Initialize Readline on demand

Eliminate NCDIRECT_OPTION_NO_READLINE (it was only introduced in
Notcurses 2.1.6). Add a new function, ncdirect_readline(). Upon
first call to this function, initialize libreadline. Destroy
libreadline in ncdirect_stop() iff we initialized it. Add
hilodirect guessing game PoC from #1325. Rename
notcurses_directmode.3 to notcurses_direct.3. Closes #1326.

NEWS.md

@@ -4,6 +4,10 @@ rearrangements of Notcurses.
 * 2.1.8 (not yet released):
   * The `notcurses-tetris` binary has been renamed `nctetris`.
   * The new function `channel_set_palindex()` has been added.
+  * `NCDIRECT_OPTION_NO_READLINE` has been removed after a short life.
+  * `ncdirect_readline()` has been added. The first time used, it initializes
+    Readline. Readline will be destroyed by ncdirect_stop() if it was ever
+    initialized.
 
 * 2.1.7 (2021-01-21):
   * Notcurses has been split into two libraries, `notcurses-core` and

TERMINALS.md

@@ -29,7 +29,7 @@ relies on the font. Patches to correct/complete this table are very welcome!
 | mlterm          | ❌    |?       |`TERM=mlterm-256color`           | Do not set `COLORTERM`. `mlterm-direct` gives strange results. |
 | PuTTY           | ❌    |❌      |`TERM=putty-256color` `COLORTERM=24bit` | |
 | rxvt            | ?     |?       |                                 | |
-| Sakura          | ✅    |?       |`TERM=vte-256color` `COLORTERM=24bit` | No terminfo entry? |
+| Sakura          | ✅    |?       |`TERM=vte-256color` `COLORTERM=24bit` | VTE-derived, no terminfo entry. |
 | GNU Screen      | ❌    |?       |`TERM=screen.OLDTERM`            | Must be compiled with `--enable-256color`. `TERM` should typically be `screen.` suffixed by the appropriate `TERM` value for the true connected terminal, e.g. `screen.vte-256color`. See below. |
 | st ("suckless") | ✅    |?       |`TERM=st-256color` `COLORTERM=24bit` | |
 | Terminator      | ?     |?       | ?                               | |

USAGE.md

@@ -340,6 +340,11 @@ struct ncdirect* ncdirect_core_init(const char* termtype, FILE* fp, uint64_t fla
 // echo and line buffering are turned off.
 #define NCDIRECT_OPTION_INHIBIT_CBREAK      0x0002ull
 
+// We typically install a signal handler for SIG{INT, SEGV, ABRT, QUIT} that
+// restores the screen, and then calls the old signal handler. Set to inhibit
+// registration of these signal handlers. Chosen to match fullscreen mode.
+#define NCDIRECT_OPTION_NO_QUIT_SIGHANDLERS 0x0008ull
+
 // Release 'nc' and any associated resources. 0 on success, non-0 on failure.
 int ncdirect_stop(struct ncdirect* nc);
 ```
@@ -348,6 +353,12 @@ This context must be destroyed using `ncdirect_stop()`. The following functions
 are available for direct mode:
 
 ```c
+// Read a (heap-allocated) line of text using the Readline library Initializes
+// Readline the first time it's called. For input to be echoed to the terminal,
+// it is necessary that NCDIRECT_OPTION_INHIBIT_CBREAK be provided to
+// ncdirect_init(). Returns NULL on error.
+API char* ncdirect_readline(struct ncdirect* nc, const char* prompt);
+
 int ncdirect_fg_rgb(struct ncdirect* nc, unsigned rgb);
 int ncdirect_bg_rgb(struct ncdirect* nc, unsigned rgb);
 

doc/examples/src/directmode.md

@@ -7,7 +7,7 @@ rendering; output is intended to appear immediately (subject to buffering). It
 is still necessary to have a valid `TERM` environment variable identifying a
 valid terminfo database entry for the running terminal.
 
-The authoritative reference for direct mode is the `notcurses_directmode(3)`
+The authoritative reference for direct mode is the `notcurses_direct(3)`
 man page.
 
 Enter direct mode with a call to `ncdirect_init()`. It takes three arguments:

doc/man/index.html

@@ -44,7 +44,7 @@
    <a href="notcurses_cell.3.html">notcurses_cell</a>—operations on <tt>nccell</tt> objects<br/>
    <a href="notcurses_channels.3.html">notcurses_channels</a>—operations on the <tt>channel</tt> type<br/>
    <a href="notcurses_core.3.html">notcurses_core</a>—linking against a minimal Notcurses<br/>
-   <a href="notcurses_directmode.3.html">notcurses_directmode</a>—minimal notcurses instances for styling text<br/>
+   <a href="notcurses_direct.3.html">notcurses_direct</a>—minimal notcurses instances for styling text<br/>
    <a href="notcurses_fade.3.html">notcurses_fade</a>—fading and pulsing for <tt>ncplane</tt>s<br/>
    <a href="notcurses_fds.3.html">notcurses_fds</a>—dumping file descriptors/subprocesses to <tt>ncplane</tt>s<br/>
    <a href="notcurses_init.3.html">notcurses_init</a>—initialization<br/>

doc/man/man3/notcurses.3.md

@@ -47,7 +47,7 @@ for the actual terminal must be available.
 **ncdirect_init(3)** makes available a very restricted subset of
 Notcurses functionality. This subset is intended to be interleaved with
 user-generated output, and is limited to coloring and styling. Direct mode is
-documented in **notcurses_directmode(3)**.
+documented in **notcurses_direct(3)**.
 
