Put event fields on their own lines in line-rendering mode

examples/basic.stdout

@@ -6,7 +6,8 @@
 1:main│ ├┐basic::server host="localhost", port=8080
 1:main│ │└┐basic::conn peer_addr="82.9.9.9", port=42381
 1:main│ │ ├─  Xms DEBUG basic connected
-1:main│ │ ├─  Xms DEBUG basic message received, length=2
+1:main│ │ ├─┬─  Xms DEBUG basic message received
+1:main│ │ │ └─ length=2
 1:main│ │┌┘basic::conn peer_addr="82.9.9.9", port=42381
 1:main│ ├┘basic::server host="localhost", port=8080
 1:main│ ├┐basic::server host="localhost", port=8080
@@ -21,15 +22,19 @@
 1:main│ ├┘basic::server host="localhost", port=8080
 1:main│ ├┐basic::server host="localhost", port=8080
 1:main│ │└┐basic::conn peer_addr="82.9.9.9", port=42381
-1:main│ │ ├─  Xms WARN basic weak encryption requested, algo="xor"
-1:main│ │ ├─  Xms DEBUG basic response sent, length=8
+1:main│ │ ├─┬─  Xms WARN basic weak encryption requested
+1:main│ │ │ └─ algo="xor"
+1:main│ │ ├─┬─  Xms DEBUG basic response sent
+1:main│ │ │ └─ length=8
 1:main│ │ ├─  Xms DEBUG basic disconnected
 1:main│ │┌┘basic::conn peer_addr="82.9.9.9", port=42381
 1:main│ ├┘basic::server host="localhost", port=8080
 1:main│ ├┐basic::server host="localhost", port=8080
 1:main│ │└┐basic::conn peer_addr="8.8.8.8", port=18230
-1:main│ │ ├─  Xms DEBUG basic message received, length=5
-1:main│ │ ├─  Xms DEBUG basic response sent, length=8
+1:main│ │ ├─┬─  Xms DEBUG basic message received
+1:main│ │ │ └─ length=5
+1:main│ │ ├─┬─  Xms DEBUG basic response sent
+1:main│ │ │ └─ length=8
 1:main│ │ ├─  Xms DEBUG basic disconnected
 1:main│ │┌┘basic::conn peer_addr="8.8.8.8", port=18230
 1:main│ ├┘basic::server host="localhost", port=8080

examples/quiet.stdout

@@ -4,7 +4,8 @@
 1:main│ ├─  Xms INFO quiet listening
 1:main│ ├─┐quiet::conn peer_addr="82.9.9.9", port=42381
 1:main│ │ ├─  Xms DEBUG quiet connected
-1:main│ │ ├─  Xms DEBUG quiet message received, length=2
+1:main│ │ ├─┬─  Xms DEBUG quiet message received
+1:main│ │ │ └─ length=2
 1:main│ ├─┘
 1:main│ ├─┐quiet::conn peer_addr="8.8.8.8", port=18230
 1:main│ │ ├─  Xms DEBUG quiet connected
@@ -13,13 +14,17 @@
 1:main│ │ ├─  Xms ERROR quiet hello
 1:main│ ├─┘
 1:main│ ├─┐quiet::conn peer_addr="82.9.9.9", port=42381
-1:main│ │ ├─  Xms WARN quiet weak encryption requested, algo="xor"
-1:main│ │ ├─  Xms DEBUG quiet response sent, length=8
+1:main│ │ ├─┬─  Xms WARN quiet weak encryption requested
+1:main│ │ │ └─ algo="xor"
+1:main│ │ ├─┬─  Xms DEBUG quiet response sent
+1:main│ │ │ └─ length=8
 1:main│ │ ├─  Xms DEBUG quiet disconnected
 1:main│ ├─┘
 1:main│ ├─┐quiet::conn peer_addr="8.8.8.8", port=18230
-1:main│ │ ├─  Xms DEBUG quiet message received, length=5
-1:main│ │ ├─  Xms DEBUG quiet response sent, length=8
+1:main│ │ ├─┬─  Xms DEBUG quiet message received
+1:main│ │ │ └─ length=5
+1:main│ │ ├─┬─  Xms DEBUG quiet response sent
+1:main│ │ │ └─ length=8
 1:main│ │ ├─  Xms DEBUG quiet disconnected
 1:main│ ├─┘
 1:main│ ├─  Xs  WARN quiet internal error

src/format.rs

@@ -13,6 +13,7 @@ const LINE_HORIZ: &str = "─";
 pub(crate) const LINE_BRANCH: &str = "├";
 pub(crate) const LINE_CLOSE: &str = "┘";
 pub(crate) const LINE_OPEN: &str = "┐";
+pub(crate) const ARGS_BRANCH: &str = "┬";
 
 #[derive(Copy, Clone)]
 pub(crate) enum SpanMode {
@@ -227,7 +228,7 @@ pub struct FmtEvent<'a> {
 impl<'a> Visit for FmtEvent<'a> {
     fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
         let buf = &mut self.bufs.current_buf;
-        let comma = if self.comma { "," } else { "" };
+        let comma = if self.comma { "\n" } else { "" };
         match field.name() {
             "message" => {
                 write!(buf, "{} {:?}", comma, value).unwrap();
@@ -372,6 +373,12 @@ fn indent_block_with_lines(
         }
         SpanMode::Event => {
             buf.push_str(LINE_BRANCH);
+            if lines.len() > 1 {
+                for _ in 0..(indent_amount - 1) {
+                    buf.push_str(LINE_HORIZ);
+                }
+                buf.push_str(ARGS_BRANCH);
+            }
 
             // add `indent_amount - 1` horizontal lines before the span/event
             for _ in 0..(indent_amount - 1) {
@@ -393,8 +400,16 @@ fn indent_block_with_lines(
     }
 
     // add all of the actual content, with each line preceded by the indent string
-    for line in &lines[1..] {
+    for (i, line) in lines[1..].iter().enumerate() {
         buf.push_str(&s);
+        // Magic number `2` means "last entry" because we iterate from `1`
+        // and then restart indexing at `0`.
+        if i == lines.len() - 2 {
+            buf.push_str("└");
+        } else {
+            buf.push_str(LINE_BRANCH);
+        }
+        buf.push_str(LINE_HORIZ);
         buf.push_str(line);
         buf.push('\n');
     }