Fix panic when drawing at the edge of the screen.

When pressing tab at the edge of the screen, Helix panics in debug mode
subtracting position.col - self.offset.col.

I don't fully understand the logic here, but if cut_off_start < width,
then self.offset.col - position.col < width (from the definition of
cut_off_start), and so self.position.col + width > self.offset.col,
meaning in_bounds is true and the second condition is currently
unreachable.

I believe these conditions should be reversed so that the logic for
rendering partially visible characters can apply properly.

helix-term/src/ui/document.rs

@@ -435,14 +435,7 @@ impl<'a> TextRenderer<'a> {
 
         let in_bounds = self.column_in_bounds(position.col + width - 1);
 
-        if in_bounds {
-            self.surface.set_string(
-                self.viewport.x + (position.col - self.offset.col) as u16,
-                self.viewport.y + position.row as u16,
-                grapheme,
-                style,
-            );
-        } else if cut_off_start != 0 && cut_off_start < width {
+        if cut_off_start != 0 && cut_off_start < width {
             // partially on screen
             let rect = Rect::new(
                 self.viewport.x,
@@ -451,6 +444,13 @@ impl<'a> TextRenderer<'a> {
                 1,
             );
             self.surface.set_style(rect, style);
+        } else if in_bounds {
+            self.surface.set_string(
+                self.viewport.x + (position.col - self.offset.col) as u16,
+                self.viewport.y + position.row as u16,
+                grapheme,
+                style,
+            );
         }
 
         if *is_in_indent_area && !is_whitespace {