constellation: Stop assuming that the viewport is shared by all WebViews (#36312)

The `Constellation` previously held a `window_size` member, but this
assumes that all `WebView`s have the same size. This change removes that
assumption as well as making sure that all `WebView`s pass their size
and HiDIP scaling to the `Constellation` when they are created.

In addition

- `WindowSizeData` is renamed to `ViewportDetails`, as it was
holding more than just the size and it didn't necessarily correspond to
  a "window." It's used for tracking viewport data, whether for an
  `<iframe>` or the main `WebView` viewport.
- `ViewportDetails` is stored more consistently so that conceptually an
  `<iframe>` can also have its own HiDPI scaling. This isn't something
  we necessarily want, but it makes everything conceptually simpler.

The goal with this change is to work toward allowing per-`WebView` HiDPI
scaling and sizing. There are still some corresponding changes in the
compositor to make that happen, but they will in a subsequent change.

Testing: This is covered by existing tests. There should be no behavior
changes.
Fixes: This is part of #36232.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/shared/constellation/lib.rs

@@ -17,17 +17,18 @@ use base::Epoch;
 use base::cross_process_instant::CrossProcessInstant;
 use base::id::{PipelineId, ScrollTreeNodeId, WebViewId};
 use bitflags::bitflags;
-use embedder_traits::{Cursor, InputEvent, MediaSessionActionType, Theme, WebDriverCommandMsg};
-use euclid::{Scale, Size2D, Vector2D};
+use embedder_traits::{
+    Cursor, InputEvent, MediaSessionActionType, Theme, ViewportDetails, WebDriverCommandMsg,
+};
+use euclid::Vector2D;
 use ipc_channel::ipc::IpcSender;
 use malloc_size_of::malloc_size_of_is_0;
 use malloc_size_of_derive::MallocSizeOf;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use servo_url::ServoUrl;
 use strum_macros::IntoStaticStr;
-use style_traits::CSSPixel;
 use webrender_api::ExternalScrollId;
-use webrender_api::units::{DevicePixel, LayoutPixel};
+use webrender_api::units::LayoutPixel;
 
 /// Messages to the constellation.
 #[derive(IntoStaticStr)]
@@ -47,8 +48,8 @@ pub enum ConstellationMsg {
     ClearCache,
     /// Request to traverse the joint session history of the provided browsing context.
     TraverseHistory(WebViewId, TraversalDirection),
-    /// Inform the constellation of a window being resized.
-    WindowSize(WebViewId, WindowSizeData, WindowSizeType),
+    /// Inform the Constellation that a `WebView`'s [`ViewportDetails`] have changed.
+    ChangeViewportDetails(WebViewId, ViewportDetails, WindowSizeType),
     /// Inform the constellation of a theme change.
     ThemeChange(Theme),
     /// Requests that the constellation instruct layout to begin a new tick of the animation.
@@ -60,7 +61,7 @@ pub enum ConstellationMsg {
     /// A log entry, with the top-level browsing context id and thread name
     LogEntry(Option<WebViewId>, Option<String>, LogEntry),
     /// Create a new top level browsing context.
-    NewWebView(ServoUrl, WebViewId),
+    NewWebView(ServoUrl, WebViewId, ViewportDetails),
     /// Close a top level browsing context.
     CloseWebView(WebViewId),
     /// Panic a top level browsing context.
@@ -115,17 +116,6 @@ pub enum LogEntry {
     Warn(String),
 }
 
-/// Data about the window size.
-#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize)]
-pub struct WindowSizeData {
-    /// The size of the initial layout viewport, before parsing an
-    /// <http://www.w3.org/TR/css-device-adapt/#initial-viewport>
-    pub initial_viewport: Size2D<f32, CSSPixel>,
-
-    /// The resolution of the window in dppx, not including any "pinch zoom" factor.
-    pub device_pixel_ratio: Scale<f32, CSSPixel, DevicePixel>,
-}
-
 /// The type of window size change.
 #[derive(Clone, Copy, Debug, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
 pub enum WindowSizeType {

components/shared/embedder/lib.rs

@@ -19,6 +19,7 @@ use std::sync::Arc;
 
 use base::id::{PipelineId, WebViewId};
 use crossbeam_channel::Sender;
+use euclid::{Scale, Size2D};
 use http::{HeaderMap, Method, StatusCode};
 use ipc_channel::ipc::IpcSender;
 pub use keyboard_types::{KeyboardEvent, Modifiers};
@@ -29,8 +30,9 @@ use pixels::Image;
 use serde::{Deserialize, Serialize};
 use servo_url::ServoUrl;
 use strum_macros::IntoStaticStr;
+use style_traits::CSSPixel;
 use url::Url;
-use webrender_api::units::{DeviceIntPoint, DeviceIntRect, DeviceIntSize};
+use webrender_api::units::{DeviceIntPoint, DeviceIntRect, DeviceIntSize, DevicePixel};
 
 pub use crate::input_events::*;
 pub use crate::webdriver::*;
@@ -224,7 +226,6 @@ pub enum AllowOrDeny {
 }
 
