Getting back to where we started... (Buggy Resizing)

15 files changed, 307 insertions, 574 deletions

diff --git a/Cargo.lock b/Cargo.lock
index dc862d534..31e038a0d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -272,6 +272,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "631ae5198c9be5e753e5cc215e1bd73c2b466a3565173db433f52bb9d3e66dba"
 
 [[package]]
+name = "cassowary"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df8670b8c7b9dae1793364eafadf7239c40d669904660c5960d74cfd80b46a53"
+
+[[package]]
 name = "cc"
 version = "1.0.67"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -2345,6 +2351,7 @@ version = "0.13.0"
 dependencies = [
  "ansi_term 0.12.1",
  "async-trait",
+ "cassowary",
  "daemonize",
  "insta",
  "serde_json",
diff --git a/default-plugins/status-bar/src/main.rs b/default-plugins/status-bar/src/main.rs
index cf9445d6a..83eb50c9a 100644
--- a/default-plugins/status-bar/src/main.rs
+++ b/default-plugins/status-bar/src/main.rs
@@ -135,7 +135,7 @@ impl ZellijPlugin for State {
     fn load(&mut self) {
         set_selectable(false);
         set_invisible_borders(true);
-        set_max_height(2);
+        set_fixed_height(2);
         subscribe(&[EventType::ModeUpdate]);
     }
 
diff --git a/default-plugins/tab-bar/src/main.rs b/default-plugins/tab-bar/src/main.rs
index 46336be3d..7ff639e85 100644
--- a/default-plugins/tab-bar/src/main.rs
+++ b/default-plugins/tab-bar/src/main.rs
@@ -26,7 +26,7 @@ impl ZellijPlugin for State {
     fn load(&mut self) {
         set_selectable(false);
         set_invisible_borders(true);
-        set_max_height(1);
+        set_fixed_height(1);
         subscribe(&[EventType::TabUpdate, EventType::ModeUpdate]);
     }
 
diff --git a/zellij-server/Cargo.toml b/zellij-server/Cargo.toml
index 1168dac47..b04bd04d5 100644
--- a/zellij-server/Cargo.toml
+++ b/zellij-server/Cargo.toml
@@ -16,6 +16,7 @@ serde_json = "1.0"
 unicode-width = "0.1.8"
 wasmer = "1.0.0"
 wasmer-wasi = "1.0.0"
+cassowary = "0.3.0"
 zellij-utils = { path = "../zellij-utils/", version = "0.13.0" }
 
 [dev-dependencies]
diff --git a/zellij-server/src/lib.rs b/zellij-server/src/lib.rs
index 76b4b7b18..6e6392c2e 100644
--- a/zellij-server/src/lib.rs
+++ b/zellij-server/src/lib.rs
@@ -112,6 +112,8 @@ pub fn start_server(os_input: Box<dyn ServerOsApi>, socket_path: PathBuf) {
     daemonize::Daemonize::new()
         .working_directory(std::env::current_dir().unwrap())
         .umask(0o077)
+        // FIXME: My cherished `dbg!` was broken, so this is a hack to bring it back
+        .stderr(std::fs::File::create("dbg.log").unwrap())
         .start()
         .expect("could not daemonize the server process");
 
diff --git a/zellij-server/src/panes/plugin_pane.rs b/zellij-server/src/panes/plugin_pane.rs
index e5c5e15de..b08d528fa 100644
--- a/zellij-server/src/panes/plugin_pane.rs
+++ b/zellij-server/src/panes/plugin_pane.rs
@@ -16,8 +16,6 @@ pub(crate) struct PluginPane {
     pub position_and_size: PositionAndSize,
     pub position_and_size_override: Option<PositionAndSize>,
     pub send_plugin_instructions: SenderWithContext<PluginInstruction>,
-    pub max_height: Option<usize>,
-    pub max_width: Option<usize>,
     pub active_at: Instant,
 }
 
