ARCHITECTURE.md

@@ -1488,6 +1488,8 @@ type Terminal interface {
     ReadChar() (byte, bool)   // event loop → C char codes (arrows→hjkl, ^C→quit);
                               // ok is false when Interrupt woke the read
     Interrupt()               // wake a blocked ReadChar (signal goroutine only)
+    Repaint()                 // forced full redraw for CTRL-R
+                              // (curses clearok(curscr,TRUE)+wrefresh(curscr))
     Fini()                    // restore the device (curses endwin) on exit
 }
 
@@ -1507,16 +1509,25 @@ func (w *Window) Printwf(format string, a ...any); func (w *Window) Inch(y, x in
 func (w *Window) Clear(); func (w *Window) Clrtoeol(); func (w *Window) Standout(on bool)
 func (s *Screen) Refresh()                  // blit stdscr to the device
 func (s *Screen) RefreshWin(w *Window)      // blit any window
+func (s *Screen) Repaint()                  // force a full redraw of the device
 func (s *Screen) Fini()                     // tear the device down
 ```
 
 Ported drawing code keeps its structure: `mvaddch(y, x, ch)` →
 `g.scr.Std.MvAddCh(y, x, ch)`. Curses `mvinch` reads come from the Window
 buffer, preserving the "screen is a data structure" idiom without touching the
-real terminal. `md_readchar`'s escape decoding is deleted; tcell's `EventKey`
+real terminal. `Repaint` is the one drawing call that is not a blit: it is the
-provides decoded keys and we translate to the byte codes `command()` already
+`CTRL('R')` command's `clearok(curscr, TRUE)` plus `wrefresh(curscr)`,
-handles (KeyUp → 'k', etc.). Resize is handled by tcell, which registers only
+implemented as tcell's `Screen.Sync`, and it exists because `Render` cannot do
-SIGWINCH — SIGTSTP is not among the signals it takes, and is dropped (§9).
+its job. Both diff a new frame against the device's record of the old one and
+send nothing where they agree, which is the wrong answer precisely when the
+screen has been corrupted by something else's output — the only reason a player
+types `CTRL('R')`. Like C's, it repaints what was last drawn rather than
+re-blitting `stdscr`, so it takes no window. `md_readchar`'s escape decoding is
+deleted; tcell's `EventKey` provides decoded keys and we translate to the byte
+codes `command()` already handles (KeyUp → 'k', etc.). Resize is handled by
+tcell, which registers only SIGWINCH — SIGTSTP is not among the signals it
+takes, and is dropped (§9).
 
 Signals are handled in `cmd/rogue/main.go`: one `os/signal` channel read by one
 goroutine that reads exactly one signal, so a second signal can never call

TODO.md

@@ -34,6 +34,62 @@ wizard commands).
 
 # Completed Steps
 
+- 2026-08-09 Three small lost C behaviors (`fix/lost-c-behaviors`, closes #13):
+  grouped because each is a few lines and all are "restore something the port
+  dropped silently". (1) **"what a bizarre schtick!"**, `sticks.c` 237 — the
+  `otherwise` arm that closes `do_zap`'s switch, which `doZap` had turned into
+  doing nothing at all. Two things about it are easy to get wrong and are why
+  the fix is not one line. It is under `#ifdef MASTER`, **not** under a `wizard`
+  test, so in the MASTER build this port is it printed for every player — gating
+  it on `g.Wizard` would be issue #11's trap in reverse. And `WS_NOP` is a case
+  of that switch in its own right (`when WS_NOP: break;`), so "no handler ran"
+  cannot be the trigger: the wand of nothing does nothing _quietly_, and only a
+  kind C had no case for is bizarre. Since C's switch covers all 14 `WS_`
+  values, its `otherwise` is reachable only for an `o_which` outside the table,
+  which is exactly what `Object.hasValidWhich` already screens for — so the
+  split needed no new state, just a three-way switch on handler / valid-Which /
+  neither. All three arms fall through to `obj.Charges--`, as C's do: even the
+  bizarre schtick costs a charge. Replaces the deferral comment PR #20 left
+  there. (2) **`CTRL('R')` now actually redraws.** C is
+  `after = FALSE; clearok(curscr, TRUE); wrefresh(curscr);` (`command.c`
+  288-291); the port called `g.refresh()`, the ordinary diffing blit, **which
+  cannot fix the only situation the command exists for** — a screen corrupted by
+  something else's output leaves the game's record of it still correct, so the
+  diff sends nothing and the corruption stays. New `Terminal.Repaint` (tcell
+  `Screen.Sync`, which discards tcell's record of the terminal instead of
+  diffing against it), `Screen.Repaint`, `g.repaint()`; three implementations to
+  update, the same shape as PR #26's `ReadChar` change, so no split was needed.
