ncplane_at_cursor (#76), CCCflag, nonblocking stdin (#78) (#84)

* put stdin into nonblocking mode, retry on short write to stdout #78
* wrap getc_blocking() around a poll #78
* get CCCflag from terminfo. stop clearing the screen in render/startup
* implement ncplane_at_cursor() #76
* ncplane_at_cursor() unit test for simples #76
* PlaneAtCursorComplex unit test #76
* PlaneAtCursorInsane() unit test #76
* nplane_at_cursor: return number of bytes, not just 0/-1
* uniblock-demo: add a bunch of pages from Unicode 12
* demo: make -d delay multiplier a float
* egcpool: check offset against poolsize in check_validity()
* notcurses_init(): set smkx/rmkx to NULL with pass_through_esc
* PlaneAtCursorAttrs unit test #76
* add ncplane_styles() accessor

CMakeLists.txt

@@ -48,7 +48,7 @@ target_compile_options(notcurses
 )
 target_compile_definitions(notcurses
   PUBLIC
-    _DEFAULT_SOURCE _XOPEN_SOURCE=700
+  _DEFAULT_SOURCE _XOPEN_SOURCE=700 _GNU_SOURCE
 )
 
 file(GLOB DEMOSRCS CONFIGURE_DEPENDS src/demo/*.c)

include/notcurses.h

@@ -216,9 +216,9 @@ API int ncplane_move_below(struct ncplane* RESTRICT n, struct ncplane* RESTRICT
 // Splice ncplane 'n' out of the z-buffer, and reinsert it above 'above'.
 API int ncplane_move_above(struct ncplane* RESTRICT n, struct ncplane* RESTRICT above);
 
-// Retrieve the topmost cell at the cursor location on the specified plane,
+// Retrieve the cell at the cursor location on the specified plane, returning
-// returning it in 'c'. This copy is safe to use until the ncplane is destroyed.
+// it in 'c'. This copy is safe to use until the ncplane is destroyed/erased.
-API void ncplane_at_cursor(const struct ncplane* n, cell* c);
+API int ncplane_at_cursor(struct ncplane* n, cell* c);
 
 // Manipulate the opaque user pointer associated with this plane.
 // ncplane_set_userptr() returns the previous userptr after replacing
@@ -321,6 +321,9 @@ API void ncplane_styles_on(struct ncplane* n, unsigned stylebits);
 // Remove the specified styles from the ncplane's existing spec.
 API void ncplane_styles_off(struct ncplane* n, unsigned stylebits);
 
+// Return the current styling for this ncplane.
+API unsigned ncplane_styles(const struct ncplane* n);
+
 // Fine details about terminal
 
 // Returns a 16-bit bitmask in the LSBs of supported curses-style attributes
@@ -377,7 +380,7 @@ cell_styles_set(cell* c, unsigned stylebits){
 
 // Get the style bits, shifted over into the LSBs.
 static inline unsigned
-cell_get_style(const cell* c){
+cell_styles(const cell* c){
   return (c->attrword & CELL_STYLE_MASK) >> 16u;
 }
 
@@ -531,6 +534,10 @@ cell_egc_idx(const cell* c){
   return c->gcluster - 0x80;
 }
 
+// return a pointer to the NUL-terminated EGC referenced by 'c'. this pointer
+// is invalidated by any further operation on the plane 'n', so...watch out!
+API const char* cell_extended_gcluster(const struct ncplane* n, const cell* c);
+
 // load up six cells with the EGCs necessary to draw a box. returns 0 on
 // success, -1 on error. on error, any cells this function might
 // have loaded before the error are cell_release()d. There must be at least
@@ -592,6 +599,142 @@ API struct AVFrame* ncvisual_decode(struct ncvisual* nc);
 // appropriate size.
 API int ncvisual_render(struct ncvisual* ncv, int ystop, int xstop);
 
