selector: support non-zero default idx #302

include/notcurses.h

@@ -2123,6 +2123,9 @@ typedef struct selector_options {
   char* footer; // footer may be NULL
   struct selector_item* items; // initial items and descriptions
   unsigned itemcount; // number of initial items and descriptions
+  // default item (selected at start), must be < itemcount unless 'itemcount'
+  // is 0, in which case 'defidx' must also be 0
+  unsigned defidx;
   // maximum number of options to display at once, 0 to use all available space
   unsigned maxdisplay;
   // exhaustive styling options

src/lib/selector.c

@@ -119,12 +119,15 @@ ncselector_dim_yx(notcurses* nc, const ncselector* n, int* ncdimy, int* ncdimx){
 }
 
 ncselector* ncselector_create(ncplane* n, int y, int x, const selector_options* opts){
+  if(opts->defidx && opts->defidx >= opts->itemcount){
+    return NULL;
+  }
   ncselector* ns = malloc(sizeof(*ns));
   ns->title = opts->title ? strdup(opts->title) : NULL;
   ns->secondary = opts->secondary ? strdup(opts->secondary) : NULL;
   ns->footer = opts->footer ? strdup(opts->footer) : NULL;
-  ns->selected = 0;
-  ns->startdisp = 0;
+  ns->selected = opts->defidx;
+  ns->startdisp = opts->defidx >= opts->maxdisplay ? opts->defidx - opts->maxdisplay + 1 : 0;
   ns->longop = 0;
   ns->maxdisplay = opts->maxdisplay;
   ns->longdesc = 0;

src/poc/selector.c

@@ -35,6 +35,7 @@ int main(void){
   sopts.title = "this is an awfully long example of a selector title";
   sopts.secondary = "pick one (you will die regardless)";
   sopts.footer = "press q to exit (there is no exit)";
+  sopts.defidx = 5;
   channels_set_fg(&sopts.boxchannels, 0x20e040);
   channels_set_fg(&sopts.opchannels, 0xe08040);
   channels_set_fg(&sopts.descchannels, 0x80e040);