wayland_bridge/subcompositor.rs
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// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use crate::client::Client;
use crate::compositor::{
PlaceSubsurfaceParams, Surface, SurfaceCommand, SurfaceRelation, SurfaceRole,
};
use crate::display::Callback;
use crate::object::{NewObjectExt, ObjectRef, RequestReceiver};
use anyhow::{format_err, Error};
use fuchsia_wayland_core as wl;
use std::mem;
use wayland_server_protocol::{
WlSubcompositor, WlSubcompositorRequest, WlSubsurface, WlSubsurfaceRequest,
};
/// An implementation of the wl_subcompositor global.
///
/// wl_subcompositor provides an interface for clients to defer some composition
/// to the server. For example, a media player application may provide the
/// compositor with one surface that contains the video frames and another
/// surface that contains playback controls. Deferring this composition to the
/// server allows for the server to make certain optimizations, such as mapping
/// these surfaces to hardware layers on the display controller, if available.
///
/// Implementation Note: We currently implement the wl_subcompositor by creating
/// new scenic ShapeNodes and placing them as children of the parent node. This
/// makes for a simple implementation, but we don't support any alpha blending
/// of subsurfaces (due to limitations in how Scenic handles these use cases).
/// Scenic may be extended to handle these 2D composition use-cases, but without
/// that we'll need to do some of our own blending here.
pub struct Subcompositor;
impl Subcompositor {
/// Creates a new `Subcompositor`.
pub fn new() -> Self {
Subcompositor
}
}
impl RequestReceiver<WlSubcompositor> for Subcompositor {
fn receive(
this: ObjectRef<Self>,
request: WlSubcompositorRequest,
client: &mut Client,
) -> Result<(), Error> {
match request {
WlSubcompositorRequest::Destroy => {
client.delete_id(this.id())?;
}
WlSubcompositorRequest::GetSubsurface { id, surface, parent } => {
let subsurface = Subsurface::new(surface, parent);
let surface_ref = subsurface.surface_ref;
let parent_ref = subsurface.parent_ref;
subsurface.attach_to_parent(client)?;
let subsurface_ref = id.implement(client, subsurface)?;
surface_ref.get_mut(client)?.set_role(SurfaceRole::Subsurface(subsurface_ref))?;
parent_ref
.get_mut(client)?
.enqueue(SurfaceCommand::AddSubsurface(surface_ref, subsurface_ref));
}
}
Ok(())
}
}
/// Wayland subsurfaces may be in one of two modes, Sync (the default) or Desync.
/// When a wl_subsurface is in sync mode, a wl_surface::commit will simply
/// snapshot the set of pending state. This state will be applied (and changes
/// will appear on screen) when its parent's surface is committed.
///
/// In contrast, a surface in Desync mode will schedule an update to pixels on
/// screen in response to wl_surface::commit.
#[derive(Debug, Copy, Clone, PartialEq)]
pub enum SubsurfaceMode {
Sync,
Desync,
}
pub struct Subsurface {
/// A reference to the backing wl_surface for the subsurface.
surface_ref: ObjectRef<Surface>,
/// A reference to the backing wl_surface for the parents surface.
parent_ref: ObjectRef<Surface>,
/// The current mode of the surface.
///
/// See `SubsurfaceMode` for more details.
mode: SubsurfaceMode,
/// When in sync mode, this is the set of commands that are pending our
/// parents commit.
///
/// When in desync mode, this must be empty.
pending_commands: Vec<SurfaceCommand>,
/// When in sync mode, this is the set of wl_surface::frame callbacks that
/// are pending our parents commit.
///
/// When in desync mode, this must be empty.
pending_callbacks: Vec<ObjectRef<Callback>>,
}
impl Subsurface {
pub fn new(surface: wl::ObjectId, parent: wl::ObjectId) -> Self {
Self {
surface_ref: surface.into(),
parent_ref: parent.into(),
mode: SubsurfaceMode::Sync,
pending_commands: Vec::new(),
pending_callbacks: Vec::new(),
}
}
/// Gets the associated wl_surface for this subsurface.
pub fn surface(&self) -> ObjectRef<Surface> {
self.surface_ref
}
/// Returns true iff this subsurface is running in synchronized mode.
pub fn is_sync(&self) -> bool {
self.mode == SubsurfaceMode::Sync
}
/// Adds some `SurfaceCommand`s to this surfaces pending state.
///
/// This `pending state` is a set of operations that were committed with a
/// wl_surface::commit request, but are waiting for our parents state to
/// be committed.