+// A panelreel is an notcurses region devoted to displaying zero or more
+// line-oriented, contained panels between which the user may navigate. If at
+// least one panel exists, there is an active panel. As much of the active
+// panel as is possible is always displayed. If there is space left over, other
+// panels are included in the display. Panels can come and go at any time, and
+// can grow or shrink at any time.
+//
+// This structure is amenable to line- and page-based navigation via keystrokes,
+// scrolling gestures, trackballs, scrollwheels, touchpads, and verbal commands.
+
+enum bordermaskbits {
+  BORDERMASK_TOP    = 0x1,
+  BORDERMASK_RIGHT  = 0x2,
+  BORDERMASK_BOTTOM = 0x4,
+  BORDERMASK_LEFT   = 0x8,
+};
+
+typedef struct panelreel_options {
+  // require this many rows and columns (including borders). otherwise, a
+  // message will be displayed stating that a larger terminal is necessary, and
+  // input will be queued. if 0, no minimum will be enforced. may not be
+  // negative. note that panelreel_create() does not return error if given a
+  // WINDOW smaller than these minima; it instead patiently waits for the
+  // screen to get bigger.
+  int min_supported_cols;
+  int min_supported_rows;
+
+  // use no more than this many rows and columns (including borders). may not be
+  // less than the corresponding minimum. 0 means no maximum.
+  int max_supported_cols;
+  int max_supported_rows;
+
+  // desired offsets within the surrounding WINDOW (top right bottom left) upon
+  // creation / resize. a panelreel_move() operation updates these.
+  int toff, roff, boff, loff;
+  // is scrolling infinite (can one move down or up forever, or is an end
+  // reached?). if true, 'circular' specifies how to handle the special case of
+  // an incompletely-filled reel.
+  bool infinitescroll;
+  // is navigation circular (does moving down from the last panel move to the
+  // first, and vice versa)? only meaningful when infinitescroll is true. if
+  // infinitescroll is false, this must be false.
+  bool circular;
+  // outcurses can draw a border around the panelreel, and also around the
+  // component tablets. inhibit borders by setting all valid bits in the masks.
+  // partially inhibit borders by setting individual bits in the masks. the
+  // appropriate attr and pair values will be used to style the borders.
+  // focused and non-focused tablets can have different styles. you can instead
+  // draw your own borders, or forgo borders entirely.
+  unsigned bordermask; // bitfield; 1s will not be drawn (see bordermaskbits)
+  uint32_t borderattr; // attributes used for panelreel border, no color!
+  int borderpair;      // extended color pair for panelreel border
+  unsigned tabletmask; // bitfield; same as bordermask but for tablet borders
+  uint32_t tabletattr; // attributes used for tablet borders, no color!
+  int tabletpair;      // extended color pair for tablet borders
+  uint32_t focusedattr;// attributes used for focused tablet borders, no color!
+  int focusedpair;     // extended color pair for focused tablet borders
+} panelreel_options;
+
+struct tablet;
+struct panelreel;
+
+// Create a panelreel according to the provided specifications. Returns NULL on
+// failure. w must be a valid WINDOW*, to which offsets are relative. Note that
+// there might not be enough room for the specified offsets, in which case the
+// panelreel will be clipped on the bottom and right. A minimum number of rows
+// and columns can be enforced via popts. efd, if non-negative, is an eventfd
+// that ought be written to whenever panelreel_touch() updates a tablet (this
+// is useful in the case of nonblocking input).
+struct panelreel* panelreel_create(struct ncplane* nc,
+                                   const panelreel_options* popts,
+                                   int efd);
+
+// Tablet draw callback, provided a ncplane the first column that may be used,
+// the first row that may be used, the first column that may not be used, the
+// first row that may not be used, and a bool indicating whether output ought
+// be clipped at the top (true) or bottom (false). Rows and columns are
+// zero-indexed, and both are relative to the panel.
+//
+// Regarding clipping: it is possible that the tablet is only partially
+// displayed on the screen. If so, it is either partially present on the top of
+// the screen, or partially present at the bottom. In the former case, the top
+// is clipped (cliptop will be true), and output ought start from the end. In
+// the latter case, cliptop is false, and output ought start from the beginning.
+//
+// Returns the number of lines of output, which ought be less than or equal to
+// maxy - begy, and non-negative (negative values might be used in the future).
+typedef int (*tabletcb)(struct ncplane* p, int begx, int begy, int maxx,
+                        int maxy, bool cliptop);
+
+// Add a new tablet to the provided panelreel, having the callback object
+// opaque. Neither, either, or both of after and before may be specified. If
+// neither is specified, the new tablet can be added anywhere on the reel. If
+// one or the other is specified, the tablet will be added before or after the
+// specified tablet. If both are specifid, the tablet will be added to the
+// resulting location, assuming it is valid (after->next == before->prev); if
+// it is not valid, or there is any other error, NULL will be returned.
+struct tablet* panelreel_add(struct panelreel* pr, struct tablet* after,
+                             struct tablet *before, tabletcb cb, void* opaque);
+
+// Return the number of tablets.
+int panelreel_tabletcount(const struct panelreel* pr);
+
+// Indicate that the specified tablet has been updated in a way that would
+// change its display. This will trigger some non-negative number of callbacks
+// (though not in the caller's context).
+int panelreel_touch(struct panelreel* pr, struct tablet* t);
+
+// Delete the tablet specified by t from the panelreel specified by pr. Returns
+// -1 if the tablet cannot be found.
+int panelreel_del(struct panelreel* pr, struct tablet* t);
+
+// Delete the active tablet. Returns -1 if there are no tablets.
+int panelreel_del_focused(struct panelreel* pr);
+
+// Move to the specified location within the containing WINDOW.
+int panelreel_move(struct panelreel* pr, int x, int y);
+
+// Redraw the panelreel in its entirety, for instance after
+// clearing the screen due to external corruption, or a SIGWINCH.
+int panelreel_redraw(struct panelreel* pr);
+
+// Return the focused tablet, if any tablets are present. This is not a copy;
+// be careful to use it only for the duration of a critical section.
+struct tablet* panelreel_focused(struct panelreel* pr);
+
+// Change focus to the next tablet, if one exists
+struct tablet* panelreel_next(struct panelreel* pr);
+
+// Change focus to the previous tablet, if one exists
+struct tablet* panelreel_prev(struct panelreel* pr);
+
+// Destroy a panelreel allocated with panelreel_create(). Does not destroy the
+// underlying WINDOW. Returns non-zero on failure.
+int panelreel_destroy(struct panelreel* pr);
+
 #undef API
 
