feature: Add collapsible tree entries (#304)

Adds collapsible trees to the tree mode for processes. These can be toggled via the + or - keys and the mouse by clicking on a selected entry.

12 files changed, 309 insertions, 123 deletions

diff --git a/.vscode/settings.json b/.vscode/settings.json
index f5f60e4f..0ebd8ca7 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -48,6 +48,7 @@
     "cvars",
     "czvf",
     "denylist",
+    "eselect",
     "fedoracentos",
     "fpath",
     "fract",
diff --git a/CHANGELOG.md b/CHANGELOG.md
index eedb7ed2..8c25a651 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.5.1] - Unreleased
+
+### Features
+
+### Changes
+
+### Bug Fixes
+
 ## [0.5.0] - Unreleased
 
 ### Features
diff --git a/README.md b/README.md
index afe7df74..e3346e4c 100644
--- a/README.md
+++ b/README.md
@@ -137,6 +137,7 @@ sudo dnf install bottom
 ### Gentoo
 
 Available in [dm9pZCAq overlay](https://github.com/gentoo-mirror/dm9pZCAq)
+
 ```bash
 sudo eselect repository enable dm9pZCAq
 sudo emerge --sync dm9pZCAq
@@ -232,7 +233,6 @@ Run using `btm`.
         --hide_time                            Completely hides the time scaling.
     -k, --kelvin                               Sets the temperature type to Kelvin.
     -l, --left_legend                          Puts the CPU chart legend to the left side.
-        --no_write                             Disables writing to the config file.
     -r, --rate <MS>                            Sets a refresh rate in ms.
     -R, --regex                                Enables regex by default.
     -d, --time_delta <MS>                      The amount in ms changed upon zooming.
@@ -401,6 +401,12 @@ Note that the `and` operator takes precedence over the `or` operator.
 | ------ | --------------------------------------------------------------------- |
 | Scroll | Scrolling over an CPU core/average shows only that entry on the chart |
 
+#### Process bindings
+
+|       |                                                                                                     |
+| ----- | --------------------------------------------------------------------------------------------------- |
+| Click | If in tree mode and you click on a selected entry, it toggles whether the branch is expanded or not |
+
 ## Features
 
 As yet _another_ process/system visualization and management application, bottom supports the typical features:
@@ -742,6 +748,7 @@ Thanks to all contributors ([emoji key](https://allcontributors.org/docs/en/emoj
 
 <!-- markdownlint-enable -->
 <!-- prettier-ignore-end -->
+
 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
 ## Thanks
diff --git a/src/app.rs b/src/app.rs
index d80a206c..9f8fb577 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -697,7 +697,7 @@ impl App {
                         .process_search_state
                         .search_state
                         .is_enabled
-                        && proc_widget_state.get_cursor_position()
+                        && proc_widget_state.get_search_cursor_position()
                             < proc_widget_state
                                 .process_search_state
                                 .search_state
@@ -708,13 +708,13 @@ impl App {
                             .process_search_state
                             .search_state
                             .current_search_query
-                            .remove(proc_widget_state.get_cursor_position());
+                            .remove(proc_widget_state.get_search_cursor_position());
 
                         proc_widget_state
                             .process_search_state
                             .search_state
                             .grapheme_cursor = GraphemeCursor::new(
-                            proc_widget_state.get_cursor_position(),
+                            proc_widget_state.get_search_cursor_position(),
                             proc_widget_state
                                 .process_search_state
                                 .search_state
@@ -746,21 +746,22 @@ impl App {
                         .process_search_state
                         .search_state
                         .is_enabled
-                    && proc_widget_state.get_cursor_position() > 0
+                    && proc_widget_state.get_search_cursor_position() > 0
                 {
-                    proc_widget_state.search_walk_back(proc_widget_state.get_cursor_position());
+                    proc_widget_state
+                        .search_walk_back(proc_widget_state.get_search_cursor_position());
 
                     let removed_char = proc_widget_state
                         .process_search_state
                         .search_state
                         .current_search_query
-                        .remove(proc_widget_state.get_cursor_position());