+  Named for the curses operation, not for tcell: the interface is the game's
+  abstraction. It repaints what was last rendered — C repainted `curscr`, not
+  `stdscr` — so it takes no window, and the arm drops the `refresh()` C never
+  had there (`command` refreshes before the next key read anyway). (3) **The
+  startup greeting**, `main.c` 107-113, which existed nowhere in the tree. New
+  `game.Greeting`, printed by `cmd/rogue/main.go` before `term.New()` — the
+  port's `initscr()`. Only the wizard wording is `#ifdef MASTER`; the other is
+  unconditional. The `%d` is `dnum`, which `main.c` has just assigned to `seed`,
+  so it is `Params.Seed`. Two placement details the issue did not mention and
+  the tests now pin: the printf sits **after** `parse_opts`, so a ROGUEOPTS
+  `name=` is what the player is greeted by and the account name is only the
+  fallback (`Greeting` re-runs `ParseOpts`, which does nothing but assign into
+  fields — no RNG, no screen); and it sits after the `-s`/`-d` handling and
+  after `restore()`, which never returns, so a resumed game does not announce
+  that a dungeon is being dug (`digsNewDungeon`). The game `Greeting` parses
+  into is a throwaway but is built the way `New` builds the real one, tables and
+  home directory included, because `ParseOpts` handles every option and not just
+  the one the greeting reads: `inven=` is matched against `inv_t_name[]`, which
+  lives on the game, so a bare `&RogueGame{}` turned a legal `ROGUEOPTS` into a
+  nil dereference before the player saw a character. No RNG call is added on any
+  path and nothing under `game/testdata/` moved; `TestSeedCompatItemTables` is
+  green against the untouched golden. Mutation-proved, each new behaviour
+  deleted in turn and only its own test failing: dropping the message arm fails
+  `TestZapUnhandledWandSaysBizarreSchtick`; extending it to `WandNothing` fails
+  `TestZapWandOfNothingIsSilent`; putting `g.refresh()` back fails
+  `TestRedrawCommandForcesFullRepaint`; swapping the two wordings, or the
+  ROGUEOPTS name for the account name, fails `TestGreeting`; greeting on the
+  restore path fails `TestDigsNewDungeon`. ARCHITECTURE.md §5.3 gains `Repaint`
+  and the paragraph on why a blit cannot substitute for it. `Next Step`
+  deliberately not rotated: out-of-band issue work.
+
 - 2026-08-09 The `'+'` wizard-mode toggle (`fix/wizard-toggle-off`, closes #11):
   C's `command.c` 317-338 has a `when '+'` arm that leaves wizard mode —
   `wizard = FALSE`, `turn_see(TRUE)`, `msg("not wizard any more")` — and the

cmd/rogue/main.go

@@ -40,6 +40,15 @@ func run() int {
 		return 0
 	}
 
+	// C printed its greeting just before initscr(); here that means just
+	// before the tcell screen takes the terminal, and on stdout, exactly
+	// as C did (main.c main). C followed the printf with fflush because
+	// its stdout was buffered; os.Stdout is not, so the write is the
+	// flush.
+	if digsNewDungeon(*deathDemo, flag.Args()) {
+		_, _ = fmt.Fprint(os.Stdout, game.Greeting(params)) // CLI output
+	}
+
 	t, err := term.New()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
@@ -87,6 +96,23 @@ func run() int {
 	return 0
 }
 
+// digsNewDungeon reports whether this invocation is the one that digs a
+// fresh dungeon, and so the only one that greets.
+//
+// C's printf is the last statement before initscr(), and everything that
+// does something else has already left by then: -s scores and exits, -d
+// runs the death demo and exits, and restore() — the argc == 2 case that
+// is neither — never returns. So a saved game resumes without a greeting,
+// which is right: nothing is being dug.
+//
+// The restore test is duplicated from run's own, deliberately. Keeping
+// them as one predicate would mean deciding the startup path before the
+// terminal exists and carrying it past the error returns, which is more
+// rearrangement of run than a greeting is worth.