 #[derive(Clone, Debug, Deserialize, Serialize)]
-
 pub struct SelectElementOption {
     /// A unique identifier for the option that can be used to select it.
     pub id: usize,
@@ -244,6 +245,18 @@ pub enum SelectElementOptionOrOptgroup {
     },
 }
 
+/// Data about a `WebView` or `<iframe>` viewport: its size and also the
+/// HiDPI scale factor to use when rendering the contents.
+#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize)]
+pub struct ViewportDetails {
+    /// The size of the layout viewport.
+    pub size: Size2D<f32, CSSPixel>,
+
+    /// The scale factor to use to account for HiDPI scaling. This does not take into account
+    /// any page or pinch zoom applied by the compositor to the contents.
+    pub hidpi_scale_factor: Scale<f32, CSSPixel, DevicePixel>,
+}
+
 #[derive(Deserialize, IntoStaticStr, Serialize)]
 pub enum EmbedderMsg {
     /// A status message to be displayed by the browser chrome.
@@ -275,7 +288,7 @@ pub enum EmbedderMsg {
     /// Whether or not to allow a pipeline to load a url.
     AllowNavigationRequest(WebViewId, PipelineId, ServoUrl),
     /// Whether or not to allow script to open a new tab/browser
-    AllowOpeningWebView(WebViewId, IpcSender<Option<WebViewId>>),
+    AllowOpeningWebView(WebViewId, IpcSender<Option<(WebViewId, ViewportDetails)>>),
     /// A webview was destroyed.
     WebViewClosed(WebViewId),
     /// A webview gained focus for keyboard events.

components/shared/script/lib.rs

@@ -27,13 +27,13 @@ use base::id::{
 use bluetooth_traits::BluetoothRequest;
 use canvas_traits::webgl::WebGLPipeline;
 use constellation_traits::{
-    AnimationTickType, CompositorHitTestResult, ScrollState, WindowSizeData, WindowSizeType,
+    AnimationTickType, CompositorHitTestResult, ScrollState, WindowSizeType,
 };
 use crossbeam_channel::{RecvTimeoutError, Sender};
 use devtools_traits::{DevtoolScriptControlMsg, ScriptToDevtoolsControlMsg, WorkerId};
 use embedder_traits::input_events::InputEvent;
 use embedder_traits::user_content_manager::UserContentManager;
-use embedder_traits::{MediaSessionActionType, Theme, WebDriverScriptCommand};
+use embedder_traits::{MediaSessionActionType, Theme, ViewportDetails, WebDriverScriptCommand};
 use euclid::{Rect, Scale, Size2D, UnknownUnit};
 use http::{HeaderMap, Method};
 use ipc_channel::Error as IpcError;
@@ -176,8 +176,8 @@ pub struct NewLayoutInfo {
     pub opener: Option<BrowsingContextId>,
     /// Network request data which will be initiated by the script thread.
     pub load_data: LoadData,
-    /// Information about the initial window size.
-    pub window_size: WindowSizeData,
+    /// Initial [`ViewportDetails`] for this layout.
+    pub viewport_details: ViewportDetails,
 }
 
 /// When a pipeline is closed, should its browsing context be discarded too?
@@ -252,11 +252,11 @@ pub enum ScriptThreadMessage {
     /// Gives a channel and ID to a layout, as well as the ID of that layout's parent
     AttachLayout(NewLayoutInfo),
     /// Window resized.  Sends a DOM event eventually, but first we combine events.
-    Resize(PipelineId, WindowSizeData, WindowSizeType),
+    Resize(PipelineId, ViewportDetails, WindowSizeType),
     /// Theme changed.
     ThemeChange(PipelineId, Theme),
     /// Notifies script that window has been resized but to not take immediate action.
-    ResizeInactive(PipelineId, WindowSizeData),
+    ResizeInactive(PipelineId, ViewportDetails),
     /// Window switched from fullscreen mode.
     ExitFullScreen(PipelineId),
     /// Notifies the script that the document associated with this pipeline should 'unload'.
@@ -447,8 +447,8 @@ pub struct InitialScriptState {
     pub memory_profiler_sender: mem::ProfilerChan,
     /// A channel to the developer tools, if applicable.
     pub devtools_server_sender: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
-    /// Information about the initial window size.
-    pub window_size: WindowSizeData,
+    /// Initial [`ViewportDetails`] for the frame that is initiating this `ScriptThread`.
+    pub viewport_details: ViewportDetails,
     /// The ID of the pipeline namespace for this script thread.
     pub pipeline_namespace_id: PipelineNamespaceId,
     /// A ping will be sent on this channel once the script thread shuts down.
@@ -537,7 +537,7 @@ pub struct IFrameLoadInfoWithData {
     /// Sandbox type of this iframe
     pub sandbox: IFrameSandboxState,
     /// The initial viewport size for this iframe.
-    pub window_size: WindowSizeData,
+    pub viewport_details: ViewportDetails,
 }
 
