Initial internal support for multiple webviews (#31417)

* Add multiple concurrent top-level browsing contexts

Co-authored-by: Delan Azabani <dazabani@igalia.com>

* Rename variables and comments

There are some variable and comments still use browser as names.
This commit renames them to webview.

* Update log message from web view to webview

* Revert offscreen_framebuffer_id rename

* Rename all web view to webview

* Cargo fmt

* Fix viewport/event/clear coordinates when multiview is disabled

* Only deprecate things when multiview is enabled

* Update WebViewManger with shown and invisible sets

Replace visible_webviews and native_window_is_visible with shown_webviews
and invisible_webviews. Add 4 more methods to set them accordingly. The
behavior of is_effectively_visible will return true if the wbview is in
shown_webviews set but not in invisible_webviews.

* Update variant behaviors

* Rename WebViewVisibilityChanged to MarkWebViewInvisible

* Fix unit test by marking id 3 visible again

* Update MarkWebViewInvisible and add UnmarkWebViewInvisible

* Update format and doc comments

* Clean up doc comments

* Address style and naming changes

* Rename UpdateWebView to UpdateFrameTreeForWebView

* constellation: send frame tree unconditionally over focus and feature

* Clarify shown and invisible sets in constellation WebViewManager

* Eliminate forward_to_constellation!()

* Actually remove the unused macro

* Don’t gate compositor changes on multiview feature flag

* Update todo in mouse event dispatch

* Pass all visible webview ids in a single ReadyToPresent message

* Fix compile and lint errors

* servoshell: fix gap between minibrowser toolbar and webview

* Fix failure in /_mozilla/mozilla/window_resizeTo.html

* Fix compile warnings

* Remove stray dbg!()

* Remove confusing “effectively visible” logic (see #31815, #31816)

* Allow embedder to show/hide/raise webviews without ipc

* Update root pipeline only when painting order actually changes

* Stop gating old focus and SetFrameTree behaviour behind Cargo feature

* Use webview_id and WebViewId in webview-related code

* Improve logging of webview-related embedder events

* Allow webview Show and Raise events to optionally hide all others

* Don’t do anything in response to WebViewPaintingOrder

* Remove WebViewPaintingOrder, since its payload is unreliable

* On MoveResizeWebView, only update root pipeline if rect changed

* Rename IOCompositor methods for clarity

* compositor: add event tracing; log webview ops even without ipc

* Add temporary debug logging

* Add more temporary debug logging

* Remove temporary logging in compositor

* Remove temporary debug logging

* Add temporary debug logging, but defer I/O until panic

* Capture a backtrace with each crash log entry

* Proper error handling without panicking in WebViewManager

* Clean up imports in constellation

---------

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

components/shared/compositing/constellation_msg.rs

@@ -11,13 +11,14 @@ use gfx_traits::Epoch;
 use ipc_channel::ipc::IpcSender;
 use keyboard_types::KeyboardEvent;
 use msg::constellation_msg::{
-    BrowsingContextId, PipelineId, TopLevelBrowsingContextId, TraversalDirection,
+    BrowsingContextId, PipelineId, TopLevelBrowsingContextId, TraversalDirection, WebViewId,
 };
 use script_traits::{
     AnimationTickType, CompositorEvent, GamepadEvent, LogEntry, MediaSessionActionType,
     WebDriverCommandMsg, WindowSizeData, WindowSizeType,
 };
 use servo_url::ServoUrl;
+use webrender_api::units::DeviceRect;
 
 /// Messages to the constellation.
 pub enum ConstellationMsg {
@@ -60,9 +61,17 @@ pub enum ConstellationMsg {
     CloseWebView(TopLevelBrowsingContextId),
     /// Panic a top level browsing context.
     SendError(Option<TopLevelBrowsingContextId>, String),
-    /// Make a top-level browsing context focused.
+    /// Move and/or resize a webview to the given rect.
+    MoveResizeWebView(TopLevelBrowsingContextId, DeviceRect),
+    /// Start painting a webview, and optionally stop painting all others.
+    ShowWebView(TopLevelBrowsingContextId, bool),
+    /// Stop painting a webview.
+    HideWebView(TopLevelBrowsingContextId),
+    /// Start painting a webview on top of all others, and optionally stop painting all others.
+    RaiseWebViewToTop(TopLevelBrowsingContextId, bool),
+    /// Make a webview focused.
     FocusWebView(TopLevelBrowsingContextId),
-    /// Make none of the top-level browsing contexts focused.
+    /// Make none of the webviews focused.
     BlurWebView,
     /// Forward an event to the script task of the given pipeline.
     ForwardEvent(PipelineId, CompositorEvent),
@@ -80,16 +89,23 @@ pub enum ConstellationMsg {
     SetWebViewThrottled(TopLevelBrowsingContextId, bool),
     /// Virtual keyboard was dismissed
     IMEDismissed,
-    /// Compositing done, but external code needs to present.
-    ReadyToPresent(TopLevelBrowsingContextId),
+    /// Notify the embedder that it needs to present a new frame.
+    ReadyToPresent(Vec<WebViewId>),
     /// Gamepad state has changed
     Gamepad(GamepadEvent),
 }
 
 impl fmt::Debug for ConstellationMsg {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "ConstellationMsg::{}", self.variant_name())
+    }
+}
+
+impl ConstellationMsg {
+    /// Return the variant name, for error logging that happens after the message is consumed.
+    pub fn variant_name(&self) -> &'static str {
         use self::ConstellationMsg::*;
-        let variant = match *self {
+        match *self {
             Exit => "Exit",
             GetBrowsingContext(..) => "GetBrowsingContext",
             GetPipeline(..) => "GetPipeline",
@@ -106,6 +122,10 @@ impl fmt::Debug for ConstellationMsg {
             LogEntry(..) => "LogEntry",
             NewWebView(..) => "NewWebView",
             CloseWebView(..) => "CloseWebView",
+            MoveResizeWebView(..) => "MoveResizeWebView",
+            ShowWebView(..) => "ShowWebView",
+            HideWebView(..) => "HideWebView",
+            RaiseWebViewToTop(..) => "RaiseWebViewToTop",
             FocusWebView(..) => "FocusWebView",
             BlurWebView => "BlurWebView",
             SendError(..) => "SendError",
@@ -120,7 +140,6 @@ impl fmt::Debug for ConstellationMsg {
             ClearCache => "ClearCache",
             ReadyToPresent(..) => "ReadyToPresent",
             Gamepad(..) => "Gamepad",
-        };
-        write!(formatter, "ConstellationMsg::{}", variant)
+        }
     }
 }