feat(ux): initial layout engine (#50)

* prototype

* refactor(layout): move stuff around

* style(format): make rustfmt happy

14 files changed, 422 insertions, 5 deletions

diff --git a/src/layout.rs b/src/layout.rs
new file mode 100644
index 00000000..e80c76b2
--- /dev/null
+++ b/src/layout.rs
@@ -0,0 +1,134 @@
+use crate::terminal_pane::PositionAndSize;
+use serde::{Deserialize, Serialize};
+
+fn _debug_log_to_file(message: String) {
+    use std::fs::OpenOptions;
+    use std::io::prelude::*;
+    let mut file = OpenOptions::new()
+        .append(true)
+        .create(true)
+        .open("/tmp/mosaic-log.txt")
+        .unwrap();
+    file.write_all(message.as_bytes()).unwrap();
+    file.write_all("\n".as_bytes()).unwrap();
+}
+
+fn split_space_to_parts_vertically(
+    space_to_split: &PositionAndSize,
+    percentages: Vec<u8>,
+) -> Vec<PositionAndSize> {
+    let mut split_parts = vec![];
+    let mut current_x_position = space_to_split.x;
+    let width = space_to_split.columns - (percentages.len() - 1); // minus space for gaps
+    for percentage in percentages.iter() {
+        let columns = (width as f32 * (*percentage as f32 / 100.0)) as usize; // TODO: round properly
+        split_parts.push(PositionAndSize {
+            x: current_x_position,
+            y: space_to_split.y,
+            columns,
+            rows: space_to_split.rows,
+        });
+        current_x_position += columns + 1; // 1 for gap
+    }
+    let total_width = split_parts
+        .iter()
+        .fold(0, |total_width, part| total_width + part.columns);
+    if total_width < width {
+        // we have some extra space left, let's add it to the last part
+        let last_part_index = split_parts.len() - 1;
+        let mut last_part = split_parts.get_mut(last_part_index).unwrap();
+        last_part.columns += width - total_width;
+    }
+    split_parts
+}
+
+fn split_space_to_parts_horizontally(
+    space_to_split: &PositionAndSize,
+    percentages: Vec<u8>,
+) -> Vec<PositionAndSize> {
+    let mut split_parts = vec![];
+    let mut current_y_position = space_to_split.y;
+    let height = space_to_split.rows - (percentages.len() - 1); // minus space for gaps
+    for percentage in percentages.iter() {
+        let rows = (height as f32 * (*percentage as f32 / 100.0)) as usize; // TODO: round properly
+        split_parts.push(PositionAndSize {
+            x: space_to_split.x,
+            y: current_y_position,
+            columns: space_to_split.columns,
+            rows,
+        });
+        current_y_position += rows + 1; // 1 for gap
+    }
+    let total_height = split_parts
+        .iter()
+        .fold(0, |total_height, part| total_height + part.rows);
+    if total_height < height {
+        // we have some extra space left, let's add it to the last part
+        let last_part_index = split_parts.len() - 1;
+        let mut last_part = split_parts.get_mut(last_part_index).unwrap();
+        last_part.rows += height - total_height;
+    }
+    split_parts
+}
+
+fn split_space(space_to_split: &PositionAndSize, layout: &Layout) -> Vec<PositionAndSize> {
+    let mut pane_positions: Vec<PositionAndSize> = vec![];
+    let percentages: Vec<u8> = layout
+        .parts
+        .iter()
+        .map(|part| {
+            let split_size = part.split_size.as_ref().unwrap(); // TODO: if there is no split size, it should get the remaining "free space"
+            match split_size {
+                SplitSize::Percent(percent) => *percent,
+            }
+        })
+        .collect();
+    let split_parts = match layout.direction {
+        Direction::Vertical => split_space_to_parts_vertically(space_to_split, percentages),
+        Direction::Horizontal => split_space_to_parts_horizontally(space_to_split, percentages),
+    };
+    for (i, part) in layout.parts.iter().enumerate() {
+        let part_position_and_size = split_parts.get(i).unwrap();
+        if part.parts.len() > 0 {
+            let mut part_positions = split_space(&part_position_and_size, part);
+            pane_positions.append(&mut part_positions);
+        } else {
+            pane_positions.push(*part_position_and_size);
+        }
+    }
+    pane_positions
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub enum Direction {
+    Horizontal,
+    Vertical,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub enum SplitSize {
+    Percent(u8), // 1 to 100
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Layout {
+    pub direction: Direction,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub parts: Vec<Layout>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub split_size: Option<SplitSize>,
+}
+
+impl Layout {
+    pub fn total_panes(&self) -> usize {
+        let mut total_panes = 0;
+        total_panes += self.parts.len();
+        for part in self.parts.iter() {
+            total_panes += part.total_panes();
+        }
+        total_panes
+    }
+    pub fn position_panes_in_space(&self, space: &PositionAndSize) -> Vec<PositionAndSize> {
+        split_space(space, &self)
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index b964efa7..315e8eb1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,6 +2,7 @@
 mod tests;
 
