implement child plane scrolling #1883

doc/man/man3/notcurses_plane.3.md

@@ -383,8 +383,9 @@ other rows are moved up, the last row is cleared, and output begins at the
 beginning of the last row. This does not take place until output is generated
 (i.e. it is possible to fill a plane when scrolling is enabled).
 
-By default, planes bound to a scrolling plane will scroll along with it. This
-can be disabled with the **NCPLANE_OPTION_FIXED** flag.
+By default, planes bound to a scrolling plane will scroll along with it, if
+they intersect the plane. This can be disabled with the
+**NCPLANE_OPTION_FIXED** flag.
 
 ## Bitmaps
 

src/lib/internal.h

@@ -100,6 +100,7 @@ typedef struct ncplane {
   uint16_t stylemask;    // same deal as in a cell
   int margin_b, margin_r;// bottom and right margins, stored for resize
   bool scrolling;        // is scrolling enabled? always disabled by default
+  bool fixedbound;       // are we fixed relative to the parent's scrolling?
 } ncplane;
 
 // current presentation state of the terminal. it is carried across render

src/lib/notcurses.c

@@ -417,6 +417,7 @@ ncplane* ncplane_new_internal(notcurses* nc, ncplane* n,
     return NULL;
   }
   p->scrolling = false;
+  p->fixedbound = nopts->flags & NCPLANE_OPTION_FIXED;
   if(nopts->flags & NCPLANE_OPTION_MARGINALIZED){
     p->margin_b = nopts->margin_b;
     p->margin_r = nopts->margin_r;
@@ -1529,7 +1530,8 @@ nccell_obliterate(ncplane* n, nccell* c){
   nccell_init(c);
 }
 
-// increment y by 1 and rotate the framebuffer up one line. x moves to 0.
+// increment y by 1 and rotate the framebuffer up one line. x moves to 0. any
+// non-fixed bound planes move up 1 line if they intersect the plane.
 void scroll_down(ncplane* n){
 //fprintf(stderr, "pre-scroll: %d/%d %d/%d log: %d scrolling: %u\n", n->y, n->x, n->leny, n->lenx, n->logrow, n->scrolling);
   n->x = 0;
@@ -1546,6 +1548,12 @@ void scroll_down(ncplane* n){
   }else{
     ++n->y;
   }
+  for(struct ncplane* c = n->blist ; c ; c = c->bnext){
+    if(!c->fixedbound){
+      // FIXME ought only be performed if we intersect the parent plane
+      ncplane_moverel(c, -1, 0);
+    }
+  }
 }
 
 int nccell_width(const ncplane* n __attribute__ ((unused)), const nccell* c){