fix(panes): show visual error when unable to split panes vertically/horizontally (#2025)

* fix(panes): show visual error when failing to split pane vertically/horizontally

* fix: lockfile

12 files changed, 432 insertions, 12 deletions

diff --git a/zellij-server/src/background_jobs.rs b/zellij-server/src/background_jobs.rs
new file mode 100644
index 000000000..3c89ed064
--- /dev/null
+++ b/zellij-server/src/background_jobs.rs
@@ -0,0 +1,79 @@
+use zellij_utils::async_std::task;
+use zellij_utils::errors::{prelude::*, BackgroundJobContext, ContextType};
+
+use std::collections::HashMap;
+use std::time::{Duration, Instant};
+
+use crate::panes::PaneId;
+use crate::screen::ScreenInstruction;
+use crate::thread_bus::Bus;
+
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub enum BackgroundJob {
+    DisplayPaneError(PaneId, String),
+    Exit,
+}
+
+impl From<&BackgroundJob> for BackgroundJobContext {
+    fn from(background_job: &BackgroundJob) -> Self {
+        match *background_job {
+            BackgroundJob::DisplayPaneError(..) => BackgroundJobContext::DisplayPaneError,
+            BackgroundJob::Exit => BackgroundJobContext::Exit,
+        }
+    }
+}
+
+static FLASH_DURATION_MS: u64 = 1000;
+
+pub(crate) fn background_jobs_main(bus: Bus<BackgroundJob>) -> Result<()> {
+    let err_context = || "failed to write to pty".to_string();
+    let mut running_jobs: HashMap<BackgroundJob, Instant> = HashMap::new();
+
+    loop {
+        let (event, mut err_ctx) = bus.recv().with_context(err_context)?;
+        err_ctx.add_call(ContextType::BackgroundJob((&event).into()));
+        let job = event.clone();
+        match event {
+            BackgroundJob::DisplayPaneError(pane_id, text) => {
+                if job_already_running(job, &mut running_jobs) {
+                    continue;
+                }
+                task::spawn({
+                    let senders = bus.senders.clone();
+                    async move {
+                        let _ = senders.send_to_screen(
+                            ScreenInstruction::AddRedPaneFrameColorOverride(pane_id, Some(text)),
+                        );
+                        task::sleep(std::time::Duration::from_millis(FLASH_DURATION_MS)).await;
+                        let _ = senders.send_to_screen(
+                            ScreenInstruction::ClearPaneFrameColorOverride(pane_id),
+                        );
+                    }
+                });
+            },
+            BackgroundJob::Exit => {
+                return Ok(());
+            },
+        }
+    }
+}
+
+fn job_already_running(
+    job: BackgroundJob,
+    running_jobs: &mut HashMap<BackgroundJob, Instant>,
+) -> bool {
+    match running_jobs.get_mut(&job) {
+        Some(current_running_job_start_time) => {
+            if current_running_job_start_time.elapsed() > Duration::from_millis(FLASH_DURATION_MS) {
+                *current_running_job_start_time = Instant::now();
+                false
+            } else {
+                true
+            }
+        },
+        None => {
+            running_jobs.insert(job.clone(), Instant::now());
+            false
+        },
+    }
+}
diff --git a/zellij-server/src/lib.rs b/zellij-server/src/lib.rs
index c024a03d3..40c2edc2f 100644
--- a/zellij-server/src/lib.rs
+++ b/zellij-server/src/lib.rs
@@ -3,6 +3,7 @@ pub mod output;
 pub mod panes;
 pub mod tab;
 
+mod background_jobs;
 mod logging_pipe;
 mod plugins;
 mod pty;
@@ -13,6 +14,7 @@ mod terminal_bytes;
 mod thread_bus;
 mod ui;
 