 mod boundaries;
+mod layout;
 mod os_input_output;
 mod pty_bus;
 mod screen;
@@ -14,8 +15,10 @@ use std::sync::mpsc::{channel, Receiver, Sender};
 use std::thread;
 
 use serde::{Deserialize, Serialize};
+use serde_yaml;
 use structopt::StructOpt;
 
+use crate::layout::Layout;
 use crate::os_input_output::{get_os_input, OsApi};
 use crate::pty_bus::{PtyBus, PtyInstruction, VteEvent};
 use crate::screen::{Screen, ScreenInstruction};
@@ -43,7 +46,9 @@ pub struct Opt {
     #[structopt(long)]
     /// Maximum panes on screen, caution: opening more panes will close old ones
     max_panes: Option<usize>,
-
+    #[structopt(short, long)]
+    /// Path to a layout yaml file
+    layout: Option<PathBuf>,
     #[structopt(short, long)]
     debug: bool,
 }
@@ -140,7 +145,26 @@ pub fn start(mut os_input: Box<dyn OsApi>, opts: Opt) {
             .name("pty".to_string())
             .spawn({
                 move || {
-                    pty_bus.spawn_terminal_vertically(None);
+                    match opts.layout {
+                        Some(layout_path) => {
+                            use std::fs::File;
+                            let mut layout_file = File::open(&layout_path)
+                                .expect(&format!("cannot find layout {}", layout_path.display()));
+                            let mut layout = String::new();
+                            layout_file.read_to_string(&mut layout).expect(&format!(
+                                "could not read layout {}",
+                                layout_path.display()
+                            ));
+                            let layout: Layout = serde_yaml::from_str(&layout).expect(&format!(
+                                "could not parse layout {}",
+                                layout_path.display()
+                            ));
+                            pty_bus.spawn_terminals_for_layout(layout);
+                        }
+                        None => {
+                            pty_bus.spawn_terminal_vertically(None);
+                        }
+                    }
                     loop {
                         let event = pty_bus
                             .receive_pty_instructions
@@ -230,6 +254,9 @@ pub fn start(mut os_input: Box<dyn OsApi>, opts: Opt) {
                         ScreenInstruction::ToggleActiveTerminalFullscreen => {
                             screen.toggle_active_terminal_fullscreen();
                         }
+                        ScreenInstruction::ApplyLayout((layout, new_pane_pids)) => {
+                            screen.apply_layout(layout, new_pane_pids)
+                        }
                         ScreenInstruction::Quit => {
                             break;
                         }
diff --git a/src/pty_bus.rs b/src/pty_bus.rs
index 9f75e4b8..fed8f7f7 100644
--- a/src/pty_bus.rs
+++ b/src/pty_bus.rs
@@ -9,6 +9,7 @@ use ::std::time::{Duration, Instant};
 use ::vte;
 use std::path::PathBuf;
 
+use crate::layout::Layout;
 use crate::os_input_output::OsApi;
 use crate::ScreenInstruction;
 