+                        .remove(proc_widget_state.get_search_cursor_position());
 
                     proc_widget_state
                         .process_search_state
                         .search_state
                         .grapheme_cursor = GraphemeCursor::new(
-                        proc_widget_state.get_cursor_position(),
+                        proc_widget_state.get_search_cursor_position(),
                         proc_widget_state
                             .process_search_state
                             .search_state
@@ -838,15 +839,15 @@ impl App {
                         .get_mut_widget_state(self.current_widget.widget_id - 1)
                     {
                         if is_in_search_widget {
-                            let prev_cursor = proc_widget_state.get_cursor_position();
+                            let prev_cursor = proc_widget_state.get_search_cursor_position();
                             proc_widget_state
-                                .search_walk_back(proc_widget_state.get_cursor_position());
-                            if proc_widget_state.get_cursor_position() < prev_cursor {
+                                .search_walk_back(proc_widget_state.get_search_cursor_position());
+                            if proc_widget_state.get_search_cursor_position() < prev_cursor {
                                 let str_slice = &proc_widget_state
                                     .process_search_state
                                     .search_state
                                     .current_search_query
-                                    [proc_widget_state.get_cursor_position()..prev_cursor];
+                                    [proc_widget_state.get_search_cursor_position()..prev_cursor];
                                 proc_widget_state
                                     .process_search_state
                                     .search_state
@@ -905,15 +906,16 @@ impl App {
                         .get_mut_widget_state(self.current_widget.widget_id - 1)
                     {
                         if is_in_search_widget {
-                            let prev_cursor = proc_widget_state.get_cursor_position();
-                            proc_widget_state
-                                .search_walk_forward(proc_widget_state.get_cursor_position());
-                            if proc_widget_state.get_cursor_position() > prev_cursor {
+                            let prev_cursor = proc_widget_state.get_search_cursor_position();
+                            proc_widget_state.search_walk_forward(
+                                proc_widget_state.get_search_cursor_position(),
+                            );
+                            if proc_widget_state.get_search_cursor_position() > prev_cursor {
                                 let str_slice = &proc_widget_state
                                     .process_search_state
                                     .search_state
                                     .current_search_query
-                                    [prev_cursor..proc_widget_state.get_cursor_position()];
+                                    [prev_cursor..proc_widget_state.get_search_cursor_position()];
                                 proc_widget_state
                                     .process_search_state
                                     .search_state
@@ -1124,13 +1126,13 @@ impl App {
                             .process_search_state
                             .search_state
                             .current_search_query
-                            .insert(proc_widget_state.get_cursor_position(), caught_char);
+                            .insert(proc_widget_state.get_search_cursor_position(), caught_char);
 
                         proc_widget_state
                             .process_search_state
                             .search_state
                             .grapheme_cursor = GraphemeCursor::new(
-                            proc_widget_state.get_cursor_position(),
+                            proc_widget_state.get_search_cursor_position(),
                             proc_widget_state
                                 .process_search_state
                                 .search_state
@@ -1139,7 +1141,7 @@ impl App {
                             true,
                         );
                         proc_widget_state
-                            .search_walk_forward(proc_widget_state.get_cursor_position());
+                            .search_walk_forward(proc_widget_state.get_search_cursor_position());
 
                         proc_widget_state
                             .process_search_state
@@ -1371,8 +1373,8 @@ impl App {
             'K' | 'W' => self.move_widget_selection(&WidgetDirection::Up),