@@ -35,8 +33,6 @@ impl PluginPane {
             position_and_size,
             position_and_size_override: None,
             send_plugin_instructions,
-            max_height: None,
-            max_width: None,
             active_at: Instant::now(),
         }
     }
@@ -95,7 +91,9 @@ impl Pane for PluginPane {
     fn adjust_input_to_terminal(&self, _input_bytes: Vec<u8>) -> Vec<u8> {
         unimplemented!() // FIXME: Shouldn't need this implmented?
     }
-
+    fn position_and_size(&self) -> PositionAndSize {
+        self.position_and_size
+    }
     fn position_and_size_override(&self) -> Option<PositionAndSize> {
         self.position_and_size_override
     }
@@ -114,11 +112,13 @@ impl Pane for PluginPane {
     fn set_invisible_borders(&mut self, invisible_borders: bool) {
         self.invisible_borders = invisible_borders;
     }
-    fn set_max_height(&mut self, max_height: usize) {
-        self.max_height = Some(max_height);
+    fn set_fixed_height(&mut self, fixed_height: usize) {
+        self.position_and_size.rows = fixed_height;
+        self.position_and_size.rows_fixed = true;
     }
-    fn set_max_width(&mut self, max_width: usize) {
-        self.max_width = Some(max_width);
+    fn set_fixed_width(&mut self, fixed_width: usize) {
+        self.position_and_size.columns = fixed_width;
+        self.position_and_size.cols_fixed = true;
     }
     fn render(&mut self) -> Option<String> {
         // if self.should_render {
@@ -204,11 +204,21 @@ impl Pane for PluginPane {
     fn clear_scroll(&mut self) {
         unimplemented!()
     }
+    // FIXME: This need to be reevaluated and deleted if possible.
+    // `max` doesn't make sense when things are fixed...
     fn max_height(&self) -> Option<usize> {
-        self.max_height
+        if self.position_and_size.rows_fixed {
+            Some(self.position_and_size.rows)
+        } else {
+            None
+        }
     }
     fn max_width(&self) -> Option<usize> {
-        self.max_width
+        if self.position_and_size.cols_fixed {
+            Some(self.position_and_size.columns)
+        } else {
+            None
+        }
     }
     fn invisible_borders(&self) -> bool {
         self.invisible_borders
diff --git a/zellij-server/src/panes/terminal_pane.rs b/zellij-server/src/panes/terminal_pane.rs
index 32910618d..2dbd11a02 100644
--- a/zellij-server/src/panes/terminal_pane.rs
+++ b/zellij-server/src/panes/terminal_pane.rs
@@ -27,8 +27,6 @@ pub struct TerminalPane {
     pub selectable: bool,
     pub position_and_size: PositionAndSize,
     pub position_and_size_override: Option<PositionAndSize>,
-    pub max_height: Option<usize>,
-    pub max_width: Option<usize>,
     pub active_at: Instant,
     pub colors: Palette,
     vte_parser: vte::Parser,
@@ -52,8 +50,7 @@ impl Pane for TerminalPane {
         self.reflow_lines();
     }
     fn change_pos_and_size(&mut self, position_and_size: &PositionAndSize) {
-        self.position_and_size.columns = position_and_size.columns;
-        self.position_and_size.rows = position_and_size.rows;
+        self.position_and_size = *position_and_size;
         self.reflow_lines();
     }
     fn override_size_and_position(&mut self, x: usize, y: usize, size: &PositionAndSize) {
@@ -119,7 +116,9 @@ impl Pane for TerminalPane {
         };
         input_bytes
     }
-
+    fn position_and_size(&self) -> PositionAndSize {
+        self.position_and_size
+    }
     fn position_and_size_override(&self) -> Option<PositionAndSize> {
         self.position_and_size_override
     }
@@ -135,21 +134,17 @@ impl Pane for TerminalPane {
     fn set_selectable(&mut self, selectable: bool) {
         self.selectable = selectable;
     }
-    fn set_max_height(&mut self, max_height: usize) {
-        self.max_height = Some(max_height);
+    fn set_fixed_height(&mut self, fixed_height: usize) {
+        self.position_and_size.rows = fixed_height;