@@ -317,6 +318,29 @@ impl PtyBus {
             .send(ScreenInstruction::HorizontalSplit(pid_primary))
             .unwrap();
     }
+    pub fn spawn_terminals_for_layout(&mut self, layout: Layout) {
+        let total_panes = layout.total_panes();
+        let mut new_pane_pids = vec![];
+        for _ in 0..total_panes {
+            let (pid_primary, pid_secondary): (RawFd, RawFd) = self.os_input.spawn_terminal(None);
+            self.id_to_child_pid.insert(pid_primary, pid_secondary);
+            new_pane_pids.push(pid_primary);
+        }
+        &self
+            .send_screen_instructions
+            .send(ScreenInstruction::ApplyLayout((
+                layout,
+                new_pane_pids.clone(),
+            )));
+        for id in new_pane_pids {
+            stream_terminal_bytes(
+                id,
+                self.send_screen_instructions.clone(),
+                self.os_input.clone(),
+                self.debug_to_file,
+            );
+        }
+    }
     pub fn close_pane(&mut self, id: RawFd) {
         let child_pid = self.id_to_child_pid.get(&id).unwrap();
         self.os_input.kill(*child_pid).unwrap();
diff --git a/src/screen.rs b/src/screen.rs
index a433f02b..777b7935 100644
--- a/src/screen.rs
+++ b/src/screen.rs
@@ -5,9 +5,10 @@ use std::os::unix::io::RawFd;
 use std::sync::mpsc::{Receiver, Sender};
 
 use crate::boundaries::Boundaries;
+use crate::layout::Layout;
 use crate::os_input_output::OsApi;
 use crate::pty_bus::{PtyInstruction, VteEvent};
-use crate::terminal_pane::TerminalPane;
+use crate::terminal_pane::{PositionAndSize, TerminalPane};
 use crate::AppInstruction;
 
 /*
@@ -80,6 +81,7 @@ pub enum ScreenInstruction {
     CloseFocusedPane,
     ToggleActiveTerminalFullscreen,
     ClosePane(RawFd),
+    ApplyLayout((Layout, Vec<RawFd>)),
 }
 
 pub struct Screen {
@@ -115,6 +117,64 @@ impl Screen {
             os_api,
         }
     }
+    pub fn apply_layout(&mut self, layout: Layout, new_pids: Vec<RawFd>) {
+        self.panes_to_hide.clear();
+        // TODO: this should be an attribute on Screen instead of full_screen_ws
+        let free_space = PositionAndSize {
+            x: 0,
+            y: 0,
+            rows: self.full_screen_ws.ws_row as usize,
+            columns: self.full_screen_ws.ws_col as usize,
+        };
+        let positions_in_layout = layout.position_panes_in_space(&free_space);
+        let mut positions_and_size = positions_in_layout.iter();
+        for (pid, terminal_pane) in self.terminals.iter_mut() {
+            match positions_and_size.next() {
+                Some(position_and_size) => {
+                    terminal_pane.reset_size_and_position_override();
+                    terminal_pane.change_size_p(&position_and_size);
+                    self.os_api.set_terminal_size_using_fd(
+                        *pid,
+                        position_and_size.columns as u16,
+                        position_and_size.rows as u16,
+                    );
+                }
+                None => {
+                    // we filled the entire layout, no room for this pane
+                    // TODO: handle active terminal
+                    self.panes_to_hide.insert(*pid);
+                }
+            }
+        }
+        let mut new_pids = new_pids.iter();
+        for position_and_size in positions_and_size {
+            // there are still panes left to fill, use the pids we received in this method
+            let pid = new_pids.next().unwrap(); // if this crashes it means we got less pids than there are panes in this layout
+            let mut new_terminal = TerminalPane::new(
+                *pid,
+                self.full_screen_ws.clone(),
+                position_and_size.x,
+                position_and_size.y,
+            );
+            new_terminal.change_size_p(position_and_size);
+            self.os_api.set_terminal_size_using_fd(
+                new_terminal.pid,
+                new_terminal.get_columns() as u16,
+                new_terminal.get_rows() as u16,
+            );
+            self.terminals.insert(*pid, new_terminal);
+        }
+        for unused_pid in new_pids {
+            // this is a bit of a hack and happens because we don't have any central location that
+            // can query the screen as to how many panes it needs to create a layout
+            // fixing this will require a bit of an architecture change
+            self.send_pty_instructions
+                .send(PtyInstruction::ClosePane(*unused_pid))
+                .unwrap();
+        }
+        self.active_terminal = Some(*self.terminals.iter().next().unwrap().0);
+        self.render();
+    }
     pub fn new_pane(&mut self, pid: RawFd) {
         self.close_down_to_max_terminals();
         if self.terminals.is_empty() {
diff --git a/src/terminal_pane/terminal_pane.rs b/src/terminal_pane/terminal_pane.rs
index 3e0cdd6b..fc1cc207 100644
--- a/src/terminal_pane/terminal_pane.rs
+++ b/src/terminal_pane/terminal_pane.rs
@@ -17,6 +17,7 @@ pub struct PositionAndSize {
     pub columns: usize,
 }
 