 /// Resources required by workerglobalscopes

components/shared/script/script_msg.rs

@@ -13,8 +13,9 @@ use base::id::{
 use canvas_traits::canvas::{CanvasId, CanvasMsg};
 use constellation_traits::{LogEntry, TraversalDirection};
 use devtools_traits::{ScriptToDevtoolsControlMsg, WorkerId};
-use embedder_traits::{EmbedderMsg, MediaSessionEvent, TouchEventType, TouchSequenceId};
-use euclid::Size2D;
+use embedder_traits::{
+    EmbedderMsg, MediaSessionEvent, TouchEventType, TouchSequenceId, ViewportDetails,
+};
 use euclid::default::Size2D as UntypedSize2D;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use net_traits::CoreResourceMsg;
@@ -22,7 +23,6 @@ use net_traits::storage_thread::StorageType;
 use serde::{Deserialize, Serialize};
 use servo_url::{ImmutableOrigin, ServoUrl};
 use strum_macros::IntoStaticStr;
-use style_traits::CSSPixel;
 #[cfg(feature = "webgpu")]
 use webgpu_traits::{WebGPU, WebGPUAdapterResponse};
 use webrender_api::ImageKey;
@@ -39,8 +39,8 @@ use crate::{
 pub struct IFrameSizeMsg {
     /// The child browsing context for this iframe.
     pub browsing_context_id: BrowsingContextId,
-    /// The size of the iframe.
-    pub size: Size2D<f32, CSSPixel>,
+    /// The size and scale factor of the iframe.
+    pub size: ViewportDetails,
     /// The kind of sizing operation.
     pub type_: WindowSizeType,
 }

components/shared/script_layout/Cargo.toml

@@ -17,6 +17,7 @@ app_units = { workspace = true }
 atomic_refcell = { workspace = true }
 canvas_traits = { workspace = true }
 constellation_traits = { workspace = true }
+embedder_traits = { workspace = true }
 euclid = { workspace = true }
 fnv = { workspace = true }
 fonts = { path = "../../fonts" }

components/shared/script_layout/lib.rs

@@ -18,8 +18,8 @@ use app_units::Au;
 use atomic_refcell::AtomicRefCell;
 use base::Epoch;
 use base::id::{BrowsingContextId, PipelineId, WebViewId};
-use constellation_traits::{ScrollState, UntrustedNodeAddress, WindowSizeData};
-use euclid::Size2D;
+use constellation_traits::{ScrollState, UntrustedNodeAddress};
+use embedder_traits::ViewportDetails;
 use euclid::default::{Point2D, Rect};
 use fnv::FnvHashMap;
 use fonts::{FontContext, SystemFontServiceProxy};
@@ -47,7 +47,6 @@ use style::properties::style_structs::Font;
 use style::queries::values::PrefersColorScheme;
 use style::selector_parser::{PseudoElement, RestyleDamage, Snapshot};
 use style::stylesheets::Stylesheet;
-use style_traits::CSSPixel;
 use webrender_api::ImageKey;
 use webrender_traits::CrossProcessCompositorApi;
 
@@ -185,7 +184,7 @@ pub struct LayoutConfig {
     pub font_context: Arc<FontContext>,
     pub time_profiler_chan: time::ProfilerChan,
     pub compositor_api: CrossProcessCompositorApi,
-    pub window_size: WindowSizeData,
+    pub viewport_details: ViewportDetails,
 }
 
 pub trait LayoutFactory: Send + Sync {
@@ -386,7 +385,7 @@ pub struct Reflow {
 pub struct IFrameSize {
     pub browsing_context_id: BrowsingContextId,
     pub pipeline_id: PipelineId,
-    pub size: Size2D<f32, CSSPixel>,
+    pub viewport_details: ViewportDetails,
 }
 
 pub type IFrameSizes = FnvHashMap<BrowsingContextId, IFrameSize>;
@@ -415,8 +414,8 @@ pub struct ReflowRequest {
     pub dirty_root: Option<TrustedNodeAddress>,
     /// Whether the document's stylesheets have changed since the last script reflow.
     pub stylesheets_changed: bool,
-    /// The current window size.
-    pub window_size: WindowSizeData,
+    /// The current [`ViewportDetails`] to use for this reflow.
+    pub viewport_details: ViewportDetails,
     /// The goal of this reflow.
     pub reflow_goal: ReflowGoal,
     /// The number of objects in the dom #10110