Properly handle stacking context collection for truncated fragments

Before we did not properly descend intro truncated fragments when collecting stacking contexts. This change makes sure that we descend properly Fixes servo#18254. Fixes servo#17072.
mrobinson · Sep 14, 2017 · 4262723 · 4262723
1 parent b6b698d
commit 4262723
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Showing 4 changed files with 105 additions and 23 deletions.
diff --git a/components/layout/display_list_builder.rs b/components/layout/display_list_builder.rs
@@ -386,6 +386,10 @@ pub enum IdType {
 }
 
 pub trait FragmentDisplayListBuilding {
+    fn collect_stacking_contexts_for_blocklike_fragment(&mut self,
+                                                        state: &mut DisplayListBuildState)
+                                                        -> bool;
+
     /// Adds the display items necessary to paint the background of this fragment to the display
     /// list if necessary.
     fn build_display_list_for_background_if_applicable(&self,
@@ -857,6 +861,33 @@ fn convert_ellipse_size_keyword(keyword: ShapeExtent,
 }
 
 impl FragmentDisplayListBuilding for Fragment {
+    fn collect_stacking_contexts_for_blocklike_fragment(&mut self,
+                                                        state: &mut DisplayListBuildState)
+                                                        -> bool {
+        match self.specific {
+            SpecificFragmentInfo::InlineBlock(ref mut block_flow) => {
+                let block_flow = FlowRef::deref_mut(&mut block_flow.flow_ref);
+                block_flow.collect_stacking_contexts(state);
+                true
+            }
+            SpecificFragmentInfo::InlineAbsoluteHypothetical(ref mut block_flow) => {
+                let block_flow = FlowRef::deref_mut(&mut block_flow.flow_ref);
+                block_flow.collect_stacking_contexts(state);
+                true
+            }
+            SpecificFragmentInfo::InlineAbsolute(ref mut block_flow) => {
+                let block_flow = FlowRef::deref_mut(&mut block_flow.flow_ref);
+                block_flow.collect_stacking_contexts(state);
+                true
+            }
+            // FIXME: In the future, if #15144 is fixed we can remove this case. See #18510.
+            SpecificFragmentInfo::TruncatedFragment(ref mut info) => {
+                info.full.collect_stacking_contexts_for_blocklike_fragment(state)
+            }
+            _ => false,
+        }
+    }
+
     fn build_display_list_for_background_if_applicable(&self,
                                                        state: &mut DisplayListBuildState,
                                                        style: &ComputedValues,
@@ -2848,34 +2879,24 @@ impl InlineFlowDisplayListBuilding for InlineFlow {
                 state.containing_block_clip_and_scroll_info = state.current_clip_and_scroll_info;
             }
 
-            match fragment.specific {
-                SpecificFragmentInfo::InlineBlock(ref mut block_flow) => {
-                    let block_flow = FlowRef::deref_mut(&mut block_flow.flow_ref);
-                    block_flow.collect_stacking_contexts(state);
-                }
-                SpecificFragmentInfo::InlineAbsoluteHypothetical(ref mut block_flow) => {
-                    let block_flow = FlowRef::deref_mut(&mut block_flow.flow_ref);
-                    block_flow.collect_stacking_contexts(state);
-                }
-                SpecificFragmentInfo::InlineAbsolute(ref mut block_flow) => {
-                    let block_flow = FlowRef::deref_mut(&mut block_flow.flow_ref);
-                    block_flow.collect_stacking_contexts(state);
-                }
-                _ if fragment.establishes_stacking_context() => {
+            if !fragment.collect_stacking_contexts_for_blocklike_fragment(state) {
+                if fragment.establishes_stacking_context() {
                     fragment.stacking_context_id = fragment.stacking_context_id();
 
                     let current_stacking_context_id = state.current_stacking_context_id;
-                    let stacking_context = fragment.create_stacking_context(fragment.stacking_context_id,
-                                                                            &self.base,
-                                                                            ScrollPolicy::Scrollable,
-                                                                            StackingContextType::Real,
-                                                                            state.current_clip_and_scroll_info);
-
-                    state.add_stacking_context(current_stacking_context_id,
-                                               stacking_context);
+                    let stacking_context =
+                        fragment.create_stacking_context(fragment.stacking_context_id,
+                                                         &self.base,
+                                                         ScrollPolicy::Scrollable,
+                                                         StackingContextType::Real,
+                                                         state.current_clip_and_scroll_info);
+
+                    state.add_stacking_context(current_stacking_context_id, stacking_context);
+                } else {
+                    fragment.stacking_context_id = state.current_stacking_context_id;
                 }
-                _ => fragment.stacking_context_id = state.current_stacking_context_id,
             }
+
             state.containing_block_clip_and_scroll_info = previous_cb_clip_scroll_info;
         }
 

diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -6353,6 +6353,18 @@
      {}
     ]
    ],
+   "css/truncated_text_fragment_stacking_context.html": [
+    [
+     "/_mozilla/css/truncated_text_fragment_stacking_context.html",
+     [
+      [
+       "/_mozilla/css/truncated_text_fragment_stacking_context_ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "css/upper_id_attr.html": [
     [
      "/_mozilla/css/upper_id_attr.html",
@@ -10547,6 +10559,11 @@
      {}
     ]
    ],
+   "css/truncated_text_fragment_stacking_context_ref.html": [
+    [
+     {}
+    ]
+   ],
    "css/upper_id_attr_ref.html": [
     [
      {}
@@ -26893,6 +26910,14 @@
    "c62420cce19d1d6a7d8700275daaa5ecc10d14c7",
    "support"
   ],
+  "css/truncated_text_fragment_stacking_context.html": [
+   "453b01aec6ffd3c854fda854cf81250a332cd55c",
+   "reftest"
+  ],
+  "css/truncated_text_fragment_stacking_context_ref.html": [
+   "4cb902bb7b058748d1702b5033e8cec729431640",
+   "support"
+  ],
   "css/upper_id_attr.html": [
    "f9965c1c22379aba20ac08d03a5e0e86cb1d8b99",
    "reftest"

diff --git a/tests/wpt/mozilla/tests/css/truncated_text_fragment_stacking_context.html b/tests/wpt/mozilla/tests/css/truncated_text_fragment_stacking_context.html
@@ -0,0 +1,33 @@
+<!DOCTYPE html>
+<title>Truncated text and inline-blocks combined should not cause a panic</title>
+<link rel="match" href="truncated_text_fragment_stacking_context_ref.html" />
+<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />
+<meta name="assert" content="This test checks that truncated text and inline-blocks don't cause a panic." />
+
+<!-- We are using transparent text here to avoid having to deal with subpixel text rendering issues. -->
+<style>
+  a {
+    float: left;
+    color: transparent;
+  }
+  p, em {
+    overflow:hidden
+  }
+
+  em {
+    display: inline-block;
+    text-overflow: ellipsis;
+    color: transparent;
+  }
+
+  div {
+    position: absolute
+  }
+</style>
+
+<div style="height: 100px; width: 100px; background: green;"></div>
+
+<div>
+  <a>LINK</a>
+  <p><em>TEXT</em></p>
+</div>
diff --git a/tests/wpt/mozilla/tests/css/truncated_text_fragment_stacking_context_ref.html b/tests/wpt/mozilla/tests/css/truncated_text_fragment_stacking_context_ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<title>Truncated text and inline-blocks combined should not cause a panic</title>
+<div style="width: 100px; height: 100px; background: green"></div>