+use background_jobs::{background_jobs_main, BackgroundJob};
 use log::info;
 use pty_writer::{pty_writer_main, PtyWriteInstruction};
 use std::collections::{HashMap, HashSet};
@@ -110,6 +112,7 @@ pub(crate) struct SessionMetaData {
     pty_thread: Option<thread::JoinHandle<()>>,
     plugin_thread: Option<thread::JoinHandle<()>>,
     pty_writer_thread: Option<thread::JoinHandle<()>>,
+    background_jobs_thread: Option<thread::JoinHandle<()>>,
 }
 
 impl Drop for SessionMetaData {
@@ -118,6 +121,7 @@ impl Drop for SessionMetaData {
         let _ = self.senders.send_to_screen(ScreenInstruction::Exit);
         let _ = self.senders.send_to_plugin(PluginInstruction::Exit);
         let _ = self.senders.send_to_pty_writer(PtyWriteInstruction::Exit);
+        let _ = self.senders.send_to_background_jobs(BackgroundJob::Exit);
         if let Some(screen_thread) = self.screen_thread.take() {
             let _ = screen_thread.join();
         }
@@ -130,6 +134,9 @@ impl Drop for SessionMetaData {
         if let Some(pty_writer_thread) = self.pty_writer_thread.take() {
             let _ = pty_writer_thread.join();
         }
+        if let Some(background_jobs_thread) = self.background_jobs_thread.take() {
+            let _ = background_jobs_thread.join();
+        }
     }
 }
 
@@ -638,6 +645,10 @@ fn init_session(
         channels::unbounded();
     let to_pty_writer = SenderWithContext::new(to_pty_writer);
 
+    let (to_background_jobs, background_jobs_receiver): ChannelWithContext<BackgroundJob> =
+        channels::unbounded();
+    let to_background_jobs = SenderWithContext::new(to_background_jobs);
+
     // Determine and initialize the data directory
     let data_dir = opts.data_dir.unwrap_or_else(get_default_data_dir);
 
@@ -664,6 +675,7 @@ fn init_session(
                     Some(&to_plugin),
                     Some(&to_server),
                     Some(&to_pty_writer),
+                    Some(&to_background_jobs),
                     Some(os_input.clone()),
                 ),
                 opts.debug,
@@ -684,6 +696,7 @@ fn init_session(
                 Some(&to_plugin),
                 Some(&to_server),
                 Some(&to_pty_writer),
+                Some(&to_background_jobs),
                 Some(os_input.clone()),
             );
             let max_panes = opts.max_panes;
@@ -711,6 +724,7 @@ fn init_session(
                 Some(&to_plugin),
                 None,
                 Some(&to_pty_writer),
+                Some(&to_background_jobs),
                 None,
             );
             let store = Store::default();
@@ -738,18 +752,37 @@ fn init_session(
                 Some(&to_plugin),
                 Some(&to_server),
                 None,
+                Some(&to_background_jobs),
                 Some(os_input.clone()),
             );
             || pty_writer_main(pty_writer_bus).fatal()
         })
         .unwrap();
 
+    let background_jobs_thread = thread::Builder::new()
+        .name("background_jobs".to_string())
+        .spawn({
+            let background_jobs_bus = Bus::new(
+                vec![background_jobs_receiver],
+                Some(&to_screen),
+                Some(&to_pty),
+                Some(&to_plugin),
+                Some(&to_server),
+                Some(&to_pty_writer),
+                None,
+                Some(os_input.clone()),
+            );
+            || background_jobs_main(background_jobs_bus).fatal()
+        })
+        .unwrap();
+
     SessionMetaData {
         senders: ThreadSenders {
             to_screen: Some(to_screen),
             to_pty: Some(to_pty),
             to_plugin: Some(to_plugin),
             to_pty_writer: Some(to_pty_writer),
+            to_background_jobs: Some(to_background_jobs),
             to_server: None,
             should_silently_fail: false,
         },
@@ -760,5 +793,6 @@ fn init_session(
         pty_thread: Some(pty_thread),
         plugin_thread: Some(plugin_thread),
         pty_writer_thread: Some(pty_writer_thread),
+        background_jobs_thread: Some(background_jobs_thread),
     }
 }
diff --git a/zellij-server/src/panes/plugin_pane.rs b/zellij-server/src/panes/plugin_pane.rs
index a530b20b2..3a0ec9c83 100644
--- a/zellij-server/src/panes/plugin_pane.rs
+++ b/zellij-server/src/panes/plugin_pane.rs
@@ -64,6 +64,7 @@ pub(crate) struct PluginPane {
     prev_pane_name: String,
     frame: HashMap<ClientId, PaneFrame>,
     borderless: bool,
+    pane_frame_color_override: Option<(PaletteColor, Option<String>)>,
 }
 
