From fc390da020cec35fb330a3cd440314f43569dbcc Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Thu, 17 Jun 2021 19:34:39 -0400
Subject: [PATCH] invert DECSDM for terminals with sprixel_cursor_hack set
 #1782

---
 src/lib/internal.h | 2 +-
 src/lib/sixel.c    | 7 ++++++-
 src/lib/sprite.c   | 2 +-
 src/lib/termdesc.h | 8 +++++---
 4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/lib/internal.h b/src/lib/internal.h
index d3949f074..f0d84fc3d 100644
--- a/src/lib/internal.h
+++ b/src/lib/internal.h
@@ -867,7 +867,7 @@ int sixel_destroy(const notcurses* nc, const ncpile* p, FILE* out, sprixel* s);
 int kitty_destroy(const notcurses* nc, const ncpile* p, FILE* out, sprixel* s);
 int kitty_remove(int id, FILE* out);
 int kitty_clear_all(int fd);
-int sixel_init(int fd);
+int sixel_init(const tinfo* t, int fd);
 int sprite_init(const tinfo* t, int fd);
 int sprite_clear_all(const tinfo* t, int fd);
 int kitty_shutdown(int fd);
diff --git a/src/lib/sixel.c b/src/lib/sixel.c
index 678dc6a97..fc1eea253 100644
--- a/src/lib/sixel.c
+++ b/src/lib/sixel.c
@@ -859,10 +859,15 @@ int sixel_draw(const ncpile* p, sprixel* s, FILE* out){
   return 0;
 }
 
-int sixel_init(int fd){
+int sixel_init(const tinfo* ti, int fd){
   // \e[?8452: DECSDM private "sixel scrolling" mode keeps the sixel from
   // scrolling, but puts it at the current cursor location (as opposed to
   // the upper left corner of the screen).
+  if(ti->sprixel_cursor_hack){
+    // except MLterm (and a few others, possibly including the physical VT340),
+    // which inverts the usual sense of DECSDM.
+    return tty_emit("\e[?80l\e[?8452h", fd);
+  }
   return tty_emit("\e[?80;8452h", fd);
 }
 
diff --git a/src/lib/sprite.c b/src/lib/sprite.c
index 113622af3..a3308c1be 100644
--- a/src/lib/sprite.c
+++ b/src/lib/sprite.c
@@ -205,7 +205,7 @@ int sprite_init(const tinfo* t, int fd){
   if(t->pixel_init == NULL){
     return 0;
   }
-  return t->pixel_init(fd);
+  return t->pixel_init(t, fd);
 }
 
 uint8_t* sprixel_auxiliary_vector(const sprixel* s){
diff --git a/src/lib/termdesc.h b/src/lib/termdesc.h
index dc44dbbea..38a88cb70 100644
--- a/src/lib/termdesc.h
+++ b/src/lib/termdesc.h
@@ -126,7 +126,7 @@ typedef struct tinfo {
   // perform the inverse of pixel_wipe, restoring an annihilated sprixcell.
   int (*pixel_rebuild)(struct sprixel* s, int y, int x, uint8_t* auxvec);
   int (*pixel_remove)(int id, FILE* out); // kitty only, issue actual delete command
-  int (*pixel_init)(int fd);      // called when support is detected
+  int (*pixel_init)(const struct tinfo*, int fd); // called when support is detected
   int (*pixel_draw)(const struct ncpile* p, struct sprixel* s, FILE* out);
   int (*pixel_shutdown)(int fd);  // called during context shutdown
   int (*pixel_clear_all)(int fd); // called during startup, kitty only
@@ -140,8 +140,10 @@ typedef struct tinfo {
   bool AMflag;    // "AM" flag for automatic movement to next line
 
   // mlterm resets the cursor (i.e. makes it visible) any time you print
-  // a sprixel. we work around this spiritedly unorthodox decision.
-  bool sprixel_cursor_hack; // do sprixels reset the cursor? (mlterm)
+  // a sprixel. we work around this spiritedly unorthodox decision. it
+  // furthermore interprets DECSDM in the reverse sense of most terminals
+  // (though possibly in conformance with the actual VT340).
+  bool sprixel_cursor_hack; // mlterm fixes
 } tinfo;
 
 // retrieve the terminfo(5)-style escape 'e' from tdesc (NULL if undefined).