             'J' | 'S' => self.move_widget_selection(&WidgetDirection::Down),
             't' => self.toggle_tree_mode(),
-            '+' => self.zoom_in(),
-            '-' => self.zoom_out(),
+            '+' => self.on_plus(),
+            '-' => self.on_minus(),
             '=' => self.reset_zoom(),
             'e' => self.toggle_expand_widget(),
             's' => self.toggle_sort(),
@@ -2058,7 +2060,9 @@ impl App {
     pub fn decrement_position_count(&mut self) {
         if !self.ignore_normal_keybinds() {
             match self.current_widget.widget_type {
-                BottomWidgetType::Proc => self.increment_process_position(-1),
+                BottomWidgetType::Proc => {
+                    self.increment_process_position(-1);
+                }
                 BottomWidgetType::ProcSort => self.increment_process_sort_position(-1),
                 BottomWidgetType::Temp => self.increment_temp_position(-1),
                 BottomWidgetType::Disk => self.increment_disk_position(-1),
@@ -2071,7 +2075,9 @@ impl App {
     pub fn increment_position_count(&mut self) {
         if !self.ignore_normal_keybinds() {
             match self.current_widget.widget_type {
-                BottomWidgetType::Proc => self.increment_process_position(1),
+                BottomWidgetType::Proc => {
+                    self.increment_process_position(1);
+                }
                 BottomWidgetType::ProcSort => self.increment_process_sort_position(1),
                 BottomWidgetType::Temp => self.increment_temp_position(1),
                 BottomWidgetType::Disk => self.increment_disk_position(1),
@@ -2128,7 +2134,8 @@ impl App {
         }
     }
 
-    fn increment_process_position(&mut self, num_to_change_by: i64) {
+    /// Returns the new position.
+    fn increment_process_position(&mut self, num_to_change_by: i64) -> Option<usize> {
         if let Some(proc_widget_state) = self
             .proc_state
             .get_mut_widget_state(self.current_widget.widget_id)
@@ -2144,6 +2151,8 @@ impl App {
                 {
                     proc_widget_state.scroll_state.current_scroll_position =
                         (current_posn as i64 + num_to_change_by) as usize;
+                } else {
+                    return None;
                 }
             }
 
@@ -2152,7 +2161,11 @@ impl App {
             } else {
                 proc_widget_state.scroll_state.scroll_direction = ScrollDirection::Down;
             }
+
+            return Some(proc_widget_state.scroll_state.current_scroll_position);
         }
+
+        None
     }
 
     fn increment_temp_position(&mut self, num_to_change_by: i64) {
@@ -2245,6 +2258,53 @@ impl App {
         }
     }
 
+    fn on_plus(&mut self) {
+        if let BottomWidgetType::Proc = self.current_widget.widget_type {
+            // Toggle collapsing if tree
+            self.toggle_collapsing_process_branch();
+        } else {
+            self.zoom_in();
+        }
+    }
+
+    fn on_minus(&mut self) {
+        if let BottomWidgetType::Proc = self.current_widget.widget_type {
+            // Toggle collapsing if tree
+            self.toggle_collapsing_process_branch();
+        } else {
+            self.zoom_out();
+        }
+    }
+
+    fn toggle_collapsing_process_branch(&mut self) {
+        if let Some(proc_widget_state) = self
+            .proc_state
+            .widget_states
+            .get_mut(&self.current_widget.widget_id)
+        {
+            let current_posn = proc_widget_state.scroll_state.current_scroll_position;
+
+            if let Some(displayed_process_list) = self
+                .canvas_data
+                .finalized_process_data_map
+                .get(&self.current_widget.widget_id)
+            {
+                if let Some(corresponding_process) = displayed_process_list.get(current_posn) {
+                    let corresponding_pid = corresponding_process.pid;
+
+                    if let Some(process_data) = self
+                        .canvas_data
+                        .single_process_data
+                        .get_mut(&corresponding_pid)
+                    {
+                        process_data.is_collapsed_entry = !process_data.is_collapsed_entry;
+                        self.proc_state.force_update = Some(self.current_widget.widget_id);
+                    }
+                }
+            }
+        }
+    }
+
     fn zoom_out(&mut self) {
         match self.current_widget.widget_type {
             BottomWidgetType::Cpu => {
@@ -2464,11 +2524,12 @@ impl App {
         // Pretty dead simple - iterate through the widget map and go to the widget where the click
         // is within.
 
-        // TODO: [MOUSE] double click functionality...?
         // TODO: [REFACTOR] might want to refactor this, it's ugly as sin.
