better logging

src/main.rs

@@ -458,7 +458,7 @@ fn transform_subtitles<'a>(mut lines : Box<dyn SubsInput + 'a>, mut outfile : Bo
                             AutoMoveTag::ByIndex(idx, ref vidt) => {
                                 if num >= *idx {
                                     let dif = *vidt - would_be_shifted_start;
-                                    debug!("Move by index #{} starts at #{} ({}) -> {}, diff {}", *idx, num, subtitle.start, *vidt, dif);
+                                    debug!("Move by index #{} starts at #{} ({}), diff {}, -M{}={}", *idx, num, subtitle.start, dif, would_be_shifted_start, *vidt);
                                     opts.shift += dif;
                                     to_drop.push(i);
                                 } else if would_be_shifted_start > *vidt {
@@ -467,9 +467,9 @@ fn transform_subtitles<'a>(mut lines : Box<dyn SubsInput + 'a>, mut outfile : Bo
                                 }
                             }
                             AutoMoveTag::ByTime(ref subt, ref vidt) => {
-                                if would_be_shifted_start >= *subt {
+                                if would_be_shifted_start >= (*subt - 0.1f64) { // margin
                                     let dif = *vidt - *subt;
-                                    debug!("Move by time {} starts at #{} ({}) -> {}, diff {}", subt, num, subtitle.start, *vidt, dif);
+                                    debug!("Move by time {} starts at #{} ({}), diff {}, -M{}={}", subt, num, subtitle.start, dif, subt, *vidt);
                                     opts.shift += dif;
                                     to_drop.push(i);
                                 }
@@ -611,6 +611,14 @@ impl Sub<SubInstant> for SubInstant {
     }
 }
 
+impl Sub<f64> for SubInstant {
+    type Output = SubInstant;
+
+    fn sub(self, rhs: f64) -> Self::Output {
+        SubInstant(self.0 - rhs)
+    }
+}
+
 impl Mul<f64> for SubDuration {
     type Output = SubDuration;