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|
//! Optional endpoint encoding that retains unchanged terminal cells across projections.
use super::{CellData, PaneSurfaceFrame, ServerMessage};
use serde::{Deserialize, Serialize};
pub(crate) const CAPABILITY: &str = "surface_reuse";
pub(crate) const MESSAGE_KIND: &str = "endpoint.surface-reuse.v1";
#[derive(Serialize, Deserialize)]
struct SurfaceReuse<S> {
base_surface_revision: u64,
surface: S,
}
pub(crate) fn message(
base_surface_revision: u64,
surface: &mut PaneSurfaceFrame,
) -> serde_json::Result<Option<ServerMessage>> {
let cells = std::mem::take(&mut surface.frame.cells);
let data = serde_json::to_string(&SurfaceReuse {
base_surface_revision,
surface: &*surface,
});
surface.frame.cells = cells;
let message = ServerMessage::EndpointControl {
kind: MESSAGE_KIND.into(),
data: data?,
};
// JSON can expand non-cell data (for example escaped hyperlink URLs). A
// failed compact encoding must fall back, not strand a newer snapshot.
let size = bincode::serde::encode_into_std_write(
&message,
&mut std::io::sink(),
bincode::config::standard(),
);
match size {
Ok(size) => Ok((size <= super::MAX_FRAME_SIZE).then_some(message)),
Err(error) => {
tracing::warn!(%error, "failed to size surface reuse");
Ok(None)
}
}
}
#[derive(Default)]
struct CellBaseline {
boot_id: String,
projection_revision: u64,
surface_revision: u64,
width: u16,
height: u16,
cells: Vec<CellData>,
popup: Option<PopupBaseline>,
}
impl CellBaseline {
/// Whether a patch applies to exactly this baseline as its next revision.
fn matches_patch(&self, patch: &super::PaneSurfacePatch) -> bool {
patch.boot_id == self.boot_id
&& patch.projection_revision == self.projection_revision
&& patch.base_surface_revision == self.surface_revision
&& patch.surface_revision == self.surface_revision.saturating_add(1)
}
}
struct PopupBaseline {
terminal_id: String,
width: u16,
height: u16,
cells: Vec<CellData>,
}
fn popup_baseline(surface: &PaneSurfaceFrame) -> Option<PopupBaseline> {
surface.popup.as_ref().map(|popup| PopupBaseline {
terminal_id: popup.terminal_id.clone(),
width: popup.frame.width,
height: popup.frame.height,
cells: popup.frame.cells.clone(),
})
}
/// Connection-local decoding happens before activation and presentation filtering, so
/// switching endpoints cannot discard a baseline needed by the next wire message.
#[derive(Default)]
pub(crate) struct Decoder {
baseline: Option<CellBaseline>,
surface_delta: bool,
surface_scroll: bool,
}
impl Decoder {
pub(crate) fn new(surface_delta: bool, surface_scroll: bool) -> Self {
Self {
baseline: None,
surface_delta,
surface_scroll,
}
}
pub(crate) fn decode(&mut self, message: ServerMessage) -> Result<ServerMessage, String> {
let message = match message {
ServerMessage::EndpointControl { kind, data }
if kind == super::surface_delta::MESSAGE_KIND =>
{
if !self.surface_delta {
return Err("surface delta was not negotiated".into());
}
return self.decode_delta(&data).map(ServerMessage::PaneSurface);
}
ServerMessage::EndpointControl { kind, data }
if kind == super::surface_scroll::MESSAGE_KIND =>
{
if !self.surface_scroll {
return Err("surface scroll was not negotiated".into());
}
return self
.decode_scroll(&data)
.map(ServerMessage::PaneSurfacePatch);
}
ServerMessage::EndpointControl { kind, data } if kind == MESSAGE_KIND => {
let reuse: SurfaceReuse<PaneSurfaceFrame> = serde_json::from_str(&data)
.map_err(|error| format!("invalid surface reuse: {error}"))?;
let Some(base) = &mut self.baseline else {
return Err("surface reuse without a baseline".into());
};
let mut surface = reuse.surface;
if base.boot_id != surface.boot_id
|| base.surface_revision != reuse.base_surface_revision
|| surface.surface_revision != base.surface_revision.saturating_add(1)
|| base.width != surface.frame.width
|| base.height != surface.frame.height
|| !surface.frame.cells.is_empty()
{
return Err("surface reuse does not match its baseline".into());
}
surface.frame.cells.clone_from(&base.cells);
