correct drawtop/drawbot calculation

src/notcurses/notcurses.c

@@ -1492,29 +1492,27 @@ fprintf(stderr, "%s %p [%d:%d/%d] sel: %p selline: %d\n", as->c->name, cur, line
     cur = as->selected->next;
   }else{
     cur = as->bobjs;
-fprintf(stderr, "none selected, starting with %p\n", cur);
+fprintf(stderr, "none selected, starting with %p for %d rows\n", cur, rows);
     // if nothing was selected, we might have to clip at the top. check to see
     // if we're moving up. if so, run through all devices to get a total length,
     // and then move forward until we find the first visible one. begin
     // printing, in this case, at line 0. you've been clipped!
-    line = drawfromtop;
-    int totallines = 0;
     const blockobj* iter = cur;
-    line = rows - 1;
+    line = rows - 1; // optimistic (we hope to draw last line, might not)
     while(iter){
-      totallines += device_lines(as->expansion, iter);
       line -= device_lines(as->expansion, iter);
       iter = iter->next;
     }
-fprintf(stderr, "total lines: %d line: %d rows: %d\n", totallines, line, rows);
-    if(line > 0){ // they'll all fit, huzzah
+fprintf(stderr, "line: %d rows: %d drawfromtop: %u\n", line, rows, drawfromtop);
+    if(line >= 0){ // everything fits, huzzah
       line = 1;
     }else{
       if(drawfromtop){
         drawbottom = false;
       }else{
         drawtop = false;
       }
+      ++line; // we get one back for tossing a border
       while(cur && (line + device_lines(as->expansion, cur) < 0)){
         line += device_lines(as->expansion, cur);
         cur = cur->next;