         // TODO: [REFACTOR] Might wanna refactor ALL state things in general, currently everything
         // is grouped up as an app state.  We should separate stuff like event state and gui state and etc.
 
+        // TODO: [MOUSE] double click functionality...?  We would do this above all other actions and SC if needed.
+
         // Short circuit if we're in basic table... we might have to handle the basic table arrow
         // case here...
         if let Some(bt) = &mut self.basic_table_widget_state {
@@ -2620,9 +2681,25 @@ impl App {
                                     if let Some(visual_index) =
                                         proc_widget_state.scroll_state.table_state.selected()
                                     {
-                                        self.increment_process_position(
+                                        // If in tree mode, also check to see if this click is on
+                                        // the same entry as the already selected one - if it is,
+                                        // then we minimize.
+
+                                        let previous_scroll_position =
+                                            proc_widget_state.scroll_state.current_scroll_position;
+                                        let is_tree_mode = proc_widget_state.is_tree_mode;
+
+                                        let new_position = self.increment_process_position(
                                             offset_clicked_entry as i64 - visual_index as i64,
                                         );
+
+                                        if is_tree_mode {
+                                            if let Some(new_position) = new_position {
+                                                if previous_scroll_position == new_position {
+                                                    self.toggle_collapsing_process_branch();
+                                                }
+                                            }
+                                        }
                                     }
                                 }
                             }
diff --git a/src/app/states.rs b/src/app/states.rs
index dea49b18..12037907 100644
--- a/src/app/states.rs
+++ b/src/app/states.rs
@@ -488,7 +488,7 @@ impl ProcWidgetState {
         }
     }
 
-    pub fn get_cursor_position(&self) -> usize {
+    pub fn get_search_cursor_position(&self) -> usize {
         self.process_search_state
             .search_state
             .grapheme_cursor
diff --git a/src/canvas.rs b/src/canvas.rs
index 626f4f7f..7af29f33 100644
--- a/src/canvas.rs
+++ b/src/canvas.rs
@@ -25,6 +25,7 @@ use crate::{
     options::Config,
     utils::error,
     utils::error::BottomError,
+    Pid,
 };
 
 mod canvas_colours;
@@ -46,9 +47,9 @@ pub struct DisplayableData {
     pub network_data_tx: Vec<Point>,
     pub disk_data: Vec<Vec<String>>,
     pub temp_sensor_data: Vec<Vec<String>>,
-    pub single_process_data: Vec<ConvertedProcessData>, // Contains single process data
-    pub finalized_process_data_map: HashMap<u64, Vec<ConvertedProcessData>>, // What's actually displayed
-    pub stringified_process_data_map: HashMap<u64, Vec<(Vec<(String, Option<String>)>, bool)>>, // Represents the row and whether it is disabled
+    pub single_process_data: HashMap<Pid, ConvertedProcessData>, // Contains single process data, key is PID
+    pub finalized_process_data_map: HashMap<u64, Vec<ConvertedProcessData>>, // What's actually displayed, key is the widget ID.
+    pub stringified_process_data_map: HashMap<u64, Vec<(Vec<(String, Option<String>)>, bool)>>, // Represents the row and whether it is disabled, key is the widget ID
     pub mem_label_percent: String,
     pub swap_label_percent: String,
     pub mem_label_frac: String,
diff --git a/src/canvas/widgets/process_table.rs b/src/canvas/widgets/process_table.rs
index 0ee25b1f..22e54c16 100644
--- a/src/canvas/widgets/process_table.rs
+++ b/src/canvas/widgets/process_table.rs
@@ -506,7 +506,7 @@ impl ProcessTableWidget for Painter {
             let search_title = "> ";
 
             let num_chars_for_text = search_title.len();
-            let cursor_position = proc_widget_state.get_cursor_position();
+            let cursor_position = proc_widget_state.get_search_cursor_position();
             let current_cursor_position = proc_widget_state.get_char_cursor_position();
 
             let start_position: usize = get_search_start_position(
diff --git a/src/clap.rs b/src/clap.rs
index 5f6d7667..70972d62 100644
--- a/src/clap.rs
+++ b/src/clap.rs
@@ -143,13 +143,13 @@ Completely hides the time scaling from being shown.\n\n",
             "\
 Puts the CPU chart legend to the left side rather than the right side.\n\n",
         );
-    let no_write = Arg::with_name("no_write")
-        .long("no_write")
-        .help("Disables writing to the config file.")