 ## Output
 
@@ -165,7 +165,7 @@ order to turn most error returns into exceptions.
 **notcurses_capabilities(3)**,
 **notcurses_cell(3)**,
 **notcurses_channels(3)**,
-**notcurses_directmode(3)**,
+**notcurses_direct(3)**,
 **notcurses_fade(3)**,
 **notcurses_fds(3)**,
 **notcurses_init(3)**,

doc/man/man3/notcurses_direct.3.md

@@ -1,10 +1,10 @@
-% ncdirect_init(3)
+% notcurses_direct(3)
 % nick black <nickblack@linux.com>
 % v2.1.7
 
 # NAME
 
-ncdirect_init - minimal notcurses instances for styling text
+notcurses_direct - minimal notcurses instances for styling text
 
 # SYNOPSIS
 
@@ -13,7 +13,6 @@ ncdirect_init - minimal notcurses instances for styling text
 
 #define NCDIRECT_OPTION_INHIBIT_SETLOCALE   0x0001ull
 #define NCDIRECT_OPTION_INHIBIT_CBREAK      0x0002ull
-#define NCDIRECT_OPTION_NO_READLINE         0x0004ull
 #define NCDIRECT_OPTION_NO_QUIT_SIGHANDLERS 0x0008ull
 ```
 
@@ -85,6 +84,8 @@ ncdirect_init - minimal notcurses instances for styling text
 
 **int ncdirect_render_image(struct ncdirect* ***n***, const char* ***filename***, ncblitter_e ***blitter***, ncscale_e ***scale***);**
 
+**char* ncdirect_readline(struct ncdirect* ***n***, const char* ***prompt***);**
+
 # DESCRIPTION
 
 **ncdirect_init** prepares the **FILE** provided as **fp** for colorizing and
@@ -108,10 +109,6 @@ The following flags are defined:
     will place the terminal into cbreak mode (i.e. disabling echo and line
     buffering; see **tcgetattr(3)**).
 
-* **NCDIRECT_OPTION_NO_READLINE**: Unless this flag is set, **ncdirect_init**
-    will initialize GNU Readline so that it can be safely used together with
-    direct mode. With this flag, no calls are made to GNU Readline.
-
 * **NCDIRECT_OPTION_NO_QUIT_SIGHANDLERS**: A signal handler will usually be
     installed for **SIGINT**, **SIGQUIT**, **SIGSEGV**, **SIGTERM**, and
     **SIGABRT**, cleaning up the terminal on such exceptions. With this flag,
@@ -141,6 +138,12 @@ output stream, taking effect immediately.
 Attempting to e.g. move up while on the top row will return 0, but have no
 effect.
 
+**ncdirect_readline** uses the Readline library to read a (heap-allocated)
+line of arbitrary length, supporting line-editing controls. For more
+information, consult **readline(3)**. If you want input echoed to the
+terminal while using **ncdirect_readline**, **NCDIRECT_OPTION_INHIBIT_CBREAK**
+must be supplied to **ncdirect_init**.
+
 # RETURN VALUES
 
 **ncdirect_init** returns **NULL** on failure. Otherwise, the return value

include/notcurses/direct.h

@@ -25,11 +25,6 @@ typedef struct ncplane ncdirectv;
 // echo and input's line buffering are turned off.
 #define NCDIRECT_OPTION_INHIBIT_CBREAK      0x0002ull
 
-// We typically initialize the GNU Readline library in a way that works with
-// ncdirect. If you intend no use of GNU Readline, this flag will inhibit any
-// such setup/teardown.
-#define NCDIRECT_OPTION_NO_READLINE         0x0004ull
-
 // We typically install a signal handler for SIG{INT, SEGV, ABRT, QUIT} that
 // restores the screen, and then calls the old signal handler. Set to inhibit
 // registration of these signal handlers. Chosen to match fullscreen mode.
@@ -48,6 +43,12 @@ API struct ncdirect* ncdirect_init(const char* termtype, FILE* fp, uint64_t flag
 // allowing for a svelter binary. Link with notcurses-core if this is used.
 API struct ncdirect* ncdirect_core_init(const char* termtype, FILE* fp, uint64_t flags);
 
+// Read a (heap-allocated) line of text using the Readline library Initializes
+// Readline the first time it's called. For input to be echoed to the terminal,
+// it is necessary that NCDIRECT_OPTION_INHIBIT_CBREAK be provided to
+// ncdirect_init(). Returns NULL on error.
+API char* ncdirect_readline(struct ncdirect* nc, const char* prompt);
+
 // Direct mode. This API can be used to colorize and stylize output generated
 // outside of notcurses, without ever calling notcurses_render(). These should
 // not be intermixed with standard Notcurses rendering.

