to disk as fcm.
-	//  the emulator will be put into record mode.
-	//if we are doing neither:
-	//  then, we must discard this movie and just load the savestate
+	//complex TAS logic for loadstate
+	//fully conforms to the savestate logic documented in the Laws of TAS
+	//http://tasvideos.org/LawsOfTAS/OnSavestates.html
+	//----------------
+		
+	/*
+	Playback or Recording + Read-only
 
+    * Check that GUID of movie and savestate-movie must match or else error
+          o on error: a message informing that the savestate doesn't belong to this movie. This is a GUID mismatch error. Give user a choice to load it anyway.
+                + failstate: if use declines, loadstate attempt canceled, movie can resume as if not attempted if user has backup savstates enabled else stop movie
+    * Check that movie and savestate-movie are in same timeline. If not then this is a wrong timeline error.
+          o on error: a message informing that the savestate doesn't belong to this movie
+                + failstate: loadstate attempt canceled, movie can resume as if not attempted if user has backup savestates enabled else stop movie
+    * Check that savestate-movie is not greater than movie. If not then this is a future event error and is not allowed in read-only
+          o on error: message informing that the savestate is from a frame after the last frame of the movie
+                + failstate - loadstate attempt cancelled, movie can resume if user has backup savesattes enabled, else stop movie
+    * Check that savestate framcount <= savestate movie length. If not this is a post-movie savestate
+          o on post-movie: See post-movie event section. 
+    * All error checks have passed, state will be loaded
+    * Movie contained in the savestate will be discarded
+    * Movie is now in Playback mode 
 
+	Playback, Recording + Read+write
+
+    * Check that GUID of movie and savestate-movie must match or else error
+          o on error: a message informing that the savestate doesn't belong to this movie. This is a GUID mismatch error. Give user a choice to load it anyway.
+                + failstate: if use declines, loadstate attempt canceled, movie can resume as if not attempted (stop movie if resume fails)canceled, movie can resume if backup savestates enabled else stopmovie
+    * Check that savestate framcount <= savestate movie length. If not this is a post-movie savestate
+          o on post-movie: See post-movie event section. 
+    * savestate passed all error checks and will now be loaded in its entirety and replace movie (note: there will be no truncation yet)
+    * current framecount will be set to savestate framecount
+    * on the next frame of input, movie will be truncated to framecount
+          o (note: savestate-movie can be a future event of the movie timeline, or a completely new timeline and it is still allowed) 
+    * Rerecord count of movie will be incremented
+    * Movie is now in record mode 
+
+	Post-movie savestate event
+
+    * Whan a savestate is loaded and is determined that the savestate-movie length is less than the savestate framecount then it is a post-movie savestate. These occur when a savestate was made during Movie Finished mode. 
+	* If read+write, the entire savestate movie will be loaded and replace current movie.
+    * If read-only, the savestate movie will be discarded
+    * Mode will be switched to Move Finished
+    * Savestate will be loaded
+    * Current framecount changes to savestate framecount
+    * User will have control of input as if Movie inactive mode 
+	*/
+	
 	if(movieMode == MOVIEMODE_PLAY || movieMode == MOVIEMODE_RECORD || movieMode == MOVIEMODE_FINISHED)
 	{
 		//handle moviefile mismatch