-        .long_help(
-            "\
-Disables config changes in-app from writing to the config file.",
-        );
+    //     let no_write = Arg::with_name("no_write")
+    //         .long("no_write")
+    //         .help("Disables writing to the config file.")
+    //         .long_help(
+    //             "\
+    // Disables config changes in-app from writing to the config file.",
+    //         );
     let regex = Arg::with_name("regex")
         .short("R")
         .long("regex")
@@ -355,7 +355,7 @@ The minimum is 1s (1000), and defaults to 15s (15000).\n\n\n",
         .arg(hide_table_gap)
         .arg(hide_time)
         .arg(left_legend)
-        .arg(no_write)
+        // .arg(no_write)
         .arg(rate)
         .arg(regex)
         .arg(time_delta)
diff --git a/src/constants.rs b/src/constants.rs
index 91e9419c..0bccec77 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -158,7 +158,6 @@ lazy_static! {
     // };
 }
 
-// FIXME: [HELP] I wanna update this before release... it's missing mouse too.
 // Help text
 pub const HELP_CONTENTS_TEXT: [&str; 8] = [
     "Press the corresponding numbers to jump to the section, or scroll:",
@@ -171,7 +170,9 @@ pub const HELP_CONTENTS_TEXT: [&str; 8] = [
     "7 - Basic memory widget",
 ];
 
-pub const GENERAL_HELP_TEXT: [&str; 29] = [
+// TODO [Help]: Search in help?
+// TODO [Help]: Move to using tables for easier formatting?
+pub const GENERAL_HELP_TEXT: [&str; 30] = [
     "1 - General",
     "q, Ctrl-c        Quit",
     "Esc              Close dialog windows, search, widgets, or exit expanded mode",
@@ -201,6 +202,7 @@ pub const GENERAL_HELP_TEXT: [&str; 29] = [
     "-                Zoom out on chart (increase time range)",
     "=                Reset zoom",
     "Mouse scroll     Scroll through the tables or zoom in/out of charts by scrolling up/down",
+    "Mouse click      Selects the clicked widget, table entry, dialog option, or tab",
 ];
 
 pub const CPU_HELP_TEXT: [&str; 2] = [
@@ -208,9 +210,7 @@ pub const CPU_HELP_TEXT: [&str; 2] = [
     "Mouse scroll     Scrolling over an CPU core/average shows only that entry on the chart",
 ];
 
-// TODO [Help]: Search in help?
-// TODO [Help]: Move to using tables for easier formatting?
-pub const PROCESS_HELP_TEXT: [&str; 13] = [
+pub const PROCESS_HELP_TEXT: [&str; 14] = [
     "3 - Process widget",
     "dd               Kill the selected process",
     "c                Sort by CPU usage, press again to reverse sorting order",
@@ -224,6 +224,7 @@ pub const PROCESS_HELP_TEXT: [&str; 13] = [
     "I                Invert current sort",
     "%                Toggle between values and percentages for memory usage",
     "t, F5            Toggle tree mode",
+    "+, -, click      Collapse/expand a branch while in tree mode",
 ];
 
 pub const SEARCH_HELP_TEXT: [&str; 46] = [
diff --git a/src/data_conversion.rs b/src/data_conversion.rs
index 3b83d935..5bf31edf 100644
--- a/src/data_conversion.rs
+++ b/src/data_conversion.rs
@@ -7,7 +7,7 @@ use crate::{
 };
 use data_harvester::processes::ProcessSorting;
 use indexmap::IndexSet;
-use std::collections::{HashMap, VecDeque};
+use std::collections::{HashMap, HashSet, VecDeque};
 
 /// Point is of time, data
 type Point = (f64, f64);
@@ -66,6 +66,8 @@ pub struct ConvertedProcessData {
     pub process_description_prefix: Option<String>,
     /// Whether to mark this process entry as disabled (mostly for tree mode).
     pub is_disabled_entry: bool,
+    /// Whether this entry is collapsed, hiding all its children (for tree mode).