 #ifdef __cplusplus

src/demo/demo.c

@@ -8,6 +8,8 @@
 #include <notcurses.h>
 #include "demo.h"
 
+static const unsigned long GIG = 1000000000;
+
 struct timespec demodelay = {
   .tv_sec = 1,
   .tv_nsec = 0,
@@ -19,7 +21,7 @@ usage(const char* exe, int status){
   fprintf(out, "usage: %s [ -h ] [ -k ] [ -d ns ] [ -f renderfile ] demospec\n", exe);
   fprintf(out, " -h: this message\n");
   fprintf(out, " -k: keep screen; do not switch to alternate\n");
-  fprintf(out, " -d: delay in nanoseconds between demos\n");
+  fprintf(out, " -d: delay multiplier (float)\n");
   fprintf(out, " -f: render to file in addition to stdout\n");
   fprintf(out, "all demos are run if no specification is provided\n");
   fprintf(out, " i: run intro\n");
@@ -173,13 +175,15 @@ handle_opts(int argc, char** argv, notcurses_options* opts){
         }
         break;
       case 'd':{
-        char* eptr;
+        float f;
-        unsigned long ns = strtoul(optarg, &eptr, 0);
+        if(sscanf(optarg, "%f", &f) != 1){
-        if(*eptr){
+          fprintf(stderr, "Couldn't get a float from %s\n", optarg);
           usage(*argv, EXIT_FAILURE);
         }
-        demodelay.tv_sec = ns / 1000000000;
+        uint64_t ns = f * GIG;
-        demodelay.tv_nsec = ns % 1000000000;
+        printf("F: %f NS: %lu\n", f, ns);
+        demodelay.tv_sec = ns / GIG;
+        demodelay.tv_nsec = ns % GIG;
         break;
       }default:
         usage(*argv, EXIT_FAILURE);

