Fix #20

src/ui_model/cell.rs

@@ -63,4 +63,3 @@ impl Cell {
         self.dirty = true;
     }
 }
-

src/ui_model/line.rs

@@ -70,9 +70,12 @@ impl Line {
     fn set_cell_to_item(&mut self, new_item: &PangoItemPosition) -> bool {
         let start_item_idx = self.cell_to_item(new_item.start_cell);
         let start_item_cells_count = if start_item_idx >= 0 {
-            self.item_line[start_item_idx as usize]
-                .as_ref()
-                .map_or(-1, |item| item.cells_count as i32)
+            self.item_line[start_item_idx as usize].as_ref().map_or(
+                -1,
+                |item| {
+                    item.cells_count as i32
+                },
+            )
         } else {
             -1
         };
@@ -83,8 +86,8 @@ impl Line {
         // in case different item length was in previous iteration
         // mark all item as dirty
         if start_item_idx != new_item.start_cell as i32 ||
-            new_item.cells_count() != start_item_cells_count || start_item_idx == -1 ||
-            end_item_idx == -1
+            new_item.cells_count() != start_item_cells_count ||
+            start_item_idx == -1 || end_item_idx == -1
         {
             self.initialize_cell_item(new_item.start_cell, new_item.end_cell, new_item.item);
             true
@@ -173,7 +176,12 @@ impl Line {
     }
 
     pub fn item_len_from_idx(&self, start_idx: usize) -> usize {
-        debug_assert!(start_idx < self.line.len());
+        debug_assert!(
+            start_idx < self.line.len(),
+            "idx={}, len={}",
+            start_idx,
+            self.line.len()
+        );
 
         let item_idx = self.cell_to_item(start_idx);
 

src/ui_model/mod.rs

@@ -70,6 +70,12 @@ impl UiModel {
     }
 
     pub fn set_cursor(&mut self, row: usize, col: usize) -> ModelRectVec {
+        // it is possible in some cases that cursor moved out of visible rect
+        // see https://github.com/daa84/neovim-gtk/issues/20
+        if row >= self.model.len() || col >= self.model[row].line.len() {
+            return ModelRectVec::empty();
+        }
+
         let mut changed_region = ModelRectVec::new(self.cur_point());
 
         self.cur_row = row;

src/ui_model/model_rect.rs

@@ -9,6 +9,10 @@ pub struct ModelRectVec {
 }
 
 impl ModelRectVec {
+    pub fn empty() -> ModelRectVec {
+        ModelRectVec { list: vec![] }
+    }
+
     pub fn new(first: ModelRect) -> ModelRectVec {
         ModelRectVec { list: vec![first] }
     }
@@ -257,13 +261,7 @@ impl ModelRect {
         )
     }
 
-    pub fn from_area(
-        cell_metrics: &CellMetrics,
-        x1: f64,
-        y1: f64,
-        x2: f64,
-        y2: f64,
-    ) -> ModelRect {
+    pub fn from_area(cell_metrics: &CellMetrics, x1: f64, y1: f64, x2: f64, y2: f64) -> ModelRect {
         let &CellMetrics {
             char_width,
             line_height,