reorg: pull Teliva-specific stuff out of lua.c

It should now be easier to diff against the Lua 5.1 sources upstream.

9 files changed, 1071 insertions, 1061 deletions

diff --git a/src/Makefile b/src/Makefile
index d9ef9b1..97dd248 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -26,9 +26,9 @@ LUA_A=	liblua.a
 CORE_O=	lapi.o lcode.o ldebug.o ldo.o ldump.o lfunc.o lgc.o llex.o lmem.o \
 	lobject.o lopcodes.o lparser.o lstate.o lstring.o ltable.o ltm.o  \
 	lundump.o lvm.o lzio.o \
-	kilo.o tlv.o
-LIB_O=	lauxlib.o lbaselib.o menu.o ldblib.o liolib.o lmathlib.o \
-	loslib.o ltablib.o lstrlib.o loadlib.o linit.o
+	kilo.o tlv.o teliva.o
+LIB_O=	lauxlib.o lbaselib.o ldblib.o liolib.o lmathlib.o loslib.o \
+	ltablib.o lstrlib.o loadlib.o linit.o
 
 LUA_T=	teliva
 LUA_O=	lua.o
diff --git a/src/kilo.c b/src/kilo.c
index 4a5bf52..5eef4aa 100644
--- a/src/kilo.c
+++ b/src/kilo.c
@@ -656,15 +656,11 @@ writeerr:
 
 /* ============================= Terminal update ============================ */
 
-extern char *Previous_error;
-extern void draw_menu_item(const char* key, const char* name);
-
 static void editorMenu(void) {
     attrset(A_REVERSE);
     for (int x = 0; x < COLS; ++x)
       mvaddch(LINES-1, x, ' ');
     attrset(A_NORMAL);
-    extern int menu_column;
     menu_column = 2;
     draw_menu_item("^e", "run");
     if (Previous_error != NULL) {
@@ -695,13 +691,11 @@ static void editorMenu(void) {
     attrset(A_NORMAL);
 }
 
-extern void draw_string_on_menu (const char* s);
 static void editorFindMenu(void) {
     attrset(A_REVERSE);
     for (int x = 0; x < COLS; ++x)
       mvaddch(LINES-1, x, ' ');
     attrset(A_NORMAL);
-    extern int menu_column;
     menu_column = 2;
     draw_menu_item("^x", "cancel");
     draw_menu_item("Enter", "submit");
@@ -727,7 +721,6 @@ static void editorGoMenu(void) {
     for (int x = 0; x < COLS; ++x)
       mvaddch(LINES-1, x, ' ');
     attrset(A_NORMAL);
-    extern int menu_column;
     menu_column = 2;
     draw_menu_item("^x", "cancel");
     draw_menu_item("Enter", "submit");
@@ -736,7 +729,6 @@ static void editorGoMenu(void) {
     attrset(A_NORMAL);
 }
 
-extern int render_previous_error();
 static void editorRefreshScreen(void (*menu_func)(void)) {
     int y;
     erow *r;
@@ -1031,8 +1023,6 @@ void word_at_cursor(char* out, int capacity) {
 }
 
 /* Jump to some definition. */
-extern void save_to_current_definition_and_editor_buffer(lua_State *L, char *name);
-extern void load_editor_buffer_to_current_definition_in_image(lua_State *L);
 extern char Current_definition[];
 #define CURRENT_DEFINITION_LEN 256
 static void editorGo(lua_State* L) {
@@ -1078,7 +1068,6 @@ static void editorGo(lua_State* L) {
  * is typing stuff on the terminal. */
 static int Quit = 0;
 static int Back_to_big_picture = 0;
-extern void save_editor_state(int rowoff, int coloff, int cy, int cx);
 static void editorProcessKeypress(lua_State* L) {
     int c = getch();
 //?     mvprintw(LINES-3, 60, "key: %d\n", c);
diff --git a/src/lua.c b/src/lua.c
index 15c4f50..eedfb33 100644
--- a/src/lua.c
+++ b/src/lua.c
@@ -5,22 +5,16 @@
 */
 
 
-#include <assert.h>
-#include <ctype.h>
-#include <fcntl.h>
 #include <locale.h>
 #include <ncurses.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
-#include <unistd.h>
 
 #define lua_c
 
 #include "lua.h"
-//? #include "lstate.h"
 #include "teliva.h"
 
 #include "lauxlib.h"
@@ -77,62 +71,6 @@ static int report (lua_State *L, int status) {
 }
 
 
-/* return final y containing text */
-static int render_wrapped_text (int y, int xmin, int xmax, const char *text) {
-  int x = xmin;
-  move(y, x);
-  for (int j = 0; j < strlen(text); ++j) {
-    char c = text[j];
-    if (c != '\n') {
-      addch(text[j]);
-      ++x;
-      if (x >= xmax) {
-        ++y;
-        x = xmin;
-        move(y, x);
-      }
-    }
-    else {
-      /* newline */
-      ++y;
-      x = xmin;
-      move(y, x);
-    }
-  }
-  return y;
-}
-
-
-const char *Previous_error = NULL;
-void render_previous_error (void) {
-  if (!Previous_error) return;
-  init_pair(COLOR_PAIR_ERROR, COLOR_ERROR_FOREGROUND, COLOR_ERROR_BACKGROUND);
-  attron(COLOR_PAIR(COLOR_PAIR_ERROR));
-  render_wrapped_text(LINES-10, COLS/2, COLS, Previous_error);
-  attroff(COLOR_PAIR(COLOR_PAIR_ERROR));
-}
-
-
-extern char *strdup(const char *s);
-extern void developer_mode (lua_State *L);
-static int report_in_developer_mode (lua_State *L, int status) {
-  if (status && !lua_isnil(L, -1)) {
-    Previous_error = strdup(lua_tostring(L, -1));  /* memory leak */
-    if (Previous_error == NULL) Previous_error = "(error object is not a string)";
-    lua_pop(L, 1);
-    for (int x = 0; x < COLS; ++x) {
-      mvaddch(LINES-2, x, ' ');
-      mvaddch(LINES-1, x, ' ');
-    }
-    render_previous_error();
-    mvaddstr(LINES-1, 0, "press any key to continue");
-    getch();
-    developer_mode(L);
-  }
-  return status;
-}
-
-
 static int traceback (lua_State *L) {
   if (!lua_isstring(L, 1))  /* 'message' not a string? */
     return 1;  /* keep it intact */
@@ -153,7 +91,7 @@ static int traceback (lua_State *L) {
 }
 
 
-static int docall (lua_State *L, int narg, int clear) {
+int docall (lua_State *L, int narg, int clear) {
   int status;
   int base = lua_gettop(L) - narg;  /* function index */
   lua_pushcfunction(L, traceback);  /* push traceback function */
@@ -169,7 +107,7 @@ static int docall (lua_State *L, int narg, int clear) {
 
 
 /* initialize global binding "args" for commandline args */
-static void set_args (lua_State *L, char **argv, int n) {
+void set_args (lua_State *L, char **argv, int n) {
   int narg;
   int i;
   int argc = 0;
@@ -191,7 +129,7 @@ static int dofile (lua_State *L, const char *name) {
 }
 
 
-static int dostring (lua_State *L, const char *s, const char *name) {
+int dostring (lua_State *L, const char *s, const char *name) {
   int status = luaL_loadbuffer(L, s, strlen(s), name) || docall(L, 0, 1);
   return report_in_developer_mode(L, status);
 }
@@ -231,931 +169,6 @@ void stack_dump (lua_State *L) {
 }
 