src/demo/unicodeblocks.c

@@ -45,9 +45,39 @@ int unicodeblocks_demo(struct notcurses* nc){
     { .name = "Supplemental Mathematical Operators", .start = 0x2a00, },
     { .name = "Glagolitic, Georgian Supplement, Tifinagh", .start = 0x2c00, },
     { .name = "Supplemental Punctuation, CJK Radicals", .start = 0x2e00, },
+    { .name = "CJK Symbols and Punctuation", .start = 0x3000, },
+    { .name = "Enclosed CJK Letters and Months", .start = 0x3200, },
+    { .name = "CJK Unified Ideographs Extension A", .start = 0x3400, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x3600, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x3800, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x3a00, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x3c00, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x3e00, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x4000, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x4200, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x4400, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x4600, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x4800, },
+    { .name = "CJK Unified Ideographs Extension A (cont.)", .start = 0x4a00, },
+    { .name = "CJK Unified Ideographs Extension A, Yijang Hexagram", .start = 0x4c00, },
+    { .name = "CJK Unified Ideographs", .start = 0x4e00, },
+    { .name = "Yi Syllables", .start = 0xa000, },
+    { .name = "Yi Syllables", .start = 0xa200, },
+    { .name = "Yi Syllables, Yi Radicals, Lisu, Vai", .start = 0xa400, },
+    { .name = "Vai, Cyrillic Extended-B, Bamum, Tone Letters, Latin Extended-D", .start = 0xa600, },
+    { .name = "Halfwidth and Fullwidth Forms", .start = 0xff00, },
+    { .name = "Linear B Syllabary, Linear B Ideograms, Aegean Numbers, Phaistos Disc", .start = 0x10000, },
+    { .name = "Lycian, Carian, Coptic Epact Numbers, Old Italic, Gothic, Old Permic", .start = 0x10200, },
     { .name = "Cuneiform", .start = 0x12000, },
     { .name = "Cuneiform (cont.)", .start = 0x12200, },
     { .name = "Byzantine Musical Symbols, Musical Symbols", .start = 0x1d000, },
+    { .name = "Ancient Greek Musical Notation, Mayan Numerals, Tai Xuan Jing, Counting Rods", .start = 0x1d200, },
+    { .name = "Mathematical Alphanumeric Symbols", .start = 0x1d400, },
+    { .name = "Mathematical Alphanumeric Symbols (cont.)", .start = 0x1d600, },
+    { .name = "Sutton SignWriting", .start = 0x1d800, },
+    { .name = "Glagolitic Supplement, Nyiakeng Puachue Hmong", .start = 0x1e000, },
+    { .name = "Ottoman Siyaq Numbers", .start = 0x1ed00, },
+    { .name = "Arabic Mathematical Alphabetic Symbols", .start = 0x1ee00, },
     { .name = "Mahjong Tiles, Domino Tiles, Playing Cards", .start = 0x1f000, },
     { .name = "Enclosed Ideographic Supplement, Miscellaneous Symbols", .start = 0x1f200, },
     { .name = "Miscellaneous Symbols and Pictographs (cont.)", .start = 0x1f400, },
@@ -72,7 +102,6 @@ int unicodeblocks_demo(struct notcurses* nc){
   nstotal /= 10;
   subdelay.tv_sec = nstotal / 1000000000;
   subdelay.tv_nsec = nstotal % 1000000000;
-fprintf(stderr, "SUBDELAY: %lu %lu\n", subdelay.tv_sec, subdelay.tv_nsec);
   for(sindex = 0 ; sindex < sizeof(blocks) / sizeof(*blocks) ; ++sindex){
     uint32_t blockstart = blocks[sindex].start;
     const char* description = blocks[sindex].name;
@@ -105,7 +134,6 @@ fprintf(stderr, "SUBDELAY: %lu %lu\n", subdelay.tv_sec, subdelay.tv_nsec);
         memset(&ps, 0, sizeof(ps));
         wchar_t w = blockstart + chunk * CHUNKSIZE + z;
         char utf8arr[MB_CUR_MAX + 1];
-        // FIXME we can print wide ones here, just add an extra line
         if(wcwidth(w) >= 1 && iswprint(w)){
           int bwc = wcrtomb(utf8arr, w, &ps);
           if(bwc < 0){
@@ -122,8 +150,6 @@ fprintf(stderr, "SUBDELAY: %lu %lu\n", subdelay.tv_sec, subdelay.tv_nsec);
         if(cell_load(n, &c, utf8arr) < 0){ // FIXME check full len was eaten?
           return -1;;
         }
-        /*ncplane_fg_rgb8(n, 0xad + z, 0xd8, 0xe6);
-        ncplane_bg_rgb8(n, 0x20, 0x20, 0x20);*/
         cell_set_fg(&c, 0xad + z * 2, 0xd8, 0xe6 - z * 2);
         cell_set_bg(&c, 8 * chunk, 8 * chunk + z, 8 * chunk);
         if(ncplane_putc(n, &c) < 0){

src/lib/egcpool.h

@@ -179,6 +179,10 @@ egcpool_stash(egcpool* pool, const char* egc, size_t ulen){
 // Run a consistency check on the offset; ensure it's a valid, non-empty EGC.
 static inline bool
 egcpool_check_validity(const egcpool* pool, int offset){
+  if(offset >= pool->poolsize){
+    fprintf(stderr, "Offset (%d) greater than size (%d)\n", offset, pool->poolsize);
+    return false;
+  }
   const char* egc = pool->pool + offset;
   if(*egc == '\0'){
     fprintf(stderr, "Bad offset (%d): empty\n", offset);

src/lib/notcurses.c

@@ -1,6 +1,7 @@
 #include <ncurses.h> // needed for some definitions, see terminfo(3ncurses)
 #include <time.h>
 #include <term.h>
+#include <fcntl.h>
 #include <ctype.h>
 #include <errno.h>
 #include <stdio.h>
@@ -8,6 +9,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <signal.h>
+#include <sys/poll.h>
 #include <stdatomic.h>
 #include <sys/ioctl.h>
 #include <libavutil/version.h>
@@ -94,6 +96,7 @@ typedef struct notcurses {
 
   struct termios tpreserved; // terminal state upon entry
   bool RGBflag;   // terminfo-reported "RGB" flag for 24bpc directcolor
+  bool CCCflag;   // terminfo-reported "CCC" flag for palette set capability
   ncplane* top;   // the contents of our topmost plane (initially entire screen)
   ncplane* stdscr;// aliases some plane from the z-buffer, covers screen
   FILE* renderfp; // debugging FILE* to which renderings are written
@@ -217,6 +220,26 @@ const void* ncplane_userptr_const(const ncplane* n){
   return n->userptr;
 }
 
