fix moving cursor screen row down with row-wrapping tab characters

test/src/test_BufferView.cc

@@ -729,3 +729,31 @@ TEST(BufferViewTest, scrolls_past_empty_lines)
     bv.update();
     EXPECT_EQ(0, LineNumber(iterator));
 }
+
+TEST(BufferViewTest, moving_cursor_screen_row_down_jumps_past_wrapped_tab)
+{
+    static const char data[] =
+        "0\n"
+        "1abc\tdefghijklmnopqrstuvwxyz\n"
+        "2\n"
+        "3\n";
+    auto b = std::make_shared<Buffer>((const uint8_t *)data, strlen(data));
+    auto iterator = b->add_cursor();
+    BufferView bv(b, iterator, Cwd);
+    bv.resize(5, 10);
+    bv.update();
+    EXPECT_EQ(C('0'), **iterator);
+    EXPECT_EQ(0, bv.cursor_screen_row());
+    bv.cursor_move(BufferView::CursorMovement::SCREEN_ROW_DOWN, false);
+    bv.update();
+    EXPECT_EQ(C('1'), **iterator);
+    EXPECT_EQ(1, bv.cursor_screen_row());
+    bv.cursor_move(BufferView::CursorMovement::SCREEN_ROW_DOWN, false);
+    bv.update();
+    EXPECT_EQ(C('d'), **iterator);
+    EXPECT_EQ(2, bv.cursor_screen_row());
+    bv.cursor_move(BufferView::CursorMovement::SCREEN_ROW_DOWN, false);
+    bv.update();
+    EXPECT_EQ(C('f'), **iterator);
+    EXPECT_EQ(3, bv.cursor_screen_row());
+}