feat(ui): pane frames (new pane UI) (#643)

* work

* resize working

* move focus working

* close pane working

* selection and fullscreen working

* pane title line

* titles and conditional scroll title

* whole tab resize working

* plugin frames working

* plugin splitting working

* truncate pane frame titles

* cleanup

* panes always draw their own borders - also fix gap

* toggle pane frames

* move toggle to screen and fix some bugs

* fix plugin frame toggle

* fix terminal window resize

* fix scrolling and fullscreen bugs

* unit tests passing

* e2e tests passing and new test for new frames added

* refactor: TerminalPane and PluginPane

* refactor: Tab

* refactor: moar Tab

* refactor: Boundaries

* only render and calculate boundaries when there are no pane frames

* refactor: Layout

* fix(grid): properly resize when coming back from alternative viewport

* style: remove commented code

* style: fmt

* style: fmt

* style: fmt + clippy

* docs(changelog): update change

48 files changed, 2420 insertions, 1079 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 97f68875b..fa985b353 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
   * Bound by default to `^c` in `scroll` mode, scrolls to bottom and exists the scroll mode
 * Simplify deserialization slightly (https://github.com/zellij-org/zellij/pull/633)
 * Fix update plugin attributes on inactive tab (https://github.com/zellij-org/zellij/pull/634)
+* New pane UI: draw pane frames - can be disabled with ctrl-p + z, or through configuration (https://github.com/zellij-org/zellij/pull/643)
 
 ## [0.15.0] - 2021-07-19
 * Kill children properly (https://github.com/zellij-org/zellij/pull/601)
diff --git a/default-plugins/status-bar/src/main.rs b/default-plugins/status-bar/src/main.rs
index 83eb50c9a..dba373f6b 100644
--- a/default-plugins/status-bar/src/main.rs
+++ b/default-plugins/status-bar/src/main.rs
@@ -154,7 +154,11 @@ impl ZellijPlugin for State {
 
         let colored_elements = color_elements(self.mode_info.palette);
         let superkey = superkey(colored_elements, separator);
-        let ctrl_keys = ctrl_keys(&self.mode_info, cols - superkey.len, separator);
+        let ctrl_keys = ctrl_keys(
+            &self.mode_info,
+            cols.saturating_sub(superkey.len),
+            separator,
+        );
 
         let first_line = format!("{}{}", superkey, ctrl_keys);
         let second_line = keybinds(&self.mode_info, cols);
diff --git a/default-plugins/strider/src/state.rs b/default-plugins/strider/src/state.rs
index 0d96ae0b9..0ae84ab29 100644
--- a/default-plugins/strider/src/state.rs
+++ b/default-plugins/strider/src/state.rs
@@ -47,10 +47,10 @@ impl FsEntry {
             FsEntry::Dir(_, s) => s.to_string(),
             FsEntry::File(_, s) => pb::convert(*s as f64),
         };
-        let space = width - info.len();
+        let space = width.saturating_sub(info.len());
         let name = self.name();
-        if space - 1 < name.len() {
-            [&name[..space - 2], &info].join("~ ")
+        if space.saturating_sub(1) < name.len() {
+            [&name[..space.saturating_sub(2)], &info].join("~ ")
         } else {
             let padding = " ".repeat(space - name.len());
             [name, padding, info].concat()
diff --git a/default-plugins/tab-bar/src/line.rs b/default-plugins/tab-bar/src/line.rs
index 3ebeaac31..fc18abfd1 100644
--- a/default-plugins/tab-bar/src/line.rs
+++ b/default-plugins/tab-bar/src/line.rs
@@ -191,7 +191,7 @@ pub fn tab_line(
         &mut tabs_before_active,
         &mut tabs_after_active,
         &mut tabs_to_render,
-        cols - prefix.len,
+        cols.saturating_sub(prefix.len),
     );
 