+// is the cursor in an invalid position? it never should be, but it's probably
+// better to make sure (it's cheap) than to read from/write to random crap.
+static bool
+cursor_invalid_p(const ncplane* n){
+  if(n->y >= n->leny || n->x >= n->lenx){
+    return true;
+  }
+  if(n->y < 0 || n->x < 0){
+    return true;
+  }
+  return false;
+}
+
+int ncplane_at_cursor(ncplane* n, cell* c){
+  if(cursor_invalid_p(n)){
+    return -1;
+  }
+  return cell_duplicate(n, c, &n->fb[fbcellidx(n, n->y, n->x)]);
+}
+
 void ncplane_dim_yx(const ncplane* n, int* rows, int* cols){
   if(rows){
     *rows = n->leny;
@@ -472,6 +495,8 @@ int ncplane_resize(ncplane* n, int keepy, int keepx, int keepleny,
   return 0;
 }
 
+// find the pointer on the z-index referencing the specified plane. writing to
+// this pointer will remove the plane (and everything below it) from the stack.
 static ncplane**
 find_above_ncplane(ncplane* n){
   notcurses* nc = n->nc;
@@ -507,6 +532,7 @@ interrogate_terminfo(notcurses* nc, const notcurses_options* opts){
   char* longname_term = longname();
   fprintf(stderr, "Term: %s\n", longname_term ? longname_term : "?");
   nc->RGBflag = tigetflag("RGB") == 1;
+  nc->CCCflag = tigetflag("ccc") == 1;
   if((nc->colors = tigetnum("colors")) <= 0){
     fprintf(stderr, "This terminal doesn't appear to support colors\n");
     nc->colors = 1;
@@ -578,6 +604,8 @@ interrogate_terminfo(notcurses* nc, const notcurses_options* opts){
   if(!opts->pass_through_esc){
     term_verify_seq(&nc->smkx, "smkx");
     term_verify_seq(&nc->rmkx, "rmkx");
+  }else{
+    nc->smkx = nc->rmkx = NULL;
   }
   // Neither of these is supported on e.g. the "linux" virtual console.
   if(!opts->inhibit_alternate_screen){
@@ -590,6 +618,19 @@ interrogate_terminfo(notcurses* nc, const notcurses_options* opts){
   return 0;
 }
 
+static int
+make_nonblocking(FILE* fp){
+  int fd = fileno(fp);
+  if(fd < 0){
+    return -1;
+  }
+  int flags = fcntl(fd, F_GETFL, 0);
+  if(flags < 0){
+    return -1;
+  }
+  return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+}
+
 notcurses* notcurses_init(const notcurses_options* opts){
   struct termios modtermios;
   notcurses* ret = malloc(sizeof(*ret));
@@ -599,6 +640,10 @@ notcurses* notcurses_init(const notcurses_options* opts){
   ret->ttyfp = opts->outfp;
   ret->renderfp = opts->renderfp;
   ret->ttyinfp = stdin; // FIXME
+  if(make_nonblocking(ret->ttyinfp)){
+    free(ret);
+    return NULL;
+  }
   if((ret->ttyfd = fileno(ret->ttyfp)) < 0){
     fprintf(stderr, "No file descriptor was available in opts->outfp\n");
     free(ret);
@@ -644,7 +689,7 @@ notcurses* notcurses_init(const notcurses_options* opts){
     free_plane(ret->top);
     goto err;
   }
-  term_emit(ret->clear, ret->ttyfp, false);
+  // term_emit(ret->clear, ret->ttyfp, false);
   fprintf(ret->ttyfp, "\n"
          " notcurses %s by nick black\n"
          " terminfo from %s\n"
@@ -806,6 +851,10 @@ extended_gcluster(const ncplane* n, const cell* c){
   return n->pool.pool + idx;
 }
 
+const char* cell_extended_gcluster(const struct ncplane* n, const cell* c){
+  return extended_gcluster(n, c);
+}
+
 // write the cell's UTF-8 grapheme cluster to the provided FILE*. returns the
 // number of columns occupied by this EGC (only an approximation; it's actually
 // a property of the font being used).
@@ -835,18 +884,12 @@ term_putc(FILE* out, const ncplane* n, const cell* c){
 
 static void
 advance_cursor(ncplane* n, int cols){
-  if(n->y >= n->leny){
+  if(cursor_invalid_p(n)){
-    if(n->x >= n->lenx){
+    return; // stuck!
-      return; // stuck!
-    }
   }
   if((n->x += cols) >= n->lenx){
-    if(n->y >= n->leny){
+    ++n->y;
-      n->x = n->lenx;
+    n->x -= n->lenx;
-    }else{
-      n->x -= n->lenx;
-      ++n->y;
-    }
   }
 }
 