base.projection_revision = surface.projection_revision;
base.surface_revision = surface.surface_revision;
if self.surface_delta {
base.popup = popup_baseline(&surface);
}
return Ok(ServerMessage::PaneSurface(surface));
}
message => message,
};
match &message {
ServerMessage::PaneSurface(surface) => {
let base = self.baseline.get_or_insert_with(CellBaseline::default);
base.boot_id.clone_from(&surface.boot_id);
base.projection_revision = surface.projection_revision;
base.surface_revision = surface.surface_revision;
base.width = surface.frame.width;
base.height = surface.frame.height;
base.cells.clone_from(&surface.frame.cells);
if self.surface_delta {
base.popup = popup_baseline(surface);
}
}
ServerMessage::PaneSurfacePatch(patch) => {
if let Some(base) = &mut self.baseline {
if !base.matches_patch(patch) {
self.baseline = None;
} else {
for row in &patch.rows {
let start =
usize::from(row.y) * usize::from(base.width) + usize::from(row.x);
let end = start.saturating_add(row.cells.len());
if row.y >= base.height
|| usize::from(row.x) + row.cells.len() > usize::from(base.width)
|| end > base.cells.len()
{
return Err("surface patch exceeds the cell baseline".into());
}
base.cells[start..end].clone_from_slice(&row.cells);
}
base.surface_revision = patch.surface_revision;
}
}
}
_ => {}
}
Ok(message)
}
fn decode_scroll(&mut self, data: &str) -> Result<super::PaneSurfacePatch, String> {
let Some(base) = &mut self.baseline else {
return Err("surface scroll without a baseline".into());
};
let scroll = super::surface_scroll::decode(data)?;
if !base.matches_patch(&scroll.patch) {
return Err("surface scroll does not match its baseline".into());
}
let patch = super::surface_scroll::apply(&mut base.cells, base.width, base.height, scroll)?;
base.surface_revision = patch.surface_revision;
Ok(patch)
}
fn decode_delta(&mut self, data: &str) -> Result<PaneSurfaceFrame, String> {
use super::surface_delta::{self, GridUpdate};
let Some(base) = &mut self.baseline else {
return Err("surface delta without a baseline".into());
};
let delta = surface_delta::decode_for(data, (base.width, base.height))?;
let mut surface = delta.surface;
if surface.boot_id != base.boot_id
|| delta.base_projection_revision != base.projection_revision
|| delta.base_surface_revision != base.surface_revision
|| surface.surface_revision != base.surface_revision.saturating_add(1)
|| surface.projection_revision < base.projection_revision
|| base.cells.len() != usize::from(base.width) * usize::from(base.height)
{
return Err("surface delta does not match its baseline".into());
}
surface.frame.cells.clone_from(&base.cells);
surface_delta::apply_rows(&mut surface.frame.cells, base.width, &delta.rows);
match (&mut surface.popup, delta.popup_cells) {
(None, None) => {}
(Some(popup), Some(update)) => {
let count = usize::from(popup.frame.width) * usize::from(popup.frame.height);
match update {
GridUpdate::Replace(cells) => popup.frame.cells = cells,
GridUpdate::Patch(rows) => {
let previous = base
.popup
.as_ref()
.filter(|previous| {
previous.terminal_id == popup.terminal_id
&& previous.width == popup.frame.width
&& previous.height == popup.frame.height
&& previous.cells.len() == count
})
.ok_or("popup delta does not match its baseline")?;
popup.frame.cells.clone_from(&previous.cells);
surface_delta::apply_rows(&mut popup.frame.cells, previous.width, &rows);
}
}
}
_ => return Err("popup delta is missing or unexpected".into()),
}
for frame in
std::iter::once(&surface.frame).chain(surface.popup.as_ref().map(|popup| &popup.frame))
{
if frame.cells.iter().any(|cell| {
cell.hyperlink
.is_some_and(|index| index as usize >= frame.hyperlinks.len())
}) {
return Err("surface delta has an invalid hyperlink index".into());
}
}
// Validate the entire update before advancing either grid or revision.
surface_delta::apply_rows(&mut base.cells, base.width, &delta.rows);
base.popup = popup_baseline(&surface);
base.projection_revision = surface.projection_revision;
base.surface_revision = surface.surface_revision;
Ok(surface)
}
}
|