+    pub is_collapsed_entry: bool,
 }
 
 #[derive(Clone, Default, Debug)]
@@ -194,19 +196,17 @@ pub fn convert_cpu_data_points(
         for (itx, cpu) in data.cpu_data.iter().enumerate() {
             // Check if the vector exists yet
             if cpu_data_vector.len() <= itx {
-                let mut new_cpu_data = ConvertedCpuData::default();
-                new_cpu_data.cpu_name = if let Some(cpu_harvest) = current_data.cpu_harvest.get(itx)
-                {
-                    if let Some(cpu_count) = cpu_harvest.cpu_count {
-                        format!("{}{}", cpu_harvest.cpu_prefix, cpu_count)
+                let new_cpu_data = ConvertedCpuData {
+                    cpu_name: if let Some(cpu_harvest) = current_data.cpu_harvest.get(itx) {
+                        if let Some(cpu_count) = cpu_harvest.cpu_count {
+                            format!("{}{}", cpu_harvest.cpu_prefix, cpu_count)
+                        } else {
+                            cpu_harvest.cpu_prefix.to_string()
+                        }
                     } else {
-                        cpu_harvest.cpu_prefix.to_string()
-                    }
-                } else {
-                    String::default()
-                };
-                new_cpu_data.short_cpu_name =
-                    if let Some(cpu_harvest) = current_data.cpu_harvest.get(itx) {
+                        String::default()
+                    },
+                    short_cpu_name: if let Some(cpu_harvest) = current_data.cpu_harvest.get(itx) {
                         if let Some(cpu_count) = cpu_harvest.cpu_count {
                             cpu_count.to_string()
                         } else {
@@ -214,7 +214,10 @@ pub fn convert_cpu_data_points(
                         }
                     } else {
                         String::default()
-                    };
+                    },
+                    ..ConvertedCpuData::default()
+                };
+
                 cpu_data_vector.push(new_cpu_data);
             }
 
@@ -426,55 +429,120 @@ pub enum ProcessNamingType {
     Path,
 }
 
+/// Because we needed to UPDATE data entries rather than REPLACING entries, we instead update
+/// the existing vector.
 pub fn convert_process_data(
     current_data: &data_farmer::DataCollection,
-) -> Vec<ConvertedProcessData> {
+    existing_converted_process_data: &mut HashMap<Pid, ConvertedProcessData>,
+) {
     // TODO [THREAD]: Thread highlighting and hiding support
     // For macOS see https://github.com/hishamhm/htop/pull/848/files
 
-    current_data
-        .process_harvest
-        .iter()
-        .map(|process| {
-            let converted_rps = get_exact_byte_values(process.read_bytes_per_sec, false);
-            let converted_wps = get_exact_byte_values(process.write_bytes_per_sec, false);
-            let converted_total_read = get_exact_byte_values(process.total_read_bytes, false);
-            let converted_total_write = get_exact_byte_values(process.total_write_bytes, false);
+    let mut complete_pid_set: HashSet<Pid> =
+        existing_converted_process_data.keys().copied().collect();
 
-            let read_per_sec = format!("{:.*}{}/s", 0, converted_rps.0, converted_rps.1);
-            let write_per_sec = format!("{:.*}{}/s", 0, converted_wps.0, converted_wps.1);
-            let total_read = format!("{:.*}{}", 0, converted_total_read.0, converted_total_read.1);
-            let total_write = format!(
-                "{:.*}{}",
-                0, converted_total_write.0, converted_total_write.1
-            );
+    for process in &current_data.process_harvest {