 impl PluginPane {
@@ -102,6 +103,7 @@ impl PluginPane {
             vte_parsers: HashMap::new(),
             grids: HashMap::new(),
             style,
+            pane_frame_color_override: None,
         }
     }
 }
@@ -244,7 +246,13 @@ impl Pane for PluginPane {
         }
         if let Some(grid) = self.grids.get(&client_id) {
             let err_context = || format!("failed to render frame for client {client_id}");
-            let pane_title = if self.pane_name.is_empty()
+            let pane_title = if let Some(text_color_override) = self
+                .pane_frame_color_override
+                .as_ref()
+                .and_then(|(_color, text)| text.as_ref())
+            {
+                text_color_override.into()
+            } else if self.pane_name.is_empty()
                 && input_mode == InputMode::RenamePane
                 && frame_params.is_main_client
             {
@@ -257,12 +265,15 @@ impl Pane for PluginPane {
                 self.pane_name.clone()
             };
 
-            let frame = PaneFrame::new(
+            let mut frame = PaneFrame::new(
                 self.current_geom().into(),
                 grid.scrollback_position_and_length(),
                 pane_title,
                 frame_params,
             );
+            if let Some((frame_color_override, _text)) = self.pane_frame_color_override.as_ref() {
+                frame.override_color(*frame_color_override);
+            }
 
             let res = match self.frame.get(&client_id) {
                 // TODO: use and_then or something?
@@ -469,6 +480,17 @@ impl Pane for PluginPane {
             )]))
             .unwrap();
     }
+    fn add_red_pane_frame_color_override(&mut self, error_text: Option<String>) {
+        self.pane_frame_color_override = Some((self.style.colors.red, error_text));
+    }
+    fn clear_pane_frame_color_override(&mut self) {
+        self.pane_frame_color_override = None;
+    }
+    fn frame_color_override(&self) -> Option<PaletteColor> {
+        self.pane_frame_color_override
+            .as_ref()
+            .map(|(color, _text)| *color)
+    }
 }
 
 impl PluginPane {
diff --git a/zellij-server/src/panes/terminal_pane.rs b/zellij-server/src/panes/terminal_pane.rs
index b5c51c659..4d5ed840c 100644
--- a/zellij-server/src/panes/terminal_pane.rs
+++ b/zellij-server/src/panes/terminal_pane.rs
@@ -109,7 +109,8 @@ pub struct TerminalPane {
     is_held: Option<(Option<i32>, IsFirstRun, RunCommand)>, // a "held" pane means that its command has either exited and the pane is waiting for a
     // possible user instruction to be re-run, or that the command has not yet been run
     banner: Option<String>, // a banner to be rendered inside this TerminalPane, used for panes
-                            // held on startup and can possibly be used to display some errors
+    // held on startup and can possibly be used to display some errors
+    pane_frame_color_override: Option<(PaletteColor, Option<String>)>,
 }
 
 impl Pane for TerminalPane {
@@ -301,7 +302,13 @@ impl Pane for TerminalPane {
     ) -> Result<Option<(Vec<CharacterChunk>, Option<String>)>> {
         let err_context = || format!("failed to render frame for client {client_id}");
         // TODO: remove the cursor stuff from here
-        let pane_title = if self.pane_name.is_empty()
+        let pane_title = if let Some(text_color_override) = self
+            .pane_frame_color_override
+            .as_ref()
+            .and_then(|(_color, text)| text.as_ref())
+        {
+            text_color_override.into()
+        } else if self.pane_name.is_empty()
             && input_mode == InputMode::RenamePane
             && frame_params.is_main_client
         {
@@ -353,6 +360,9 @@ impl Pane for TerminalPane {
                 frame.add_exit_status(exit_status.as_ref().copied());
             }
         }
+        if let Some((frame_color_override, _text)) = self.pane_frame_color_override.as_ref() {
+            frame.override_color(*frame_color_override);
+        }
 
