[gnome-subtitles] Fix #622248 - Synchronize timings for all subtitles.

[Pedro Daniel da Rocha Melo e Castro <pcastro src gnome org>]

commit 508b2357a4bc7d40fb18c9f7bc24139de2226455
Author: Pedro Castro <mail pedrocastro org>
Date:   Sun Oct 10 17:22:18 2010 +0100

    Fix #622248 - Synchronize timings for all subtitles.
    
    Times weren't being calculated correctly in some situations when using the
    "sync all subtitles" option. In those situations, validation didn't allow
    synchronization to be done.

 src/SubLib/Core/Timing/SynchronizeOperator.cs |   27 +++++++++++++++++-------
 1 files changed, 19 insertions(+), 8 deletions(-)
---
diff --git a/src/SubLib/Core/Timing/SynchronizeOperator.cs b/src/SubLib/Core/Timing/SynchronizeOperator.cs
index 1030423..1ef4fe1 100644
--- a/src/SubLib/Core/Timing/SynchronizeOperator.cs
+++ b/src/SubLib/Core/Timing/SynchronizeOperator.cs
@@ -60,16 +60,25 @@ public class SynchronizeOperator {
 
 		/* Add the first subtitle if possible */
 		int firstSubtitleNumber = 0;
-		if ((subtitles.Collection.Count > 0) && (!adapted.Contains(firstSubtitleNumber))) {
+		if ((subtitles.Collection.Count > 1) && (!adapted.Contains(firstSubtitleNumber))) {
+			
+			/* Calculate sync shift and factor using the last 2 sync points */
 			SyncPoint firstSyncPoint = adapted[0];
-			Subtitle firstSyncSubtitle = subtitles.Collection[firstSyncPoint.SubtitleNumber];
+			SyncPoint secondSyncPoint = adapted[1];
+			Subtitle firstSyncPointSubtitle = subtitles.Collection[firstSyncPoint.SubtitleNumber];
+			Subtitle secondSyncPointSubtitle = subtitles.Collection[secondSyncPoint.SubtitleNumber];
+			TimeSpan shift = firstSyncPoint.Correct.Time - firstSyncPointSubtitle.Times.PreciseStart;
+			double factor = (secondSyncPoint.Correct.Time - firstSyncPoint.Correct.Time).TotalMilliseconds / (secondSyncPointSubtitle.Times.PreciseStart - firstSyncPointSubtitle.Times.PreciseStart).TotalMilliseconds;
+			
+			/* Calculate new time */
 			Subtitle firstSubtitle = subtitles.Collection[firstSubtitleNumber];
-
-			double scaleFactor = firstSyncPoint.Correct.Time.TotalMilliseconds / firstSyncSubtitle.Times.Start.TotalMilliseconds;
-			TimeSpan firstSubtitleNewTime = SyncUtil.Scale(firstSubtitle.Times.PreciseStart, TimeSpan.Zero, scaleFactor);
+			TimeSpan firstSubtitleNewTime = firstSubtitle.Times.Start + shift; //Apply shift
+			firstSubtitleNewTime = SyncUtil.Scale(firstSubtitleNewTime, TimeSpan.Zero, factor);
+			if (firstSubtitleNewTime < TimeSpan.Zero) { //Can't have negative start
+				firstSubtitleNewTime = TimeSpan.Zero;
+			}
 			int firstSubtitleNewFrame = (int)TimingUtil.TimeToFrames(firstSubtitleNewTime, subtitles.Properties.CurrentFrameRate);
 			Domain.Timing firstSubtitleNewTiming = new Domain.Timing(firstSubtitleNewFrame, firstSubtitleNewTime);
-			
 			Domain.Timing firstSubtitleCurrentTiming = new Domain.Timing(firstSubtitle.Frames.Start, firstSubtitle.Times.Start);
 			SyncPoint newFirstSyncPoint = new SyncPoint(firstSubtitleNumber, firstSubtitleCurrentTiming, firstSubtitleNewTiming);
 			adapted.Add(newFirstSyncPoint);
@@ -79,16 +88,18 @@ public class SynchronizeOperator {
 		int lastSubtitleNumber = subtitles.Collection.Count - 1;
 		if ((subtitles.Collection.Count > 1) && (!adapted.Contains(lastSubtitleNumber))) {
 
-			/* Calculate sync factor using the last 2 sync points */
+			/* Calculate sync shift and factor using the last 2 sync points */
 			SyncPoint penultSyncPoint = adapted[adapted.Count - 2];			
 			SyncPoint lastSyncPoint = adapted[adapted.Count - 1];
 			Subtitle penultSyncPointSubtitle = subtitles.Collection[penultSyncPoint.SubtitleNumber];
 			Subtitle lastSyncPointSubtitle = subtitles.Collection[lastSyncPoint.SubtitleNumber];
+			TimeSpan shift = penultSyncPoint.Correct.Time - penultSyncPointSubtitle.Times.PreciseStart;
 			double factor = (lastSyncPoint.Correct.Time - penultSyncPoint.Correct.Time).TotalMilliseconds / (lastSyncPointSubtitle.Times.PreciseStart - penultSyncPointSubtitle.Times.PreciseStart).TotalMilliseconds;
 
 			/* Calculate new time */
 			Subtitle lastSubtitle = subtitles.Collection[lastSubtitleNumber];
-			TimeSpan lastSubtitleNewTime = SyncUtil.Scale(lastSubtitle.Times.Start, lastSyncPoint.Correct.Time, factor);
+			TimeSpan lastSubtitleNewTime = lastSubtitle.Times.Start + shift; //Apply shift
+			lastSubtitleNewTime = SyncUtil.Scale(lastSubtitleNewTime, penultSyncPoint.Correct.Time, factor);
 			int lastSubtitleNewFrame = (int)TimingUtil.TimeToFrames(lastSubtitleNewTime, subtitles.Properties.CurrentFrameRate);
 			Domain.Timing lastSubtitleNewTiming = new Domain.Timing(lastSubtitleNewFrame, lastSubtitleNewTime);
 			Domain.Timing lastSubtitleCurrentTiming = new Domain.Timing(lastSubtitle.Frames.Start, lastSubtitle.Times.Start);