+#[derive(Debug)]
 pub struct TerminalPane {
     pub pid: RawFd,
     pub scroll: Scroll,
@@ -134,6 +135,12 @@ impl TerminalPane {
         self.reflow_lines();
         self.should_render = true;
     }
+    pub fn change_size_p(&mut self, position_and_size: &PositionAndSize) {
+        self.position_and_size = *position_and_size;
+        self.reflow_lines();
+        self.should_render = true;
+    }
+    // TODO: merge these two methods
     pub fn change_size(&mut self, ws: &Winsize) {
         self.position_and_size.columns = ws.ws_col as usize;
         self.position_and_size.rows = ws.ws_row as usize;
diff --git a/src/tests/fakes.rs b/src/tests/fakes.rs
index 109424cf..37d1bf79 100644
--- a/src/tests/fakes.rs
+++ b/src/tests/fakes.rs
@@ -143,7 +143,7 @@ impl OsApi for FakeInputOutput {
             .push(IoEvent::UnsetRawMode(pid));
     }
     fn spawn_terminal(&mut self, _file_to_open: Option<PathBuf>) -> (RawFd, RawFd) {
-        let next_terminal_id = { self.read_buffers.lock().unwrap().keys().len() as RawFd + 1 };
+        let next_terminal_id = self.stdin_writes.lock().unwrap().keys().len() as RawFd + 1;
         self.add_terminal(next_terminal_id);
         (next_terminal_id as i32, next_terminal_id + 1000) // secondary number is arbitrary here
     }
diff --git a/src/tests/fixtures/layouts/three-panes-with-nesting.yaml b/src/tests/fixtures/layouts/three-panes-with-nesting.yaml
new file mode 100644
index 00000000..f1e0dd7e
--- /dev/null
+++ b/src/tests/fixtures/layouts/three-panes-with-nesting.yaml
@@ -0,0 +1,16 @@
+---
+direction: Horizontal
+parts:
+  - direction: Vertical
+    parts:
+      - direction: Horizontal
+        split_size:
+          Percent: 20
+      - direction: Horizontal
+        split_size:
+          Percent: 80
+    split_size:
+      Percent: 80
+  - direction: Vertical
+    split_size:
+      Percent: 20
diff --git a/src/tests/integration/layouts.rs b/src/tests/integration/layouts.rs
new file mode 100644
index 00000000..2ab0375e
--- /dev/null
+++ b/src/tests/integration/layouts.rs
@@ -0,0 +1,51 @@
+use ::insta::assert_snapshot;
+use ::nix::pty::Winsize;
+
+use crate::tests::fakes::FakeInputOutput;
+use crate::tests::utils::commands::QUIT;
+use crate::tests::utils::get_output_frame_snapshots;
+use crate::{start, Opt};
+
+fn get_fake_os_input(fake_win_size: &Winsize) -> FakeInputOutput {
+    FakeInputOutput::new(fake_win_size.clone())
+}
+
+#[test]
+pub fn accepts_basic_layout() {
+    let fake_win_size = Winsize {
+        ws_col: 121,
+        ws_row: 20,
+        ws_xpixel: 0,
+        ws_ypixel: 0,
+    };
+    let mut fake_input_output = get_fake_os_input(&fake_win_size);
+    fake_input_output.add_terminal_input(&[QUIT]);
+    use std::path::PathBuf;
+    let mut opts = Opt::default();
+    opts.layout = Some(PathBuf::from(
+        "src/tests/fixtures/layouts/three-panes-with-nesting.yaml",
+    ));
+    start(Box::new(fake_input_output.clone()), opts);
+    let output_frames = fake_input_output
+        .stdout_writer
+        .output_frames
+        .lock()
+        .unwrap();
+    let snapshots = get_output_frame_snapshots(&output_frames, &fake_win_size);
+
+    let snapshot_count = snapshots.len();
+    let first_snapshot = snapshots.get(0).unwrap();
+    let next_to_last_snapshot = snapshots.get(snapshot_count - 2).unwrap();
+    let last_snapshot = snapshots.last().unwrap();
+    // here we only test the first, next to last and last snapshot because there's a race condition
+    // with the other snapshots. Namely all the terminals are created asynchronously and read in an
+    // async task, so we have no way to guarantee the order in which their bytes will be read, and
+    // it doesn't really matter in this context. We just want to see that the layout is initially
+    // created properly and that in the end it's populated properly with its content
+    //
+    // we read the next to last as well as the last, because the last includes the "Bye from
+    // Mosaic" message, and we also want to make sure things are fine before that
+    assert_snapshot!(first_snapshot);
+    assert_snapshot!(next_to_last_snapshot);
+    assert_snapshot!(last_snapshot);
+}
diff --git a/src/tests/integration/mod.rs b/src/tests/integration/mod.rs