         let res = match self.frame.get(&client_id) {
             // TODO: use and_then or something?
@@ -669,6 +679,17 @@ impl Pane for TerminalPane {
         }
         self.set_should_render(true);
     }
+    fn add_red_pane_frame_color_override(&mut self, error_text: Option<String>) {
+        self.pane_frame_color_override = Some((self.style.colors.red, error_text));
+    }
+    fn clear_pane_frame_color_override(&mut self) {
+        self.pane_frame_color_override = None;
+    }
+    fn frame_color_override(&self) -> Option<PaletteColor> {
+        self.pane_frame_color_override
+            .as_ref()
+            .map(|(color, _text)| *color)
+    }
 }
 
 impl TerminalPane {
@@ -717,6 +738,7 @@ impl TerminalPane {
             search_term: String::new(),
             is_held: None,
             banner: None,
+            pane_frame_color_override: None,
         }
     }
     pub fn get_x(&self) -> usize {
diff --git a/zellij-server/src/panes/tiled_panes/mod.rs b/zellij-server/src/panes/tiled_panes/mod.rs
index b5caa5916..ee752ea15 100644
--- a/zellij-server/src/panes/tiled_panes/mod.rs
+++ b/zellij-server/src/panes/tiled_panes/mod.rs
@@ -205,6 +205,19 @@ impl TiledPanes {
             })
             .collect()
     }
+    pub fn borderless_pane_geoms(&self) -> Vec<Viewport> {
+        self.panes
+            .values()
+            .filter_map(|p| {
+                let geom = p.position_and_size();
+                if p.borderless() {
+                    Some(geom.into())
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
     pub fn first_selectable_pane_id(&self) -> Option<PaneId> {
         self.panes
             .iter()
@@ -295,6 +308,19 @@ impl TiledPanes {
         }
         false
     }
+    pub fn can_split_active_pane_horizontally(&self, client_id: ClientId) -> bool {
+        let active_pane_id = &self.active_panes.get(&client_id).unwrap();
+        let active_pane = self.panes.get(active_pane_id).unwrap();
+        let full_pane_size = active_pane.position_and_size();
+        if full_pane_size.rows.is_fixed() {
+            return false;
+        }
+        if split(SplitDirection::Horizontal, &full_pane_size).is_some() {
+            true
+        } else {
+            false
+        }
+    }
     pub fn split_pane_horizontally(
         &mut self,
         pid: PaneId,
@@ -313,6 +339,19 @@ impl TiledPanes {
             self.relayout(SplitDirection::Vertical);
         }
     }
+    pub fn can_split_active_pane_vertically(&self, client_id: ClientId) -> bool {
+        let active_pane_id = &self.active_panes.get(&client_id).unwrap();
+        let active_pane = self.panes.get(active_pane_id).unwrap();
+        let full_pane_size = active_pane.position_and_size();
+        if full_pane_size.cols.is_fixed() {
+            return false;
+        }
+        if split(SplitDirection::Vertical, &full_pane_size).is_some() {
+            true
+        } else {
+            false
+        }
+    }
     pub fn split_pane_vertically(
         &mut self,
         pid: PaneId,
diff --git a/zellij-server/src/screen.rs b/zellij-server/src/screen.rs
index f304383be..9ed803bbd 100644
--- a/zellij-server/src/screen.rs
+++ b/zellij-server/src/screen.rs
@@ -224,6 +224,8 @@ pub enum ScreenInstruction {
     SearchToggleCaseSensitivity(ClientId),
     SearchToggleWholeWord(ClientId),
     SearchToggleWrap(ClientId),
+    AddRedPaneFrameColorOverride(PaneId, Option<String>), // Option<String> => optional error text
+    ClearPaneFrameColorOverride(PaneId),
 }
 