+        self.position_and_size.rows_fixed = true;
     }
-    fn set_max_width(&mut self, max_width: usize) {
-        self.max_width = Some(max_width);
+    fn set_fixed_width(&mut self, fixed_width: usize) {
+        self.position_and_size.columns = fixed_width;
+        self.position_and_size.cols_fixed = true;
     }
     fn set_invisible_borders(&mut self, _invisible_borders: bool) {
         unimplemented!();
     }
-    fn max_height(&self) -> Option<usize> {
-        self.max_height
-    }
-    fn max_width(&self) -> Option<usize> {
-        self.max_width
-    }
     fn render(&mut self) -> Option<String> {
         if self.should_render() {
             let mut vte_output = String::new();
@@ -294,8 +289,6 @@ impl TerminalPane {
             selectable: true,
             position_and_size,
             position_and_size_override: None,
-            max_height: None,
-            max_width: None,
             vte_parser: vte::Parser::new(),
             active_at: Instant::now(),
             colors: palette,
diff --git a/zellij-server/src/screen.rs b/zellij-server/src/screen.rs
index 48be44bfc..ab34dfaf5 100644
--- a/zellij-server/src/screen.rs
+++ b/zellij-server/src/screen.rs
@@ -55,7 +55,8 @@ pub(crate) enum ScreenInstruction {
     CloseFocusedPane,
     ToggleActiveTerminalFullscreen,
     SetSelectable(PaneId, bool),
-    SetMaxHeight(PaneId, usize),
+    SetFixedHeight(PaneId, usize),
+    SetFixedWidth(PaneId, usize),
     SetInvisibleBorders(PaneId, bool),
     ClosePane(PaneId),
     ApplyLayout(Layout, Vec<RawFd>),
@@ -106,7 +107,8 @@ impl From<&ScreenInstruction> for ScreenContext {
             }
             ScreenInstruction::SetSelectable(..) => ScreenContext::SetSelectable,
             ScreenInstruction::SetInvisibleBorders(..) => ScreenContext::SetInvisibleBorders,
-            ScreenInstruction::SetMaxHeight(..) => ScreenContext::SetMaxHeight,
+            ScreenInstruction::SetFixedHeight(..) => ScreenContext::SetFixedHeight,
+            ScreenInstruction::SetFixedWidth(..) => ScreenContext::SetFixedWidth,
             ScreenInstruction::ClosePane(_) => ScreenContext::ClosePane,
             ScreenInstruction::ApplyLayout(..) => ScreenContext::ApplyLayout,
             ScreenInstruction::NewTab(_) => ScreenContext::NewTab,
@@ -574,11 +576,17 @@ pub(crate) fn screen_thread_main(
                     .unwrap()
                     .set_pane_selectable(id, selectable);
             }
-            ScreenInstruction::SetMaxHeight(id, max_height) => {
+            ScreenInstruction::SetFixedHeight(id, fixed_height) => {
                 screen
                     .get_active_tab_mut()
                     .unwrap()
-                    .set_pane_max_height(id, max_height);
+                    .set_pane_fixed_height(id, fixed_height);
+            }
+            ScreenInstruction::SetFixedWidth(id, fixed_width) => {
+                screen
+                    .get_active_tab_mut()
+                    .unwrap()
+                    .set_pane_fixed_width(id, fixed_width);
             }
             ScreenInstruction::SetInvisibleBorders(id, invisible_borders) => {
                 screen
diff --git a/zellij-server/src/tab.rs b/zellij-server/src/tab.rs
index 7daf20925..45f386c72 100644
--- a/zellij-server/src/tab.rs
+++ b/zellij-server/src/tab.rs
@@ -104,15 +104,15 @@ pub trait Pane {
     fn handle_pty_bytes(&mut self, bytes: VteBytes);
     fn cursor_coordinates(&self) -> Option<(usize, usize)>;
     fn adjust_input_to_terminal(&self, input_bytes: Vec<u8>) -> Vec<u8>;
-
+    fn position_and_size(&self) -> PositionAndSize;
     fn position_and_size_override(&self) -> Option<PositionAndSize>;
     fn should_render(&self) -> bool;
     fn set_should_render(&mut self, should_render: bool);
     fn selectable(&self) -> bool;
     fn set_selectable(&mut self, selectable: bool);
     fn set_invisible_borders(&mut self, invisible_borders: bool);
