Add help overlay with keyboard shortcuts (h/F1/?)

Full-screen popup showing all keybindings grouped by category:
navigation, sorting, process management, and general controls.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

systats.py

@@ -437,6 +437,37 @@ C_POPUP_BG = 12
 C_POPUP_HL = 13
 
 
+HELP_LINES = [
+    ("NAVIGATION", ""),
+    ("j / Down", "Move cursor down"),
+    ("k / Up", "Move cursor up"),
+    ("PgDn", "Scroll down 20"),
+    ("PgUp", "Scroll up 20"),
+    ("Home", "Go to top"),
+    ("End", "Go to bottom"),
+    ("", ""),
+    ("SORTING", ""),
+    ("c", "Sort by CPU%"),
+    ("m", "Sort by MEM%"),
+    ("p", "Sort by PID"),
+    ("n", "Sort by name"),
+    ("r", "Reverse sort order"),
+    ("", ""),
+    ("PROCESS MGMT", ""),
+    ("T", "Send SIGTERM to process"),
+    ("K", "Send SIGKILL to process"),
+    ("F9", "Signal menu (choose signal)"),
+    ("+ / F8", "Renice process"),
+    ("- / F7", "Renice process (negative)"),
+    ("d / F5 / Enter", "Process details"),
+    ("/ / f", "Filter processes"),
+    ("", ""),
+    ("GENERAL", ""),
+    ("h / F1 / ?", "Toggle this help"),
+    ("q / Q / Esc", "Quit"),
+]
+
+
 class ProcessManager:
     """Interactive process management: kill, nice, filter, details."""
 
@@ -586,6 +617,7 @@ class Renderer:
         self.data = data
         self.scroll_offset = 0
         self.proc_mgr = ProcessManager()
+        self.show_help = False
 
     def draw(self):
         self.scr.erase()
@@ -623,6 +655,10 @@ class Renderer:
         # Processes (rest of screen)
         self._draw_processes(y, 0, w, h - y)
 
+        # Help overlay
+        if self.show_help:
+            self._draw_help(h, w)
+
         self.scr.refresh()
 
     def _draw_header(self, y, w):
@@ -1029,6 +1065,41 @@ class Renderer:
                    " Enter:apply  Esc:cancel ".center(popup_w),
                    curses.color_pair(C_POPUP_BG) | curses.A_DIM)
 
+    def _draw_help(self, h, w):
+        popup_w = min(w - 4, 52)
+        popup_h = min(h - 2, len(HELP_LINES) + 4)
+        mx = (w - popup_w) // 2
+        my = (h - popup_h) // 2
+
+        # Background
+        for row in range(popup_h):
+            safe_addstr(self.scr, my + row, mx, " " * popup_w, curses.color_pair(C_POPUP_BG))
+
+        # Title
+        title = " SYSTATS - Keyboard Shortcuts "
+        safe_addstr(self.scr, my, mx, title.center(popup_w),
+                   curses.color_pair(C_POPUP_HL) | curses.A_BOLD)
+        safe_addstr(self.scr, my + 1, mx, "\u2500" * popup_w, curses.color_pair(C_POPUP_BG))
+
+        for i, (key, desc) in enumerate(HELP_LINES):
+            row_y = my + 2 + i
+            if row_y >= my + popup_h - 1:
+                break
+            if not key and not desc:
+                continue
+            if not desc:
+                # Section header
+                safe_addstr(self.scr, row_y, mx + 2, key,
+                           curses.color_pair(C_POPUP_HL) | curses.A_BOLD)
+            else:
+                line = f"  {key:<20s} {desc}"
+                safe_addstr(self.scr, row_y, mx, line[:popup_w].ljust(popup_w),
+                           curses.color_pair(C_POPUP_BG))
+
+        safe_addstr(self.scr, my + popup_h - 1, mx,
+                   " Press h, F1 or ? to close ".center(popup_w),
+                   curses.color_pair(C_POPUP_BG) | curses.A_DIM)
+
     def _draw_filter_bar(self, y, x, w):
         pm = self.proc_mgr
         bar = f" Filter: {pm.filter_text}_ "
@@ -1060,6 +1131,12 @@ def main(stdscr):
         processes = pm.filtered_processes(data.processes)
         max_idx = max(0, len(processes) - 1)
 
+        # ── Help overlay ──
+        if renderer.show_help:
+            if key in (ord("h"), ord("?"), curses.KEY_F1, 27):
+                renderer.show_help = False
+            continue
+
         # ── Filter mode input ──
         if pm.filter_mode:
             if key == 27:  # ESC
@@ -1122,6 +1199,8 @@ def main(stdscr):
             break
         elif key == 27:  # ESC
             break
+        elif key in (ord("h"), ord("?"), curses.KEY_F1):
+            renderer.show_help = True
         elif key == ord("c"):
             data.process_sort = "cpu"
             data.process_sort_reverse = True