ncplane_putstr_aligned(), use it in intro #102

include/notcurses.h

@@ -433,6 +433,16 @@ ncplane_putwegc_yx(struct ncplane* n, int y, int x, const wchar_t* gclust,
 // which were written before the error.
 API int ncplane_putstr(struct ncplane* n, const char* gclustarr);
 
+// Alignment within the ncplane. Left/right-justified, or centered.
+typedef enum {
+  NCALIGN_LEFT,
+  NCALIGN_CENTER,
+  NCALIGN_RIGHT,
+} ncalign_e;
+
+API int ncplane_putstr_aligned(struct ncplane* n, int y, const char* s,
+                               ncalign_e atype);
+
 static inline int
 ncplane_putstr_yx(struct ncplane* n, int y, int x, const char* gclustarr){
   if(ncplane_cursor_move_yx(n, y, x)){

src/demo/demo.c

@@ -100,30 +100,21 @@ intro(struct notcurses* nc){
   if(ncplane_set_bg_rgb(ncp, 0, 40, 0)){
     return -1;
   }
-  if(ncplane_cursor_move_yx(ncp, rows / 2 - 2, (cols - strlen(s1) + 4) / 2)){
+  if(ncplane_putstr_aligned(ncp, rows / 2 - 2, s1, NCALIGN_CENTER) != (int)strlen(s1)){
-    return -1;
-  }
-  if(ncplane_putstr(ncp, s1) != (int)strlen(s1)){
-    return -1;
-  }
-  if(ncplane_cursor_move_yx(ncp, rows / 2, (cols - strlen(str) + 4) / 2)){
     return -1;
   }
   ncplane_styles_on(ncp, CELL_STYLE_ITALIC | CELL_STYLE_BOLD);
-  if(ncplane_putstr(ncp, str) != (int)strlen(str)){
+  if(ncplane_putstr_aligned(ncp, rows / 2, str, NCALIGN_CENTER) != (int)strlen(str)){
     return -1;
   }
   ncplane_styles_off(ncp, CELL_STYLE_ITALIC | CELL_STYLE_BOLD);
   const wchar_t wstr[] = L"▏▁ ▂ ▃ ▄ ▅ ▆ ▇ █ █ ▇ ▆ ▅ ▄ ▃ ▂ ▁▕";
-  char mbstr[128];
+  // FIXME need NCALIGN_CENTER
-  if(wcstombs(mbstr, wstr, sizeof(mbstr)) <= 0){
-    return -1;
-  }
   if(ncplane_cursor_move_yx(ncp, rows / 2 - 5, (cols - wcslen(wstr) + 4) / 2)){
     return -1;
   }
-  if(ncplane_putstr(ncp, mbstr) != (int)strlen(mbstr)){
+  if(ncplane_putwstr(ncp, wstr) != (int)wcslen(wstr)){
-    return -1;
+    //return -1;
   }
   if(notcurses_render(nc)){
     return -1;

src/lib/notcurses.c

@@ -112,6 +112,55 @@ drop_signals(notcurses* nc){
   return 0;
 }
 
+// make a heap-allocated wchar_t expansion of the multibyte string at s
+wchar_t* wchar_from_utf8(const char* s){
+  mbstate_t ps;
+  memset(&ps, 0, sizeof(ps));
+  // worst case is a wchar_t for every byte of input (all-ASCII case)
+  const size_t maxw = strlen(s) + 1;
+  wchar_t* dst = malloc(sizeof(*dst) * maxw);
+  size_t wcount = mbsrtowcs(dst, &s, maxw, &ps);
+  if(wcount == (size_t)-1){
+    free(dst);
+    return NULL;
+  }
+  if(s){
+    free(dst);
+    return NULL;
+  }
+  return dst;
+}
+
+int ncplane_putstr_aligned(ncplane* n, int y, const char* s, ncalign_e atype){
+  wchar_t* w = wchar_from_utf8(s);
+  if(w == NULL){
+    return -1;
+  }
+  int width = wcswidth(w, INT_MAX);
+  free(w);
+  int cols;
+  int xpos;
+  switch(atype){
+    case NCALIGN_LEFT:
+      xpos = 0;
+      break;
+    case NCALIGN_CENTER:
+      ncplane_dim_yx(n, NULL, &cols);
+      xpos = (cols - width) / 2;
+      break;
+    case NCALIGN_RIGHT:
+      ncplane_dim_yx(n, NULL, &cols);
+      xpos = cols - width;
+      break;
+    default:
+      return -1;
+  }
+  if(ncplane_cursor_move_yx(n, y, xpos)){
+    return -1;
+  }
+  return ncplane_putstr(n, s);
+}
+
 static inline uint64_t
 timespec_to_ns(const struct timespec* t){
   return t->tv_sec * NANOSECS_IN_SEC + t->tv_nsec;