 
-static int binding_exists (lua_State *L, const char *name) {
-  int result = 0;
-  lua_getglobal(L, name);
-  result = !lua_isnil(L, -1);
-  lua_pop(L, 1);
-  return result;
-}
-
-
-static const char *special_history_keys[] = {
-  "__teliva_timestamp",
-  "__teliva_undo",
-  "__teliva_note",
-  NULL,
-};
-
-int is_special_history_key(const char *key) {
-  for (const char **curr = special_history_keys; *curr != NULL; ++curr) {
-    if (strcmp(*curr, key) == 0)
-      return 1;
-  }
-  return 0;
-}
-
-
-/* when found, return 1 and leave string on top of stack
- * when not found, return 0
- * caller is responsible for cleaning up the stack. */
-static int look_up_definition (lua_State *L, const char *name) {
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  /* iterate over mutations in teliva_program history in reverse order */
-  int history_array_size = luaL_getn(L, history_array);
-  for (int i = history_array_size; i > 0; --i) {
-    lua_rawgeti(L, history_array, i);
-    int table = lua_gettop(L);
-    /* iterate over bindings */
-    /* really we expect only one */
-    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
-      const char* key = lua_tostring(L, -2);
-      if (strcmp(key, "__teliva_undo") == 0) {
-        int next_i = lua_tointeger(L, -1);
-        assert(next_i < i);
-        i = next_i + 1;  /* account for decrement */
-        lua_pop(L, 1);
-        break;
-      }
-      if (is_special_history_key(key)) continue;
-      if (strcmp(key, name) == 0)
-        return 1;
-    }
-    lua_pop(L, 1);
-  }
-  lua_pop(L, 1);
-  return 0;
-}
-
-
-int load_definitions(lua_State *L) {
-  int status;
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  /* iterate over mutations in teliva_program history in reverse order */
-  int history_array_size = luaL_getn(L, history_array);
-  for (int i = history_array_size; i > 0; --i) {
-    lua_rawgeti(L, history_array, i);
-    int table = lua_gettop(L);
-    /* iterate over bindings */
-    /* really we expect only one */
-    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
-      const char* key = lua_tostring(L, -2);
-      if (strcmp(key, "__teliva_undo") == 0) {
-        int next_i = lua_tointeger(L, -1);
-        assert(next_i < i);
-        i = next_i + 1;  /* account for decrement */
-        lua_pop(L, 1);
-        break;
-      }
-      if (is_special_history_key(key)) continue;
-      if (binding_exists(L, key))
-        continue;  // most recent binding trumps older ones
-      const char* value = lua_tostring(L, -1);
-      status = dostring(L, value, key);
-      if (status != 0) return report_in_developer_mode(L, status);
-    }
-    lua_pop(L, 1);
-  }
-  lua_pop(L, 1);
-  return 0;
-}
-
-
-int run_tests(lua_State *L) {
-  clear();
-  lua_pushinteger(L, 0);
-  lua_setglobal(L, "teliva_num_test_failures");
-  lua_pushnil(L);
-  lua_setglobal(L, "teliva_first_failure");
-  lua_pushvalue(L, LUA_GLOBALSINDEX);
-  int table = lua_gettop(L);
-  for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
-    const char* key = lua_tostring(L, -2);
-    if (strncmp("test_", key, strlen("test_")) != 0) continue;
-    if (!lua_isfunction(L, -1)) continue;
-    int status = lua_pcall(L, 0, 0, 0);
-    if (status) {
-      printw("E%d: %s", status, lua_tostring(L, -1));
-      /* increment teliva_num_test_failures */
-      lua_getglobal(L, "teliva_num_test_failures");
-      int num_failures = lua_tointeger(L, -1);
-      lua_pop(L, 1);
-      lua_pushinteger(L, num_failures+1);
-      lua_setglobal(L, "teliva_num_test_failures");
-      /* if unset, set teliva_first_failure */
-      lua_getglobal(L, "teliva_first_failure");
-      int first_failure_clear = lua_isnil(L, -1);
-      lua_pop(L, 1);
-      if (first_failure_clear)
-        lua_setglobal(L, "teliva_first_failure");
-    }
-    lua_pushnil(L);  /* just to undo loop update */
-  }
-  lua_pop(L, 1);
-  lua_getglobal(L, "teliva_num_test_failures");
-  int num_failures = lua_tointeger(L, -1);
-  lua_pop(L, 1);
-  if (num_failures == 0) return 0;
-  if (num_failures == 1)
-    addstr("1 failure");
-  else
-    printw("%d failures", num_failures);
-  getch();
-  /* take first failure back to developer mode */
-  lua_getglobal(L, "teliva_first_failure");
-  assert(!lua_isnil(L, -1));
-  return 1;
-}
-
-
-void clear_call_graph(lua_State *L) {
-  int oldtop = lua_gettop(L);
-  luaL_newmetatable(L, "__teliva_call_graph_depth");
-  int cgt = lua_gettop(L);
-  lua_pushnil(L);
-  while (lua_next(L, cgt) != 0) {
-    lua_pop(L, 1);  /* old value */
-    lua_pushvalue(L, -1);  /* duplicate key */
-    lua_pushnil(L);  /* new value */
-    lua_settable(L, cgt);
-    /* one copy of key left for lua_next */
-  }
-  lua_pop(L, 1);
-  assert(lua_gettop(L) == oldtop);
-}
-
-
-char *Image_name = NULL;
-extern void load_tlv (lua_State *L, char *filename);
-static int handle_image (lua_State *L, char **argv, int n) {
-  int status;
-  set_args(L, argv, n);
-  /* parse and load file contents (teliva_program array) */
-  Image_name = argv[n];
-  load_tlv(L, Image_name);
-//?   save_tlv(L, Image_name);  // manual test; should always return identical result, modulo key order
-//?   exit(1);
-  status = load_definitions(L);
-  if (status != 0) return 0;
-  status = run_tests(L);
-  if (status != 0) return report_in_developer_mode(L, status);
-  /* clear callgraph stats from running tests */
-  clear_call_graph(L);
-  /* call main() */
-  lua_getglobal(L, "main");
-  status = docall(L, 0, 1);
-  if (status != 0) return report_in_developer_mode(L, status);
-  return 0;
-}
-
-
-#define CURRENT_DEFINITION_LEN 256
-char Current_definition[CURRENT_DEFINITION_LEN+1] = {0};
-
-extern int mkstemp(char *template);
-extern FILE *fdopen(int fd, const char *mode);
-void save_editor_state (int rowoff, int coloff, int cy, int cx) {
-  if (strlen(Current_definition) == 0) return;
-  char outfilename[] = "teliva_editor_state_XXXXXX";
-  int outfd = mkstemp(outfilename);
-  if (outfd == -1) {
-    endwin();
-    perror("error in creating temporary file");
-    abort();
-  }
-  FILE *out = fdopen(outfd, "w");
-  assert(out != NULL);
-  fprintf(out, "- image: %s\n", Image_name);
-  fprintf(out, "  definition: %s\n", Current_definition);
-  fprintf(out, "  rowoff: %d\n", rowoff);
-  fprintf(out, "  coloff: %d\n", coloff);
-  fprintf(out, "  cy: %d\n", cy);
-  fprintf(out, "  cx: %d\n", cx);
-  fclose(out);
-  rename(outfilename, "teliva_editor_state");
-}
-
-void save_to_current_definition_and_editor_buffer (lua_State *L, const char *definition) {
-  int oldtop = lua_gettop(L);
-  strncpy(Current_definition, definition, CURRENT_DEFINITION_LEN);
-  int status = look_up_definition(L, Current_definition);
-  char outfilename[] = "teliva_editor_buffer_XXXXXX";
-  int outfd = mkstemp(outfilename);
-  if (outfd == -1) {
-    endwin();
-    perror("save_to_current_definition_and_editor_buffer: error in creating temporary file");
-    abort();
-  }
-  FILE *out = fdopen(outfd, "w");
-  assert(out != NULL);
-  if (status)
-    fprintf(out, "%s", lua_tostring(L, -1));
-  fclose(out);
-  rename(outfilename, "teliva_editor_buffer");
-  lua_settop(L, oldtop);
-}
-
-
-/* I don't understand the best way to read all of a text file.
- * I'm currently using fread, but its error handling is really designed for
- * binary data containing fixed-size records. */
-static void read_editor_buffer (char *out, int capacity) {
-  FILE *in = fopen("teliva_editor_buffer", "r");
-  fread(out, capacity, 1, in);  /* TODO: handle overly large file */
-  fclose(in);
-}
-
-
-static void update_definition (lua_State *L, const char *name, char *new_contents) {
-  int oldtop = lua_gettop(L);
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  /* create a new table containing a single binding */
-  lua_createtable(L, /*number of fields per mutation*/2, 0);
-  lua_pushstring(L, new_contents);
-  assert(strlen(name) > 0);
-  lua_setfield(L, -2, name);
-  /* include timestamp at which binding was created */
-  time_t t;
-  time(&t);
-  char *time_string = ctime(&t);
-  lua_pushstring(L, time_string);
-  lua_setfield(L, -2, "__teliva_timestamp");
-  /* append the new table to the history of mutations */
-  int history_array_size = luaL_getn(L, history_array);
-  ++history_array_size;
-  lua_rawseti(L, history_array, history_array_size);
-  lua_settop(L, oldtop);
-}
-
-
-extern void save_tlv (lua_State *L, char *filename);
-int load_editor_buffer_to_current_definition_in_image(lua_State *L) {
-  char new_contents[8192] = {0};
-  read_editor_buffer(new_contents, 8190);
-  update_definition(L, Current_definition, new_contents);
-  save_tlv(L, Image_name);
-  /* reload binding */
-  return luaL_loadbuffer(L, new_contents, strlen(new_contents), Current_definition)
-      || docall(L, 0, 1);
-}
-
-
-/* return true if user chose to back into the big picture view */
-/* But only if there are no errors. Otherwise things can get confusing. */
-extern int edit (lua_State *L, char *filename);
-extern int resumeEdit (lua_State *L);
-int edit_current_definition (lua_State *L) {
-  int back_to_big_picture = edit(L, "teliva_editor_buffer");
-  // error handling
-  int oldtop = lua_gettop(L);
-  while (1) {
-    int status;
-    status = load_editor_buffer_to_current_definition_in_image(L);
-    if (status == 0 || lua_isnil(L, -1))
-      break;
-    Previous_error = lua_tostring(L, -1);
-    if (Previous_error == NULL) Previous_error = "(error object is not a string)";
-    back_to_big_picture = resumeEdit(L);
-    lua_pop(L, 1);
-  }
-  if (lua_gettop(L) != oldtop) {
-    endwin();
-    printf("edit_current_definition: memory leak %d -> %d\n", oldtop, lua_gettop(L));
-    exit(1);
-  }
-  return back_to_big_picture;
-}
-
-
-extern void draw_menu_item (const char* key, const char* name);
-extern void draw_string_on_menu (const char* s);
-static void recent_changes_menu (int cursor, int history_array_size) {
-  attrset(A_REVERSE);
-  for (int x = 0; x < COLS; ++x)
-    mvaddch(LINES-1, x, ' ');
-  attrset(A_NORMAL);
-  extern int menu_column;
-  menu_column = 2;
-  draw_menu_item("^x", "go back");
-  /* draw_menu_item("↓|space", "older"); */
-  attroff(A_REVERSE);
-  mvaddstr(LINES-1, menu_column, " ↓");
-  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("|");
-  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("space ");
-  menu_column += 9;  /* strlen isn't sufficient */
-  attron(A_REVERSE);
-  draw_string_on_menu("older");
-  /* draw_menu_item("↑|backspace|delete|^h", "newer"); */
-  attroff(A_REVERSE);
