improv: show ellipsis if nothing else fits

If buffer is small enough that char+ellipsis doesn't fit, then show
ellipsis alone. If buffer is smaller than ellipsis, show nothing.

src/shape.rs

@@ -1860,11 +1860,26 @@ impl ShapeLine {
                 current_visual_line.w = starting_line.w + ending_line.w + ellipsis_w;
                 current_visual_line.spaces = starting_line.spaces + ending_line.spaces;
             }
+            None if forward_pass_overflowed && width > ellipsis_w => {
+                // buffer is small enough that the forward pass didn't fit
+                // only show the ellipsis
+                current_visual_line
+                    .ranges
+                    .push(self.ellipsis_vlrange(if self.rtl {
+                        unicode_bidi::Level::rtl()
+                    } else {
+                        unicode_bidi::Level::ltr()
+                    }));
+                current_visual_line.ellipsized = true;
+                current_visual_line.w = ellipsis_w;
+                current_visual_line.spaces = 0;
+            }
             _ => {
                 // everything fit in the forward pass
                 current_visual_line.ranges = starting_line.ranges;
                 current_visual_line.w = starting_line.w;
                 current_visual_line.spaces = starting_line.spaces;
+                current_visual_line.ellipsized = false;
             }
         }
     }

tests/ellipsize_rendering.rs

@@ -183,3 +183,16 @@ fn test_ellipsize_bidi_isolates_middle_bug() {
         .canvas(220, 50)
         .validate_text_rendering();
 }
+
+#[test]
+fn test_ellipsize_ltr_middle_small_buffer() {
+    let attrs = Attrs::new().family(Family::Name("Inter"));
+    DrawTestCfg::new("ellipsize_ltr_middle_small_buffer")
+        .font_size(20., 26.)
+        .font_attrs(attrs)
+        .text("A/B Tester x8 Mono")
+        .wrap(Wrap::None)
+        .ellipsize(Ellipsize::Middle(EllipsizeHeightLimit::Lines(1)))
+        .canvas(30, 100)
+        .validate_text_rendering();
+}

tests/images/ellipsize_ltr_middle_small_buffer.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:4cfbb42f584b56040a99ddb82eebdecc967a89ce340d393aa651c2a441fd7fcf
+size 764