@@ -882,7 +925,7 @@ term_setstyles(const notcurses* nc, FILE* out, uint32_t* curattr, const cell* c)
   if(cell_inherits_style(c)){
     return 0; // change nothing
   }
-  uint32_t cellattr = cell_get_style(c);
+  uint32_t cellattr = cell_styles(c);
   if(cellattr == *curattr){
     return 0; // happy agreement, change nothing
   }
@@ -973,6 +1016,36 @@ int ncplane_move_bottom(ncplane* n){
   return 0;
 }
 
+static int
+blocking_write(int fd, const char* buf, size_t buflen){
+  size_t written = 0;
+  do{
+    ssize_t w = write(fd, buf + written, buflen - written);
+    if(w < 0){
+      if(errno != EAGAIN && errno != EWOULDBLOCK){
+        return -1;
+      }
+    }else{
+      written += w;
+    }
+  }while(written < buflen);
+  return 0;
+}
+
+// determine the best palette for the current frame, and write the necessary
+// escape sequences to 'out'.
+static int
+prep_optimized_palette(notcurses* nc, FILE* out){
+  if(nc->RGBflag){
+    return 0; // DirectColor, no need to write palette
+  }
+  if(!nc->CCCflag){
+    return 0; // can't change palette
+  }
+  // FIXME
+  return 0;
+}
+
 // FIXME this needs to keep an invalidation bitmap, rather than blitting the
 // world every time
 int notcurses_render(notcurses* nc){
@@ -986,8 +1059,11 @@ int notcurses_render(notcurses* nc){
   if(out == NULL){
     return -1;
   }
+  prep_optimized_palette(nc, out); // FIXME do what on failure?
   uint32_t curattr = 0; // current attributes set (does not include colors)
-  term_emit(nc->clear, out, false);
+  // no need to write a clearscreen, since we update everything that's been
+  // changed. just move the physical cursor to the upper left corner.
+  term_emit(tiparm(nc->cup, 0, 0), out, false);
   unsigned lastr, lastg, lastb;
   unsigned lastbr, lastbg, lastbb;
   // we can elide a color escape iff the color has not changed between the two
@@ -1060,8 +1136,8 @@ int notcurses_render(notcurses* nc){
   }
   ret |= fclose(out);
   fflush(nc->ttyfp);
-  ssize_t w = write(nc->ttyfd, buf, buflen);
+  fprintf(nc->ttyfp, "%s", buf);
-  if(w < 0 || (size_t)w != buflen){
+  if(blocking_write(nc->ttyfd, buf, buflen)){
     ret = -1;
   }
 /*fprintf(stderr, "%lu/%lu %lu/%lu %lu/%lu\n", defaultelisions, defaultemissions,
@@ -1119,7 +1195,7 @@ int cell_duplicate(ncplane* n, cell* targ, const cell* c){
 }
 
 int ncplane_putc(ncplane* n, const cell* c){
-  if(n->y >= n->leny || n->x >= n->lenx){
+  if(cursor_invalid_p(n)){
     return -1;
   }
   cell* targ = &n->fb[fbcellidx(n, n->y, n->x)];
@@ -1230,6 +1306,10 @@ void ncplane_styles_set(ncplane* n, unsigned stylebits){
                 ((stylebits & 0xffff) << 16u);
 }
 
+unsigned ncplane_styles(const ncplane* n){
+  return (n->attrword & CELL_STYLE_MASK) >> 16u;
+}
+
 int ncplane_printf(ncplane* n, const char* format, ...){
   int ret;
   va_list va;
@@ -1365,6 +1445,7 @@ handle_getc(const notcurses* nc __attribute__ ((unused)), cell* c, int kpress,
   if(kpress == 0x04){ // ctrl-d
     return -1;
   }
+  // FIXME look for keypad
   if(kpress < 0x80){
     c->gcluster = kpress;
   }else{
@@ -1387,18 +1468,31 @@ int notcurses_getc(const notcurses* nc, cell* c, ncspecial_key* special){
   return handle_getc(nc, c, r, special);
 }
 
+// we set our infd to non-blocking on entry, so to do a blocking call (without
+// burning cpu) we'll need to set up a poll().
 int notcurses_getc_blocking(const notcurses* nc, cell* c, ncspecial_key* special){
-  int r = getc(nc->ttyinfp);
+  struct pollfd pfd = {
-  if(r < 0){
+    .fd = fileno(nc->ttyinfp),
-    if(errno == EINTR){
+    .events = POLLIN | POLLRDHUP,
-      if(resize_seen){
+    .revents = 0,
-        resize_seen = 0;
+  };
-        c->gcluster = 0;
+  int pret;
-        *special = NCKEY_RESIZE;
+  while((pret = poll(&pfd, 1, -1)) >= 0){
-        return 1;
+    if(pret == 0){
-      }
+      continue;
+    }
+    int r = getc(nc->ttyinfp);
+    if(r < 0){
+      if(errno == EINTR){
+        if(resize_seen){
+          resize_seen = 0;
+          c->gcluster = 0;
+          *special = NCKEY_RESIZE;
+          return 1;
+        }
+      }
+      return handle_getc(nc, c, r, special);
     }
-    return r;
   }
-  return handle_getc(nc, c, r, special);
+  return -1;
 }

tests/ncplane.cpp

@@ -1,3 +1,4 @@
+#include <cstdlib>
 #include <notcurses.h>
 #include "main.h"
 