src/lib/direct.cpp

@@ -309,7 +309,7 @@ detect_cursor_inversion_wrapper(ncdirect* n, int* y, int* x){
 
 // no terminfo capability for this. dangerous--it involves writing controls to
 // the terminal, and then reading a response. many things can distupt this
-// non-atomic procedure.
+// non-atomic procedure, leading to unexpected results. a garbage function.
 int ncdirect_cursor_yx(ncdirect* n, int* y, int* x){
   struct termios termio, oldtermios;
   // this is only meaningful for real terminals
@@ -321,7 +321,7 @@ int ncdirect_cursor_yx(ncdirect* n, int* y, int* x){
     return -1;
   }
   memcpy(&oldtermios, &termio, sizeof(termio));
-  // we should already be in cbreak mode from ncdirect_init(), but just in case
+  // we might already be in cbreak mode from ncdirect_init(), but just in case
   // it got changed by the client code since then, duck into cbreak mode anew.
   termio.c_lflag &= ~(ICANON | ECHO);
   if(tcsetattr(n->ctermfd, TCSAFLUSH, &termio)){
@@ -597,7 +597,7 @@ static int
 ncdirect_stop_minimal(void* vnc){
   ncdirect* nc = static_cast<ncdirect*>(vnc);
   int ret = drop_signals(nc);
-  if(!(nc->flags & NCDIRECT_OPTION_NO_READLINE)){
+  if(nc->initialized_readline){
     rl_deprep_terminal();
   }
   if(nc->tcache.op && term_emit("op", nc->tcache.op, nc->ttyfp, true)){
@@ -673,13 +673,7 @@ ncdirect* ncdirect_core_init(const char* termtype, FILE* outfp, uint64_t flags){
   if(interrogate_terminfo(&ret->tcache, shortname_term)){
     goto err;
   }
-  ret->channels = 0;
   ncdirect_set_styles(ret, 0);
-  if(!(flags & NCDIRECT_OPTION_NO_READLINE)){
-    rl_outstream = stderr;
-    rl_instream = stdin;
-    rl_prep_terminal(1); // 1 == read 8-bit input
-  }
   return ret;
 
 err:
@@ -701,6 +695,16 @@ int ncdirect_stop(ncdirect* nc){
   return ret;
 }
 
+char* ncdirect_readline(ncdirect* n, const char* prompt){
+  if(!n->initialized_readline){
+    rl_outstream = n->ttyfp;
+    rl_instream = stdin;
+    rl_prep_terminal(1); // 1 == read 8-bit input
+    n->initialized_readline = true;
+  }
+  return readline(prompt);
+}
+
 static inline int
 ncdirect_style_emit(ncdirect* n, unsigned stylebits, FILE* out){
   int r = -1;

src/lib/internal.h

@@ -310,6 +310,7 @@ typedef struct ncdirect {
   // typical order. we detect it the first time ncdirect_cursor_yx() is called.
   bool detected_cursor_inversion; // have we performed inversion testing?
   bool inverted_cursor;      // does the terminal return inverted coordinates?
+  bool initialized_readline; // have we initialized Readline?
   uint64_t flags;            // copied in ncdirect_init() from param
 } ncdirect;
 

src/poc/hilodirect.c

@@ -0,0 +1,39 @@
+#include <limits.h>
+#include <notcurses/direct.h>
+
+int main(void){
+  srand(time(NULL)); // gross
+  long guess, secret = random();
+  struct ncdirect* n = ncdirect_core_init(NULL, stdout, NCDIRECT_OPTION_INHIBIT_CBREAK);
+  if(n == NULL){
+    return EXIT_FAILURE;
+  }
+  int r = 0;
+  do{
+    if(!(r |= (ncdirect_set_fg_default(n)))){
+      if(!(r |= (printf("Guess the long: ") < 0))){
+        if(!fflush(stdout)){
+          int rargs = scanf("%ld", &guess); // super shitty to the max
+          if(rargs != 1){
+            fprintf(stderr, "Die, infidel!\n");
+            ncdirect_stop(n);
+            return EXIT_FAILURE;
+          }
+          int offoom = labs(__builtin_clzl(guess) - __builtin_clzl(secret));
+          if(guess > secret){
+            r |= ncdirect_set_fg_rgb8(n, 0x40, 0x80, offoom * 6);
+            r |= (printf("\tLOL jabronies guess %ld. Too high!\n", guess) < 0);
+          }else if(guess < secret){
+            r |= ncdirect_set_fg_rgb8(n, offoom * 6, 0x80, 0x40);
+            r |= (printf("\tSpineless worm! %ld? Too low!\n", guess) < 0);
+          }
+        }
+      }
+    }
+  }while(guess != secret && !r);
+  if(r || printf("You enjoy 20/20 vision into the minds of antimen!\n") < 0){
+    ncdirect_stop(n);
+    return EXIT_FAILURE;
+  }
+  return ncdirect_stop(n) ? EXIT_FAILURE : EXIT_SUCCESS;
+}