fix backwards rendering

2025-11-09 15:56:00 +01:00
parent 73700baf87
commit 56c2c21021
3 changed files with 183 additions and 25 deletions
@@ -790,13 +790,14 @@ class TestBidirectionalLayouter:

        current_start = RenderingPosition(block_index=5)
        target_end = RenderingPosition(block_index=10)
-        actual_end = RenderingPosition(block_index=12)  # Overshot
+        actual_end = RenderingPosition(block_index=12)  # Overshot (went too far)

        adjusted = layouter._adjust_start_estimate(
            current_start, target_end, actual_end)

-        # Should move start forward (increase block_index)
-        assert adjusted.block_index > current_start.block_index
+        # Overshot means we rendered too far forward
+        # So we need to start EARLIER (decrease block_index) to not go as far
+        assert adjusted.block_index < current_start.block_index

    def test_adjust_start_estimate_undershot(self):
        """Test adjustment when forward render undershoots target."""
@@ -804,13 +805,14 @@ class TestBidirectionalLayouter:

        current_start = RenderingPosition(block_index=5)
        target_end = RenderingPosition(block_index=10)
-        actual_end = RenderingPosition(block_index=8)  # Undershot
+        actual_end = RenderingPosition(block_index=8)  # Undershot (didn't go far enough)

        adjusted = layouter._adjust_start_estimate(
            current_start, target_end, actual_end)

-        # Should move start backward (decrease block_index)
-        assert adjusted.block_index <= current_start.block_index
+        # Undershot means we didn't render far enough forward
+        # So we need to start LATER (increase block_index) to include more content
+        assert adjusted.block_index > current_start.block_index

    def test_adjust_start_estimate_exact(self):
        """Test adjustment when forward render hits target exactly."""