-    fn set_max_height(&mut self, max_height: usize);
-    fn set_max_width(&mut self, max_width: usize);
+    fn set_fixed_height(&mut self, fixed_height: usize);
+    fn set_fixed_width(&mut self, fixed_width: usize);
     fn render(&mut self) -> Option<String>;
     fn pid(&self) -> PaneId;
     fn reduce_height_down(&mut self, count: usize);
@@ -178,15 +178,6 @@ pub trait Pane {
         std::cmp::min(self.x() + self.columns(), other.x() + other.columns())
             - std::cmp::max(self.x(), other.x())
     }
-    fn position_and_size(&self) -> PositionAndSize {
-        PositionAndSize {
-            x: self.x(),
-            y: self.y(),
-            columns: self.columns(),
-            rows: self.rows(),
-            ..Default::default()
-        }
-    }
     fn can_increase_height_by(&self, increase_by: usize) -> bool {
         self.max_height()
             .map(|max_height| self.rows() + increase_by <= max_height)
@@ -294,12 +285,6 @@ impl Tab {
                 match positions_and_size.next() {
                     Some((_, position_and_size)) => {
                         terminal_pane.reset_size_and_position_override();
-                        if let Some(max_rows) = position_and_size.max_rows {
-                            terminal_pane.set_max_height(max_rows);
-                        }
-                        if let Some(max_columns) = position_and_size.max_columns {
-                            terminal_pane.set_max_width(max_columns);
-                        }
                         terminal_pane.change_pos_and_size(&position_and_size);
                         self.os_api.set_terminal_size_using_fd(
                             *pid,
@@ -317,24 +302,18 @@ impl Tab {
         }
         let mut new_pids = new_pids.iter();
         for (layout, position_and_size) in positions_and_size {
-            // Just a regular terminal
+            // A plugin pane
             if let Some(plugin) = &layout.plugin {
                 let (pid_tx, pid_rx) = channel();
                 self.senders
                     .send_to_plugin(PluginInstruction::Load(pid_tx, plugin.clone()))
                     .unwrap();
                 let pid = pid_rx.recv().unwrap();
-                let mut new_plugin = PluginPane::new(
+                let new_plugin = PluginPane::new(
                     pid,
                     *position_and_size,
                     self.senders.to_plugin.as_ref().unwrap().clone(),
                 );
-                if let Some(max_rows) = position_and_size.max_rows {
-                    new_plugin.set_max_height(max_rows);
-                }
-                if let Some(max_columns) = position_and_size.max_columns {
-                    new_plugin.set_max_width(max_columns);
-                }
                 self.panes.insert(PaneId::Plugin(pid), Box::new(new_plugin));
                 // Send an initial mode update to the newly loaded plugin only!
                 self.senders
@@ -2121,9 +2100,14 @@ impl Tab {
             pane.set_invisible_borders(invisible_borders);
         }
     }
-    pub fn set_pane_max_height(&mut self, id: PaneId, max_height: usize) {
+    pub fn set_pane_fixed_height(&mut self, id: PaneId, fixed_height: usize) {
+        if let Some(pane) = self.panes.get_mut(&id) {
+            pane.set_fixed_height(fixed_height);
+        }
+    }
+    pub fn set_pane_fixed_width(&mut self, id: PaneId, fixed_width: usize) {
         if let Some(pane) = self.panes.get_mut(&id) {
-            pane.set_max_height(max_height);
+            pane.set_fixed_width(fixed_width);
         }
     }
     pub fn close_pane(&mut self, id: PaneId) {
diff --git a/zellij-server/src/ui/layout.rs b/zellij-server/src/ui/layout.rs
index a9af665fa..7a19d889a 100644
--- a/zellij-server/src/ui/layout.rs
+++ b/zellij-server/src/ui/layout.rs
@@ -19,17 +19,14 @@ fn split_space_to_parts_vertically(
 