 impl From<&ScreenInstruction> for ScreenContext {
@@ -355,6 +357,12 @@ impl From<&ScreenInstruction> for ScreenContext {
             },
             ScreenInstruction::SearchToggleWholeWord(..) => ScreenContext::SearchToggleWholeWord,
             ScreenInstruction::SearchToggleWrap(..) => ScreenContext::SearchToggleWrap,
+            ScreenInstruction::AddRedPaneFrameColorOverride(..) => {
+                ScreenContext::AddRedPaneFrameColorOverride
+            },
+            ScreenInstruction::ClearPaneFrameColorOverride(..) => {
+                ScreenContext::ClearPaneFrameColorOverride
+            },
         }
     }
 }
@@ -2112,6 +2120,26 @@ pub(crate) fn screen_thread_main(
                 screen.render()?;
                 screen.unblock_input()?;
             },
+            ScreenInstruction::AddRedPaneFrameColorOverride(pane_id, error_text) => {
+                let all_tabs = screen.get_tabs_mut();
+                for tab in all_tabs.values_mut() {
+                    if tab.has_pane_with_pid(&pane_id) {
+                        tab.add_red_pane_frame_color_override(pane_id, error_text);
+                        break;
+                    }
+                }
+                screen.render()?;
+            },
+            ScreenInstruction::ClearPaneFrameColorOverride(pane_id) => {
+                let all_tabs = screen.get_tabs_mut();
+                for tab in all_tabs.values_mut() {
+                    if tab.has_pane_with_pid(&pane_id) {
+                        tab.clear_pane_frame_color_override(pane_id);
+                        break;
+                    }
+                }
+                screen.render()?;
+            },
         }
     }
     Ok(())
diff --git a/zellij-server/src/tab/mod.rs b/zellij-server/src/tab/mod.rs
index 63573a08e..a841b39ae 100644
--- a/zellij-server/src/tab/mod.rs
+++ b/zellij-server/src/tab/mod.rs
@@ -13,6 +13,7 @@ use zellij_utils::input::command::RunCommand;
 use zellij_utils::position::{Column, Line};
 use zellij_utils::{position::Position, serde};
 
+use crate::background_jobs::BackgroundJob;
 use crate::pty_writer::PtyWriteInstruction;
 use crate::screen::CopyOptions;
 use crate::ui::pane_boundaries_frame::FrameParams;
@@ -386,6 +387,9 @@ pub trait Pane {
     fn hold(&mut self, _exit_status: Option<i32>, _is_first_run: bool, _run_command: RunCommand) {
         // No-op by default, only terminal panes support holding
     }
+    fn add_red_pane_frame_color_override(&mut self, _error_text: Option<String>);
+    fn clear_pane_frame_color_override(&mut self);
+    fn frame_color_override(&self) -> Option<PaletteColor>;
 }
 
