From ed8c369d4e0e9b7f73da5404b99d2b9238b351ab Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Sun, 4 Jul 2021 03:29:32 -0400
Subject: [PATCH] on pile change, clear old sprixels #1875

---
 src/lib/internal.h  |  6 ++++++
 src/lib/notcurses.c |  1 +
 src/lib/render.c    | 14 +++++++++++---
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/lib/internal.h b/src/lib/internal.h
index d453c96b9..a03a8a964 100644
--- a/src/lib/internal.h
+++ b/src/lib/internal.h
@@ -472,6 +472,12 @@ typedef struct notcurses {
   // we keep a copy of the last rendered frame. this facilitates O(1)
   // notcurses_at_yx() and O(1) damage detection (at the cost of some memory).
   nccell* lastframe;// last rasterized framebuffer, NULL until first raster
+  // the last pile we rasterized. NULL until we've rasterized once. might
+  // be invalid due to the pile being destroyed; you are only allowed to
+  // evaluate it for equality to the pile being currently rasterized. when
+  // we switch piles, we need to clear all displayed sprixels, and
+  // invalidate the new pile's, pursuant to their display.
+  ncpile* last_pile;
   egcpool pool;   // egcpool for lastframe
 
   int lfdimx;     // dimensions of lastframe, unchanged by screen resize
diff --git a/src/lib/notcurses.c b/src/lib/notcurses.c
index e092b21a8..353fc2a76 100644
--- a/src/lib/notcurses.c
+++ b/src/lib/notcurses.c
@@ -1036,6 +1036,7 @@ notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
   if(ret == NULL){
     return ret;
   }
+  ret->last_pile = NULL;
   ret->rstate.mstream = NULL;
   ret->rstate.mstreamfp = NULL;
   ret->loglevel = opts->loglevel;
diff --git a/src/lib/render.c b/src/lib/render.c
index 474833bee..6dcfd1228 100644
--- a/src/lib/render.c
+++ b/src/lib/render.c
@@ -1119,12 +1119,16 @@ raster_and_write(notcurses* nc, ncpile* p, FILE* out){
       return -1;
     }
   }
+  // if the last pile was different from this one, we need clear all old
+  // sprixels (and invalidate all those of the current pile -- FIXME).
+  if(nc->last_pile != p){
+    if(sprite_clear_all(&nc->tcache, out)){
+      return -1;
+    }
+  }
   if(notcurses_rasterize_inner(nc, p, out, &useasu) < 0){
     return -1;
   }
-  int ret = 0;
-  sigset_t oldmask;
-  block_signals(&oldmask);
   // if we loaded a BSU into the front, but don't actually want to use it,
   // we start printing after the BSU.
   size_t moffset = 0;
@@ -1135,6 +1139,9 @@ raster_and_write(notcurses* nc, ncpile* p, FILE* out){
       moffset = strlen(basu);
     }
   }
+  int ret = 0;
+  sigset_t oldmask;
+  block_signals(&oldmask);
   if(blocking_write(fileno(nc->ttyfp), nc->rstate.mstream + moffset,
                     nc->rstate.mstrsize - moffset)){
     ret = -1;
@@ -1165,6 +1172,7 @@ notcurses_rasterize(notcurses* nc, ncpile* p, FILE* out){
   if(cursory >= 0){
     notcurses_cursor_enable(nc, cursory, cursorx);
   }
+  nc->last_pile = p;
   return ret;
 }