identify the cause of #3

Author: thjbdvlt

src/pix_grid.rs

@@ -148,17 +148,19 @@ pub fn cursor_x(
         return (space_width, x, 0.0);
     };
 
-    // FIXME (#3): cursor on multibyte char isn't visible. (e.g. on 2nd byte of "é")
-    // the issue comes from "cursor_width", which is set to `0`.
     if col + n > cursor_col {
-        let m = cursor_col - col;
-        let text = line.to_string(col, col + n);
         let analysis = item.analysis();
-        let (start, end) = (
-            unscale!(glyph_string.index_to_x(&text, analysis, m as i32, false)),
-            unscale!(glyph_string.index_to_x(&text, analysis, m as i32, true)),
-        );
-        cursor_width = end - start;
+
+        // We can't use the same technique as in PixLine::update, because items are typically grouped in words and here we need to analyse position and width inside a word.
+        // TODO: optimize
+        let mut s = String::new();
+        for cell in line.line[col..cursor_col].iter() {
+            s.push_str(&cell.ch);
+        }
+        let start = unscale!(glyph_string.index_to_x(&s, analysis, s.len() as i32, false));
+        let mut glyphs = pango::GlyphString::new();
+        pango::shape(&line.line[cursor_col].ch, analysis, &mut glyphs);
+        cursor_width = unscale!(glyphs.width());
         x += start;
         prefix = start;
     }

src/ui_model/item.rs

@@ -57,6 +57,10 @@ impl Item {
         }
     }
 
+    pub fn width(&self) -> i32 {
+        self.glyphs().as_ref().map(|g| g.width()).unwrap_or(0)
+    }
+
     pub fn new_render_node(
         &self,
         color: &color::Color,

src/ui_model/line.rs

@@ -35,14 +35,6 @@ impl Line {
         }
     }
 
-    pub fn to_string(&self, start_index: usize, end_index: usize) -> String {
-        let mut s = String::new();
-        for i in self.line[start_index..end_index].iter() {
-            s.push_str(&i.ch);
-        }
-        s
-    }
-
     pub fn swap_with(&mut self, target: &mut Self, left: usize, right: usize) {
         // swap is faster then clone
         target.line[left..=right].swap_with_slice(&mut self.line[left..=right]);
@@ -220,6 +212,14 @@ impl Line {
     pub fn is_binded_to_item(&self, cell_idx: usize) -> bool {
         self.cell_to_item[cell_idx] >= 0
     }
+
+    pub fn width(&self, index: usize) -> i32 {
+        if let Some(item_line) = self.item_line.get(index).map(|i| i.first()) {
+            item_line.iter().map(|i| i.width()).sum()
+        } else {
+            0
+        }
+    }
 }
 
 impl Index<usize> for Line {