From b00cd5cbc3ba1ae1ee8e9fb8c7f7ccfd596c082d Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Tue, 1 Dec 2020 17:55:17 +0530
Subject: [PATCH] Match save/restore cursor behavior of other terms

For the sake of interoperability. This means that doing a DECRC without
a prior DECSC is now undefined. However, one can now issue multiple
DECRC for a single DECSC. Fixes #1264
---
 docs/changelog.rst |  4 ++++
 kitty/screen.c     | 13 ++++++-------
 kitty/screen.h     | 10 ++--------
 3 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index a9ba357d1..6314bc22b 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -38,6 +38,10 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Fix one ANSI formatting escape code not being removed from the pager history
   buffer when piping it as plain text (:iss:`3132`)
 
+- Match the save/restore cursor behavior of other terminals, for the sake of
+  interoperability. This means that doing a DECRC without a prior DECSC is now
+  undefined (:iss:`1264`)
+
 
 0.19.2 [2020-11-13]
 -------------------
diff --git a/kitty/screen.c b/kitty/screen.c
index f1b4e6c43..c0152c323 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -149,6 +149,8 @@ void
 screen_reset(Screen *self) {
     if (self->linebuf == self->alt_linebuf) screen_toggle_screen_buffer(self, true, true);
     if (self->overlay_line.is_active) deactivate_overlay_line(self);
+    self->main_savepoint.is_valid = false;
+    self->alt_savepoint.is_valid = false;
     linebuf_clear(self->linebuf, BLANK_CHAR);
     historybuf_clear(self->historybuf);
     clear_hyperlink_pool(self->hyperlink_pool);
@@ -1096,14 +1098,13 @@ screen_linefeed(Screen *self) {
 
 void
 screen_save_cursor(Screen *self) {
-    SavepointBuffer *pts = self->linebuf == self->main_linebuf ? &self->main_savepoints : &self->alt_savepoints;
-    Savepoint *sp;
-    buffer_push(pts, sp);
+    Savepoint *sp = self->linebuf == self->main_linebuf ? &self->main_savepoint : &self->alt_savepoint;
     cursor_copy_to(self->cursor, &(sp->cursor));
     sp->mDECOM = self->modes.mDECOM;
     sp->mDECAWM = self->modes.mDECAWM;
     sp->mDECSCNM = self->modes.mDECSCNM;
     COPY_CHARSETS(self, sp);
+    sp->is_valid = true;
 }
 
 void
@@ -1115,10 +1116,8 @@ screen_save_modes(Screen *self) {
 
 void
 screen_restore_cursor(Screen *self) {
-    SavepointBuffer *pts = self->linebuf == self->main_linebuf ? &self->main_savepoints : &self->alt_savepoints;
-    Savepoint *sp;
-    buffer_pop(pts, sp);
-    if (sp == NULL) {
+    Savepoint *sp = self->linebuf == self->main_linebuf ? &self->main_savepoint : &self->alt_savepoint;
+    if (!sp->is_valid) {
         screen_cursor_position(self, 1, 1);
         screen_reset_mode(self, DECOM);
         RESET_CHARSETS;
diff --git a/kitty/screen.h b/kitty/screen.h
index 6546ae244..7affb4441 100644
--- a/kitty/screen.h
+++ b/kitty/screen.h
@@ -58,16 +58,10 @@ typedef struct {
     bool use_latin1;
     Cursor cursor;
     bool mDECOM, mDECAWM, mDECSCNM;
-
+    bool is_valid;
 } Savepoint;
 
 
-typedef struct {
-    Savepoint buf[SAVEPOINTS_SZ];
-    index_type start_of_data, count;
-} SavepointBuffer;
-
-
 typedef struct {
     ScreenModes buf[SAVEPOINTS_SZ];
     index_type start_of_data, count;
@@ -97,7 +91,7 @@ typedef struct {
     } last_rendered;
     bool use_latin1, is_dirty, scroll_changed, reload_all_gpu_data;
     Cursor *cursor;
-    SavepointBuffer main_savepoints, alt_savepoints;
+    Savepoint main_savepoint, alt_savepoint;
     SavemodesBuffer modes_savepoints;
     PyObject *callbacks, *test_child;
     LineBuf *linebuf, *main_linebuf, *alt_linebuf;