From c69849ffb15a8c03b7c80d7785d4d965c4a24cea Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Mon, 4 Oct 2021 01:48:50 -0400
Subject: [PATCH] track unknown background color if we can't learn it #2226

---
 src/info/main.c    | 10 +++++++---
 src/lib/render.c   |  3 ++-
 src/lib/termdesc.c | 11 +++++++----
 src/lib/termdesc.h |  3 ++-
 4 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/info/main.c b/src/info/main.c
index 8771398bb..bab26c7cb 100644
--- a/src/info/main.c
+++ b/src/info/main.c
@@ -337,9 +337,13 @@ display_logo(struct ncplane* n, const char* path){
 
 static void
 tinfo_debug_bitmaps(struct ncplane* n, const tinfo* ti, const char* indent){
-  ncplane_printf(n, "%sdefbg 0x%06lx %sconsidered transparent", indent,
-                 ti->bg_collides_default & 0xfffffful,
-                 (ti->bg_collides_default & 0x01000000) ? "" : "not ");
+  if(!(ti->bg_collides_default & 0x80000000)){
+    ncplane_printf(n, "%sdefbg 0x%06lx %sconsidered transparent", indent,
+                  ti->bg_collides_default & 0xfffffful,
+                  (ti->bg_collides_default & 0x01000000) ? "" : "not ");
+  }else{
+    ncplane_printf(n, "couldn't detect default background");
+  }
   finish_line(n);
   ncpixelimpl_e blit = notcurses_check_pixel_support(ncplane_notcurses(n));
   switch(blit){
diff --git a/src/lib/render.c b/src/lib/render.c
index 43888bc7c..4ae582854 100644
--- a/src/lib/render.c
+++ b/src/lib/render.c
@@ -146,6 +146,7 @@ static uint32_t
 highcontrast(const tinfo* ti, uint32_t bchannel){
   unsigned r, g, b;
   if(ncchannel_default_p(bchannel)){
+    // FIXME what if we couldn't identify the background color?
     r = ncchannel_r(ti->bg_collides_default);
     g = ncchannel_g(ti->bg_collides_default);
     b = ncchannel_b(ti->bg_collides_default);
@@ -691,7 +692,7 @@ term_bg_rgb8(const tinfo* ti, fbuf* f, unsigned r, unsigned g, unsigned b){
   // we're also in that case working with hopefully more robust terminals.
   // If it doesn't work, eh, it doesn't work. Fuck the world; save yourself.
   if(ti->caps.rgb){
-    if(ti->bg_collides_default){
+    if((ti->bg_collides_default & 0xff000000) == 0x01000000){
       if((r == (ti->bg_collides_default & 0xff0000lu)) &&
          (g == (ti->bg_collides_default & 0xff00lu)) &&
          (b == (ti->bg_collides_default & 0xfflu))){
diff --git a/src/lib/termdesc.c b/src/lib/termdesc.c
index d6ed8a591..1b30e14dd 100644
--- a/src/lib/termdesc.c
+++ b/src/lib/termdesc.c
@@ -721,6 +721,7 @@ int interrogate_terminfo(tinfo* ti, const char* termtype, FILE* out, unsigned ut
   }
   *cursor_x = *cursor_y = -1;
   memset(ti, 0, sizeof(*ti));
+  ti->bg_collides_default = 0xfe000000;
   ti->qterm = TERMINAL_UNKNOWN;
   // we don't need a controlling tty for everything we do; allow a failure here
   ti->ttyfd = get_tty_fd(out);
@@ -951,7 +952,11 @@ int interrogate_terminfo(tinfo* ti, const char* termtype, FILE* out, unsigned ut
       ti->cellpixy = ti->pixy / ti->default_rows;
       ti->cellpixx = ti->pixx / ti->default_cols;
     }
-    ti->bg_collides_default = iresp->bg;
+    if(iresp->got_bg){
+      // reset the 0xfe000000 we loaded during initialization. if we're
+      // kitty, we'll add the 0x01000000 in during heuristics.
+      ti->bg_collides_default = iresp->bg;
+    }
     // kitty trumps sixel, when both are available
     if((kitty_graphics = iresp->kitty_graphics) == 0){
       ti->color_registers = iresp->color_registers;
@@ -959,9 +964,7 @@ int interrogate_terminfo(tinfo* ti, const char* termtype, FILE* out, unsigned ut
       ti->sixel_maxx = iresp->sixelx;
     }
     free(iresp);
-  }
-  if(nocbreak){
-    if(ti->ttyfd >= 0){
+    if(nocbreak){
       // FIXME do this in input later, upon signaling completion?
       if(tcsetattr(ti->ttyfd, TCSANOW, ti->tpreserved)){
         goto err;
diff --git a/src/lib/termdesc.h b/src/lib/termdesc.h
index 6119319f5..686d3d2f6 100644
--- a/src/lib/termdesc.h
+++ b/src/lib/termdesc.h
@@ -112,7 +112,8 @@ typedef struct tinfo {
   // kitty interprets an RGB background that matches the default background
   // color *as* the default background, meaning it'll be translucent if
   // background_opaque is in use. detect this, and avoid the default if so.
-  // bg_collides_default is either 0x0000000 or (if in use) 0x1RRGGBB.
+  // bg_collides_default is either:
+  // 0xfexxxxxxx (unknown), 0x00RRGGBB (no collide), or 0x01RRGGBB (collides).
   uint32_t bg_collides_default;
 
   // bitmap support. if we support bitmaps, pixel_implementation will be a