direct mode: use cbreak mode for terminal

* factor out cbreak_mode() #919
* call it from direct mode when we have a terminal fd
* restore the terminal state in ncdirect_stop()

src/lib/direct.cpp

@@ -426,7 +426,12 @@ ncdirect* ncdirect_init(const char* termtype, FILE* outfp){
   ret->ttyfp = outfp;
   memset(&ret->palette, 0, sizeof(ret->palette));
   // we don't need a controlling tty for everything we do; allow a failure here
-  ret->ctermfd = get_controlling_tty(ret->ttyfp);
+  if((ret->ctermfd = get_controlling_tty(ret->ttyfp)) >= 0){
+    if(cbreak_mode(ret->ctermfd, &ret->tpreserved)){
+      delete(ret);
+      return nullptr;
+    }
+  }
   int termerr;
   if(setupterm(termtype, ret->ctermfd, &termerr) != OK){
     fprintf(stderr, "Terminfo error %d (see terminfo(3ncurses))\n", termerr);
@@ -468,6 +473,7 @@ int ncdirect_stop(ncdirect* nc){
       if(nc->tcache.cnorm && tty_emit("cnorm", nc->tcache.cnorm, nc->ctermfd)){
         ret = -1;
       }
+      tcsetattr(nc->ctermfd, TCSANOW, &nc->tpreserved);
       ret |= close(nc->ctermfd);
     }
     delete(nc);

src/lib/internal.h

@@ -261,6 +261,7 @@ typedef struct ncdirect {
   uint16_t stylemask;        // current styles
   bool fgdefault, bgdefault; // are FG/BG currently using default colors?
   bool utf8;                 // are we using utf-8 encoding, as hoped?
+  struct termios tpreserved; // terminal state upon entry
 } ncdirect;
 
 typedef struct notcurses {
@@ -966,6 +967,8 @@ cellcmp_and_dupfar(egcpool* dampool, cell* damcell,
   return 1;
 }
 
+int cbreak_mode(int ttyfd, struct termios* tpreserved);
+
 #ifdef __cplusplus
 }
 #endif

src/lib/notcurses.c

@@ -819,6 +819,28 @@ get_tty_fd(notcurses* nc, FILE* ttyfp){
   return fd;
 }
 
+int cbreak_mode(int ttyfd, struct termios* tpreserved){
+  if(tcgetattr(ttyfd, tpreserved)){
+    fprintf(stderr, "Couldn't preserve terminal state for %d (%s)\n", ttyfd, strerror(errno));
+    return -1;
+  }
+  // assume it's not a true terminal (e.g. we might be redirected to a file)
+  struct termios modtermios;
+  memcpy(&modtermios, tpreserved, sizeof(modtermios));
+  // see termios(3). disabling ECHO and ICANON means input will not be echoed
+  // to the screen, input is made available without enter-based buffering, and
+  // line editing is disabled. since we have not gone into raw mode, ctrl+c
+  // etc. still have their typical effects. ICRNL maps return to 13 (Ctrl+M)
+  // instead of 10 (Ctrl+J).
+  modtermios.c_lflag &= (~ECHO & ~ICANON);
+  modtermios.c_iflag &= (~ICRNL);
+  if(tcsetattr(ttyfd, TCSANOW, &modtermios)){
+    fprintf(stderr, "Error disabling echo / canonical on %d (%s)\n", ttyfd, strerror(errno));
+    return -1;
+  }
+  return 0;
+}
+
 notcurses* notcurses_init(const notcurses_options* opts, FILE* outfp){
   notcurses_options defaultopts;
   memset(&defaultopts, 0, sizeof(defaultopts));
@@ -893,27 +915,9 @@ notcurses* notcurses_init(const notcurses_options* opts, FILE* outfp){
   is_linux_console(ret, !!(opts->flags & NCOPTION_NO_FONT_CHANGES));
   notcurses_mouse_disable(ret);
   if(ret->ttyfd >= 0){
-    if(tcgetattr(ret->ttyfd, &ret->tpreserved)){
-      logerror(ret, "Couldn't preserve terminal state for %d (%s)\n", ret->ttyfd, strerror(errno));
+    if(cbreak_mode(ret->ttyfd, &ret->tpreserved)){
       free(ret);
       return NULL;
-      // assume it's not a true terminal (e.g. we might be redirected to a file)
-    }else{
-      struct termios modtermios;
-      memcpy(&modtermios, &ret->tpreserved, sizeof(modtermios));
-      // see termios(3). disabling ECHO and ICANON means input will not be echoed
-      // to the screen, input is made available without enter-based buffering, and
-      // line editing is disabled. since we have not gone into raw mode, ctrl+c
-      // etc. still have their typical effects. ICRNL maps return to 13 (Ctrl+M)
-      // instead of 10 (Ctrl+J).
-      modtermios.c_lflag &= (~ECHO & ~ICANON);
-      modtermios.c_iflag &= (~ICRNL);
-      if(tcsetattr(ret->ttyfd, TCSANOW, &modtermios)){
-        fprintf(stderr, "Error disabling echo / canonical on %d (%s)\n",
-                ret->ttyfd, strerror(errno));
-        free(ret);
-        return NULL;
-      }
     }
   }
   if(setup_signals(ret,