+func digsNewDungeon(deathDemo bool, args []string) bool {
+	return !deathDemo && len(args) != 1
+}
+
 // loadParams gathers the game parameters from the environment: home
 // directory, ROGUEOPTS, user name, wizard mode, and the dungeon seed
 // (main.c's startup).

cmd/rogue/main_test.go

@@ -380,3 +380,40 @@ func (s *stuckSaver) AutoSaveOnSignal(time.Duration) bool {
 
 	return true
 }
+
+// TestDigsNewDungeon pins which invocations reach C's greeting. In main.c
+// the printf is the last statement before initscr(), so -s and -d, which
+// exit earlier, never see it, and neither does a restored game, because
+// restore() does not return. The saved-game case is the one worth having
+// a test for: resuming a dungeon must not announce that one is being dug.
+func TestDigsNewDungeon(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name      string
+		deathDemo bool
+		args      []string
+		want      bool
+	}{
+		{name: "new game", args: nil, want: true},
+		{name: "restore a save", args: []string{"rogue.save"}, want: false},
+		{name: "death demo", deathDemo: true, want: false},
+		{
+			name:      "death demo wins over a save argument",
+			deathDemo: true,
+			args:      []string{"rogue.save"},
+			want:      false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			if got := digsNewDungeon(tc.deathDemo, tc.args); got != tc.want {
+				t.Errorf("digsNewDungeon(%v, %v) = %v, want %v",
+					tc.deathDemo, tc.args, got, tc.want)
+			}
+		})
+	}
+}

game/autosave_test.go

@@ -457,6 +457,10 @@ func newBlockingTerm() *blockingTerm {
 
 func (t *blockingTerm) Render(*Window) {}
 
+// Repaint has nothing to redraw: this terminal exists for its input
+// behaviour, and no autosave test types CTRL-R.
+func (t *blockingTerm) Repaint() {}
+
 func (t *blockingTerm) Fini() {}
 
 // Interrupt wakes a blocked ReadChar; called from the saving goroutine.

game/command_test.go

@@ -0,0 +1,37 @@
+//nolint:testpackage // white-box tests reach unexported state (approved 2026-07-07)
+package game
+
+import "testing"
+
+// TestRedrawCommandForcesFullRepaint pins CTRL-R to a forced repaint
+// rather than an ordinary refresh. C's arm is "after = FALSE;
+// clearok(curscr, TRUE); wrefresh(curscr);" (command.c), and the
+// clearok is the command: a diffing refresh compares the new frame
+// against the device's record of the old one and sends nothing when they
+// agree, which is exactly the situation after some other program has
+// scribbled on the terminal. Only the terminal can tell the difference,
+// so the test watches the terminal rather than the window contents.
+func TestRedrawCommandForcesFullRepaint(t *testing.T) {
+	t.Parallel()
+
+	g := mkGameInput(t)
+
+	term, ok := g.scr.term.(*testTerm)
+	if !ok {
+		t.Fatal("game terminal is not a testTerm")
+	}
+
+	before := term.repaints
+	g.After = true
+
+	g.dispatch(CTRL('R'))
+
+	if term.repaints != before+1 {
+		t.Errorf("terminal repainted %d times, want %d: CTRL-R did not force "+
+			"a full redraw", term.repaints-before, 1)
+	}
+
+	if g.After {
+		t.Error("CTRL-R consumed a turn; C sets after = FALSE")
+	}
+}

game/effects_test.go

@@ -194,6 +194,74 @@ func TestZapSlowMonster(t *testing.T) {
 	}
 }
 
+// bizarreSchtick is C's message for a zap that matched no case at all
+// (sticks.c do_zap, the "otherwise" arm). Shared by the pair of tests
+// below so that the one asserting it appears and the one asserting it
+// does not can never drift apart.
+const bizarreSchtick = "what a bizarre schtick!"
+
+// TestZapUnhandledWandSaysBizarreSchtick pins the closing arm of C's zap
+// switch. Every WS_ kind has a case, so the arm is reachable only for an
+// o_which outside the table — here a wand one past the end, the state a
+// corrupt save file can still describe. C's message is not gated on the
+// wizard flag, only on the MASTER build this port is, so no test setup
+// turns it on.
