Auto merge of #22396 - jdm:no-spam-iframe-size, r=asajeffrey

Reduce unnecessary iframe size messages

This should be an improvement on pages that include iframes, since we currently run two layout jobs for every display-oriented layout request. When building the display list, we send a message to the constellation that includes the sizes of all iframes present, and the constellation sends resize messages to the script thread. This results in a mouse event on the outer page causing all frames to be re-laid out even if no changes occurred to the iframe sizes, which is ridiculous.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #22394
- [x] These changes do not require tests because there is no way to test this internal detail.

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5 files changed, 76 insertions, 21 deletions

diff --git a/components/constellation/constellation.rs b/components/constellation/constellation.rs
index 80214a67a99..ec4c1f94273 100644
--- a/components/constellation/constellation.rs
+++ b/components/constellation/constellation.rs
@@ -146,9 +146,9 @@ use script_traits::{DocumentActivity, DocumentState, LayoutControlMsg, LoadData}
 use script_traits::{
     IFrameLoadInfo, IFrameLoadInfoWithData, IFrameSandboxState, TimerSchedulerMsg,
 };
+use script_traits::{IFrameSizeMsg, WindowSizeData, WindowSizeType};
 use script_traits::{LayoutMsg as FromLayoutMsg, ScriptMsg as FromScriptMsg, ScriptThreadFactory};
 use script_traits::{SWManagerMsg, ScopeThings, UpdatePipelineIdReason, WebDriverCommandMsg};
-use script_traits::{WindowSizeData, WindowSizeType};
 use serde::{Deserialize, Serialize};
 use servo_config::opts;
 use servo_config::prefs::PREFS;
@@ -1837,17 +1837,14 @@ where
         }
     }
 
-    fn handle_iframe_size_msg(
-        &mut self,
-        iframe_sizes: Vec<(BrowsingContextId, TypedSize2D<f32, CSSPixel>)>,
-    ) {
-        for (browsing_context_id, size) in iframe_sizes {
+    fn handle_iframe_size_msg(&mut self, iframe_sizes: Vec<IFrameSizeMsg>) {
+        for IFrameSizeMsg { data, type_ } in iframe_sizes {
             let window_size = WindowSizeData {
-                initial_viewport: size,
+                initial_viewport: data.size,
                 device_pixel_ratio: self.window_size.device_pixel_ratio,
             };
 
-            self.resize_browsing_context(window_size, WindowSizeType::Initial, browsing_context_id);
+            self.resize_browsing_context(window_size, type_, data.id);
         }
     }
 
diff --git a/components/layout/display_list/builder.rs b/components/layout/display_list/builder.rs
index 18fb0980fcd..a6e77fe78b8 100644
--- a/components/layout/display_list/builder.rs
+++ b/components/layout/display_list/builder.rs
@@ -37,9 +37,10 @@ use gfx::text::glyph::ByteIndex;
 use gfx::text::TextRun;
 use gfx_traits::{combine_id_with_fragment_type, FragmentType, StackingContextId};
 use ipc_channel::ipc;
-use msg::constellation_msg::{BrowsingContextId, PipelineId};
+use msg::constellation_msg::PipelineId;
 use net_traits::image_cache::UsePlaceholder;
 use range::Range;
+use script_traits::IFrameSize;
 use servo_config::opts;
 use servo_geometry::MaxRect;
 use std::default::Default;
@@ -61,7 +62,6 @@ use style::values::generics::background::BackgroundSize;
 use style::values::generics::image::{GradientKind, Image, PaintWorklet};
 use style::values::{Either, RGBA};
 use style_traits::cursor::CursorKind;
-use style_traits::CSSPixel;
 use style_traits::ToCss;
 use webrender_api::{
     self, BorderDetails, BorderRadius, BorderSide, BoxShadowClipMode, ColorF, ColorU,
@@ -318,7 +318,7 @@ pub struct DisplayListBuildState<'a> {
 
