constellation: Use FnvHashMap for hashmaps that use ids as keys (#39106)

FNV is faster for hashing less than 16 bytes of data and the
cryptographic properties of the default HashMap are not needed for the
various ids.

Testing: This does not change functionality.

Signed-off-by: Narfinger <Narfinger@users.noreply.github.com>

components/shared/compositing/Cargo.toml

@@ -22,6 +22,7 @@ crossbeam-channel = { workspace = true }
 dpi = { version = "0.1" }
 embedder_traits = { workspace = true }
 euclid = { workspace = true }
+fnv = { workspace = true }
 gleam = { workspace = true }
 glow = { workspace = true }
 image = { workspace = true }

components/shared/compositing/display_list.rs

@@ -12,6 +12,7 @@ use base::print_tree::PrintTree;
 use bitflags::bitflags;
 use embedder_traits::ViewportDetails;
 use euclid::SideOffsets2D;
+use fnv::FnvHashMap;
 use malloc_size_of_derive::MallocSizeOf;
 use serde::{Deserialize, Serialize};
 use servo_geometry::FastLayoutTransform;
@@ -558,7 +559,10 @@ impl ScrollTree {
 
     /// Given a set of all scroll offsets coming from the Servo renderer, update all of the offsets
     /// for nodes that actually exist in this tree.
-    pub fn set_all_scroll_offsets(&mut self, offsets: &HashMap<ExternalScrollId, LayoutVector2D>) {
+    pub fn set_all_scroll_offsets(
+        &mut self,
+        offsets: &FnvHashMap<ExternalScrollId, LayoutVector2D>,
+    ) {
         for node in self.nodes.iter_mut() {
             if let SpatialTreeNodeInfo::Scroll(ref mut scroll_info) = node.info {
                 if let Some(offset) = offsets.get(&scroll_info.external_id) {
@@ -583,7 +587,7 @@ impl ScrollTree {
 
     /// Collect all of the scroll offsets of the scrolling nodes of this tree into a
     /// [`HashMap`] which can be applied to another tree.
-    pub fn scroll_offsets(&self) -> HashMap<ExternalScrollId, LayoutVector2D> {
+    pub fn scroll_offsets(&self) -> FnvHashMap<ExternalScrollId, LayoutVector2D> {
         HashMap::from_iter(self.nodes.iter().filter_map(|node| match node.info {
             SpatialTreeNodeInfo::Scroll(ref scroll_info) => {
                 Some((scroll_info.external_id, scroll_info.offset))

components/shared/constellation/Cargo.toml

@@ -23,6 +23,7 @@ devtools_traits = { workspace = true }
 embedder_traits = { workspace = true }
 euclid = { workspace = true }
 fonts_traits = { workspace = true }
+fnv = { workspace = true }
 http = { workspace = true }
 hyper_serde = { workspace = true }
 ipc-channel = { workspace = true }

components/shared/constellation/from_script_message.rs

@@ -4,7 +4,6 @@
 
 //! Messages send from the ScriptThread to the Constellation.
 
-use std::collections::HashMap;
 use std::fmt;
 
 use base::Epoch;
@@ -22,6 +21,7 @@ use embedder_traits::{
     ViewportDetails, WebDriverMessageId,
 };
 use euclid::default::Size2D as UntypedSize2D;
+use fnv::FnvHashMap;
 use fonts_traits::SystemFontServiceProxySender;
 use http::{HeaderMap, Method};
 use ipc_channel::ipc::IpcSender;
@@ -492,7 +492,7 @@ pub enum ScriptToConstellationMessage {
         /* The ids of ports transferred successfully */
         Vec<MessagePortId>,
         /* The ids, and buffers, of ports whose transfer failed */
-        HashMap<MessagePortId, PortTransferInfo>,
+        FnvHashMap<MessagePortId, PortTransferInfo>,
     ),
     /// A new message-port was created or transferred, with corresponding control-sender.
     NewMessagePort(MessagePortRouterId, MessagePortId),

components/shared/constellation/lib.rs

@@ -11,7 +11,7 @@
 mod from_script_message;
 mod structured_data;
 
-use std::collections::{HashMap, VecDeque};
+use std::collections::VecDeque;
 use std::fmt;
 use std::time::Duration;
 
