From 74803ab3775ffdb8160ab79fd621f18d8e586813 Mon Sep 17 00:00:00 2001
From: "Paul \"LeoNerd\" Evans" <leonerd@leonerd.org.uk>
Date: Thu, 1 Sep 2022 23:38:09 +0100
Subject: [PATCH] Recognise ED 3 as request to clear scrollback (MR428671)
 (thanks Russell McClellan)

---
 include/vterm.h     |  2 ++
 src/screen.c        | 11 +++++++++++
 src/state.c         |  6 ++++++
 t/13state_edit.test |  6 +++++-
 t/harness.c         | 23 +++++++++++++++++++++++
 5 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/include/vterm.h b/include/vterm.h
index 8785794e..8106a543 100644
--- a/include/vterm.h
+++ b/include/vterm.h
@@ -427,6 +427,7 @@ typedef struct {
   int (*bell)(void *user);
   int (*resize)(int rows, int cols, VTermStateFields *fields, void *user);
   int (*setlineinfo)(int row, const VTermLineInfo *newinfo, const VTermLineInfo *oldinfo, void *user);
+  int (*sb_clear)(void *user);
 } VTermStateCallbacks;
 
 typedef struct {
@@ -522,6 +523,7 @@ typedef struct {
   int (*resize)(int rows, int cols, void *user);
   int (*sb_pushline)(int cols, const VTermScreenCell *cells, void *user);
   int (*sb_popline)(int cols, VTermScreenCell *cells, void *user);
+  int (*sb_clear)(void* user);
 } VTermScreenCallbacks;
 
 VTermScreen *vterm_obtain_screen(VTerm *vt);
diff --git a/src/screen.c b/src/screen.c
index 37159199..db019f18 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -670,6 +670,16 @@ static int setlineinfo(int row, const VTermLineInfo *newinfo, const VTermLineInf
   return 1;
 }
 
+static int sb_clear(void *user) {
+  VTermScreen *screen = user;
+
+  if(screen->callbacks && screen->callbacks->sb_clear)
+    if((*screen->callbacks->sb_clear)(screen->cbdata))
+      return 1;
+
+  return 0;
+}
+
 static VTermStateCallbacks state_cbs = {
   .putglyph    = &putglyph,
   .movecursor  = &movecursor,
@@ -680,6 +690,7 @@ static VTermStateCallbacks state_cbs = {
   .bell        = &bell,
   .resize      = &resize,
   .setlineinfo = &setlineinfo,
+  .sb_clear    = &sb_clear,
 };
 
 static VTermScreen *screen_new(VTerm *vt)
diff --git a/src/state.c b/src/state.c
index 8792c142..af4bb0a6 100644
--- a/src/state.c
+++ b/src/state.c
@@ -1091,6 +1091,12 @@ static int on_csi(const char *leader, const long args[], int argcount, const cha
         set_lineinfo(state, row, FORCE, DWL_OFF, DHL_OFF);
       erase(state, rect, selective);
       break;
+
+    case 3:
+      if(state->callbacks && state->callbacks->sb_clear)
+        if((*state->callbacks->sb_clear)(state->cbdata))
+          return 1;
+      break;
     }
     break;
 
diff --git a/t/13state_edit.test b/t/13state_edit.test
index b435655e..d3f3e9e4 100644
--- a/t/13state_edit.test
+++ b/t/13state_edit.test
@@ -1,6 +1,6 @@
 INIT
 UTF8 1
-WANTSTATE se
+WANTSTATE seb
 
 !ICH
 RESET
@@ -242,6 +242,10 @@ PUSH "\e[2J"
   erase 0..25,0..80
   ?cursor = 1,1
 
+!ED 3
+PUSH "\e[3J"
+  sb_clear
+
 !SED
 RESET
   erase 0..25,0..80
diff --git a/t/harness.c b/t/harness.c
index e75f9c35..1c080423 100644
--- a/t/harness.c
+++ b/t/harness.c
@@ -449,6 +449,15 @@ static int state_setlineinfo(int row, const VTermLineInfo *newinfo, const VTermL
   return 1;
 }
 
+static int want_state_scrollback = 0;
+static int state_sb_clear(void *user) {
+  if(!want_state_scrollback)
+    return 1;
+
+  printf("sb_clear\n");
+  return 0;
+}
+
 VTermStateCallbacks state_cbs = {
   .putglyph    = state_putglyph,
   .movecursor  = movecursor,
@@ -458,6 +467,7 @@ VTermStateCallbacks state_cbs = {
   .setpenattr  = state_setpenattr,
   .settermprop = settermprop,
   .setlineinfo = state_setlineinfo,
+  .sb_clear    = state_sb_clear,
 };
 
 static int selection_set(VTermSelectionMask mask, VTermStringFragment frag, void *user)
@@ -567,6 +577,15 @@ static int screen_sb_popline(int cols, VTermScreenCell *cells, void *user)
   return 1;
 }
 
+static int screen_sb_clear(void *user)
+{
+  if(!want_screen_scrollback)
+    return 1;
+
+  printf("sb_clear\n");
+  return 0;
+}
+
 VTermScreenCallbacks screen_cbs = {
   .damage      = screen_damage,
   .moverect    = moverect,
@@ -574,6 +593,7 @@ VTermScreenCallbacks screen_cbs = {
   .settermprop = settermprop,
   .sb_pushline = screen_sb_pushline,
   .sb_popline  = screen_sb_popline,
+  .sb_clear    = screen_sb_clear,
 };
 
 int main(int argc, char **argv)
@@ -644,6 +664,9 @@ int main(int argc, char **argv)
         case 'f':
           vterm_state_set_unrecognised_fallbacks(state, sense ? &fallbacks : NULL, NULL);
           break;
+        case 'b':
+          want_state_scrollback = sense;
+          break;
         default:
           fprintf(stderr, "Unrecognised WANTSTATE flag '%c'\n", line[i]);
         }