stylo: only clear relevant origins when medium features change.

Bug: 1389871
Reviewed-by: heycam
MozReview-Commit-ID: 6ocZc1u1TbU

components/style/stylist.rs

@@ -40,7 +40,7 @@ use style_traits::viewport::ViewportConstraints;
 #[cfg(feature = "gecko")]
 use stylesheets::{CounterStyleRule, FontFaceRule};
 use stylesheets::{CssRule, StyleRule};
-use stylesheets::{StylesheetInDocument, Origin, PerOrigin, PerOriginClear};
+use stylesheets::{StylesheetInDocument, Origin, OriginSet, PerOrigin, PerOriginClear};
 use stylesheets::UserAgentStylesheets;
 use stylesheets::keyframes_rule::KeyframesAnimation;
 use stylesheets::viewport_rule::{self, MaybeNew, ViewportRule};
@@ -977,16 +977,16 @@ impl Stylist {
             stylesheets.iter().map(|s| &**s),
             guard
         );
-        self.is_device_dirty |= features_changed;
+        self.is_device_dirty |= !features_changed.is_empty();
     }
 
     /// Returns whether, given a media feature change, any previously-applicable
-    /// style has become non-applicable, or vice-versa.
+    /// style has become non-applicable, or vice-versa for each origin.
     pub fn media_features_change_changed_style<'a, I, S>(
         &self,
         stylesheets: I,
         guard: &SharedRwLockReadGuard,
-    ) -> bool
+    ) -> OriginSet
     where
         I: Iterator<Item = &'a S>,
         S: StylesheetInDocument + ToMediaListKey + 'static,
@@ -995,11 +995,18 @@ impl Stylist {
 
         debug!("Stylist::media_features_change_changed_style");
 
-        for stylesheet in stylesheets {
+        let mut origins = OriginSet::empty();
+
+        'stylesheets_loop: for stylesheet in stylesheets {
             let effective_now =
                 stylesheet.is_effective_for_device(&self.device, guard);
 
             let origin = stylesheet.origin(guard);
+
+            if origins.contains(origin.into()) {
+                continue;
+            }
+
             let origin_cascade_data =
                 self.cascade_data.borrow_for_origin(&origin);
 
@@ -1011,7 +1018,8 @@ impl Stylist {
             if effective_now != effective_then {
                 debug!(" > Stylesheet changed -> {}, {}",
                        effective_then, effective_now);
-                return true
+                origins |= origin;
+                continue;
             }
 
             if !effective_now {
@@ -1051,7 +1059,8 @@ impl Stylist {
                         if effective_now != effective_then {
                             debug!(" > @import rule changed {} -> {}",
                                    effective_then, effective_now);
-                            return true;
+                            origins |= origin;
+                            continue 'stylesheets_loop;
                         }
 
                         if !effective_now {
@@ -1070,7 +1079,8 @@ impl Stylist {
                         if effective_now != effective_then {
                             debug!(" > @media rule changed {} -> {}",
                                    effective_then, effective_now);
-                            return true;
+                            origins |= origin;
+                            continue 'stylesheets_loop;
                         }
 
                         if !effective_now {
@@ -1081,7 +1091,7 @@ impl Stylist {
             }
         }
 
-        return false;
+        return origins
     }
 
     /// Returns the viewport constraints that apply to this document because of

ports/geckolib/glue.rs

@@ -899,7 +899,7 @@ pub extern "C" fn Servo_StyleSet_AppendStyleSheet(
 pub extern "C" fn Servo_StyleSet_MediumFeaturesChanged(
     raw_data: RawServoStyleSetBorrowed,
     viewport_units_used: *mut bool,
-) -> bool {
+) -> OriginFlags {
     let global_style_data = &*GLOBAL_STYLE_DATA;
     let guard = global_style_data.shared_lock.read();
 
@@ -919,12 +919,13 @@ pub extern "C" fn Servo_StyleSet_MediumFeaturesChanged(
         *viewport_units_used = data.stylist.device().used_viewport_size();
     }
     data.stylist.device_mut().reset_computed_values();
-    let rules_changed = data.stylist.media_features_change_changed_style(
-        data.stylesheets.iter(),
-        &guard,
-    );
+    let origins_in_which_rules_changed =
+        data.stylist.media_features_change_changed_style(
+            data.stylesheets.iter(),
+            &guard,
+        );
 
-    rules_changed
+    OriginFlags::from(origins_in_which_rules_changed)
 }
 
 #[no_mangle]