@@ -22,6 +22,7 @@ use embedder_traits::{
     CompositorHitTestResult, FocusId, InputEvent, JavaScriptEvaluationId, MediaSessionActionType,
     Theme, TraversalId, ViewportDetails, WebDriverCommandMsg, WebDriverCommandResponse,
 };
+use fnv::FnvHashMap;
 pub use from_script_message::*;
 use ipc_channel::ipc::IpcSender;
 use malloc_size_of_derive::MallocSizeOf;
@@ -41,7 +42,7 @@ pub enum EmbedderToConstellationMessage {
     /// Exit the constellation.
     Exit,
     /// Query the constellation to see if the current compositor output is stable
-    IsReadyToSaveImage(HashMap<PipelineId, Epoch>),
+    IsReadyToSaveImage(FnvHashMap<PipelineId, Epoch>),
     /// Whether to allow script to navigate.
     AllowNavigationResponse(PipelineId, bool),
     /// Request to load a page.
@@ -94,7 +95,7 @@ pub enum EmbedderToConstellationMessage {
     SetWebViewThrottled(WebViewId, bool),
     /// The Servo renderer scrolled and is updating the scroll states of the nodes in the
     /// given pipeline via the constellation.
-    SetScrollStates(PipelineId, HashMap<ExternalScrollId, LayoutVector2D>),
+    SetScrollStates(PipelineId, FnvHashMap<ExternalScrollId, LayoutVector2D>),
     /// Notify the constellation that a particular paint metric event has happened for the given pipeline.
     PaintMetric(PipelineId, PaintMetricEvent),
     /// Evaluate a JavaScript string in the context of a `WebView`. When execution is complete or an
@@ -180,7 +181,7 @@ pub struct PortTransferInfo {
 #[allow(clippy::large_enum_variant)]
 pub enum MessagePortMsg {
     /// Complete the transfer for a batch of ports.
-    CompleteTransfer(HashMap<MessagePortId, PortTransferInfo>),
+    CompleteTransfer(FnvHashMap<MessagePortId, PortTransferInfo>),
     /// Complete the transfer of a single port,
     /// whose transfer was pending because it had been requested
     /// while a previous failed transfer was being rolled-back.

components/shared/layout/lib.rs

@@ -12,7 +12,6 @@ mod layout_damage;
 pub mod wrapper_traits;
 
 use std::any::Any;
-use std::collections::HashMap;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicIsize, AtomicU64, Ordering};
 use std::thread::JoinHandle;
@@ -281,7 +280,7 @@ pub trait Layout {
     /// Set the scroll states of this layout after a compositor scroll.
     fn set_scroll_offsets_from_renderer(
         &mut self,
-        scroll_states: &HashMap<ExternalScrollId, LayoutVector2D>,
+        scroll_states: &FnvHashMap<ExternalScrollId, LayoutVector2D>,
     );
 
     /// Get the scroll offset of the given scroll node with id of [`ExternalScrollId`] or `None` if it does

components/shared/script/Cargo.toml

@@ -26,6 +26,7 @@ crossbeam-channel = { workspace = true }
 devtools_traits = { workspace = true }
 embedder_traits = { workspace = true }
 euclid = { workspace = true }
+fnv = { workspace = true }
 ipc-channel = { workspace = true }
 keyboard-types = { workspace = true }
 malloc_size_of = { workspace = true }

components/shared/script/lib.rs

@@ -9,7 +9,6 @@
 #![deny(missing_docs)]
 #![deny(unsafe_code)]
 
-use std::collections::HashMap;
 use std::fmt;
 use std::sync::Arc;
 
@@ -33,6 +32,7 @@ use embedder_traits::{
     MediaSessionActionType, ScriptToEmbedderChan, Theme, ViewportDetails, WebDriverScriptCommand,
 };
 use euclid::{Rect, Scale, Size2D, UnknownUnit};
+use fnv::FnvHashMap;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use keyboard_types::Modifiers;
 use malloc_size_of_derive::MallocSizeOf;
@@ -253,7 +253,7 @@ pub enum ScriptThreadMessage {
     SetWebGPUPort(IpcReceiver<WebGPUMsg>),
     /// The compositor scrolled and is updating the scroll states of the nodes in the given
     /// pipeline via the Constellation.
-    SetScrollStates(PipelineId, HashMap<ExternalScrollId, LayoutVector2D>),
+    SetScrollStates(PipelineId, FnvHashMap<ExternalScrollId, LayoutVector2D>),
     /// Evaluate the given JavaScript and return a result via a corresponding message
     /// to the Constellation.
     EvaluateJavaScript(PipelineId, JavaScriptEvaluationId, String),