Implement a grace period (3000ms) for process selection in which the …

…list is not reordered

src/metrics.rs

@@ -676,9 +676,8 @@ impl CPUTimeApp {
         }
     }
 
-    fn update_process_list(&mut self) {
+    fn update_process_list(&mut self, keep_order: bool) {
         debug!("Updating Process List");
-        self.processes.clear();
         let process_list = self.system.get_process_list();
         let mut current_pids: HashSet<i32> = HashSet::with_capacity(process_list.len());
         let mut top_pid: Option<i32> = None;
@@ -770,10 +769,15 @@ impl CPUTimeApp {
                 }
                 self.process_map.insert(zprocess.pid, zprocess);
             }
-            self.processes.push(*pid);
             current_pids.insert(*pid);
         }
 
+        if keep_order {
+            self.processes.retain(|pid| current_pids.contains(pid));
+        } else {
+            self.processes = current_pids.iter().cloned().collect();
+        }
+
         // remove pids that are gone
         self.process_map.retain(|&k, _| current_pids.contains(&k));
 
@@ -818,7 +822,9 @@ impl CPUTimeApp {
             }
         }
 
-        self.sort_process_table();
+        if !keep_order {
+            self.sort_process_table();
+        }
     }
 
     pub fn sort_process_table(&mut self) {
@@ -968,7 +974,7 @@ impl CPUTimeApp {
             .add_value_to("cpu_usage_histogram", self.cpu_utilization);
     }
 
-    pub async fn update(&mut self, width: u16) {
+    pub async fn update(&mut self, width: u16, keep_order: bool) {
         debug!("Updating Metrics");
         self.system.refresh_all();
         self.update_cpu().await;
@@ -994,7 +1000,7 @@ impl CPUTimeApp {
         self.net_out = net.get_outcome();
         self.histogram_map.add_value_to("net_in", self.net_in);
         self.histogram_map.add_value_to("net_out", self.net_out);
-        self.update_process_list();
+        self.update_process_list(keep_order);
         self.update_frequency().await;
         self.update_disk(width);
         self.get_platform().await;

src/render.rs

@@ -16,7 +16,7 @@ use std::borrow::Cow;
 use std::io;
 use std::io::Stdout;
 use std::path::PathBuf;
-use std::time::{Duration, UNIX_EPOCH};
+use std::time::{Duration, Instant, UNIX_EPOCH};
 use sysinfo::DiskExt;
 use termion::event::Key;
 use termion::input::MouseTerminal;
@@ -33,6 +33,8 @@ use tui::widgets::{
 use tui::Frame;
 use tui::Terminal;
 
+const PROCESS_SELECTION_GRACE: Duration = Duration::from_millis(2000);
+
 type ZBackend = TermionBackend<AlternateScreen<MouseTerminal<RawTerminal<Stdout>>>>;
 
 macro_rules! float_to_byte_string {
@@ -1259,6 +1261,7 @@ pub struct TerminalRenderer {
     show_find: bool,
     filter: String,
     highlighted_row: usize,
+    selection_grace_start: Option<Instant>,
 }
 
 impl<'a> TerminalRenderer {
@@ -1322,6 +1325,7 @@ impl<'a> TerminalRenderer {
             show_find: false,
             filter: String::from(""),
             highlighted_row: 0,
+            selection_grace_start: None,
         }
     }
 
@@ -1471,7 +1475,16 @@ impl<'a> TerminalRenderer {
             Event::Input(input) => input,
             Event::Tick => {
                 debug!("Event Tick");
-                self.app.update(width).await;
+
+                if let Some(start) = self.selection_grace_start {
+                    if start.elapsed() > PROCESS_SELECTION_GRACE {
+                        self.selection_grace_start = None;
+                    }
+                }
+
+                self.app
+                    .update(width, self.selection_grace_start.is_some())
+                    .await;
                 self.update_number += 1;
                 if self.update_number == self.zoom_factor {
                     self.update_number = 0;
@@ -1514,6 +1527,7 @@ impl<'a> TerminalRenderer {
             (_, Key::Up) => {
                 if self.app.selected_process.is_some() {
                 } else if !process_table.is_empty() {
+                    self.selection_grace_start = Some(Instant::now());
                     if self.highlighted_row != 0 {
                         self.highlighted_row -= 1;
                     }
@@ -1527,6 +1541,7 @@ impl<'a> TerminalRenderer {
             (_, Key::Down) => {
                 if self.app.selected_process.is_some() {
                 } else if !process_table.is_empty() {
+                    self.selection_grace_start = Some(Instant::now());
                     if self.highlighted_row < process_table.len() - 1 {
                         self.highlighted_row += 1;
                     }