-  mvaddstr(LINES-1, menu_column, " ↑");
-  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("|");
-  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("backspace");
-  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("|");
-  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("delete");
-  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("|");
-  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
-  addstr("^h ");
-  menu_column += 23;
-  attron(A_REVERSE);
-  draw_string_on_menu("newer");
-  draw_menu_item("^e", "edit note");
-  if (cursor < history_array_size)
-    draw_menu_item("^u", "undo everything after this");
-  attrset(A_NORMAL);
-}
-
-
-/* return final y containing text */
-static int render_wrapped_lua_text (int y, int xmin, int xmax, const char *text) {
-  int x = xmin;
-  move(y, x);
-  for (int j = 0; j < strlen(text); ++j) {
-    char c = text[j];
-    if (c == '-' && j+1 < strlen(text) && text[j+1] == '-')
-      attron(COLOR_PAIR(COLOR_PAIR_LUA_COMMENT));
-    if (c != '\n') {
-      addch(text[j]);
-      ++x;
-      if (x >= xmax) {
-        ++y;
-        x = xmin;
-        move(y, x);
-      }
-    }
-    else {
-      /* newline */
-      ++y;
-      x = xmin;
-      move(y, x);
-      attroff(COLOR_PAIR(COLOR_PAIR_LUA_COMMENT));
-    }
-  }
-  return y;
-}
-
-
-void render_recent_changes (lua_State *L, int start_index) {
-  clear();
-  attrset(A_BOLD);
-  mvaddstr(1, 0, "Recent changes");
-  attrset(A_NORMAL);
-  int oldtop = lua_gettop(L);
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  int history_array_size = luaL_getn(L, history_array);
-  int y = 3;
-  attron(A_REVERSE);
-  for (int i = start_index; i > 0; --i) {
-    attron(A_BOLD);
-    mvprintw(y, 0, "%3d. ", i);
-    attrset(A_NORMAL);
-    lua_rawgeti(L, history_array, i);
-    int t = lua_gettop(L);
-    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
-      if (strcmp(lua_tostring(L, -2), "__teliva_undo") == 0) {
-        addstr("undo to ");
-        attron(A_BOLD);
-        printw("%d", lua_tointeger(L, -1));
-        attroff(A_BOLD);
-        y++;
-        continue;
-      }
-      const char *definition_name = lua_tostring(L, -2);
-      if (is_special_history_key(definition_name)) continue;
-      addstr(definition_name);
-      /* save timestamp of binding if available */
-      lua_getfield(L, t, "__teliva_timestamp");
-      if (!lua_isnil(L, -1)) {
-        char buffer[128] = {0};
-        strncpy(buffer, lua_tostring(L, -1), 120);
-        if (buffer[strlen(buffer)-1] == '\n')
-          buffer[strlen(buffer)-1] = '\0';
-        attron(COLOR_PAIR(COLOR_PAIR_FADE));
-        printw("  %s", buffer);
-        attroff(COLOR_PAIR(COLOR_PAIR_FADE));
-      }
-      lua_pop(L, 1);
-      lua_getfield(L, t, "__teliva_note");
-      if (!lua_isnil(L, -1)) {
-        attron(COLOR_PAIR(COLOR_PAIR_FADE));
-        printw("  -- %s", lua_tostring(L, -1));
-        attroff(COLOR_PAIR(COLOR_PAIR_FADE));
-      }
-      lua_pop(L, 1);
-      y++;
-      const char *definition_contents = lua_tostring(L, -1);
-      y = render_wrapped_lua_text(y, 0, COLS, definition_contents);
-      y++;
-      if (y >= LINES-1) break;  /* leave cruft on the stack */
-    }
-    lua_settop(L, t);  /* clean up cruft on the stack */
-    lua_pop(L, 1);  // history element
-    y++;
-    if (y >= LINES-1) break;
-  }
-  lua_pop(L, 1);  // history array
-  if (lua_gettop(L) != oldtop) {
-    endwin();
-    printf("render_recent_changes: memory leak %d -> %d\n", oldtop, lua_gettop(L));
-    exit(1);
-  }
-  recent_changes_menu(start_index, history_array_size);
-  refresh();
-}
-
-
-void add_undo_event(lua_State *L, int cursor) {
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  /* create a new table containing the undo event */
-  lua_createtable(L, /*number of fields per mutation*/2, 0);
-  lua_pushinteger(L, cursor);
-  lua_setfield(L, -2, "__teliva_undo");
-  /* include timestamp at which event was created */
-  time_t t;
-  time(&t);
-  char *time_string = ctime(&t);
-  lua_pushstring(L, time_string);
-  lua_setfield(L, -2, "__teliva_timestamp");
-  /* append the new table to the history of mutations */
-  int history_array_size = luaL_getn(L, history_array);
-  ++history_array_size;
-  lua_rawseti(L, history_array, history_array_size);
-  /* clean up */
-  lua_pop(L, 1);
-}
-
-
-void save_note_to_editor_buffer (lua_State *L, int cursor) {
-  lua_getglobal(L, "teliva_program");
-  lua_rawgeti(L, -1, cursor);
-  lua_getfield(L, -1, "__teliva_note");
-  const char *contents = lua_tostring(L, -1);
-  char outfilename[] = "teliva_editor_buffer_XXXXXX";
-  int outfd = mkstemp(outfilename);
-  if (outfd == -1) {
-    endwin();
-    perror("save_note_to_editor_buffer: error in creating temporary file");
-    abort();
-  }
-  FILE *out = fdopen(outfd, "w");
-  assert(out != NULL);
-  if (contents != NULL)
-    fprintf(out, "%s", contents);
-  fclose(out);
-  rename(outfilename, "teliva_editor_buffer");
-  lua_pop(L, 3);  /* contents, table at cursor, teliva_program */
-}
-
-
-void load_note_from_editor_buffer (lua_State *L, int cursor) {
-  lua_getglobal(L, "teliva_program");
-  char new_contents[8192] = {0};
-  read_editor_buffer(new_contents, 8190);
-  lua_rawgeti(L, -1, cursor);
-  lua_pushstring(L, new_contents);
-  lua_setfield(L, -2, "__teliva_note");
-  lua_pop(L, 2);  /* table at cursor, teliva_program */
-}
-
-
-void recent_changes_view (lua_State *L) {
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  assert(history_array == 1);
-  int history_array_size = luaL_getn(L, history_array);
-  int cursor = history_array_size;
-  lua_pop(L, 1);
-  int quit = 0;
-  while (!quit) {
-    /* refresh state after each operation so we pick up modifications */
-    render_recent_changes(L, cursor);
-    int c = getch();
-    switch (c) {
-      case CTRL_X:
-        quit = 1;
-        break;
-      case KEY_DOWN:
-      case ' ':
-        if (cursor > 1) --cursor;
-        break;
-      case KEY_UP:
-      case KEY_BACKSPACE:
-      case DELETE:
-      case CTRL_H:
-        if (cursor < history_array_size) ++cursor;
-        break;
-      case CTRL_E:
-        save_note_to_editor_buffer(L, cursor);
-        /* big picture hotkey unnecessarily available here */
-        /* TODO: go hotkey is misleading. edits will not be persisted until you return to recent changes */
-        edit(L, "teliva_editor_buffer");
-        load_note_from_editor_buffer(L, cursor);
-        save_tlv(L, Image_name);
-        break;
-      case CTRL_U:
-        if (cursor < history_array_size) {
-          add_undo_event(L, cursor);
-          save_tlv(L, Image_name);
-        }
-        break;
-    }
-  }
-}
-
-
-extern void draw_menu_item (const char* key, const char* name);
-static void big_picture_menu (void) {
-  attrset(A_REVERSE);
-  for (int x = 0; x < COLS; ++x)
-    mvaddch(LINES-1, x, ' ');
-  attrset(A_NORMAL);
-  extern int menu_column;
-  menu_column = 2;
-  draw_menu_item("^x", "go back");
-  draw_menu_item("^g", "go to highlight");
-  draw_menu_item("Enter", "submit");
-  draw_menu_item("^h", "backspace");
-  draw_menu_item("^u", "clear");
-  draw_menu_item("^r", "recent changes");
-  attrset(A_NORMAL);
-}
-
-
-static int is_current_definition(lua_State *L, const char *definition_name, int current_history_array_index, int history_array_location, int history_array_size) {
-  /* Sequentially scan back through history_array until current_history_array_index.
-   * Is there an earlier definition of definition_name? */
-  int oldtop = lua_gettop(L);
-  int found = 0;
-  for (int i = history_array_size; i > current_history_array_index; --i) {
-    lua_rawgeti(L, history_array_location, i);
-    int t = lua_gettop(L);
-    for (lua_pushnil(L); lua_next(L, t) != 0;) {
-      lua_pop(L, 1);  // value
-      const char *curr = lua_tostring(L, -1);
-      if (strcmp(curr, definition_name) == 0) {
-        found = 1;
-        lua_pop(L, 1); // key
-        break;
-      }
-      // leave key on stack for next iteration
-    }
-    lua_pop(L, 1);  // history element
-    if (found)
-      break;
-  }
-  if(oldtop != lua_gettop(L)) {
-    endwin();
-    printf("%d %d\n", oldtop, lua_gettop(L));
-    exit(1);
-  }
-  return !found;
-}
-
-
-void draw_definition_name (const char *definition_name) {
-  attron(COLOR_PAIR(COLOR_PAIR_SELECTABLE));
-  addstr(" ");
-  addstr(definition_name);
-  addstr(" ");
-  attroff(COLOR_PAIR(COLOR_PAIR_SELECTABLE));
-  addstr("  ");
-}
-
-
-void draw_highlighted_definition_name (const char *definition_name) {
-  attron(A_REVERSE);
-  addstr(" ");
-  addstr(definition_name);
-  addstr(" ");
-  attroff(A_REVERSE);
-  addstr("  ");
-}
-
-
-/* return true if submitted */
-void big_picture_view (lua_State *L) {
-  /* Without any intervening edits, big_picture_view always stably renders
-   * definitions in exactly the same spatial order, both in levels from top to
-   * bottom and in indexes within each level from left to right. */
-  int highlight_level = 0;
-  int highlight_index_within_level = 0;
-  int level_size[30] = {0};  /* number of indexes within each level */
-  char highlight[CURRENT_DEFINITION_LEN+1] = {0};
-restart:
-  clear();
-  luaL_newmetatable(L, "__teliva_call_graph_depth");
-  int cgt = lua_gettop(L);
-  // special-case: we don't instrument the call to main, but it's always at depth 1
-  lua_pushinteger(L, 1);
-  lua_setfield(L, cgt, "main");
-  // segment definitions by depth
-  lua_getglobal(L, "teliva_program");
-  int history_array = lua_gettop(L);
-  int history_array_size = luaL_getn(L, history_array);
-
-  int y = 1;
-  attrset(A_BOLD);
-  mvaddstr(y, 0, "Big picture");
-  attrset(A_NORMAL);
-  y += 2;
-  mvaddstr(y, 0, "data:           ");
-  // first: data (non-functions) that's not the Teliva menu or curses variables
-  if (highlight_level < 0) highlight_level = 0;
-  int level = 0;
-  int index_within_level = 0;
-  for (int i = history_array_size; i > 0; --i) {
-    lua_rawgeti(L, history_array, i);
-    int t = lua_gettop(L);
-    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
-      const char *definition_name = lua_tostring(L, -2);
-      if (is_special_history_key(definition_name)) continue;
-      lua_getglobal(L, definition_name);
-      int is_userdata = lua_isuserdata(L, -1);
-      int is_function = lua_isfunction(L, -1);
-      lua_pop(L, 1);
-      if (strcmp(definition_name, "menu") != 0  // required by all Teliva programs
-          && !is_function  // functions are not data
-          && !is_userdata  // including curses window objects
