ls-fonts --text used wrong per-glyph text

It was showing the whole text for the cluster for each shaped
glyph.

Fix it up to map back to the corresponding cell range and
extract the text from the line.

Include the x_advance metric in the output while we're in
there.

refs: #1333

wezterm-gui/src/main.rs

@@ -503,9 +503,17 @@ pub fn run_ls_fonts(config: config::ConfigHandle, cmd: &LsFontsCommand) -> anyho
             // revised list that includes system fallbacks!
             let handles = font.clone_handles();
 
-            for info in infos {
+            let mut iter = infos.iter().peekable();
+            while let Some(info) = iter.next() {
+                let idx = cluster.byte_to_cell_idx(info.cluster as usize);
+                let text = if let Some(ahead) = iter.peek() {
+                    line.columns_as_str(idx..cluster.byte_to_cell_idx(ahead.cluster as usize))
+                } else {
+                    line.columns_as_str(idx..line.cells().len())
+                };
+
                 let parsed = &handles[info.font_idx];
-                let escaped = format!("{}", cluster.text.escape_unicode());
+                let escaped = format!("{}", text.escape_unicode());
                 if config.custom_block_glyphs {
                     if let Some(block) = customglyph::BlockKey::from_str(&text) {
                         println!(
@@ -517,9 +525,10 @@ pub fn run_ls_fonts(config: config::ConfigHandle, cmd: &LsFontsCommand) -> anyho
                 }
 
                 println!(
-                    "{:4} {:12} glyph={:<4} {}\n{:29}{}",
-                    cluster.text,
+                    "{:4} {:12} x_adv={:<2} glyph={:<4} {}\n{:38}{}",
+                    text,
                     escaped,
+                    info.x_advance.get(),
                     info.glyph_pos,
                     parsed.lua_name(),
                     "",