 #[derive(Clone, Debug)]
@@ -618,14 +622,18 @@ impl Tab {
                         .send_to_pty(PtyInstruction::ClosePane(PaneId::Terminal(*unused_pid)))
                         .with_context(err_context)?;
                 }
-                // FIXME: This is another hack to crop the viewport to fixed-size panes. Once you can have
-                // non-fixed panes that are part of the viewport, get rid of this!
+
+                // here we offset the viewport from borderless panes that are on the edges of the
+                // screen, this is so that when we don't have pane boundaries (eg. when they were
+                // disabled by the user) boundaries won't be drawn around these panes
+                // geometrically, we can only do this with panes that are on the edges of the
+                // screen - so it's mostly a best-effort thing
                 let display_area = {
                     let display_area = self.display_area.borrow();
                     *display_area
                 };
                 self.resize_whole_tab(display_area);
-                let boundary_geoms = self.tiled_panes.fixed_pane_geoms();
+                let boundary_geoms = self.tiled_panes.borderless_pane_geoms();
                 for geom in boundary_geoms {
                     self.offset_viewport(&geom)
                 }
@@ -1035,6 +1043,20 @@ impl Tab {
                 self.should_clear_display_before_rendering = true;
                 self.tiled_panes.focus_pane(pid, client_id);
             }
+        } else {
+            log::error!("No room to split pane horizontally");
+            if let Some(active_pane_id) = self.tiled_panes.get_active_pane_id(client_id) {
+                self.senders
+                    .send_to_background_jobs(BackgroundJob::DisplayPaneError(
+                        active_pane_id,
+                        "TOO SMALL!".into(),
+                    ))
+                    .with_context(err_context)?;
+            }
+            self.senders
+                .send_to_pty(PtyInstruction::ClosePane(pid))
+                .with_context(err_context)?;
+            return Ok(());
         }
         Ok(())
     }
@@ -1075,6 +1097,20 @@ impl Tab {
                 self.should_clear_display_before_rendering = true;
                 self.tiled_panes.focus_pane(pid, client_id);
             }
+        } else {
+            log::error!("No room to split pane vertically");
+            if let Some(active_pane_id) = self.tiled_panes.get_active_pane_id(client_id) {
+                self.senders
+                    .send_to_background_jobs(BackgroundJob::DisplayPaneError(
+                        active_pane_id,
+                        "TOO SMALL!".into(),
+                    ))
+                    .with_context(err_context)?;
+            }
+            self.senders
+                .send_to_pty(PtyInstruction::ClosePane(pid))
+                .with_context(err_context)?;
+            return Ok(());
         }
         Ok(())
     }
@@ -1139,6 +1175,11 @@ impl Tab {
                 .values()
                 .any(|s_p| s_p.pid() == PaneId::Plugin(plugin_id))
     }
+    pub fn has_pane_with_pid(&self, pid: &PaneId) -> bool {
+        self.tiled_panes.panes_contain(pid)
+            || self.floating_panes.panes_contain(pid)
+            || self.suppressed_panes.values().any(|s_p| s_p.pid() == *pid)
+    }
     pub fn handle_pty_bytes(&mut self, pid: u32, bytes: VteBytes) -> Result<()> {
         if self.is_pending {
             self.pending_instructions
@@ -2809,6 +2850,39 @@ impl Tab {
         self.is_pending
     }
 
+    pub fn add_red_pane_frame_color_override(
+        &mut self,
+        pane_id: PaneId,
+        error_text: Option<String>,
+    ) {
+        if let Some(pane) = self
+            .tiled_panes
+            .get_pane_mut(pane_id)
+            .or_else(|| self.floating_panes.get_pane_mut(pane_id))
+            .or_else(|| {
+                self.suppressed_panes
+                    .values_mut()
+                    .find(|s_p| s_p.pid() == pane_id)
+            })
+        {
+            pane.add_red_pane_frame_color_override(error_text);
+        }
+    }
+    pub fn clear_pane_frame_color_override(&mut self, pane_id: PaneId) {
+        if let Some(pane) = self
+            .tiled_panes
+            .get_pane_mut(pane_id)
+            .or_else(|| self.floating_panes.get_pane_mut(pane_id))
+            .or_else(|| {
+                self.suppressed_panes
+                    .values_mut()
+                    .find(|s_p| s_p.pid() == pane_id)
+            })
+        {
+            pane.clear_pane_frame_color_override();
+        }
+    }
+
     fn show_floating_panes(&mut self) {
         // this function is to be preferred to directly invoking floating_panes.toggle_show_panes(true)
         self.floating_panes.toggle_show_panes(true);
diff --git a/zellij-server/src/tab/unit/tab_tests.rs b/zellij-server/src/tab/unit/tab_tests.rs
index a676f3c68..192c55e3e 100644
--- a/zellij-server/src/tab/unit/tab_tests.rs
+++ b/zellij-server/src/tab/unit/tab_tests.rs
@@ -10,7 +10,7 @@ use crate::{
 use std::path::PathBuf;
 use zellij_utils::data::{Direction, Resize, ResizeStrategy};
 use zellij_utils::errors::prelude::*;
-use zellij_utils::input::layout::PaneLayout;
+use zellij_utils::input::layout::{PaneLayout, SplitDirection, SplitSize};
 use zellij_utils::ipc::IpcReceiverWithContext;
 use zellij_utils::pane_size::{Size, SizeInPixels};
 
@@ -187,6 +187,62 @@ fn create_new_tab(size: Size) -> Tab {
     tab
 }
 
+fn create_new_tab_with_layout(size: Size, layout: PaneLayout) -> Tab {
+    let inde