-                           // (unlikely to have an interesting definition)
-      ) {
-        if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
-          if (level == highlight_level && index_within_level == highlight_index_within_level) {
-            draw_highlighted_definition_name(definition_name);
-            strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
-          } else {
-            draw_definition_name(definition_name);
-          }
-          ++index_within_level;
-        }
-      }
-    }
-    lua_pop(L, 1);  // history element
-  }
-
-  // second: menu and other userdata
-  for (int i = history_array_size; i > 0; --i) {
-    lua_rawgeti(L, history_array, i);
-    int t = lua_gettop(L);
-    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
-      const char* definition_name = lua_tostring(L, -2);
-      if (is_special_history_key(definition_name)) continue;
-      lua_getglobal(L, definition_name);
-      int is_userdata = lua_isuserdata(L, -1);
-      lua_pop(L, 1);
-      if (strcmp(definition_name, "menu") == 0
-          || is_userdata  // including curses window objects
-      ) {
-        if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
-          if (level == highlight_level && index_within_level == highlight_index_within_level) {
-            draw_highlighted_definition_name(definition_name);
-            strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
-          } else {
-            draw_definition_name(definition_name);
-          }
-          ++index_within_level;
-        }
-      }
-    }
-    lua_pop(L, 1);  // history element
-  }
-  level_size[level] = index_within_level;
-  level++;
-
-  // functions by level
-  y += 2;
-  mvprintw(y, 0, "functions: ");
-  y++;
-  for (int depth = 1; ; ++depth) {
-    mvaddstr(y, 0, "                ");
-    bool drew_anything = false;
-    index_within_level = 0;
-    for (int i = history_array_size; i > 0; --i) {
-      lua_rawgeti(L, history_array, i);
-      int t = lua_gettop(L);
-      for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
-        const char* definition_name = lua_tostring(L, -2);
-        if (is_special_history_key(definition_name)) continue;
-        lua_getfield(L, cgt, definition_name);
-        int definition_depth = lua_tointeger(L, -1);
-        if (definition_depth == depth) {
-          if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
-            if (level == highlight_level && index_within_level == highlight_index_within_level) {
-              draw_highlighted_definition_name(definition_name);
-              strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
-            } else {
-              draw_definition_name(definition_name);
-            }
-            ++index_within_level;
-          }
-          drew_anything = true;
-        }
-        lua_pop(L, 1);  // depth of value
-      }
-      lua_pop(L, 1);  // history element
-    }
-    y += 2;
-    if (!drew_anything) break;
-    level_size[level] = index_within_level;
-    level++;
-  }
-
-  // unused functions
-  mvaddstr(y, 0, "                ");
-  /* no need to level++ because the final iteration above didn't draw anything */
-  index_within_level = 0;
-  for (int i = history_array_size; i > 0; --i) {
-    lua_rawgeti(L, history_array, i);
-    int t = lua_gettop(L);
-    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
-      const char* definition_name = lua_tostring(L, -2);
-      if (is_special_history_key(definition_name)) continue;
-      lua_getglobal(L, definition_name);
-      int is_function = lua_isfunction(L, -1);
-      lua_pop(L, 1);
-      lua_getfield(L, cgt, definition_name);
-      if (is_function && lua_isnoneornil(L, -1)) {
-        if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
-          if (level == highlight_level && index_within_level == highlight_index_within_level) {
-            draw_highlighted_definition_name(definition_name);
-            strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
-          } else {
-            draw_definition_name(definition_name);
-          }
-          ++index_within_level;
-        }
-      }
-      lua_pop(L, 1);  // depth of value
-    }
-    lua_pop(L, 1);  // history element
-  }
-  level_size[level] = index_within_level;
-  int max_level = level;
-
-  lua_settop(L, 0);
-  render_previous_error();
-
-  char query[CURRENT_DEFINITION_LEN+1] = {0};
-  int qlen = 0;
-  while (1) {
-    big_picture_menu();
-    for (int x = 0; x < COLS; ++x)
-      mvaddch(LINES-2, x, ' ');
-//?     mvprintw(20, 60, "%d %d\n", highlight_level, highlight_index_within_level);
-    mvprintw(LINES-2, 0, "Edit: %s", query);
-    int c = getch();
-    if (c == KEY_BACKSPACE || c == DELETE || c == CTRL_H) {
-      if (qlen != 0) query[--qlen] = '\0';
-    } else if (c == CTRL_X) {
-      return;
-    } else if (c == ENTER) {
-      if (query[0] != '\0') {
-        save_to_current_definition_and_editor_buffer(L, query);
-        int back_to_big_picture = edit_current_definition(L);
-        if (back_to_big_picture) goto restart;
-        return;
-      }
-    } else if (c == CTRL_U) {
-      qlen = 0;
-      query[qlen] = '\0';
-    } else if (c == CTRL_R) {
-      recent_changes_view(L);
-      goto restart;
-    } else if (c == KEY_LEFT) {
-      highlight_index_within_level--;
-      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
-      goto restart;
-    } else if (c == KEY_RIGHT) {
-      highlight_index_within_level++;
-      if (highlight_index_within_level >= level_size[highlight_level])
-        highlight_index_within_level = level_size[highlight_level]-1;
-      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
-      goto restart;
-    } else if (c == KEY_UP) {
-      highlight_level--;
-      if (highlight_level < 0) highlight_level = 0;
-      if (highlight_index_within_level >= level_size[highlight_level])
-        highlight_index_within_level = level_size[highlight_level]-1;
-      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
-      goto restart;
-    } else if (c == KEY_DOWN) {
-      highlight_level++;
-      if (highlight_level > max_level) highlight_level = max_level;
-      if (highlight_index_within_level >= level_size[highlight_level])
-        highlight_index_within_level = level_size[highlight_level]-1;
-      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
-      goto restart;
-    } else if (c == CTRL_G) {
-      save_to_current_definition_and_editor_buffer(L, highlight);
-      int back_to_big_picture = edit_current_definition(L);
-      if (back_to_big_picture) goto restart;
-      return;
-    } else if (isprint(c)) {
-      if (qlen < CURRENT_DEFINITION_LEN) {
-          query[qlen++] = c;
-          query[qlen] = '\0';
-      }
-    }
-  }
-  /* never gets here */
-}
-
-
-/* return true if:
- *  - editor_state exists, and
- *  - editor_state is applicable to the current image
- * Implicitly loads current editor state. */
-void teliva_load_definition (lua_State *L, FILE *in);
-int editor_view_in_progress (lua_State *L) {
-  FILE *in = fopen("teliva_editor_state", "r");
-  if (in == NULL) return 0;
-  int oldtop = lua_gettop(L);
-  teliva_load_definition(L, in);
-  int t = lua_gettop(L);
-  lua_getfield(L, t, "image");
-  const char *image_name  = lua_tostring(L, -1);
-  int result = (strcmp(image_name, Image_name) == 0);
-  lua_pop(L, 1);  /* image value */
-  lua_setglobal(L, "__teliva_editor_state");
-  assert(lua_gettop(L) == oldtop);
-  return result;
-}
-
-extern int edit_from(lua_State *L, char *filename, int rowoff, int coloff, int cy, int cx);
-int restore_editor_view (lua_State *L) {
-  lua_getglobal(L, "__teliva_editor_state");
-  int editor_state_index = lua_gettop(L);
-  lua_getfield(L, editor_state_index, "definition");
-  const char *definition = lua_tostring(L, -1);
-  save_to_current_definition_and_editor_buffer(L, definition);
-  lua_getfield(L, editor_state_index, "rowoff");
-  int rowoff = lua_tointeger(L, -1);
-  lua_getfield(L, editor_state_index, "coloff");
-  int coloff = lua_tointeger(L, -1);
-  lua_getfield(L, editor_state_index, "cy");
-  int cy = lua_tointeger(L, -1);
-  lua_getfield(L, editor_state_index, "cx");
-  int cx = lua_tointeger(L, -1);
-  lua_settop(L, editor_state_index);
-  int back_to_big_picture = edit_from(L, "teliva_editor_buffer", rowoff, coloff, cy, cx);
-  // error handling
-  int oldtop = lua_gettop(L);
-  while (1) {
-    int status;
-    status = load_editor_buffer_to_current_definition_in_image(L);
-    if (status == 0 || lua_isnil(L, -1))
-      break;
-    Previous_error = lua_tostring(L, -1);
-    if (Previous_error == NULL) Previous_error = "(error object is not a string)";
-    back_to_big_picture = resumeEdit(L);
-    lua_pop(L, 1);
-  }
-  if (lua_gettop(L) != oldtop) {
-    endwin();
-    printf("edit_from: memory leak %d -> %d\n", oldtop, lua_gettop(L));
-    exit(1);
-  }
-  return back_to_big_picture;
-}
-
-
-char **Argv = NULL;
-extern void cleanup_curses (void);
-void developer_mode (lua_State *L) {
-  /* clobber the app's ncurses colors; we'll restart the app when we rerun it. */
-  assume_default_colors(COLOR_FOREGROUND, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_NORMAL, COLOR_FOREGROUND, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_SELECTABLE, COLOR_SELECTABLE_FOREGROUND, COLOR_SELECTABLE_BACKGROUND);
-  init_pair(COLOR_PAIR_FADE, COLOR_FADE, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_MENU_ALTERNATE, COLOR_MENU_ALTERNATE, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_LUA_COMMENT, COLOR_LUA_COMMENT, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_LUA_KEYWORD, COLOR_LUA_KEYWORD, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_LUA_CONSTANT, COLOR_LUA_CONSTANT, COLOR_BACKGROUND);
-  init_pair(COLOR_PAIR_MATCH, COLOR_MATCH_FOREGROUND, COLOR_MATCH_BACKGROUND);
-  init_pair(COLOR_PAIR_ERROR, COLOR_ERROR_FOREGROUND, COLOR_ERROR_BACKGROUND);
-  nodelay(stdscr, 0);  /* always make getch() block in developer mode */
-  curs_set(1);  /* always display cursor in developer mode */
-  int switch_to_big_picture_view = 1;
-  if (editor_view_in_progress(L))
-    switch_to_big_picture_view = restore_editor_view(L);
-  if (switch_to_big_picture_view)
-    big_picture_view(L);
-  cleanup_curses();
-  execv(Argv[0], Argv);
-  /* never returns */
-}
-
-
 static int handle_luainit (lua_State *L) {
   const char *init = getenv(LUA_INIT);
   if (init == NULL) return 0;  /* status OK */
@@ -1226,14 +239,7 @@ static int pmain (lua_State *L) {
 }
 
