make contents_diff include bell state

i don't think it makes sense for contents_formatted to include this

5 files changed, 73 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c268b6c..1dca708 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,8 @@
 * Clearing a cell now sets all of that cell's attributes to the current
   attribute set, since different terminals render different things for an empty
   cell based on the attributes.
+* `Screen::contents_diff` now includes audible and visual bells when
+  appropriate.
 
 ## [0.4.0] - 2019-11-08
 
diff --git a/src/screen.rs b/src/screen.rs
index c2eaf0e..d4613f0 100644
--- a/src/screen.rs
+++ b/src/screen.rs
@@ -246,6 +246,12 @@ impl Screen {
             prev.attrs,
         );
         self.attrs.write_escape_code_diff(contents, &prev_attrs);
+        if self.audible_bell_count != prev.audible_bell_count {
+            crate::term::AudibleBell::default().write_buf(contents);
+        }
+        if self.visual_bell_count != prev.visual_bell_count {
+            crate::term::VisualBell::default().write_buf(contents);
+        }
     }
 
     /// Returns a sequence of terminal byte streams sufficient to turn the
@@ -307,18 +313,26 @@ impl Screen {
         &self.icon_name
     }
 
-    /// Returns the total number of audible bells seen so far.
+    /// Returns a value which changes every time an audible bell is received.
     ///
     /// Typically you would store this number after each call to `process`,
     /// and trigger an audible bell whenever it changes.
+    ///
+    /// You shouldn't rely on the exact value returned here, since the exact
+    /// value will not be maintained by `contents_formatted` or
+    /// `contents_diff`.
     pub fn audible_bell_count(&self) -> usize {
         self.audible_bell_count
     }
 
-    /// Returns the total number of visual bells seen so far.
+    /// Returns a value which changes every time an visual bell is received.
     ///
     /// Typically you would store this number after each call to `process`,
     /// and trigger an visual bell whenever it changes.
+    ///
+    /// You shouldn't rely on the exact value returned here, since the exact
+    /// value will not be maintained by `contents_formatted` or
+    /// `contents_diff`.
     pub fn visual_bell_count(&self) -> usize {
         self.visual_bell_count
     }
diff --git a/src/term.rs b/src/term.rs
index 1e69d07..c988702 100644
--- a/src/term.rs
+++ b/src/term.rs
@@ -344,3 +344,23 @@ impl BufWrite for MoveFromTo {
         }
     }
 }
+
+#[derive(Default, Debug)]
+#[must_use = "this struct does nothing unless you call write_buf"]
+pub struct AudibleBell;
+
+impl BufWrite for AudibleBell {
+    fn write_buf(&self, buf: &mut Vec<u8>) {
+        buf.push(b'\x07');
+    }
+}
+
+#[derive(Default, Debug)]
+#[must_use = "this struct does nothing unless you call write_buf"]
+pub struct VisualBell;
+
+impl BufWrite for VisualBell {
+    fn write_buf(&self, buf: &mut Vec<u8>) {
+        buf.extend_from_slice(b"\x1bg");
+    }
+}
diff --git a/tests/control.rs b/tests/control.rs
index aba6915..8372cea 100644
--- a/tests/control.rs
+++ b/tests/control.rs
@@ -5,15 +5,31 @@ fn bel() {
     let mut parser = vt100::Parser::default();
     assert_eq!(parser.screen().audible_bell_count(), 0);
 
+    let screen = parser.screen().clone();
     parser.process(b"\x07");
     assert_eq!(parser.screen().audible_bell_count(), 1);
     assert_eq!(parser.screen().audible_bell_count(), 1);
+    assert_eq!(parser.screen().contents_diff(&screen), b"\x07");
 
+    let screen = parser.screen().clone();
     parser.process(b"\x07");
     assert_eq!(parser.screen().audible_bell_count(), 2);
+    assert_eq!(parser.screen().contents_diff(&screen), b"\x07");
 
+    let screen = parser.screen().clone();
     parser.process(b"\x07\x07\x07");
     assert_eq!(parser.screen().audible_bell_count(), 5);
+    assert_eq!(parser.screen().contents_diff(&screen), b"\x07");
+
+    let screen = parser.screen().clone();
+    parser.process(b"foo");
+    assert_eq!(parser.screen().audible_bell_count(), 5);
+    assert_eq!(parser.screen().contents_diff(&screen), b"foo");
+
+    let screen = parser.screen().clone();
+    parser.process(b"ba\x07r");
+    assert_eq!(parser.screen().audible_bell_count(), 6);
+    assert_eq!(parser.screen().contents_diff(&screen), b"bar\x07");
 }
 
 #[test]
diff --git a/tests/escape.rs b/tests/escape.rs
index e08a402..96ee762 100644
--- a/tests/escape.rs
+++ b/tests/escape.rs
@@ -125,13 +125,32 @@ fn ris() {
 fn vb() {
     let mut parser = vt100::Parser::default();
     assert_eq!(parser.screen().visual_bell_count(), 0);
+
+    let screen = parser.screen().clone();
     parser.process(b"\x1bg");
     assert_eq!(parser.screen().visual_bell_count(), 1);
     assert_eq!(parser.screen().visual_bell_count(), 1);
+    assert_eq!(parser.screen().contents_diff(&screen), b"\x1bg");
+
+    let screen = parser.screen().clone();
     parser.process(b"\x1bg");
     assert_eq!(parser.screen().visual_bell_count(), 2);
+    assert_eq!(parser.screen().contents_diff(&screen), b"\x1bg");
+
+    let screen = parser.screen().clone();
     parser.process(b"\x1bg\x1bg\x1bg");
     assert_eq!(parser.screen().visual_bell_count(), 5);
+    assert_eq!(parser.screen().contents_diff(&screen), b"\x1bg");
+
+    let screen = parser.screen().clone();
+    parser.process(b"foo");
+    assert_eq!(parser.screen().visual_bell_count(), 5);
+    assert_eq!(parser.screen().contents_diff(&screen), b"foo");
+
+    let screen = parser.screen().clone();
+    parser.process(b"ba\x1bgr");
+    assert_eq!(parser.screen().visual_bell_count(), 6);
+    assert_eq!(parser.screen().contents_diff(&screen), b"bar\x1bg");
 }
 
 #[test]