     // First fit in the parameterized sizes
     for size in sizes {
-        let (columns, max_columns) = match size {
+        let columns = match size {
             Some(SplitSize::Percent(percent)) => {
-                ((max_width as f32 * (percent as f32 / 100.0)) as usize, None)
+                (max_width as f32 * (percent as f32 / 100.0)) as usize
             } // TODO: round properly
-            Some(SplitSize::Fixed(size)) => (size as usize, Some(size as usize)),
+            Some(SplitSize::Fixed(size)) => size as usize,
             None => {
                 parts_to_grow.push(current_x_position);
-                (
-                    1, // This is grown later on
-                    None,
-                )
+                1 // This is grown later on
             }
         };
         split_parts.push(PositionAndSize {
@@ -37,7 +34,6 @@ fn split_space_to_parts_vertically(
             y: space_to_split.y,
             columns,
             rows: space_to_split.rows,
-            max_columns,
             ..Default::default()
         });
         current_width += columns;
@@ -87,18 +83,14 @@ fn split_space_to_parts_horizontally(
     let mut parts_to_grow = Vec::new();
 
     for size in sizes {
-        let (rows, max_rows) = match size {
-            Some(SplitSize::Percent(percent)) => (
-                (max_height as f32 * (percent as f32 / 100.0)) as usize,
-                None,
-            ), // TODO: round properly
-            Some(SplitSize::Fixed(size)) => (size as usize, Some(size as usize)),
+        let rows = match size {
+            Some(SplitSize::Percent(percent)) => {
+                (max_height as f32 * (percent as f32 / 100.0)) as usize
+            } // TODO: round properly
+            Some(SplitSize::Fixed(size)) => size as usize,
             None => {
                 parts_to_grow.push(current_y_position);
-                (
-                    1, // This is grown later on
-                    None,
-                )
+                1 // This is grown later on
             }
         };
         split_parts.push(PositionAndSize {
@@ -106,7 +98,6 @@ fn split_space_to_parts_horizontally(
             y: current_y_position,
             columns: space_to_split.columns,
             rows,
-            max_rows,
             ..Default::default()
         });
         current_height += rows;
diff --git a/zellij-server/src/ui/pane_resizer.rs b/zellij-server/src/ui/pane_resizer.rs
index b2001945e..73673a9c5 100644
--- a/zellij-server/src/ui/pane_resizer.rs
+++ b/zellij-server/src/ui/pane_resizer.rs
@@ -1,531 +1,247 @@
 use crate::{os_input_output::ServerOsApi, panes::PaneId, tab::Pane};
+use cassowary::{
+    strength::{REQUIRED, STRONG},
+    Constraint, Solver, Variable,
+    WeightedRelation::*,
+};
 use std::{
-    cmp::Ordering,
     collections::{BTreeMap, HashSet},
+    ops::Not,
 };
 use zellij_utils::pane_size::PositionAndSize;
 