index 677af578..bcd78ad9 100644
--- a/src/tests/integration/mod.rs
+++ b/src/tests/integration/mod.rs
@@ -1,6 +1,7 @@
 pub mod basic;
 pub mod close_pane;
 pub mod compatibility;
+pub mod layouts;
 pub mod resize_down;
 pub mod resize_left;
 pub mod resize_right;
diff --git a/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout-2.snap b/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout-2.snap
new file mode 100644
index 00000000..548e6394
--- /dev/null
+++ b/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout-2.snap
@@ -0,0 +1,24 @@
+---
+source: src/tests/integration/layouts.rs
+expression: next_to_last_snapshot
+---
+line6-bbbbbbbbbbbbbbbbbb│line6-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line7-bbbbbbbbbbbbbbbbbb│line7-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line8-bbbbbbbbbbbbbbbbbb│line8-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line9-bbbbbbbbbbbbbbbbbb│line9-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line10-bbbbbbbbbbbbbbbbb│line10-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line11-bbbbbbbbbbbbbbbbb│line11-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line12-bbbbbbbbbbbbbbbbb│line12-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line13-bbbbbbbbbbbbbbbbb│line13-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line14-bbbbbbbbbbbbbbbbb│line14-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line15-bbbbbbbbbbbbbbbbb│line15-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line16-bbbbbbbbbbbbbbbbb│line16-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line17-bbbbbbbbbbbbbbbbb│line17-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line18-bbbbbbbbbbbbbbbbb│line18-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line19-bbbbbbbbbbbbbbbbb│line19-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+prompt $ █              │prompt $                                                                                        
+────────────────────────┴────────────────────────────────────────────────────────────────────────────────────────────────
+line17-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+line18-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+line19-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+prompt $                                                                                                                 
diff --git a/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout-3.snap b/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout-3.snap
new file mode 100644
index 00000000..f22002f3
--- /dev/null
+++ b/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout-3.snap
@@ -0,0 +1,24 @@
+---
+source: src/tests/integration/layouts.rs
+expression: last_snapshot
+---
+line7-bbbbbbbbbbbbbbbbbb│line7-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line8-bbbbbbbbbbbbbbbbbb│line8-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line9-bbbbbbbbbbbbbbbbbb│line9-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line10-bbbbbbbbbbbbbbbbb│line10-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line11-bbbbbbbbbbbbbbbbb│line11-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line12-bbbbbbbbbbbbbbbbb│line12-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line13-bbbbbbbbbbbbbbbbb│line13-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line14-bbbbbbbbbbbbbbbbb│line14-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line15-bbbbbbbbbbbbbbbbb│line15-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line16-bbbbbbbbbbbbbbbbb│line16-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line17-bbbbbbbbbbbbbbbbb│line17-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line18-bbbbbbbbbbbbbbbbb│line18-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+line19-bbbbbbbbbbbbbbbbb│line19-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+prompt $                │prompt $                                                                                        
+────────────────────────┴────────────────────────────────────────────────────────────────────────────────────────────────
+line17-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+line18-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+line19-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+prompt $                                                                                                                 
