fix: graphemes with multi codepoint on multiple visual lines

- The logic for graphemes with multiple codepoints was working when they
  were on a single visual line, however on multiple visual lines the
  lines after the one that contained such grapheme weren't taking that
  into consideration.

2 files changed, 157 insertions, 93 deletions

diff --git a/src/text.rs b/src/text.rs
index 143a78d..851e77b 100644
--- a/src/text.rs
+++ b/src/text.rs
@@ -819,60 +819,92 @@ fn highlight_line(
 ) -> impl Iterator<Item = (f32, f32)> + '_ {
     let layout = line.layout_opt().map(Vec::as_slice).unwrap_or_default();
 
-    layout.iter().map(move |visual_line| {
-        let start = visual_line
-            .glyphs
-            .first()
-            .map(|glyph| glyph.start)
-            .unwrap_or(0);
-        let end = visual_line
-            .glyphs
-            .last()
-            .map(|glyph| glyph.end)
-            .unwrap_or(0);
-
-        let mut range = start.max(from)..end.min(to);
-
-        let x_offset = visual_line
-            .glyphs
-            .first()
-            .map(|glyph| glyph.x)
-            .unwrap_or_default();
+    // Check for multi codepoint glyphs for each previous visual line
+    let mut previous_diff = 0;
+    let previous_lines_diff = line
+        .layout_opt()
+        .map(Vec::as_slice)
+        .unwrap_or_default()
+        .iter()
+        .enumerate()
+        .map(move |(line_nr, visual_line)| {
+            if line_nr == 0 {
+                let current_diff = previous_diff
+                    + visual_line
+                        .glyphs
+                        .iter()
+                        .fold(0, |d, g| d + g.start.abs_diff(g.end) - 1);
+                previous_diff = current_diff;
+                0
+            } else {
+                let current_diff = previous_diff
+                    + visual_line
+                        .glyphs
+                        .iter()
+                        .fold(0, |d, g| d + g.start.abs_diff(g.end) - 1);
+                let previous_diff_temp = previous_diff;
+                previous_diff = current_diff;
+                previous_diff_temp
+            }
+        });
 
-        if range.is_empty() {
-            (x_offset, 0.0)
-        } else if range.start == start && range.end == end {
-            (x_offset, visual_line.w)
-        } else {
-            let mut x = 0.0;
-            let mut width = 0.0;
-            for glyph in &visual_line.glyphs {
-                let glyph_count = glyph.start.abs_diff(glyph.end);
+    layout.iter().zip(previous_lines_diff).map(
+        move |(visual_line, previous_lines_diff)| {
+            let start = visual_line
+                .glyphs
+                .first()
+                .map(|glyph| glyph.start)
+                .unwrap_or(0);
+            let end = visual_line
+                .glyphs
+                .last()
+                .map(|glyph| glyph.end)
+                .unwrap_or(0);
+
+            let to = to + previous_lines_diff;
+            let mut range = start.max(from)..end.min(to);
+
+            let x_offset = visual_line
+                .glyphs
+                .first()
+                .map(|glyph| glyph.x)
+                .unwrap_or_default();
+
+            if range.is_empty() {
+                (x_offset, 0.0)
+            } else if range.start == start && range.end == end {
+                (x_offset, visual_line.w)
+            } else {
+                let mut x = 0.0;
+                let mut width = 0.0;
+                for glyph in &visual_line.glyphs {
+                    let glyph_count = glyph.start.abs_diff(glyph.end);
+
+                    // Check for multi codepoint glyphs before or within the range
+                    if glyph_count > 1 {
+                        if range.start > glyph.start {
+                            range.start += glyph_count - 1;
+                            range.end += glyph_count - 1;
+                        } else if range.end > glyph.start {
+                            range.end += glyph_count - 1;
+                        }
+                    }
 
-                // Check for multi codepoint glyphs before or within the range
-                if glyph_count > 1 {
                     if range.start > glyph.start {
-                        range.start += glyph_count - 1;
-                        range.end += glyph_count - 1;
-                    } else if range.end > glyph.start {
-                        range.end += glyph_count - 1;
+                        x += glyph.w;
                     }
-                }
 
-                if range.start > glyph.start {
-                    x += glyph.w;
+                    if range.start <= glyph.start && range.end > glyph.start {
+                        width += glyph.w;
+                    } else if range.end <= glyph.start {
+                        break;
+                    }
                 }
 
