fix: keep remote surface updates incremental (#4209)

refs #3769

refs #3745

1 files changed, 99 insertions, 0 deletions

diff --git a/src/protocol/surface_reuse.rs b/src/protocol/surface_reuse.rs
index bba85824..aa2187d4 100644
--- a/src/protocol/surface_reuse.rs
+++ b/src/protocol/surface_reuse.rs
@@ -50,6 +50,23 @@ struct CellBaseline {
     width: u16,
     height: u16,
     cells: Vec<CellData>,
+    popup: Option<PopupBaseline>,
+}
+
+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
@@ -57,11 +74,27 @@ struct CellBaseline {
 #[derive(Default)]
 pub(crate) struct Decoder {
     baseline: Option<CellBaseline>,
+    surface_delta: bool,
 }
 
 impl Decoder {
+    pub(crate) fn new(surface_delta: bool) -> Self {
+        Self {
+            baseline: None,
+            surface_delta,
+        }
+    }
+
     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 == MESSAGE_KIND => {
                 let reuse: SurfaceReuse<PaneSurfaceFrame> = serde_json::from_str(&data)
                     .map_err(|error| format!("invalid surface reuse: {error}"))?;
@@ -81,6 +114,9 @@ impl Decoder {
                 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,
@@ -94,6 +130,9 @@ impl Decoder {
                 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 {
@@ -124,4 +163,64 @@ impl Decoder {
         }
         Ok(message)
     }
+
+    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)
+    }
 }