script: Chain up keyboard scrolling to parent <iframe>s (#39469)

When an `<iframe>` cannot scroll because the size of the frame is
greater than or
equal to the size of page contents, chain up the keyboard scroll
operation to the parent frame.

Testing: A new Servo-only WPT tests is added, though needs to be
manually
run with `--product servodriver`.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Delan Azabani <dazabani@igalia.com>

components/shared/constellation/Cargo.toml

@@ -26,6 +26,7 @@ fonts_traits = { workspace = true }
 http = { workspace = true }
 hyper_serde = { workspace = true }
 ipc-channel = { workspace = true }
+keyboard-types = { workspace = true }
 log = { workspace = true }
 malloc_size_of = { workspace = true }
 malloc_size_of_derive = { workspace = true }

components/shared/constellation/from_script_message.rs

@@ -480,6 +480,27 @@ pub struct IFrameSizeMsg {
     pub type_: WindowSizeType,
 }
 
+/// An enum that describe a type of keyboard scroll.
+#[derive(Clone, Copy, Debug, Deserialize, Serialize)]
+pub enum KeyboardScroll {
+    /// Scroll the container one line up.
+    Up,
+    /// Scroll the container one line down.
+    Down,
+    /// Scroll the container one "line" left.
+    Left,
+    /// Scroll the container one "line" right.
+    Right,
+    /// Scroll the container one page up.
+    PageUp,
+    /// Scroll the container one page down.
+    PageDown,
+    /// Scroll the container to the vertical start.
+    Home,
+    /// Scroll the container to the vertical end.
+    End,
+}
+
 /// Messages from the script to the constellation.
 #[derive(Deserialize, IntoStaticStr, Serialize)]
 pub enum ScriptToConstellationMessage {
@@ -665,6 +686,8 @@ pub enum ScriptToConstellationMessage {
     ),
     /// Notify the completion of a webdriver command.
     WebDriverInputComplete(WebDriverMessageId),
+    /// Forward a keyboard scroll operation from an `<iframe>` to a parent pipeline.
+    ForwardKeyboardScroll(PipelineId, KeyboardScroll),
 }
 
 impl fmt::Debug for ScriptToConstellationMessage {

components/shared/layout/lib.rs

@@ -306,9 +306,11 @@ pub trait Layout {
     fn query_client_rect(&self, node: TrustedNodeAddress) -> Rect<i32>;
     fn query_element_inner_outer_text(&self, node: TrustedNodeAddress) -> String;
     fn query_offset_parent(&self, node: TrustedNodeAddress) -> OffsetParentResponse;
+    /// Query the scroll container for the given node. If node is `None`, the scroll container for
+    /// the viewport is returned.
     fn query_scroll_container(
         &self,
-        node: TrustedNodeAddress,
+        node: Option<TrustedNodeAddress>,
         flags: ScrollContainerQueryFlags,
     ) -> Option<ScrollContainerResponse>;
     fn query_resolved_style(
@@ -377,7 +379,7 @@ bitflags! {
     }
 }
 
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, MallocSizeOf)]
 pub struct AxesOverflow {
     pub x: Overflow,
     pub y: Overflow,
@@ -401,9 +403,18 @@ impl From<&ComputedValues> for AxesOverflow {
     }
 }
 
+impl AxesOverflow {
+    pub fn to_scrollable(&self) -> Self {
+        Self {
+            x: self.x.to_scrollable(),
+            y: self.y.to_scrollable(),
+        }
+    }
+}
+
 #[derive(Clone)]
 pub enum ScrollContainerResponse {
-    Viewport,
+    Viewport(AxesOverflow),
     Element(UntrustedNodeAddress, AxesOverflow),
 }
 

components/shared/script/lib.rs

@@ -21,8 +21,8 @@ use bluetooth_traits::BluetoothRequest;
 use canvas_traits::webgl::WebGLPipeline;
 use compositing_traits::CrossProcessCompositorApi;
 use constellation_traits::{
-    LoadData, NavigationHistoryBehavior, ScriptToConstellationChan, StructuredSerializedData,
-    WindowSizeType,
+    KeyboardScroll, LoadData, NavigationHistoryBehavior, ScriptToConstellationChan,
+    StructuredSerializedData, WindowSizeType,
 };
 use crossbeam_channel::{RecvTimeoutError, Sender};
 use devtools_traits::ScriptToDevtoolsControlMsg;
@@ -265,6 +265,8 @@ pub enum ScriptThreadMessage {
     /// asynchronous image uploads for the given `Pipeline`. These are mainly used
     /// by canvas to perform uploads while the display list is being built.
     NoLongerWaitingOnAsychronousImageUpdates(PipelineId),
+    /// Forward a keyboard scroll operation from an `<iframe>` to a parent pipeline.
+    ForwardKeyboardScroll(PipelineId, KeyboardScroll),
 }
 
 impl fmt::Debug for ScriptThreadMessage {