+Bye from Mosaic!█                                                                                                        
diff --git a/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout.snap b/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout.snap
new file mode 100644
index 00000000..9f6550c2
--- /dev/null
+++ b/src/tests/integration/snapshots/mosaic__tests__integration__layouts__accepts_basic_layout.snap
@@ -0,0 +1,24 @@
+---
+source: src/tests/integration/layouts.rs
+expression: first_snapshot
+---
+█                       │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+                        │                                                                                                
+────────────────────────┴────────────────────────────────────────────────────────────────────────────────────────────────
+                                                                                                                         
+                                                                                                                         
+                                                                                                                         
+                                                                                                                         
diff --git a/src/tests/possible_tty_inputs.rs b/src/tests/possible_tty_inputs.rs
index 6730591f..3d22bab6 100644
--- a/src/tests/possible_tty_inputs.rs
+++ b/src/tests/possible_tty_inputs.rs
@@ -1,6 +1,6 @@
 use crate::tests::tty_inputs::{
     COL_10, COL_121, COL_14, COL_15, COL_19, COL_20, COL_24, COL_29, COL_30, COL_34, COL_39,
-    COL_40, COL_50, COL_60, COL_70, COL_90,
+    COL_40, COL_50, COL_60, COL_70, COL_90, COL_96,
 };
 use std::collections::HashMap;
 use std::fs;
@@ -65,6 +65,7 @@ pub fn get_possible_tty_inputs() -> HashMap<u16, Bytes> {
     let col_60_bytes = Bytes::new().content_from_str(&COL_60);
     let col_70_bytes = Bytes::new().content_from_str(&COL_70);
     let col_90_bytes = Bytes::new().content_from_str(&COL_90);
+    let col_96_bytes = Bytes::new().content_from_str(&COL_96);
     let col_121_bytes = Bytes::new().content_from_str(&COL_121);
     possible_inputs.insert(10, col_10_bytes);
     possible_inputs.insert(14, col_14_bytes);
@@ -81,6 +82,7 @@ pub fn get_possible_tty_inputs() -> HashMap<u16, Bytes> {
     possible_inputs.insert(60, col_60_bytes);
     possible_inputs.insert(70, col_70_bytes);
     possible_inputs.insert(90, col_90_bytes);
+    possible_inputs.insert(96, col_96_bytes);
     possible_inputs.insert(121, col_121_bytes);
     possible_inputs
 }
diff --git a/src/tests/tty_inputs.rs b/src/tests/tty_inputs.rs
index 485585d3..387724cc 100644
--- a/src/tests/tty_inputs.rs
+++ b/src/tests/tty_inputs.rs
@@ -364,3 +364,26 @@ pub const COL_90: [&str; 20] = [
     "line19-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
     "prompt $ ",
 ];
+
+pub const COL_96: [&str; 20] = [
+    "line1-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line2-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line3-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line4-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line5-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line6-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line7-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line8-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line9-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line10-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line11-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line12-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line13-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line14-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line15-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line16-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line17-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line18-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "line19-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n",
+    "prompt $ ",
+];