Add "r" (resize) event as the first event when appending

This ensures the appended events are can rely on their assumed terminal
window size.

Addresses part of #636.

src/cmd/convert.rs

@@ -33,7 +33,7 @@ impl cli::Convert {
         match format {
             Format::AsciicastV3 => Box::new(AsciicastV3Encoder::new(false)),
             Format::AsciicastV2 => Box::new(AsciicastV2Encoder::new(false, 0)),
-            Format::Raw => Box::new(RawEncoder::new(false)),
+            Format::Raw => Box::new(RawEncoder::new()),
             Format::Txt => Box::new(TextEncoder::new()),
         }
     }

src/cmd/session.rs

@@ -289,7 +289,7 @@ impl cli::Session {
 
             Format::Raw => {
                 let writer = Box::new(file);
-                let encoder = Box::new(RawEncoder::new(append));
+                let encoder = Box::new(RawEncoder::new());
 
                 FileWriterStarter {
                     writer,

src/encoder/asciicast.rs

@@ -16,7 +16,8 @@ impl AsciicastV2Encoder {
 impl super::Encoder for AsciicastV2Encoder {
     fn header(&mut self, header: &Header) -> Vec<u8> {
         if self.append {
-            Vec::new()
+            let size = (header.term_cols, header.term_rows);
+            self.inner.event(&Event::resize(0, size))
         } else {
             self.inner.header(header)
         }
@@ -47,7 +48,8 @@ impl AsciicastV3Encoder {
 impl super::Encoder for AsciicastV3Encoder {
     fn header(&mut self, header: &Header) -> Vec<u8> {
         if self.append {
-            Vec::new()
+            let size = (header.term_cols, header.term_rows);
+            self.inner.event(&Event::resize(0, size))
         } else {
             self.inner.header(header)
         }

src/encoder/raw.rs

@@ -1,22 +1,16 @@
 use crate::asciicast::{Event, EventData, Header};
 
-pub struct RawEncoder {
-    append: bool,
-}
+pub struct RawEncoder;
 
 impl RawEncoder {
-    pub fn new(append: bool) -> Self {
-        RawEncoder { append }
+    pub fn new() -> Self {
+        RawEncoder
     }
 }
 
 impl super::Encoder for RawEncoder {
     fn header(&mut self, header: &Header) -> Vec<u8> {
-        if self.append {
-            Vec::new()
-        } else {
-            format!("\x1b[8;{};{}t", header.term_rows, header.term_cols).into_bytes()
-        }
+        format!("\x1b[8;{};{}t", header.term_rows, header.term_cols).into_bytes()
     }
 
     fn event(&mut self, event: Event) -> Vec<u8> {
@@ -40,7 +34,7 @@ mod tests {
 
     #[test]
     fn encoder() {
-        let mut enc = RawEncoder::new(false);
+        let mut enc = RawEncoder::new();
 
         let header = Header {
             term_cols: 100,