-pub(crate) struct PaneResizer<'a> {
+const GAP_SIZE: usize = 1; // Panes are separated by this number of rows / columns
+
+pub struct PaneResizer<'a> {
     panes: &'a mut BTreeMap<PaneId, Box<dyn Pane>>,
+    vars: BTreeMap<PaneId, (Variable, Variable)>,
+    solver: Solver,
     os_api: &'a mut Box<dyn ServerOsApi>,
 }
 
+#[derive(Debug, Clone, Copy)]
+enum Direction {
+    Horizontal,
+    Vertical,
+}
+
+impl Not for Direction {
+    type Output = Self;
+
+    fn not(self) -> Self::Output {
+        match self {
+            Direction::Horizontal => Direction::Vertical,
+            Direction::Vertical => Direction::Horizontal,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Span {
+    pid: PaneId,
+    direction: Direction,
+    fixed: bool,
+    pos: usize,
+    size: usize,
+    pos_var: Variable,
+    size_var: Variable,
+}
+
 // TODO: currently there are some functions here duplicated with Tab
 // all resizing functions should move here
 
+// FIXME:
+// 1. Rounding causes a loss of ratios, I need to store an internal f64 for
+//    each pane as well as the displayed usize and add custom rounding logic.
+// 2. Vertical resizing doesn't seem to respect the space consumed by the tab
+//    and status bars?
+// 3. A 2x2 layout and simultaneous vertical + horizontal resizing sometimes
+//    leads to unsolvable constraints? Maybe related to 2 (and possibly 1).
+//    I should sanity-check the `spans_in_boundary()` here!
+
 impl<'a> PaneResizer<'a> {
     pub fn new(
         panes: &'a mut BTreeMap<PaneId, Box<dyn Pane>>,
         os_api: &'a mut Box<dyn ServerOsApi>,
     ) -> Self {
-        PaneResizer { panes, os_api }
+        let mut vars = BTreeMap::new();
+        for &k in panes.keys() {
+            vars.insert(k, (Variable::new(), Variable::new()));
+        }
+        PaneResizer {
+            panes,
+            vars,
+            solver: Solver::new(),
+            os_api,
+        }
     }
+
     pub fn resize(
         &mut self,
-        mut current_size: PositionAndSize,
+        current_size: PositionAndSize,
         new_size: PositionAndSize,
     ) -> Option<(isize, isize)> {
-        // (column_difference, row_difference)
-        let mut successfully_resized = false;
-        let mut column_difference: isize = 0;
-        let mut row_difference: isize = 0;
-        match new_size.columns.cmp(&current_size.columns) {
-            Ordering::Greater => {
-                let increase_by = new_size.columns - current_size.columns;
-                if let Some(panes_to_resize) = find_increasable_vertical_chain(
-                    &self.panes,
-                    increase_by,
-                    current_size.columns,
-                    current_size.rows,
-                ) {
-                    self.increase_panes_right_and_push_adjacents_right(
-                        panes_to_resize,
-                        increase_by,
-                    );
-                    column_difference = new_size.columns as isize - current_size.columns as isize;
-                    current_size.columns =
-                        (current_size.columns as isize + column_difference) as usize;
-                    successfully_resized = true;
-                };
-            }
-            Ordering::Less => {
-                let reduce_by = current_size.columns - new_size.columns;
-                if let Some(panes_to_resize) = find_reducible_vertical_chain(
-                    &self.panes,
-                    reduce_by,
-                    current_size.columns,
-                    current_size.rows,
-                ) {
-                    self.reduce_panes_left_and_pull_adjacents_left(panes_to_resize, reduce_by);
-                    column_difference = new_size.columns as isize - current_size.columns as isize;
-                    current_size.columns =
-                        (current_size.columns as isize + column_difference) as usize;
-                    successfully_resized = true;
-                };
-            }
-            Ordering::Equal => (),
-        }
-        match new_size.rows.cmp(&current_size.rows) {
-            Ordering::Greater => {
-                let increase_by = new_size.rows - current_size.rows;
-                if let Some(panes_to_resize) = find_increasable_horizontal_chain(
-                    &self.panes,
-                    increase_by,
-                    current_size.columns,
-                    current_size.rows,
-                ) {
-                    self.increase_panes_down_and_push_down_adjacents(panes_to_resize, increase_by);
-                    row_difference = new_size.rows as isize - current_size.rows as isize;
-                    current_size.rows = (current_size.rows as isize + row_difference) as usize;
-                    successfully_resized = true;
-                };
-            }
-            Ordering::Less => {
-                let reduce_by = current_size.rows - new_size.rows;
-                if let Some(panes_to_resize) = find_reducible_horizontal_chain(