@@ -394,3 +395,148 @@ TEST_F(NcplaneTest, GrowPlane) {
   // FIXME check dims, pos
   ASSERT_EQ(0, ncplane_destroy(newp));
 }
+
+// we ought be able to see what we're about to render, or have just rendered, or
+// in any case whatever's in the virtual framebuffer for a plane
+TEST_F(NcplaneTest, PlaneAtCursorSimples){
+  const char STR1[] = "Jackdaws love my big sphinx of quartz";
+  const char STR2[] = "Cwm fjord bank glyphs vext quiz";
+  const char STR3[] = "Pack my box with five dozen liquor jugs";
+  ncplane_styles_set(n_, 0);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 0, 0));
+  ASSERT_LT(0, ncplane_putstr(n_, STR1));
+  int dimy, dimx;
+  ncplane_dim_yx(n_, &dimy, &dimx);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 1, dimx - strlen(STR2)));
+  ASSERT_LT(0, ncplane_putstr(n_, STR2));
+  int y, x;
+  ncplane_cursor_yx(n_, &y, &x);
+  ASSERT_EQ(2, y);
+  ASSERT_EQ(0, x);
+  ASSERT_LT(0, ncplane_putstr(n_, STR3));
+  cell testcell = CELL_TRIVIAL_INITIALIZER;
+  ASSERT_EQ(0, ncplane_at_cursor(n_, &testcell)); // want nothing at the cursor
+  EXPECT_EQ(0, testcell.gcluster);
+  EXPECT_EQ(0, testcell.attrword);
+  EXPECT_EQ(0, testcell.channels);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 0, 0));
+  ASSERT_LT(0, ncplane_at_cursor(n_, &testcell)); // want first char of STR1
+  EXPECT_EQ(STR1[0], testcell.gcluster);
+  EXPECT_EQ(0, testcell.attrword);
+  EXPECT_EQ(0, testcell.channels);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 1, dimx - 1));
+  ASSERT_LT(0, ncplane_at_cursor(n_, &testcell)); // want last char of STR2
+  EXPECT_EQ(STR2[strlen(STR2) - 1], testcell.gcluster);
+  EXPECT_EQ(0, testcell.attrword);
+  EXPECT_EQ(0, testcell.channels);
+  // FIXME maybe check all cells?
+  EXPECT_EQ(0, notcurses_render(nc_));
+}
+
+// ensure we read back what's expected for latinesque complex characters
+TEST_F(NcplaneTest, PlaneAtCursorComplex){
+  const char STR1[] = "Σιβυλλα τι θελεις; respondebat illa:";
+  const char STR2[] = "αποθανειν θελω";
+  const char STR3[] = "Война и мир"; // just thrown in to complicate things
+  ncplane_styles_set(n_, 0);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 0, 0));
+  ASSERT_LT(0, ncplane_putstr(n_, STR1));
+  int dimy, dimx;
+  ncplane_dim_yx(n_, &dimy, &dimx);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 1, dimx - mbstowcs(NULL, STR2, 0)));
+  ASSERT_LT(0, ncplane_putstr(n_, STR2));
+  int y, x;
+  ncplane_cursor_yx(n_, &y, &x);
+  ASSERT_EQ(2, y);
+  ASSERT_EQ(0, x);
+  ASSERT_LT(0, ncplane_putstr(n_, STR3));
+  cell testcell = CELL_TRIVIAL_INITIALIZER;
+  ncplane_at_cursor(n_, &testcell); // should be nothing at the cursor
+  EXPECT_EQ(0, testcell.gcluster);
+  EXPECT_EQ(0, testcell.attrword);
+  EXPECT_EQ(0, testcell.channels);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 0, 0));
+  ASSERT_LT(0, ncplane_at_cursor(n_, &testcell)); // want first char of STR1
+  EXPECT_STREQ("Σ", cell_extended_gcluster(n_, &testcell));
+  EXPECT_EQ(0, testcell.attrword);
+  EXPECT_EQ(0, testcell.channels);
+  ASSERT_EQ(0, ncplane_cursor_move_yx(n_, 1, dimx - mbstowcs(NULL, STR2, 0)));
+  ASSERT_LT(0, ncplane_at_cursor(n_, &testcell)); // want first char of STR2