     let mut tab_line: Vec<LinePart> = vec![];
@@ -200,7 +200,7 @@ pub fn tab_line(
             &mut tabs_before_active,
             &mut tabs_to_render,
             &mut tab_line,
-            cols - prefix.len,
+            cols.saturating_sub(prefix.len),
             palette,
             tab_separator(capabilities),
         );
@@ -210,7 +210,7 @@ pub fn tab_line(
         add_next_tabs_msg(
             &mut tabs_after_active,
             &mut tab_line,
-            cols - prefix.len,
+            cols.saturating_sub(prefix.len),
             palette,
             tab_separator(capabilities),
         );
diff --git a/src/tests/e2e/cases.rs b/src/tests/e2e/cases.rs
index 8d41d44f9..d28ae2f76 100644
--- a/src/tests/e2e/cases.rs
+++ b/src/tests/e2e/cases.rs
@@ -221,26 +221,26 @@ pub fn scrolling_inside_a_pane() {
                 let mut step_is_complete = false;
                 if remote_terminal.cursor_position_is(63, 2) && remote_terminal.tip_appears() {
                     // cursor is in the newly opened second pane
-                    remote_terminal.send_key(&format!("{:0<57}", "line1 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line2 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line3 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line4 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line5 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line6 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line7 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line8 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line9 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line10 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line11 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line12 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line13 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line14 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line15 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line16 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line17 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line18 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<59}", "line19 ").as_bytes());
-                    remote_terminal.send_key(&format!("{:0<58}", "line20 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<56}", "line1 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line2 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line3 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line4 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line5 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line6 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line7 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line8 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line9 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line10 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line11 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line12 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line13 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line14 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line15 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line16 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line17 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line18 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<58}", "line19 ").as_bytes());
+                    remote_terminal.send_key(&format!("{:0<57}", "line20 ").as_bytes());
                     step_is_complete = true;
                 }
                 step_is_complete
@@ -250,7 +250,7 @@ pub fn scrolling_inside_a_pane() {
             name: "Scroll up inside pane",
             instruction: |mut remote_terminal: RemoteTerminal| -> bool {
                 let mut step_is_complete = false;
-                if remote_terminal.cursor_position_is(119, 20) {
+                if remote_terminal.cursor_position_is(118, 20) {
                     // all lines have been written to the pane
                     remote_terminal.send_key(&SCROLL_MODE);
                     remote_terminal.send_key(&SCROLL_UP_IN_SCROLL_MODE);
@@ -263,7 +263,7 @@ pub fn scrolling_inside_a_pane() {
             name: "Wait for scroll to finish",
             instruction: |remote_terminal: RemoteTerminal| -> bool {
                 let mut step_is_complete = false;
-                if remote_terminal.cursor_position_is(119, 20)
+                if remote_terminal.cursor_position_is(118, 20)
                     && remote_terminal.snapshot_contains("line1 ")
                 {
                     // scrolled up one line
@@ -321,7 +321,7 @@ pub fn toggle_pane_fullscreen() {
             name: "Wait for pane to become fullscreen",
             instruction: |remote_terminal: RemoteTerminal| -> bool {
                 let mut step_is_complete = false;
-                if remote_terminal.cursor_position_is(2, 0) {
+                if remote_terminal.cursor_position_is(2, 2) {
                     // cursor is in full screen pane now
                     step_is_complete = true;
                 }
@@ -785,9 +785,9 @@ pub fn accepts_basic_layout() {
             name: "Wait for app to load",
             instruction: |remote_terminal: RemoteTerminal| -> bool {
                 let mut step_is_complete = false;
-                if remote_terminal.cursor_position_is(2, 0)
-                    && remote_terminal.snapshot_contains("$ █                    │$")
-                    && remote_terminal.snapshot_contains("$                                                                                                                       ") {
+                if remote_terminal.cursor_position_is(3, 1)
+                    && remote_terminal.snapshot_contains("$ █                   ││$")
+                    && remote_terminal.snapshot_contains("$                                                                                                                     ") {
                     step_is_complete = true;
                 }
                 step_is_complete
@@ -839,7 +839,7 @@ fn focus_pane_with_mouse() {
             name: "Wait for left pane to be focused",
             instruction: |remote_terminal: RemoteTerminal| -> bool {
                 let mut step_is_complete = false;
-                if remote_terminal.cursor_position_is(2, 2) && remote_terminal.tip_appears() {
+                if remote_terminal.cursor_position_is(3, 2) && remote_terminal.tip_appears() {
                     // cursor is in the newly opened second pane
                     step_is_complete = true;
                 }
@@ -884,26 +884,26 @@ pub fn scrolling_inside_a_pane_with_mouse() {
                     let mut step_is_complete = false;
                     if remote_terminal.cursor_position_is(63, 2) && remote_terminal.tip_appears() {
                         // cursor is in the newly opened second pane
-                        remote_terminal.send_key(&format!("{:0<57}", "line1 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line2 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line3 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line4 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line5 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line6 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line7 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line8 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line9 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line10 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line11 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line12 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line13 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line14 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line15 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line16 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line17 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line18 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<59}", "line19 ").as_bytes());
-                        remote_terminal.send_key(&format!("{:0<58}", "line20 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<56}", "line1 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line2 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line3 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line4 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line5 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line6 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line7 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line8 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line9 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line10 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line11 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line12 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line13 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line14 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line15 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line16 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line17 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line18 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<58}", "line19 ").as_bytes());
+                        remote_terminal.send_key(&format!("{:0<57}", "line20 ").as_bytes());
                         step_is_complete = true;
                     }