diff --git a/components/layout/block.rs b/components/layout/block.rs
index 75dcc9afd72..d3b42c2ded0 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -1390,8 +1390,22 @@ impl BlockFlow {
// and its inline-size is our content inline-size.
let kid_mode = flow::base(kid).writing_mode;
{
+ // Don't assign positions to children unless they're going to be reflowed.
+ // Otherwise, the position we assign might be incorrect and never fixed up. (Issue
+ // #13704.)
+ //
+ // For instance, floats have their true inline position calculated in
+ // `assign_block_size()`, which won't do anything unless `REFLOW` is set. So, if a
+ // float child does not have `REFLOW` set, we must be careful to avoid touching its
+ // inline position, as no logic will run afterward to set its true value.
let kid_base = flow::mut_base(kid);
- if kid_base.flags.contains(INLINE_POSITION_IS_STATIC) {
+ let reflow_damage = if kid_base.flags.contains(IS_ABSOLUTELY_POSITIONED) {
+ REFLOW_OUT_OF_FLOW
+ } else {
+ REFLOW
+ };
+ if kid_base.flags.contains(INLINE_POSITION_IS_STATIC) &&
+ kid_base.restyle_damage.contains(reflow_damage) {
kid_base.position.start.i =
if kid_mode.is_bidi_ltr() == containing_block_mode.is_bidi_ltr() {
inline_start_content_edge
diff --git a/tests/html/incremental_float.html b/tests/html/incremental_float.html
new file mode 100644
index 00000000000..f1d0adc08d8
--- /dev/null
+++ b/tests/html/incremental_float.html
@@ -0,0 +1,20 @@
+
+
+
+Mouse over the preceding gray square. It should change color but remain in place.
+