+func TestZapUnhandledWandSaysBizarreSchtick(t *testing.T) {
+	t.Parallel()
+
+	g := mkGameInput(t)
+	wand := malformed(KindWand)
+	wand.Charges = 3
+	ch := give(g, wand)
+
+	setInput(t, g, ch)
+	g.Msgs.Huh = ""
+
+	g.doZap()
+
+	if g.Msgs.Huh != bizarreSchtick {
+		t.Errorf("message = %q, want %q", g.Msgs.Huh, bizarreSchtick)
+	}
+
+	// C falls out of the switch into o_charges-- from the otherwise arm
+	// as much as from any other.
+	if wand.Charges != 2 {
+		t.Errorf("charges = %d after zapping, want 2", wand.Charges)
+	}
+}
+
+// TestZapWandOfNothingIsSilent is the other half, and the reason the
+// message cannot simply be attached to "no handler ran". WS_NOP is a case
+// of C's switch in its own right — "when WS_NOP: break;" — so the wand
+// that does nothing does it quietly, and only a kind C had no case for
+// is bizarre.
+func TestZapWandOfNothingIsSilent(t *testing.T) {
+	t.Parallel()
+
+	g := mkGameInput(t)
+	stick := newObject()
+	stick.Kind = KindWand
+	stick.Which = int(WandNothing)
+	g.fixStick(stick)
+	ch := give(g, stick)
+
+	setInput(t, g, ch)
+
+	charges := stick.Charges
+	g.Msgs.Huh = ""
+
+	g.doZap()
+
+	if g.Msgs.Huh == bizarreSchtick {
+		t.Errorf("the wand of nothing said %q; WS_NOP is a case of C's "+
+			"switch, not an unhandled kind", bizarreSchtick)
+	}
+
+	if stick.Charges != charges-1 {
+		t.Error("zap did not use a charge")
+	}
+}
+
 func TestParseOpts(t *testing.T) {
 	t.Parallel()
 

game/game.go

@@ -1,6 +1,8 @@
 //nolint:mnd // C-faithful literals; names hurt C-greppability (approved 2026-07-07)
 package game
 
+import "fmt"
+
 // ItemLore is the per-game item identity state: the randomized appearance
 // names and the seven mutable ObjInfo tables (extern.c/init.c).
 type ItemLore struct {
@@ -151,6 +153,54 @@ type RogueGame struct {
 	data *gameData
 }
 
+// Greeting is the line C printed on stdout while the player waited for
+// the dungeon to be dug, immediately before initscr() (main.c main). The
+// caller prints it before the terminal package takes the screen, which is
+// where initscr() sat; there is no trailing newline in either wording,
+// because C followed the printf with fflush and let curses have the
+// display.
+//
+// Only the wizard wording is #ifdef MASTER in C, and it carries the
+// dungeon number, which is the seed (main.c assigns seed = dnum right
+// after choosing dnum). The other wording is unconditional.
+//
+// The name is C's whoami, resolved the way main.c resolves it: parse_opts
+// runs before the printf, so a ROGUEOPTS "name=" setting is what the
+// player is greeted by, and the account name is only the fallback. New
+// does the same parse a moment later; doing it here too is safe because
+// ParseOpts does nothing but assign into the fields it is handed — no
+// RNG, no screen — so it cannot disturb the item tables the seed-compat
+// golden pins.
+//
+// The game it parses into is a throwaway, but it is built the way New
+// builds the real one, because ParseOpts handles every option and not
+// just the one this function reads: "inven=" is matched against the
+// inv_t_name[] table and "file=~/..." against the home directory, both
+// of which live on the game. A greeting that skimped on them faulted on
+// a perfectly legal ROGUEOPTS before the player saw a single character.
+func Greeting(params Params) string {
+	whoami := params.Name
+
+	if params.RogueOpts != "" {
+		opts := &RogueGame{
+			data:   newGameData(),
+			Whoami: params.Name,
+			Home:   params.Home,
+		}
+		opts.ParseOpts(params.RogueOpts)
+
+		whoami = opts.Whoami
+	}
+
+	if params.Wizard {
+		return fmt.Sprintf("Hello %s, welcome to dungeon #%d",
+			whoami, params.Seed)
+	}
+
+	return fmt.Sprintf(
+		"Hello %s, just a moment while I dig the dungeon...", whoami)
+}
+
 // New builds a game from params, seeds the RNG, and randomizes the item
 // appearance tables (the front half of main.c main(); the player roll-up
 // and first level arrive with later porting phases).