///
/// Subsurfaces in desync mode have no pending state, as their state is
/// applied immediately upon wl_surface::commit.
pub fn add_pending_commands(&mut self, mut commands: Vec<SurfaceCommand>) {
assert!(self.is_sync(), "Desync subsurfaces have no pending state");
self.pending_commands.append(&mut commands);
}
/// Extracts the set of pending `SurfaceCommand`s and frame Callbacks for
/// this subsurface, resetting both to empty vectors.
pub fn take_pending_state(&mut self) -> (Vec<SurfaceCommand>, Vec<ObjectRef<Callback>>) {
let commands = mem::replace(&mut self.pending_commands, Vec::new());
let callbacks = mem::replace(&mut self.pending_callbacks, Vec::new());
(commands, callbacks)
}
pub fn finalize_commit(&mut self, callbacks: &mut Vec<ObjectRef<Callback>>) -> bool {
if self.is_sync() {
// If we're in sync mode, we just defer the callbacks until our
// parents state is applied.
self.pending_callbacks.append(callbacks);
false
} else {
true
}
}
fn attach_to_parent(&self, client: &mut Client) -> Result<(), Error> {
let flatland = match self.parent_ref.get(client)?.flatland() {
Some(s) => s,
None => return Err(format_err!("Parent surface has no flatland instance!")),
};
self.surface_ref.get_mut(client)?.set_flatland(flatland.clone())?;
// Unwrap here since we have just determined both surfaces have a
// flatland instance, which is the only prerequisite for having a transform.
let parent_transform = self.parent_ref.get(client)?.transform().unwrap();
let child_transform = self.surface_ref.get(client)?.transform().unwrap();
flatland
.borrow()
.proxy()
.add_child(&parent_transform, &child_transform)
.expect("fidl error");
Ok(())
}
fn detach_from_parent(&self, client: &Client) -> Result<(), Error> {
if let Some(flatland) = self.parent_ref.get(client)?.flatland() {
// Unwrap here since we have just determined parent surface has a
// flatland instance, which is the only prerequisite for having a
// transform.
let parent_transform = *self.parent_ref.get(client)?.transform().unwrap();
if let Some(child_transform) = self.surface_ref.get(client)?.transform() {
flatland
.borrow()
.proxy()
.remove_child(&parent_transform, &child_transform)
.expect("fidl error");
}
}
Ok(())
}
}
impl RequestReceiver<WlSubsurface> for Subsurface {
fn receive(
this: ObjectRef<Self>,
request: WlSubsurfaceRequest,
client: &mut Client,
) -> Result<(), Error> {
match request {
WlSubsurfaceRequest::Destroy => {
let parent_ref = {
let subsurface = this.get(client)?;
subsurface.detach_from_parent(client)?;
subsurface.parent_ref
};
parent_ref.get_mut(client)?.detach_subsurface(this);
client.delete_id(this.id())?;
}
WlSubsurfaceRequest::SetPosition { x, y } => {
let surface_ref = this.get(client)?.surface_ref;
surface_ref.get_mut(client)?.enqueue(SurfaceCommand::SetPosition(x, y));
}
WlSubsurfaceRequest::PlaceAbove { sibling } => {
let parent_ref = this.get(client)?.parent_ref;
parent_ref.get_mut(client)?.enqueue(SurfaceCommand::PlaceSubsurface(
PlaceSubsurfaceParams {
subsurface: this,
sibling: sibling.into(),
relation: SurfaceRelation::Above,
},
));
}
WlSubsurfaceRequest::PlaceBelow { sibling } => {
let parent_ref = this.get(client)?.parent_ref;
parent_ref.get_mut(client)?.enqueue(SurfaceCommand::PlaceSubsurface(
PlaceSubsurfaceParams {
subsurface: this,
sibling: sibling.into(),
relation: SurfaceRelation::Below,
},
));
}
// Note that SetSync and SetDesync are not double buffered as is
// most state:
//
// This state is applied when the parent surface's wl_surface
// state is applied, regardless of the sub-surface's mode. As the
// exception, set_sync and set_desync are effective immediately.
WlSubsurfaceRequest::SetSync => {
this.get_mut(client)?.mode = SubsurfaceMode::Sync;
}
WlSubsurfaceRequest::SetDesync => {
let (commands, callbacks, surface_ref) = {
let this = this.get_mut(client)?;
let (commands, callbacks) = this.take_pending_state();
(commands, callbacks, this.surface_ref)
};
// TODO(tjdetwiler): We should instead schedule these callbacks
// on the wl_surface immediately. This needs a small refactor of
// wl_surface to make this possible.
assert!(callbacks.is_empty());
let surface = surface_ref.get_mut(client)?;
for command in commands {
surface.enqueue(command);
}
this.get_mut(client)?.mode = SubsurfaceMode::Desync;
}
}
Ok(())
}
}