 
-extern void draw_menu (lua_State *);
-void render_trusted_teliva_data (lua_State *L) {
-  init_pair(COLOR_PAIR_ERROR, COLOR_ERROR_FOREGROUND, COLOR_ERROR_BACKGROUND);
-  init_pair(COLOR_PAIR_MENU, COLOR_FOREGROUND, COLOR_BACKGROUND);
-  draw_menu(L);
-}
-
-
+extern void cleanup_curses(void);
 int main (int argc, char **argv) {
   int status;
   struct Smain s;
diff --git a/src/lua.h b/src/lua.h
index 71bfbbf..b54a6d1 100644
--- a/src/lua.h
+++ b/src/lua.h
@@ -23,6 +23,9 @@
 #define LUA_AUTHORS 	"R. Ierusalimschy, L. H. de Figueiredo & W. Celes"
 
 
+extern char *Image_name;
+
+
 /* mark for precompiled code (`<esc>Lua') */
 #define	LUA_SIGNATURE	"\033Lua"
 
diff --git a/src/menu.c b/src/menu.c
deleted file mode 100644
index 72f95ba..0000000
--- a/src/menu.c
+++ /dev/null
@@ -1,49 +0,0 @@
-#include <ncurses.h>
-#include <string.h>
-
-#include "lua.h"
-#include "lauxlib.h"
-#include "teliva.h"
-
-
-int menu_column = 0;
-void draw_string_on_menu (const char* s) {
-  mvaddstr(LINES-1, menu_column, " ");
-  ++menu_column;
-  mvaddstr(LINES-1, menu_column, s);
-  menu_column += strlen(s);
-  mvaddstr(LINES-1, menu_column, " ");
-  ++menu_column;
-}
-void draw_menu_item (const char* key, const char* name) {
-  attroff(A_REVERSE);
-  draw_string_on_menu(key);
-  attron(A_REVERSE);
-  draw_string_on_menu(name);
-}
-
-void draw_menu (lua_State *L) {
-  attron(A_BOLD|A_REVERSE|COLOR_PAIR(COLOR_PAIR_MENU));
-  for (int x = 0; x < COLS; ++x)
-    mvaddch(LINES-1, x, ' ');
-  menu_column = 2;
-  draw_menu_item("^x", "exit");
-  draw_menu_item("^e", "edit");
-
-  /* render any app-specific items */
-  lua_getglobal(L, "menu");
-  int table = lua_gettop(L);
-  if (lua_istable(L, -1)) {
-    for (int i = 1; i <= luaL_getn(L, table); ++i) {
-      lua_rawgeti(L, table, i);
-      int menu_item = lua_gettop(L);
-      lua_rawgeti(L, menu_item, 1);  /* key */
-      lua_rawgeti(L, menu_item, 2);  /* value */
-      draw_menu_item(lua_tostring(L, -2), lua_tostring(L, -1));
-      lua_pop(L, 3);
-    }
-  }
-
-  lua_pop(L, 1);
-  attrset(A_NORMAL);
-}
diff --git a/src/teliva.c b/src/teliva.c
new file mode 100644
index 0000000..9a6ec3e
--- /dev/null
+++ b/src/teliva.c
@@ -0,0 +1,1008 @@
+#include <assert.h>
+#include <ctype.h>
+#include <ncurses.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "lua.h"
+#include "lauxlib.h"
+#include "teliva.h"
+#include "tlv.h"
+
+/*** Standard UI elements */
+
+int menu_column = 0;
+
+void draw_string_on_menu(const char* s) {
+  mvaddstr(LINES-1, menu_column, " ");
+  ++menu_column;
+  mvaddstr(LINES-1, menu_column, s);
+  menu_column += strlen(s);
+  mvaddstr(LINES-1, menu_column, " ");
+  ++menu_column;
+}
+
+void draw_menu_item(const char* key, const char* name) {
+  attroff(A_REVERSE);
+  draw_string_on_menu(key);
+  attron(A_REVERSE);
+  draw_string_on_menu(name);
+}
+
+static void draw_menu(lua_State* L) {
+  attron(A_BOLD|A_REVERSE|COLOR_PAIR(COLOR_PAIR_MENU));
+  for (int x = 0; x < COLS; ++x)
+    mvaddch(LINES-1, x, ' ');
+  menu_column = 2;
+  draw_menu_item("^x", "exit");
+  draw_menu_item("^e", "edit");
+
+  /* render any app-specific items */
+  lua_getglobal(L, "menu");
+  int table = lua_gettop(L);
+  if (lua_istable(L, -1)) {
+    for (int i = 1; i <= luaL_getn(L, table); ++i) {
+      lua_rawgeti(L, table, i);
+      int menu_item = lua_gettop(L);
+      lua_rawgeti(L, menu_item, 1);  /* key */
+      lua_rawgeti(L, menu_item, 2);  /* value */
+      draw_menu_item(lua_tostring(L, -2), lua_tostring(L, -1));
+      lua_pop(L, 3);
+    }
+  }
+
+  lua_pop(L, 1);
+  attrset(A_NORMAL);
+}
+
+void render_trusted_teliva_data(lua_State* L) {
+  init_pair(COLOR_PAIR_ERROR, COLOR_ERROR_FOREGROUND, COLOR_ERROR_BACKGROUND);
+  init_pair(COLOR_PAIR_MENU, COLOR_FOREGROUND, COLOR_BACKGROUND);
+  draw_menu(L);
+}
+
+/*** Error reporting */
+
+const char* Previous_error = NULL;
+
+/* return final y containing text */
+static int render_wrapped_text(int y, int xmin, int xmax, const char* text) {
+  int x = xmin;
+  move(y, x);
+  for (int j = 0; j < strlen(text); ++j) {
+    char c = text[j];
+    if (c != '\n') {
+      addch(text[j]);
+      ++x;
+      if (x >= xmax) {
+        ++y;
+        x = xmin;
+        move(y, x);
+      }
+    }
+    else {
+      /* newline */
+      ++y;
+      x = xmin;
+      move(y, x);
+    }
+  }
+  return y;
+}
+
+void render_previous_error(void) {
+  if (!Previous_error) return;
+  init_pair(COLOR_PAIR_ERROR, COLOR_ERROR_FOREGROUND, COLOR_ERROR_BACKGROUND);
+  attron(COLOR_PAIR(COLOR_PAIR_ERROR));
+  render_wrapped_text(LINES-10, COLS/2, COLS, Previous_error);
+  attroff(COLOR_PAIR(COLOR_PAIR_ERROR));
+}
+
+extern char* strdup(const char* s);
+extern void developer_mode(lua_State* L);
+int report_in_developer_mode(lua_State* L, int status) {
+  if (status && !lua_isnil(L, -1)) {
+    Previous_error = strdup(lua_tostring(L, -1));  /* memory leak */
+    if (Previous_error == NULL) Previous_error = "(error object is not a string)";
+    lua_pop(L, 1);
+    for (int x = 0; x < COLS; ++x) {
+      mvaddch(LINES-2, x, ' ');
+      mvaddch(LINES-1, x, ' ');
+    }
+    render_previous_error();
+    mvaddstr(LINES-1, 0, "press any key to continue");
+    getch();
+    developer_mode(L);
+  }
+  return status;
+}
+
+/*** Developer mode, big picture view */
+
+#define CURRENT_DEFINITION_LEN 256
+
+static void big_picture_menu(void) {
+  attrset(A_REVERSE);
+  for (int x = 0; x < COLS; ++x)
+    mvaddch(LINES-1, x, ' ');
+  attrset(A_NORMAL);
+  menu_column = 2;
+  draw_menu_item("^x", "go back");
+  draw_menu_item("^g", "go to highlight");
+  draw_menu_item("Enter", "submit");
+  draw_menu_item("^h", "backspace");
+  draw_menu_item("^u", "clear");
+  draw_menu_item("^r", "recent changes");
+  attrset(A_NORMAL);
+}
+
+static int is_current_definition(lua_State* L, const char* definition_name, int current_history_array_index, int history_array_location, int history_array_size) {
+  /* Sequentially scan back through history_array until current_history_array_index.
+   * Is there an earlier definition of definition_name? */
+  int oldtop = lua_gettop(L);
+  int found = 0;
+  for (int i = history_array_size; i > current_history_array_index; --i) {
+    lua_rawgeti(L, history_array_location, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0;) {
+      lua_pop(L, 1);  // value
+      const char* curr = lua_tostring(L, -1);
+      if (strcmp(curr, definition_name) == 0) {
+        found = 1;
+        lua_pop(L, 1); // key
+        break;
+      }
+      // leave key on stack for next iteration
+    }
+    lua_pop(L, 1);  // history element
+    if (found)
+      break;
+  }
+  if(oldtop != lua_gettop(L)) {
+    endwin();
+    printf("%d %d\n", oldtop, lua_gettop(L));
+    exit(1);
+  }
+  return !found;
+}
+
+void draw_definition_name(const char* definition_name) {
+  attron(COLOR_PAIR(COLOR_PAIR_SELECTABLE));
+  addstr(" ");
+  addstr(definition_name);
+  addstr(" ");
+  attroff(COLOR_PAIR(COLOR_PAIR_SELECTABLE));
+  addstr("  ");
+}
+
+void draw_highlighted_definition_name(const char* definition_name) {
+  attron(A_REVERSE);
+  addstr(" ");
+  addstr(definition_name);
+  addstr(" ");
+  attroff(A_REVERSE);
+  addstr("  ");
+}
+
+/* return true if submitted */
+static int edit_current_definition(lua_State* L);
+static void recent_changes_view(lua_State* L);
+void big_picture_view(lua_State* L) {
+  /* Without any intervening edits, big_picture_view always stably renders
+   * definitions in exactly the same spatial order, both in levels from top to
+   * bottom and in indexes within each level from left to right. */
+  int highlight_level = 0;
+  int highlight_index_within_level = 0;
+  int level_size[30] = {0};  /* number of indexes within each level */
+  char highlight[CURRENT_DEFINITION_LEN+1] = {0};
+restart:
+  clear();
+  luaL_newmetatable(L, "__teliva_call_graph_depth");
+  int cgt = lua_gettop(L);
+  // special-case: we don't instrument the call to main, but it's always at depth 1
+  lua_pushinteger(L, 1);
+  lua_setfield(L, cgt, "main");
+  // segment definitions by depth
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  int history_array_size = luaL_getn(L, history_array);
+
+  int y = 1;
+  attrset(A_BOLD);
+  mvaddstr(y, 0, "Big picture");
+  attrset(A_NORMAL);
+  y += 2;
+  mvaddstr(y, 0, "data:           ");
+  // first: data (non-functions) that's not the Teliva menu or curses variables
+  if (highlight_level < 0) highlight_level = 0;
+  int level = 0;
+  int index_within_level = 0;
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
+      const char* definition_name = lua_tostring(L, -2);
+      if (is_special_history_key(definition_name)) continue;
+      lua_getglobal(L, definition_name);
+      int is_userdata = lua_isuserdata(L, -1);
+      int is_function = lua_isfunction(L, -1);
+      lua_pop(L, 1);
+      if (strcmp(definition_name, "menu") != 0  // required by all Teliva programs
+          && !is_function  // functions are not data
+          && !is_userdata  // including curses window objects
+                           // (unlikely to have an interesting definition)
+      ) {
+        if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
+          if (level == highlight_level && index_within_level == highlight_index_within_level) {
+            draw_highlighted_definition_name(definition_name);
+            strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
+          } else {
+            draw_definition_name(definition_name);
+          }
+          ++index_within_level;
+        }
+      }
+    }
+    lua_pop(L, 1);  // history element
+  }
+
+  // second: menu and other userdata
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
+      const char* definition_name = lua_tostring(L, -2);
+      if (is_special_history_key(definition_name)) continue;
+      lua_getglobal(L, definition_name);
+      int is_userdata = lua_isuserdata(L, -1);
+      lua_pop(L, 1);
+      if (strcmp(definition_name, "menu") == 0
+          || is_userdata  // including curses window objects
+      ) {
+        if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
+          if (level == highlight_level && index_within_level == highlight_index_within_level) {
+            draw_highlighted_definition_name(definition_name);
+            strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
+          } else {
+            draw_definition_name(definition_name);
+          }
+          ++index_within_level;
+        }
+      }
+    }
+    lua_pop(L, 1);  // history element
+  }
+  level_size[level] = index_within_level;
+  level++;
+
+  // functions by level
+  y += 2;
+  mvprintw(y, 0, "functions: ");
+  y++;
+  for (int depth = 1; ; ++depth) {
+    mvaddstr(y, 0, "                ");
+    bool drew_anything = false;
+    index_within_level = 0;
+    for (int i = history_array_size; i > 0; --i) {
+      lua_rawgeti(L, history_array, i);
+      int t = lua_gettop(L);
+      for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
+        const char* definition_name = lua_tostring(L, -2);
+        if (is_special_history_key(definition_name)) continue;
+        lua_getfield(L, cgt, definition_name);
+        int definition_depth = lua_tointeger(L, -1);
+        if (definition_depth == depth) {
+          if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
+            if (level == highlight_level && index_within_level == highlight_index_within_level) {
+              draw_highlighted_definition_name(definition_name);
+              strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
+            } else {
+              draw_definition_name(definition_name);
+            }
+            ++index_within_level;
+          }
+          drew_anything = true;
+        }
+        lua_pop(L, 1);  // depth of value
+      }
+      lua_pop(L, 1);  // history element
+    }
+    y += 2;
+    if (!drew_anything) break;
+    level_size[level] = index_within_level;
+    level++;
+  }
+
+  // unused functions
+  mvaddstr(y, 0, "                ");
+  /* no need to level++ because the final iteration above didn't draw anything */