+        let converted_rps = get_exact_byte_values(process.read_bytes_per_sec, false);
+        let converted_wps = get_exact_byte_values(process.write_bytes_per_sec, false);
+        let converted_total_read = get_exact_byte_values(process.total_read_bytes, false);
+        let converted_total_write = get_exact_byte_values(process.total_write_bytes, false);
 
-            ConvertedProcessData {
-                pid: process.pid,
-                ppid: process.parent_pid,
-                is_thread: None,
-                name: process.name.to_string(),
-                command: process.command.to_string(),
-                cpu_percent_usage: process.cpu_usage_percent,
-                mem_percent_usage: process.mem_usage_percent,
-                mem_usage_bytes: process.mem_usage_bytes,
-                mem_usage_str: get_exact_byte_values(process.mem_usage_bytes, false),
-                group_pids: vec![process.pid],
-                read_per_sec,
-                write_per_sec,
-                total_read,
-                total_write,
-                rps_f64: process.read_bytes_per_sec as f64,
-                wps_f64: process.write_bytes_per_sec as f64,
-                tr_f64: process.total_read_bytes as f64,
-                tw_f64: process.total_write_bytes as f64,
-                process_state: process.process_state.to_owned(),
-                process_char: process.process_state_char,
-                process_description_prefix: None,
-                is_disabled_entry: false,
+        let read_per_sec = format!("{:.*}{}/s", 0, converted_rps.0, converted_rps.1);
+        let write_per_sec = format!("{:.*}{}/s", 0, converted_wps.0, converted_wps.1);
+        let total_read = format!("{:.*}{}", 0, converted_total_read.0, converted_total_read.1);
+        let total_write = format!(
+            "{:.*}{}",
+            0, converted_total_write.0, converted_total_write.1
+        );
+
+        if let Some(process_entry) = existing_converted_process_data.get_mut(&process.pid) {
+            complete_pid_set.remove(&process.pid);
+
+            // Very dumb way to see if there's PID reuse...
+            if process_entry.ppid == process.parent_pid {
+                process_entry.name = process.name.to_string();
+                process_entry.command = process.command.to_string();
+                process_entry.cpu_percent_usage = process.cpu_usage_percent;
+                process_entry.mem_percent_usage = process.mem_usage_percent;
+                process_entry.mem_usage_bytes = process.mem_usage_bytes;
+                process_entry.mem_usage_str = get_exact_byte_values(process.mem_usage_bytes, false);
+                process_entry.group_pids = vec![process.pid];
+                process_entry.read_per_sec = read_per_sec;
+                process_entry.write_per_sec = write_per_sec;
+                process_entry.total_read = total_read;
+                process_entry.total_write = total_write;
+                process_entry.rps_f64 = process.read_bytes_per_sec as f64;
+                process_entry.wps_f64 = process.write_bytes_per_sec as f64;
+                process_entry.tr_f64 = process.total_read_bytes as f64;
+                process_entry.tw_f64 = process.total_write_bytes as f64;
+                process_entry.process_state = process.process_state.to_owned();
+                process_entry.process_char = process.process_state_char;
+                process_entry.process_description_prefix = None;
+                process_entry.is_disabled_entry = false;
+            } else {
+                // ...I hate that I can't combine if let and an if statement in one line...