     /// Vector containing iframe sizes, used to inform the constellation about
     /// new iframe sizes
-    pub iframe_sizes: Vec<(BrowsingContextId, TypedSize2D<f32, CSSPixel>)>,
+    pub iframe_sizes: Vec<IFrameSize>,
 
     /// Stores text runs to answer text queries used to place a cursor inside text.
     pub indexable_text: IndexableText,
@@ -1785,9 +1785,10 @@ impl Fragment {
                     }));
 
                     let size = Size2D::new(item.bounds().size.width, item.bounds().size.height);
-                    state
-                        .iframe_sizes
-                        .push((browsing_context_id, TypedSize2D::from_untyped(&size)));
+                    state.iframe_sizes.push(IFrameSize {
+                        id: browsing_context_id,
+                        size: TypedSize2D::from_untyped(&size),
+                    });
 
                     state.add_display_item(item);
                 }
diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index d0c4cd9e4da..ecc4153ab71 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -68,8 +68,8 @@ use metrics::{PaintTimeMetrics, ProfilerMetadataFactory, ProgressiveWebMetric};
 use msg::constellation_msg::{
     BackgroundHangMonitor, BackgroundHangMonitorRegister, HangAnnotation,
 };
+use msg::constellation_msg::{BrowsingContextId, MonitoredComponentId, TopLevelBrowsingContextId};
 use msg::constellation_msg::{LayoutHangAnnotation, MonitoredComponentType, PipelineId};
-use msg::constellation_msg::{MonitoredComponentId, TopLevelBrowsingContextId};
 use net_traits::image_cache::{ImageCache, UsePlaceholder};
 use parking_lot::RwLock;
 use profile_traits::mem::{self as profile_mem, Report, ReportKind, ReportsChan};
@@ -82,7 +82,7 @@ use script_layout_interface::rpc::{LayoutRPC, OffsetParentResponse, StyleRespons
 use script_layout_interface::wrapper_traits::LayoutNode;
 use script_traits::Painter;
 use script_traits::{ConstellationControlMsg, LayoutControlMsg, LayoutMsg as ConstellationMsg};
-use script_traits::{DrawAPaintImageResult, PaintWorkletError};
+use script_traits::{DrawAPaintImageResult, IFrameSizeMsg, PaintWorkletError, WindowSizeType};
 use script_traits::{ScrollState, UntrustedNodeAddress};
 use selectors::Element;
 use servo_arc::Arc as ServoArc;
@@ -241,6 +241,9 @@ pub struct LayoutThread {
 
     /// The time a layout query has waited before serviced by layout thread.
     layout_query_waiting_time: Histogram,
+
+    /// The sizes of all iframes encountered during the last layout operation.
+    last_iframe_sizes: RefCell<HashMap<BrowsingContextId, TypedSize2D<f32, CSSPixel>>>,
 }
 
 impl LayoutThreadFactory for LayoutThread {
@@ -544,6 +547,7 @@ impl LayoutThread {
             },
             paint_time_metrics: paint_time_metrics,
             layout_query_waiting_time: Histogram::new(),
+            last_iframe_sizes: Default::default(),
         }
     }
 
@@ -1054,9 +1058,41 @@ impl LayoutThread {
                             // it with an empty vector
                             let iframe_sizes =
                                 std::mem::replace(&mut build_state.iframe_sizes, vec![]);
-                            let msg = ConstellationMsg::IFrameSizes(iframe_sizes);
-                            if let Err(e) = self.constellation_chan.send(msg) {
-                                warn!("Layout resize to constellation failed ({}).", e);
+                            // Collect the last frame's iframe sizes to compute any differences.
+                            // Every frame starts with a fresh collection so that any removed
+                            // iframes do not linger.
+                            let last_iframe_sizes = std::mem::replace(
+                                &mut *self.last_iframe_sizes.borrow_mut(),
+                                HashMap::default(),
+                            );
+                            let mut size_messages = vec![];
+                            for new_size in iframe_sizes {
+                                // Only notify the constellation about existing iframes
+                                // that have a new size, or iframes that did not previously
+                                // exist.
+                                if let Some(old_size) = last_iframe_sizes.get(&new_size.id) {
+                                    if *old_size != new_size.size {
+                                        size_messages.push(IFrameSizeMsg {
+                                            data: new_size,
+                                            type_: WindowSizeType::Resize,
+                                        });
+                                    }
+                                } else {
+                                    size_messages.push(IFrameSizeMsg {
+                                        data: new_size,
+                                        type_: WindowSizeType::Initial,
+                                    });
+                                }
+                                self.last_iframe_sizes
+                                    .borrow_mut()
+                                    .insert(new_size.id, new_size.size);
+                            }
+
+                            if !size_messages.is_empty() {
+                                let msg = ConstellationMsg::IFrameSizes(size_messages);
+                                if let Err(e) = self.constellation_chan.send(msg) {
+                                    warn!("Layout resize to constellation failed ({}).", e);
+                                }
                             }
                         }
 