+  index_within_level = 0;
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
+      const char* definition_name = lua_tostring(L, -2);
+      if (is_special_history_key(definition_name)) continue;
+      lua_getglobal(L, definition_name);
+      int is_function = lua_isfunction(L, -1);
+      lua_pop(L, 1);
+      lua_getfield(L, cgt, definition_name);
+      if (is_function && lua_isnoneornil(L, -1)) {
+        if (is_current_definition(L, definition_name, i, history_array, history_array_size)) {
+          if (level == highlight_level && index_within_level == highlight_index_within_level) {
+            draw_highlighted_definition_name(definition_name);
+            strncpy(highlight, definition_name, CURRENT_DEFINITION_LEN);
+          } else {
+            draw_definition_name(definition_name);
+          }
+          ++index_within_level;
+        }
+      }
+      lua_pop(L, 1);  // depth of value
+    }
+    lua_pop(L, 1);  // history element
+  }
+  level_size[level] = index_within_level;
+  int max_level = level;
+
+  lua_settop(L, 0);
+  render_previous_error();
+
+  char query[CURRENT_DEFINITION_LEN+1] = {0};
+  int qlen = 0;
+  while (1) {
+    big_picture_menu();
+    for (int x = 0; x < COLS; ++x)
+      mvaddch(LINES-2, x, ' ');
+//?     mvprintw(20, 60, "%d %d\n", highlight_level, highlight_index_within_level);
+    mvprintw(LINES-2, 0, "Edit: %s", query);
+    int c = getch();
+    if (c == KEY_BACKSPACE || c == DELETE || c == CTRL_H) {
+      if (qlen != 0) query[--qlen] = '\0';
+    } else if (c == CTRL_X) {
+      return;
+    } else if (c == ENTER) {
+      if (query[0] != '\0') {
+        save_to_current_definition_and_editor_buffer(L, query);
+        int back_to_big_picture = edit_current_definition(L);
+        if (back_to_big_picture) goto restart;
+        return;
+      }
+    } else if (c == CTRL_U) {
+      qlen = 0;
+      query[qlen] = '\0';
+    } else if (c == CTRL_R) {
+      recent_changes_view(L);
+      goto restart;
+    } else if (c == KEY_LEFT) {
+      highlight_index_within_level--;
+      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
+      goto restart;
+    } else if (c == KEY_RIGHT) {
+      highlight_index_within_level++;
+      if (highlight_index_within_level >= level_size[highlight_level])
+        highlight_index_within_level = level_size[highlight_level]-1;
+      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
+      goto restart;
+    } else if (c == KEY_UP) {
+      highlight_level--;
+      if (highlight_level < 0) highlight_level = 0;
+      if (highlight_index_within_level >= level_size[highlight_level])
+        highlight_index_within_level = level_size[highlight_level]-1;
+      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
+      goto restart;
+    } else if (c == KEY_DOWN) {
+      highlight_level++;
+      if (highlight_level > max_level) highlight_level = max_level;
+      if (highlight_index_within_level >= level_size[highlight_level])
+        highlight_index_within_level = level_size[highlight_level]-1;
+      if (highlight_index_within_level < 0) highlight_index_within_level = 0;
+      goto restart;
+    } else if (c == CTRL_G) {
+      save_to_current_definition_and_editor_buffer(L, highlight);
+      int back_to_big_picture = edit_current_definition(L);
+      if (back_to_big_picture) goto restart;
+      return;
+    } else if (isprint(c)) {
+      if (qlen < CURRENT_DEFINITION_LEN) {
+          query[qlen++] = c;
+          query[qlen] = '\0';
+      }
+    }
+  }
+  /* never gets here */
+}
+
+/* return true if:
+ *  - editor_state exists, and
+ *  - editor_state is applicable to the current image
+ * Implicitly loads current editor state. */
+int editor_view_in_progress(lua_State* L) {
+  FILE* in = fopen("teliva_editor_state", "r");
+  if (in == NULL) return 0;
+  int oldtop = lua_gettop(L);
+  teliva_load_definition(L, in);
+  int t = lua_gettop(L);
+  lua_getfield(L, t, "image");
+  const char* image_name  = lua_tostring(L, -1);
+  int result = (strcmp(image_name, Image_name) == 0);
+  lua_pop(L, 1);  /* image value */
+  lua_setglobal(L, "__teliva_editor_state");
+  assert(lua_gettop(L) == oldtop);
+  return result;
+}
+
+extern int load_editor_buffer_to_current_definition_in_image(lua_State* L);
+extern int resumeEdit(lua_State* L);
+extern int edit_from(lua_State* L, char* filename, int rowoff, int coloff, int cy, int cx);
+int restore_editor_view(lua_State* L) {
+  lua_getglobal(L, "__teliva_editor_state");
+  int editor_state_index = lua_gettop(L);
+  lua_getfield(L, editor_state_index, "definition");
+  const char* definition = lua_tostring(L, -1);
+  save_to_current_definition_and_editor_buffer(L, definition);
+  lua_getfield(L, editor_state_index, "rowoff");
+  int rowoff = lua_tointeger(L, -1);
+  lua_getfield(L, editor_state_index, "coloff");
+  int coloff = lua_tointeger(L, -1);
+  lua_getfield(L, editor_state_index, "cy");
+  int cy = lua_tointeger(L, -1);
+  lua_getfield(L, editor_state_index, "cx");
+  int cx = lua_tointeger(L, -1);
+  lua_settop(L, editor_state_index);
+  int back_to_big_picture = edit_from(L, "teliva_editor_buffer", rowoff, coloff, cy, cx);
+  // error handling
+  int oldtop = lua_gettop(L);
+  while (1) {
+    int status;
+    status = load_editor_buffer_to_current_definition_in_image(L);
+    if (status == 0 || lua_isnil(L, -1))
+      break;
+    Previous_error = lua_tostring(L, -1);
+    if (Previous_error == NULL) Previous_error = "(error object is not a string)";
+    back_to_big_picture = resumeEdit(L);
+    lua_pop(L, 1);
+  }
+  if (lua_gettop(L) != oldtop) {
+    endwin();
+    printf("edit_from: memory leak %d -> %d\n", oldtop, lua_gettop(L));
+    exit(1);
+  }
+  return back_to_big_picture;
+}
+
+char** Argv = NULL;
+extern void cleanup_curses(void);
+void developer_mode(lua_State* L) {
+  /* clobber the app's ncurses colors; we'll restart the app when we rerun it. */
+  assume_default_colors(COLOR_FOREGROUND, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_NORMAL, COLOR_FOREGROUND, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_SELECTABLE, COLOR_SELECTABLE_FOREGROUND, COLOR_SELECTABLE_BACKGROUND);
+  init_pair(COLOR_PAIR_FADE, COLOR_FADE, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_MENU_ALTERNATE, COLOR_MENU_ALTERNATE, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_LUA_COMMENT, COLOR_LUA_COMMENT, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_LUA_KEYWORD, COLOR_LUA_KEYWORD, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_LUA_CONSTANT, COLOR_LUA_CONSTANT, COLOR_BACKGROUND);
+  init_pair(COLOR_PAIR_MATCH, COLOR_MATCH_FOREGROUND, COLOR_MATCH_BACKGROUND);
+  init_pair(COLOR_PAIR_ERROR, COLOR_ERROR_FOREGROUND, COLOR_ERROR_BACKGROUND);
+  nodelay(stdscr, 0);  /* always make getch() block in developer mode */
+  curs_set(1);  /* always display cursor in developer mode */
+  int switch_to_big_picture_view = 1;
+  if (editor_view_in_progress(L))
+    switch_to_big_picture_view = restore_editor_view(L);
+  if (switch_to_big_picture_view)
+    big_picture_view(L);
+  cleanup_curses();
+  execv(Argv[0], Argv);
+  /* never returns */
+}
+
+char Current_definition[CURRENT_DEFINITION_LEN+1] = {0};
+
+extern int mkstemp(char* template);
+extern FILE* fdopen(int fd, const char* mode);
+void save_editor_state(int rowoff, int coloff, int cy, int cx) {
+  if (strlen(Current_definition) == 0) return;
+  char outfilename[] = "teliva_editor_state_XXXXXX";
+  int outfd = mkstemp(outfilename);
+  if (outfd == -1) {
+    endwin();
+    perror("error in creating temporary file");
+    abort();
+  }
+  FILE* out = fdopen(outfd, "w");
+  assert(out != NULL);
+  fprintf(out, "- image: %s\n", Image_name);
+  fprintf(out, "  definition: %s\n", Current_definition);
+  fprintf(out, "  rowoff: %d\n", rowoff);
+  fprintf(out, "  coloff: %d\n", coloff);
+  fprintf(out, "  cy: %d\n", cy);
+  fprintf(out, "  cx: %d\n", cx);
+  fclose(out);
+  rename(outfilename, "teliva_editor_state");
+}
+
+/* when found, return 1 and leave string on top of stack
+ * when not found, return 0
+ * caller is responsible for cleaning up the stack. */
+static int look_up_definition (lua_State* L, const char* name) {
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  /* iterate over mutations in teliva_program history in reverse order */
+  int history_array_size = luaL_getn(L, history_array);
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int table = lua_gettop(L);
+    /* iterate over bindings */
+    /* really we expect only one */
+    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
+      const char* key = lua_tostring(L, -2);
+      if (strcmp(key, "__teliva_undo") == 0) {
+        int next_i = lua_tointeger(L, -1);
+        assert(next_i < i);
+        i = next_i + 1;  /* account for decrement */
+        lua_pop(L, 1);
+        break;
+      }
+      if (is_special_history_key(key)) continue;
+      if (strcmp(key, name) == 0)
+        return 1;
+    }
+    lua_pop(L, 1);
+  }
+  lua_pop(L, 1);
+  return 0;
+}
+
+void save_to_current_definition_and_editor_buffer(lua_State* L, const char* definition) {
+  int oldtop = lua_gettop(L);
+  strncpy(Current_definition, definition, CURRENT_DEFINITION_LEN);
+  int status = look_up_definition(L, Current_definition);
+  char outfilename[] = "teliva_editor_buffer_XXXXXX";
+  int outfd = mkstemp(outfilename);
+  if (outfd == -1) {
+    endwin();
+    perror("save_to_current_definition_and_editor_buffer: error in creating temporary file");
+    abort();
+  }
+  FILE* out = fdopen(outfd, "w");
+  assert(out != NULL);
+  if (status)
+    fprintf(out, "%s", lua_tostring(L, -1));
+  fclose(out);
+  rename(outfilename, "teliva_editor_buffer");
+  lua_settop(L, oldtop);
+}
+
+/* I don't understand the best way to read all of a text file.
+ * I'm currently using fread, but its error handling is really designed for
+ * binary data containing fixed-size records. */
+static void read_editor_buffer(char* out, int capacity) {
+  FILE* in = fopen("teliva_editor_buffer", "r");
+  fread(out, capacity, 1, in);  /* TODO: handle overly large file */
+  fclose(in);
+}
+
+static void update_definition(lua_State* L, const char* name, char* new_contents) {
+  int oldtop = lua_gettop(L);
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  /* create a new table containing a single binding */
+  lua_createtable(L, /*number of fields per mutation*/2, 0);
+  lua_pushstring(L, new_contents);
+  assert(strlen(name) > 0);
+  lua_setfield(L, -2, name);
+  /* include timestamp at which binding was created */
+  time_t t;
+  time(&t);
+  char* time_string = ctime(&t);
+  lua_pushstring(L, time_string);
+  lua_setfield(L, -2, "__teliva_timestamp");
+  /* append the new table to the history of mutations */
+  int history_array_size = luaL_getn(L, history_array);
+  ++history_array_size;
+  lua_rawseti(L, history_array, history_array_size);
+  lua_settop(L, oldtop);
+}
+
+extern void save_tlv(lua_State* L, char* filename);
+extern int docall(lua_State* L, int narg, int clear);
+extern int load_editor_buffer_to_current_definition_in_image(lua_State* L) {
+  char new_contents[8192] = {0};
+  read_editor_buffer(new_contents, 8190);
+  update_definition(L, Current_definition, new_contents);
+  save_tlv(L, Image_name);
+  /* reload binding */
+  return luaL_loadbuffer(L, new_contents, strlen(new_contents), Current_definition)
+      || docall(L, 0, 1);
+}
+
+/* return true if user chose to back into the big picture view */
+/* But only if there are no errors. Otherwise things can get confusing. */
+extern int edit(lua_State* L, char* filename);
+static int edit_current_definition(lua_State* L) {
+  int back_to_big_picture = edit(L, "teliva_editor_buffer");
+  // error handling
+  int oldtop = lua_gettop(L);
+  while (1) {
+    int status;
+    status = load_editor_buffer_to_current_definition_in_image(L);
+    if (status == 0 || lua_isnil(L, -1))
+      break;
+    Previous_error = lua_tostring(L, -1);
+    if (Previous_error == NULL) Previous_error = "(error object is not a string)";
+    back_to_big_picture = resumeEdit(L);