+                *process_entry = ConvertedProcessData {
+                    pid: process.pid,
+                    ppid: process.parent_pid,
+                    is_thread: None,
+                    name: process.name.to_string(),
+                    command: process.command.to_string(),
+                    cpu_percent_usage: process.cpu_usage_percent,
+                    mem_percent_usage: process.mem_usage_percent,
+                    mem_usage_bytes: process.mem_usage_bytes,
+                    mem_usage_str: get_exact_byte_values(process.mem_usage_bytes, false),
+                    group_pids: vec![process.pid],
+                    read_per_sec,
+                    write_per_sec,
+                    total_read,
+                    total_write,
+                    rps_f64: process.read_bytes_per_sec as f64,
+                    wps_f64: process.write_bytes_per_sec as f64,
+                    tr_f64: process.total_read_bytes as f64,
+                    tw_f64: process.total_write_bytes as f64,
+                    process_state: process.process_state.to_owned(),
+                    process_char: process.process_state_char,
+                    process_description_prefix: None,
+                    is_disabled_entry: false,
+                    is_collapsed_entry: false,
+                };
             }
-        })
-        .collect::<Vec<_>>()
+        } else {
+            existing_converted_process_data.insert(
+                process.pid,
+                ConvertedProcessData {
+                    pid: process.pid,
+                    ppid: process.parent_pid,
+                    is_thread: None,
+                    name: process.name.to_string(),
+                    command: process.command.to_string(),
+                    cpu_percent_usage: process.cpu_usage_percent,
+                    mem_percent_usage: process.mem_usage_percent,
+                    mem_usage_bytes: process.mem_usage_bytes,
+                    mem_usage_str: get_exact_byte_values(process.mem_usage_bytes, false),
+                    group_pids: vec![process.pid],
+                    read_per_sec,
+                    write_per_sec,
+                    total_read,
+                    total_write,
+                    rps_f64: process.read_bytes_per_sec as f64,
+                    wps_f64: process.write_bytes_per_sec as f64,
+                    tr_f64: process.total_read_bytes as f64,
+                    tw_f64: process.total_write_bytes as f64,
+                    process_state: process.process_state.to_owned(),
+                    process_char: process.process_state_char,
+                    process_description_prefix: None,
+                    is_disabled_entry: false,
+                    is_collapsed_entry: false,
+                },
+            );
+        }
+    }
+
+    // Now clean up any spare entries that weren't visited, to avoid clutter:
+    complete_pid_set.iter().for_each(|pid| {
+        existing_converted_process_data.remove(pid);
+    })
 }
 
 const BRANCH_ENDING: char = '└';
@@ -483,32 +551,36 @@ const BRANCH_SPLIT: char = '├';
 const BRANCH_HORIZONTAL: char = '─';
 
 pub fn tree_process_data(
-    single_process_data: &[ConvertedProcessData], is_using_command: bool,
-    sort_type: &ProcessSorting, is_sort_descending: bool,
+    filtered_process_data: &[ConvertedProcessData], is_using_command: bool,
+    sorting_type: &ProcessSorting, is_sort_descending: bool,
 ) -> Vec<ConvertedProcessData> {
-    // FIXME: [TREE] Allow for collapsing entries.
     // TODO: [TREE] Option to sort usage by total branch usage or individual value usage?
 
     // Let's first build up a (really terrible) parent -> child mapping...
     // At the same time, let's make a mapping of PID -> process data!
     let mut parent_child_mapping: HashMap<Pid, IndexSet<Pid>> = HashMap::default();
-    let mut pid_process_mapping: HashMap<Pid, &ConvertedProcessData> = HashMap::default();
+    let mut pid_process_mapping: HashMap<Pid, &ConvertedProcessData> = HashMap::default(); // We actually already have this stored, but it's unfiltered... oh well.
     let mut orphan_set: IndexSet<Pid> = IndexSet::new();
+    let mut collapsed_set: IndexSet<Pid> = IndexSet::new();
 
-    single_process_data.iter().for_each(|process| {
+    filtered_process_data.iter().for_each(|process| {
         if let Some(ppid) = process.ppid {
             orphan_set.insert(ppid);
         }
         orphan_set.insert(process.pid);
     });
 
-    single_process_data.iter().for_each(|process| {
+    filtered_process_data.iter().for_each(|process| {
         // Create a mapping for the process if it DNE.
         parent_child_mapping
             .entry(process.pid)
             .or_insert_with(IndexSet::new);
         pid_process_mapping.insert(process.pid, process);
 
+        if process.is_collapsed_entry {
+            collapsed_set.insert(process.pid);
+        }
+
         // Insert its mapping to the process' parent if needed (create if it DNE).
         if let Some(ppid) = process.ppid {
             orphan_set.remove(&process.pid);
@@ -521,8 +593,8 @@ pub fn tree_process_data(
 
     // Keep only orphans, or promote children o