-                if range.start <= glyph.start && range.end > glyph.start {
-                    width += glyph.w;
-                } else if range.end <= glyph.start {
-                    break;
-                }
+                (x_offset + x, width)
             }
-
-            (x_offset + x, width)
-        }
-    })
+        },
+    )
 }
 
 fn visual_lines_offset(line: usize, buffer: &cosmic_text::Buffer) -> i32 {
diff --git a/src/text/rich.rs b/src/text/rich.rs
index 597fa26..865f64a 100644
--- a/src/text/rich.rs
+++ b/src/text/rich.rs
@@ -971,60 +971,92 @@ fn highlight_line(
 ) -> impl Iterator<Item = (f32, f32)> + '_ {
     let layout = line.layout_opt().map(Vec::as_slice).unwrap_or_default();
 
-    layout.iter().map(move |visual_line| {
-        let start = visual_line
-            .glyphs
-            .first()
-            .map(|glyph| glyph.start)
-            .unwrap_or(0);
-        let end = visual_line
-            .glyphs
-            .last()
-            .map(|glyph| glyph.end)
-            .unwrap_or(0);
-
-        let mut range = start.max(from)..end.min(to);
-
-        let x_offset = visual_line
-            .glyphs
-            .first()
-            .map(|glyph| glyph.x)
-            .unwrap_or_default();
-
-        if range.is_empty() {
-            (x_offset, 0.0)
-        } else if range.start == start && range.end == end {
-            (x_offset, visual_line.w)
-        } else {
-            let mut x = 0.0;
-            let mut width = 0.0;
-            for glyph in &visual_line.glyphs {
-                let glyph_count = glyph.start.abs_diff(glyph.end);
+    // Check for multi codepoint glyphs for each previous visual line
+    let mut previous_diff = 0;
+    let previous_lines_diff = line
+        .layout_opt()
+        .map(Vec::as_slice)
+        .unwrap_or_default()
+        .iter()
+        .enumerate()
+        .map(move |(line_nr, visual_line)| {
+            if line_nr == 0 {
+                let current_diff = previous_diff
+                    + visual_line
+                        .glyphs
+                        .iter()
+                        .fold(0, |d, g| d + g.start.abs_diff(g.end) - 1);
+                previous_diff = current_diff;
+                0
+            } else {
+                let current_diff = previous_diff
+                    + visual_line
+                        .glyphs
+                        .iter()
+                        .fold(0, |d, g| d + g.start.abs_diff(g.end) - 1);
+                let previous_diff_temp = previous_diff;
+                previous_diff = current_diff;
+                previous_diff_temp
+            }
+        });
+
+    layout.iter().zip(previous_lines_diff).map(
+        move |(visual_line, previous_lines_diff)| {
+            let start = visual_line
+                .glyphs
+                .first()
+                .map(|glyph| glyph.start)
+                .unwrap_or(0);
+            let end = visual_line
+                .glyphs
+                .last()
+                .map(|glyph| glyph.end)
+                .unwrap_or(0);
+
+            let to = to + previous_lines_diff;
+            let mut range = start.max(from)..end.min(to);
+
+            let x_offset = visual_line
+                .glyphs
+                .first()
+                .map(|glyph| glyph.x)
+                .unwrap_or_default();
+
+            if range.is_empty() {
+                (x_offset, 0.0)
+            } else if range.start == start && range.end == end {
+                (x_offset, visual_line.w)
+            } else {
+                let mut x = 0.0;
+                let mut width = 0.0;
+                for glyph in &visual_line.glyphs {
+                    let glyph_count = glyph.start.abs_diff(glyph.end);
+
+                    // Check for multi codepoint glyphs before or within the range
+                    if glyph_count > 1 {
+                        if range.start > glyph.start {
+                            range.start += glyph_count - 1;
+                            range.end += glyph_count - 1;
+                        } else if range.end > glyph.start {
+                            range.end += glyph_count - 1;
+                        }
+                    }
 
-                // Check for multi codepoint glyphs before or within the range
-                if glyph_count > 1 {
                     if range.start > glyph.start {
-                        range.start += glyph_count - 1;
-                        range.end += glyph_count - 1;
-                    } else if range.end > glyph.start {
-                        range.end += glyph_count - 1;
+                        x += glyph.w;
                     }
-                }
 
-                if range.start > glyph.start {
-                    x += glyph.w;
+                    if range.start <= glyph.start && range.end > glyph.start {
+                        width += glyph.w;
+                    } else if range.end <= glyph.start {
+                        break;
+                    }
                 }
 
-                if range.start <= glyph.start && range.end > glyph.start {
-                    width += glyph.w;
-                } else if range.end <= glyph.start {
-                    break;
-                }
+                (x_offset + x, width)
             }
-
-            (x_offset + x, width)
-        }
-    })
+        },
+    )
 }
 
 fn visual_lines_offset(line: usize, buffer: &cosmic_text::Buffer) -> i32 {