+    lua_pop(L, 1);
+  }
+  if (lua_gettop(L) != oldtop) {
+    endwin();
+    printf("edit_current_definition: memory leak %d -> %d\n", oldtop, lua_gettop(L));
+    exit(1);
+  }
+  return back_to_big_picture;
+}
+
+static void recent_changes_menu(int cursor, int history_array_size) {
+  attrset(A_REVERSE);
+  for (int x = 0; x < COLS; ++x)
+    mvaddch(LINES-1, x, ' ');
+  attrset(A_NORMAL);
+  menu_column = 2;
+  draw_menu_item("^x", "go back");
+  /* draw_menu_item("↓|space", "older"); */
+  attroff(A_REVERSE);
+  mvaddstr(LINES-1, menu_column, " ↓");
+  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("|");
+  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("space ");
+  menu_column += 9;  /* strlen isn't sufficient */
+  attron(A_REVERSE);
+  draw_string_on_menu("older");
+  /* draw_menu_item("↑|backspace|delete|^h", "newer"); */
+  attroff(A_REVERSE);
+  mvaddstr(LINES-1, menu_column, " ↑");
+  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("|");
+  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("backspace");
+  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("|");
+  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("delete");
+  attron(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("|");
+  attroff(COLOR_PAIR(COLOR_PAIR_MENU_ALTERNATE));
+  addstr("^h ");
+  menu_column += 23;
+  attron(A_REVERSE);
+  draw_string_on_menu("newer");
+  draw_menu_item("^e", "edit note");
+  if (cursor < history_array_size)
+    draw_menu_item("^u", "undo everything after this");
+  attrset(A_NORMAL);
+}
+
+/* return final y containing text */
+static int render_wrapped_lua_text(int y, int xmin, int xmax, const char* text) {
+  int x = xmin;
+  move(y, x);
+  for (int j = 0; j < strlen(text); ++j) {
+    char c = text[j];
+    if (c == '-' && j+1 < strlen(text) && text[j+1] == '-')
+      attron(COLOR_PAIR(COLOR_PAIR_LUA_COMMENT));
+    if (c != '\n') {
+      addch(text[j]);
+      ++x;
+      if (x >= xmax) {
+        ++y;
+        x = xmin;
+        move(y, x);
+      }
+    }
+    else {
+      /* newline */
+      ++y;
+      x = xmin;
+      move(y, x);
+      attroff(COLOR_PAIR(COLOR_PAIR_LUA_COMMENT));
+    }
+  }
+  return y;
+}
+
+static void render_recent_changes(lua_State* L, int start_index) {
+  clear();
+  attrset(A_BOLD);
+  mvaddstr(1, 0, "Recent changes");
+  attrset(A_NORMAL);
+  int oldtop = lua_gettop(L);
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  int history_array_size = luaL_getn(L, history_array);
+  int y = 3;
+  attron(A_REVERSE);
+  for (int i = start_index; i > 0; --i) {
+    attron(A_BOLD);
+    mvprintw(y, 0, "%3d. ", i);
+    attrset(A_NORMAL);
+    lua_rawgeti(L, history_array, i);
+    int t = lua_gettop(L);
+    for (lua_pushnil(L); lua_next(L, t) != 0; lua_pop(L, 1)) {
+      if (strcmp(lua_tostring(L, -2), "__teliva_undo") == 0) {
+        addstr("undo to ");
+        attron(A_BOLD);
+        printw("%d", lua_tointeger(L, -1));
+        attroff(A_BOLD);
+        y++;
+        continue;
+      }
+      const char* definition_name = lua_tostring(L, -2);
+      if (is_special_history_key(definition_name)) continue;
+      addstr(definition_name);
+      /* save timestamp of binding if available */
+      lua_getfield(L, t, "__teliva_timestamp");
+      if (!lua_isnil(L, -1)) {
+        char buffer[128] = {0};
+        strncpy(buffer, lua_tostring(L, -1), 120);
+        if (buffer[strlen(buffer)-1] == '\n')
+          buffer[strlen(buffer)-1] = '\0';
+        attron(COLOR_PAIR(COLOR_PAIR_FADE));
+        printw("  %s", buffer);
+        attroff(COLOR_PAIR(COLOR_PAIR_FADE));
+      }
+      lua_pop(L, 1);
+      lua_getfield(L, t, "__teliva_note");
+      if (!lua_isnil(L, -1)) {
+        attron(COLOR_PAIR(COLOR_PAIR_FADE));
+        printw("  -- %s", lua_tostring(L, -1));
+        attroff(COLOR_PAIR(COLOR_PAIR_FADE));
+      }
+      lua_pop(L, 1);
+      y++;
+      const char* definition_contents = lua_tostring(L, -1);
+      y = render_wrapped_lua_text(y, 0, COLS, definition_contents);
+      y++;
+      if (y >= LINES-1) break;  /* leave cruft on the stack */
+    }
+    lua_settop(L, t);  /* clean up cruft on the stack */
+    lua_pop(L, 1);  // history element
+    y++;
+    if (y >= LINES-1) break;
+  }
+  lua_pop(L, 1);  // history array
+  if (lua_gettop(L) != oldtop) {
+    endwin();
+    printf("render_recent_changes: memory leak %d -> %d\n", oldtop, lua_gettop(L));
+    exit(1);
+  }
+  recent_changes_menu(start_index, history_array_size);
+  refresh();
+}
+
+static void add_undo_event(lua_State* L, int cursor) {
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  /* create a new table containing the undo event */
+  lua_createtable(L, /*number of fields per mutation*/2, 0);
+  lua_pushinteger(L, cursor);
+  lua_setfield(L, -2, "__teliva_undo");
+  /* include timestamp at which event was created */
+  time_t t;
+  time(&t);
+  char* time_string = ctime(&t);
+  lua_pushstring(L, time_string);
+  lua_setfield(L, -2, "__teliva_timestamp");
+  /* append the new table to the history of mutations */
+  int history_array_size = luaL_getn(L, history_array);
+  ++history_array_size;
+  lua_rawseti(L, history_array, history_array_size);
+  /* clean up */
+  lua_pop(L, 1);
+}
+
+static void save_note_to_editor_buffer(lua_State* L, int cursor) {
+  lua_getglobal(L, "teliva_program");
+  lua_rawgeti(L, -1, cursor);
+  lua_getfield(L, -1, "__teliva_note");
+  const char* contents = lua_tostring(L, -1);
+  char outfilename[] = "teliva_editor_buffer_XXXXXX";
+  int outfd = mkstemp(outfilename);
+  if (outfd == -1) {
+    endwin();
+    perror("save_note_to_editor_buffer: error in creating temporary file");
+    abort();
+  }
+  FILE* out = fdopen(outfd, "w");
+  assert(out != NULL);
+  if (contents != NULL)
+    fprintf(out, "%s", contents);
+  fclose(out);
+  rename(outfilename, "teliva_editor_buffer");
+  lua_pop(L, 3);  /* contents, table at cursor, teliva_program */
+}
+
+static void load_note_from_editor_buffer(lua_State* L, int cursor) {
+  lua_getglobal(L, "teliva_program");
+  char new_contents[8192] = {0};
+  read_editor_buffer(new_contents, 8190);
+  lua_rawgeti(L, -1, cursor);
+  lua_pushstring(L, new_contents);
+  lua_setfield(L, -2, "__teliva_note");
+  lua_pop(L, 2);  /* table at cursor, teliva_program */
+}
+
+static void recent_changes_view(lua_State* L) {
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  assert(history_array == 1);
+  int history_array_size = luaL_getn(L, history_array);
+  int cursor = history_array_size;
+  lua_pop(L, 1);
+  int quit = 0;
+  while (!quit) {
+    /* refresh state after each operation so we pick up modifications */
+    render_recent_changes(L, cursor);
+    int c = getch();
+    switch (c) {
+      case CTRL_X:
+        quit = 1;
+        break;
+      case KEY_DOWN:
+      case ' ':
+        if (cursor > 1) --cursor;
+        break;
+      case KEY_UP:
+      case KEY_BACKSPACE:
+      case DELETE:
+      case CTRL_H:
+        if (cursor < history_array_size) ++cursor;
+        break;
+      case CTRL_E:
+        save_note_to_editor_buffer(L, cursor);
+        /* big picture hotkey unnecessarily available here */
+        /* TODO: go hotkey is misleading. edits will not be persisted until you return to recent changes */
+        edit(L, "teliva_editor_buffer");
+        load_note_from_editor_buffer(L, cursor);
+        save_tlv(L, Image_name);
+        break;
+      case CTRL_U:
+        if (cursor < history_array_size) {
+          add_undo_event(L, cursor);
+          save_tlv(L, Image_name);
+        }
+        break;
+    }
+  }
+}
+
+static int binding_exists (lua_State *L, const char *name) {
+  int result = 0;
+  lua_getglobal(L, name);
+  result = !lua_isnil(L, -1);
+  lua_pop(L, 1);
+  return result;
+}
+
+extern int dostring(lua_State* L, const char* s, const char* name);
+static int load_definitions(lua_State* L) {
+  int status;
+  lua_getglobal(L, "teliva_program");
+  int history_array = lua_gettop(L);
+  /* iterate over mutations in teliva_program history in reverse order */
+  int history_array_size = luaL_getn(L, history_array);
+  for (int i = history_array_size; i > 0; --i) {
+    lua_rawgeti(L, history_array, i);
+    int table = lua_gettop(L);
+    /* iterate over bindings */
+    /* really we expect only one */
+    for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
+      const char* key = lua_tostring(L, -2);
+      if (strcmp(key, "__teliva_undo") == 0) {
+        int next_i = lua_tointeger(L, -1);
+        assert(next_i < i);
+        i = next_i + 1;  /* account for decrement */
+        lua_pop(L, 1);
+        break;
+      }
+      if (is_special_history_key(key)) continue;
+      if (binding_exists(L, key))
+        continue;  // most recent binding trumps older ones
+      const char* value = lua_tostring(L, -1);
+      status = dostring(L, value, key);
+      if (status != 0) return report_in_developer_mode(L, status);
+    }
+    lua_pop(L, 1);
+  }
+  lua_pop(L, 1);
+  return 0;
+}
+
+static int run_tests(lua_State* L) {
+  clear();
+  lua_pushinteger(L, 0);
+  lua_setglobal(L, "teliva_num_test_failures");
+  lua_pushnil(L);
+  lua_setglobal(L, "teliva_first_failure");
+  lua_pushvalue(L, LUA_GLOBALSINDEX);
+  int table = lua_gettop(L);
+  for (lua_pushnil(L); lua_next(L, table) != 0; lua_pop(L, 1)) {
+    const char* key = lua_tostring(L, -2);
+    if (strncmp("test_", key, strlen("test_")) != 0) continue;
+    if (!lua_isfunction(L, -1)) continue;
+    int status = lua_pcall(L, 0, 0, 0);
+    if (status) {
+      printw("E%d: %s", status, lua_tostring(L, -1));
+      /* increment teliva_num_test_failures */
+      lua_getglobal(L, "teliva_num_test_failures");
+      int num_failures = lua_tointeger(L, -1);
+      lua_pop(L, 1);
+      lua_pushinteger(L, num_failures+1);
+      lua_setglobal(L, "teliva_num_test_failures");
+      /* if unset, set teliva_first_failure */
+      lua_getglobal(L, "teliva_first_failure");
+      int first_failure_clear = lua_isnil(L, -1);
+      lua_pop(L, 1);
+      if (first_failure_clear)
+        lua_setglobal(L, "teliva_first_failure");
+    }
+    lua_pushnil(L);  /* just to undo loop update */
+  }
+  lua_pop(L, 1);
+  lua_getglobal(L, "teliva_num_test_failures");
+  int num_failures = lua_tointeger(L, -1);
+  lua_pop(L, 1);
+  if (num_failures == 0) return 0;
+  if (num_failures == 1)
+    addstr("1 failure");
+  else
+    printw("%d failures", num_failures);
+  getch();
+  /* take first failure back to developer mode */
+  lua_getglobal(L, "teliva_first_failure");
+  assert(!lua_isnil(L, -1));
+  return 1;
+}
+
+static void clear_call_graph(lua_State* L) {
+  int oldtop = lua_gettop(L);
+  luaL_newmetatable(L, "__teliva_call_graph_depth");
+  int cgt = lua_gettop(L);
+  lua_pushnil(L);
+  while (lua_next(L, cgt) != 0) {
+    lua_pop(L, 1);  /* old value */
+    lua_pushvalue(L, -1);  /* duplicate key */
+    lua_pushnil(L);  /* new value */
+    lua_settable(L, cgt);
+    /* one copy of key left for lua_next */
+  }
+  lua_pop(L, 1);
+  assert(lua_gettop(L) == oldtop);
+}
+
+
+char* Image_name = NULL;
+extern void set_args (lua_State *L, char **argv, int n);
+extern void load_tlv(lua_State* L, char* filename);
+int handle_image(lua_State* L, char** argv, int n) {
+  int status;
+  set_args(L, argv, n);
+  /* parse and load file contents (teliva_program array) */
+  Image_name = argv[n];
+  load_tlv(L, Image_name);
+//?   save_tlv(L, Image_name);  // manual test; should always return identical result, modulo key order
+//?   exit(1);
+  status = load_definitions(L);
+  if (status != 0) return 0;
+  status = run_tests(L);
+  if (status != 0) return report_in_developer_mode(L, status);
+  /* clear callgraph stats from running tests */
+  clear_call_graph(L);
+  /* call main() */
+  lua_getglobal(L, "main");
+  status = docall(L, 0, 1);
+  if (status != 0) return report_in_developer_mode(L, status);
+  return 0;
+}
diff --git a/src/teliva.h b/src/teliva.h
index bb8964a..50b1b0e 100644
--- a/src/teliva.h
+++ b/src/teliva.h
@@ -1,6 +1,35 @@
 #ifndef __TELIVA_H__
 #define __TELIVA_H__
 