game/greeting_test.go

@@ -0,0 +1,80 @@
+//nolint:testpackage // white-box tests reach unexported state (approved 2026-07-07)
+package game
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestGreeting pins both wordings of main.c's pre-initscr printf byte for
+// byte. The wizard one carries dnum, which main.c has just assigned to
+// seed, so it is the seed the player sees. Neither ends in a newline: C
+// printed, flushed, and handed the display to curses.
+func TestGreeting(t *testing.T) {
+	t.Parallel()
+
+	// The account name main.c copies into whoami when ROGUEOPTS does not
+	// name the player itself.
+	const account = "conan"
+
+	cases := []struct {
+		name   string
+		params Params
+		want   string
+	}{
+		{
+			name:   "normal",
+			params: Params{Name: account, Seed: 4242},
+			want:   "Hello conan, just a moment while I dig the dungeon...",
+		},
+		{
+			name:   "wizard names the dungeon",
+			params: Params{Name: account, Seed: 4242, Wizard: true},
+			want:   "Hello conan, welcome to dungeon #4242",
+		},
+		{
+			// parse_opts runs before the printf in main.c, and whoami
+			// falls back to the account name only when ROGUEOPTS left it
+			// empty, so the option is what the player is greeted by.
+			name: "ROGUEOPTS name wins over the account name",
+			params: Params{
+				Name: account, Seed: 7, RogueOpts: "name=Rodney",
+			},
+			want: "Hello Rodney, just a moment while I dig the dungeon...",
+		},
+		{
+			name: "ROGUEOPTS without a name keeps the account name",
+			params: Params{
+				Name: account, Seed: 7, RogueOpts: "terse,fruit=mango",
+			},
+			want: "Hello conan, just a moment while I dig the dungeon...",
+		},
+		{
+			// ParseOpts reaches every option, not just name=, and the
+			// inventory style is matched against a table (options.c
+			// parse_opts, inv_t_name[]) that lives in the game data. A
+			// greeting parsed on a game without those tables faulted on
+			// this ROGUEOPTS before it could print anything at all.
+			name: "ROGUEOPTS inventory style parses without a fault",
+			params: Params{
+				Name: account, Seed: 7, RogueOpts: "inven=slow,name=Rodney",
+			},
+			want: "Hello Rodney, just a moment while I dig the dungeon...",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := Greeting(tc.params)
+			if got != tc.want {
+				t.Errorf("Greeting() = %q, want %q", got, tc.want)
+			}
+
+			if strings.HasSuffix(got, "\n") {
+				t.Error("greeting ends in a newline; C's printf did not")
+			}
+		})
+	}
+}

game/screen.go

@@ -23,6 +23,15 @@ type Terminal interface {
 	// the one Terminal method called from another goroutine, so an
 	// implementation must be safe to call concurrently with ReadChar.
 	Interrupt()
+	// Repaint forces the device to redraw every cell it is showing, the
+	// redraw command's whole point (curses clearok(curscr, TRUE) followed
+	// by wrefresh(curscr)). Render cannot stand in for it: a device that
+	// diffs against its own idea of what is on screen will do nothing at
+	// all when the screen has been corrupted by something else's output,
+	// which is the case the player types CTRL-R for. It repaints what was
+	// last rendered — C repainted curscr, not stdscr — so it neither
+	// needs nor takes a window.
+	Repaint()
 	// Fini restores the device to its pre-game state (curses endwin). The
 	// game calls it on its way out, since one game run is one process.
 	Fini()
@@ -223,6 +232,14 @@ func (s *Screen) Refresh() {
 	}
 }
 
+// Repaint forces the device to redraw everything it is showing, if there
+// is a device (curses clearok(curscr, TRUE) + wrefresh(curscr)).