+  EXPECT_STREQ("α", cell_extended_gcluster(n_, &testcell));
+  EXPECT_EQ(0, testcell.attrword);
+  EXPECT_EQ(0, testcell.channels);
+  // FIXME maybe check all cells?
+  EXPECT_EQ(0, notcurses_render(nc_));
+}
+
+// half-width, double-width, huge-yet-narrow, all that crap
+TEST_F(NcplaneTest, PlaneAtCursorInsane){
+  const char EGC0[] = "\uffe0"; // fullwidth cent sign ￠
+  const char EGC1[] = "\u00c5"; // neutral A with ring above Å
+  const char EGC2[] = "\u20a9"; // half-width won ₩
+  const char EGC3[] = "\u212b"; // ambiguous angstrom Å
+  const char EGC4[] = "\ufdfd"; // neutral yet huge bismillah ﷽
+  std::array<cell, 5> tcells;
+  for(auto i = 0u ; i < tcells.size() ; ++i){
+    cell_init(&tcells[i]);
+  }
+  ASSERT_LT(1, cell_load(n_, &tcells[0], EGC0));
+  ASSERT_LT(1, cell_load(n_, &tcells[1], EGC1));
+  ASSERT_LT(1, cell_load(n_, &tcells[2], EGC2));
+  ASSERT_LT(1, cell_load(n_, &tcells[3], EGC3));
+  ASSERT_LT(1, cell_load(n_, &tcells[4], EGC4));
+  for(auto i = 0u ; i < tcells.size() ; ++i){
+    ASSERT_LT(1, ncplane_putc(n_, &tcells[i]));
+  }
+  EXPECT_EQ(0, notcurses_render(nc_));
+  int x = 0;
+  for(auto i = 0u ; i < tcells.size() ; ++i){
+    EXPECT_EQ(0, ncplane_cursor_move_yx(n_, 0, x));
+    cell testcell = CELL_TRIVIAL_INITIALIZER;
+    ASSERT_LT(0, ncplane_at_cursor(n_, &testcell));
+    EXPECT_STREQ(cell_extended_gcluster(n_, &tcells[i]),
+                 cell_extended_gcluster(n_, &testcell));
+    EXPECT_EQ(0, testcell.attrword);
+    wchar_t w;
+    ASSERT_LT(0, mbtowc(&w, cell_extended_gcluster(n_, &tcells[i]), MB_CUR_MAX));
+    if(wcwidth(w) == 2){
+      EXPECT_EQ(CELL_WIDEASIAN_MASK, testcell.channels);
+      ++x;
+    }else{
+      EXPECT_EQ(0, testcell.channels);
+    }
+    ++x;
+  }
+}
+
+// test that we read back correct attrs/colors despite changing defaults
+TEST_F(NcplaneTest, PlaneAtCursorAttrs){
+  const char STR1[] = "this has been a world destroyer production";
+  const char STR2[] = "not to mention dank";
+  const char STR3[] = "da chronic lives";
+  ncplane_styles_set(n_, CELL_STYLE_BOLD);
+  ASSERT_LT(0, ncplane_putstr(n_, STR1));
+  int y, x;
+  ncplane_cursor_yx(n_, &y, &x);
+  EXPECT_EQ(0, ncplane_cursor_move_yx(n_, y + 1, x - strlen(STR2)));
+  ncplane_styles_on(n_, CELL_STYLE_ITALIC);
+  ASSERT_LT(0, ncplane_putstr(n_, STR2));
+  EXPECT_EQ(0, ncplane_cursor_move_yx(n_, y + 2, x - strlen(STR3)));
+  ncplane_styles_off(n_, CELL_STYLE_BOLD);
+  ASSERT_LT(0, ncplane_putstr(n_, STR3));
+  ncplane_styles_off(n_, CELL_STYLE_ITALIC);
+  EXPECT_EQ(0, notcurses_render(nc_));
+  int newx;
+  ncplane_cursor_yx(n_, &y, &newx);
+  EXPECT_EQ(newx, x);
+  cell testcell = CELL_TRIVIAL_INITIALIZER;
+  EXPECT_EQ(0, ncplane_cursor_move_yx(n_, y - 2, x - 1));
+  ASSERT_EQ(1, ncplane_at_cursor(n_, &testcell));
+  EXPECT_EQ(testcell.gcluster, STR1[strlen(STR1) - 1]);
+  EXPECT_EQ(0, ncplane_cursor_move_yx(n_, y - 1, x - 1));
+  ASSERT_EQ(1, ncplane_at_cursor(n_, &testcell));
+  EXPECT_EQ(testcell.gcluster, STR2[strlen(STR2) - 1]);
+  EXPECT_EQ(0, ncplane_cursor_move_yx(n_, y, x - 1));
+  ASSERT_EQ(1, ncplane_at_cursor(n_, &testcell));
+  EXPECT_EQ(testcell.gcluster, STR3[strlen(STR3) - 1]);
+}