+/* Each category of primitives below shows a few options from high to low
+ * levels of abstraction.
+ * (Lower levels aren't complete or well-designed, just what code outside
+ * teliva.c needs.) */
+
+/* Integrate with Lua VM */
+extern char** Argv;
+extern int handle_image(lua_State* L, char** argv, int n);
+
+extern int load_editor_buffer_to_current_definition_in_image(lua_State* L);
+extern void save_to_current_definition_and_editor_buffer(lua_State* L, const char* definition);
+extern void save_editor_state(int rowoff, int coloff, int cy, int cx);
+
+/* Standard UI elements */
+extern void render_trusted_teliva_data(lua_State* L);
+
+extern void draw_menu_item(const char* key, const char* name);
+
+extern void draw_string_on_menu(const char* s);
+
+extern int menu_column;
+
+/* Error reporting */
+
+extern const char* Previous_error;
+extern int report_in_developer_mode(lua_State* L, int status);
+
+extern void render_previous_error(void);
+
 // Some names for hotkeys beyond those provided by ncurses.
 
 enum KEY_ACTION {
diff --git a/src/tlv.c b/src/tlv.c
index cca8f6e..815f713 100644
--- a/src/tlv.c
+++ b/src/tlv.c
@@ -184,3 +184,18 @@ void save_tlv(lua_State* L, char* filename) {
   rename(outfilename, filename);
   lua_pop(L, 1);
 }
+
+static const char* special_history_keys[] = {
+  "__teliva_timestamp",
+  "__teliva_undo",
+  "__teliva_note",
+  NULL,
+};
+
+int is_special_history_key(const char* key) {
+  for (const char** curr = special_history_keys; *curr != NULL; ++curr) {
+    if (strcmp(*curr, key) == 0)
+      return 1;
+  }
+  return 0;
+}
diff --git a/src/tlv.h b/src/tlv.h
new file mode 100644
index 0000000..0a3e97b
--- /dev/null
+++ b/src/tlv.h
@@ -0,0 +1,9 @@
+#ifndef __TLV_H__
+#define __TLV_H__
+
+/* Helpers for working with the .tlv file format */
+
+extern void teliva_load_definition (lua_State* L, FILE* in);
+int is_special_history_key(const char* key);
+
+#endif