+func (s *Screen) Repaint() {
+	if s.term != nil {
+		s.term.Repaint()
+	}
+}
+
 // Fini restores the terminal device, if there is one (curses endwin).
 func (s *Screen) Fini() {
 	if s.term != nil {
@@ -263,3 +280,4 @@ func (g *RogueGame) standend()                 { g.scr.Std.Standout(false) }
 func (g *RogueGame) clear()                    { g.scr.Std.Clear() }
 func (g *RogueGame) clrtoeol()                 { g.scr.Std.Clrtoeol() }
 func (g *RogueGame) refresh()                  { g.scr.Refresh() }
+func (g *RogueGame) repaint()                  { g.scr.Repaint() }

game/sticks.go

@@ -31,14 +31,30 @@ func (g *RogueGame) doZap() {
 		return
 	}
 
-	// A malformed Which yields no handler, which is exactly what C did in a
+	// C's switch has a case for every one of the 14 WS_ kinds, so its
-	// non-MASTER build: its do_zap switch matched no case, fell out, and
+	// closing "otherwise: msg(...)" arm is reachable only for an o_which
-	// still ran o_charges--. (The MASTER-only "what a bizarre schtick!"
+	// outside the table — the malformed objects hasValidWhich screens
-	// message for that arm is issue #13, not this bounds fix.)
+	// for, which is why no handler and a legal Which can only mean WS_NOP.
-	if h := g.data.zapHandler(obj); h != nil {
+	//
+	// The message is under #ifdef MASTER, not under a wizard test: C
+	// printed it for every player of a MASTER build, which is the build
+	// this port is (see the '+' command, issue #11). Do not gate it on
+	// g.Wizard.
+	//
+	// WS_NOP is a case of its own ("when WS_NOP: break;"): the wand that
+	// deliberately does nothing says nothing either. All three arms fall
+	// out of the switch into o_charges--, so even the bizarre schtick
+	// costs a charge.
+	h := g.data.zapHandler(obj)
+
+	switch {
+	case h != nil:
 		if !h(g, obj) {
 			return // the zap aborted; no charge is used
 		}
+	case obj.hasValidWhich(): // WS_NOP
+	default:
+		g.msg("what a bizarre schtick!")
 	}
 
 	obj.Charges--

game/tables.go

@@ -785,7 +785,10 @@ func newGameData() *gameData {
 			},
 			CTRL('R'): func(g *RogueGame) {
 				g.After = false
-				g.refresh()
+				// C forces a full repaint here (clearok + wrefresh on
+				// curscr), not the diffing refresh: the command exists
+				// for screens the game's own record no longer matches.
+				g.repaint()
 			},
 			'v': func(g *RogueGame) {
 				g.After = false

game/term_test.go

@@ -8,10 +8,18 @@ type testTerm struct {
 	input []byte
 	pos   int
 	tick  int
+	// repaints counts forced full redraws. Rendering is a no-op here, so
+	// counting is the only way a headless test can tell that CTRL-R asked
+	// for a repaint rather than an ordinary refresh — the two are
+	// indistinguishable in the window contents, which is the whole reason
+	// the bug this replaces went unnoticed.
+	repaints int
 }
 
 func (t *testTerm) Render(*Window) {}
 
+func (t *testTerm) Repaint() { t.repaints++ }
+
 func (t *testTerm) Fini() {}
 
 // Interrupt has nothing to wake: this terminal's ReadChar never blocks.

game/wizard_test.go

@@ -187,8 +187,9 @@ func malformed(kind ObjectKind) *Object {
 }
 
 // TestZapMalformedWandDoesNotPanic covers the sticks.go dispatch. C's
-// non-MASTER do_zap matched no case and still ran o_charges--, so the
+// do_zap matched no case and still ran o_charges--, so the charge must be
-// charge must be spent even though nothing happens.
+// spent even though the zap did nothing. What it says while doing nothing
+// belongs to TestZapUnhandledWandSaysBizarreSchtick.
 func TestZapMalformedWandDoesNotPanic(t *testing.T) {
 	t.Parallel()
 

term/tcell.go

@@ -78,6 +78,16 @@ func (t *Tcell) Render(w *game.Window) {
 	t.screen.Show()
 }
 
+// Repaint redraws the whole physical screen from tcell's content buffer
+// — which holds what Render last blitted, so this is C's clearok(curscr,
+// TRUE) + wrefresh(curscr) (command.c, the CTRL('R') arm) rather than a
+// fresh draw of stdscr. Sync throws away tcell's record of what the
+// terminal is showing, so unlike Show it repaints cells it believes are
+// already correct, which is what makes it fix a corrupted screen.
+func (t *Tcell) Repaint() {
+	t.screen.Sync()
+}
+
 // ReadChar blocks for the next key, translated to the byte codes the C
 // game reads: arrows become hjkl, control keys their C0 codes. ok is
 // false when Interrupt woke the read instead of a key arriving.