improve help text, add duration clipping

src/main.rs

@@ -22,24 +22,30 @@ fn main() {
     let argv =
         clap::App::new("srtune")
             .version(env!("CARGO_PKG_VERSION"))
-            .about("Modify a .srt file to match a video. Input and output can be a file or stream, \
-            so you pipe multiple invocations to create more complex operations. However, a single \
+            .about("\
+            'srtune' helps you edit a .srt file to match a video. Input and output can be either a file, or a stream, \
+            so you can pipe multiple invocations to create more complex operations. However, a single \
             invocation should suffice in most cases.\n\
             \n\
-            Times are specified with colons and always include seconds  (HH:MM:SS, MM:SS, 0:SS). \
-            Decimal point can be either period or comma, so times can be copied directly from the \
+            Times are specified with colons (required) and always include seconds (HH:MM:SS, MM:SS, 0:SS, :SS). \
+            Decimal point in the seconds part, if needed, can be either a period or a comma; times can be copied from the \
             .srt file. Numbers without colons are assumed to be subtitle indices.\n\
             \n\
             The tool can be used iteratively, adjusting the invocation until the generated \
-            subtitle file matches the audio track. As such, times accepted by its parameters \
-            are, by default, the ones seen in the output file (after shifts and moving), while \
-            indices are those from the input file.\n\
+            subtitle file matches the audio track. You can reload the file in VLC by dragging it \
+            onto the player window. To make this work, subtitle times specified in arguments are the \
+            ones seen in the output file (after shifts and moving), while entry indices are those from the input file.\n\
+            \n\
+            Using indices makes it easier to specify a subtitle to alter, but it is tied to the one .srt file. \
+            Times are harder to write, but the one configuration will work for any locatization or variant of the file,\
+            so long as it is intended for the same version of the movie. Enable debug logging with '-v' to see times \
+            you can use in place of indices.
             \n\
             Indices are normally not renumbered, so the output file can be used as a reference \
-            for both times and indices. The flag '--renumber' will give each output entry a new \
-            sequential number. Please note that, once renumbered, the indices in the output file \
-            should no longer be used in the command invocation, as there can be a mismatch. They \
-            can be used when piped into a new process, of course.
+            for both times and indices when you work out the right set of arguments. The flag '--renumber' \
+            will give each output entry a new sequential number. Please note that, once renumbered, \
+            the indices in the output file should no longer be used in the command invocation, \
+            as there can be (and often will be) differences from the original file.\
             ")
             .arg(clap::Arg::with_name("input")
                      .value_name("INFILE")
@@ -210,7 +216,6 @@ fn main() {
         }
         None => (/* no automoves */)
     }
-    debug!("Automove: {:?}", automove);
 
     let inf = argv.value_of("input");
     let outf = argv.value_of("output");
@@ -359,11 +364,13 @@ enum AutoMoveTag {
     ByIndex(u32, SubInstant)
 }
 
-#[derive(Debug,Default,Clone,Copy)]
+#[derive(Debug,Default,Clone)]
 struct IterState {
     start_time : Option<SubInstant>,
     renumber_i : u32,
     timeline_head : SubInstant,
+    /// Queue last item for duration clipping
+    queued : Option<Subtitle>,
 }
 
 fn transform_subtitles<'a>(mut lines : Box<dyn SubsInput + 'a>, mut outfile : Box<dyn SubsOutput + 'a>, mut opts : TransformOpts) {
@@ -443,11 +450,8 @@ fn transform_subtitles<'a>(mut lines : Box<dyn SubsInput + 'a>, mut outfile : Bo
 
                     subtitle.dur *= opts.durscale;
 
-                    // TODO prevent durations overlap (will need to buffer one entry)
-
                     let would_be_shifted_start = subtitle.start + opts.shift;
 
-                    // TODO use drain_filter when stable
                     let mut to_drop = vec![];
                     for (i, amove) in opts.automove.iter().enumerate() {
                         match amove {
@@ -502,7 +506,17 @@ fn transform_subtitles<'a>(mut lines : Box<dyn SubsInput + 'a>, mut outfile : Bo
                         istate.renumber_i += 1;
                         subtitle.num = istate.renumber_i;
                     }
-                    outfile.emit(subtitle);
+
+                    if let Some(mut q) = istate.queued.take() {
+                        if q.start + q.dur > subtitle.start {
+                            let clipped = subtitle.start - q.start;
+                            debug!("Clipping duration of #{} ({}) to avoid overlap: {} -> {}", q.num, q.start, q.dur, clipped);
+                            q.dur = clipped;
+                        }
+                        outfile.emit(q);
+                    }
+
+                    istate.queued = Some(subtitle);
                 }
             }
             Err(e) => {
@@ -514,6 +528,11 @@ fn transform_subtitles<'a>(mut lines : Box<dyn SubsInput + 'a>, mut outfile : Bo
             }
         }
     }
+
+    // emit the last entry
+    if let Some(q) = istate.queued.take() {
+        outfile.emit(q);
+    }
 }
 
 //region Time types