diff --git a/components/script_traits/lib.rs b/components/script_traits/lib.rs
index b97544f9223..c033b491e35 100644
--- a/components/script_traits/lib.rs
+++ b/components/script_traits/lib.rs
@@ -61,7 +61,9 @@ use webvr_traits::{WebVREvent, WebVRMsg};
 pub use crate::script_msg::{
     DOMMessage, SWManagerMsg, SWManagerSenders, ScopeThings, ServiceWorkerMsg,
 };
-pub use crate::script_msg::{EventResult, LayoutMsg, LogEntry, ScriptMsg};
+pub use crate::script_msg::{
+    EventResult, IFrameSize, IFrameSizeMsg, LayoutMsg, LogEntry, ScriptMsg,
+};
 
 /// The address of a node. Layout sends these back. They must be validated via
 /// `from_untrusted_node_address` before they can be used, because we do not trust layout.
diff --git a/components/script_traits/script_msg.rs b/components/script_traits/script_msg.rs
index a63462fd83f..7d5ce79e2f6 100644
--- a/components/script_traits/script_msg.rs
+++ b/components/script_traits/script_msg.rs
@@ -9,6 +9,7 @@ use crate::IFrameLoadInfo;
 use crate::IFrameLoadInfoWithData;
 use crate::LayoutControlMsg;
 use crate::LoadData;
+use crate::WindowSizeType;
 use crate::WorkerGlobalScopeInit;
 use crate::WorkerScriptLoadOrigin;
 use canvas_traits::canvas::{CanvasId, CanvasMsg};
@@ -30,13 +31,31 @@ use style_traits::viewport::ViewportConstraints;
 use style_traits::CSSPixel;
 use webrender_api::{DeviceIntPoint, DeviceIntSize};
 
+/// A particular iframe's size, associated with a browsing context.
+#[derive(Clone, Copy, Debug, Deserialize, Serialize)]
+pub struct IFrameSize {
+    /// The child browsing context for this iframe.
+    pub id: BrowsingContextId,
+    /// The size of the iframe.
+    pub size: TypedSize2D<f32, CSSPixel>,
+}
+
+/// An iframe sizing operation.
+#[derive(Clone, Copy, Debug, Deserialize, Serialize)]
+pub struct IFrameSizeMsg {
+    /// The iframe sizing data.
+    pub data: IFrameSize,
+    /// The kind of sizing operation.
+    pub type_: WindowSizeType,
+}
+
 /// Messages from the layout to the constellation.
 #[derive(Deserialize, Serialize)]
 pub enum LayoutMsg {
     /// Indicates whether this pipeline is currently running animations.
     ChangeRunningAnimationsState(PipelineId, AnimationState),
     /// Inform the constellation of the size of the iframe's viewport.
-    IFrameSizes(Vec<(BrowsingContextId, TypedSize2D<f32, CSSPixel>)>),
+    IFrameSizes(Vec<IFrameSizeMsg>),
     /// Requests that the constellation inform the compositor that it needs to record
     /// the time when the frame with the given ID (epoch) is painted.
     PendingPaintMetric(PipelineId, Epoch),