Add a 'premove' state-layer callback to inform the higher layer befor…

…e scroll-based moves happen

include/vterm.h

@@ -437,6 +437,8 @@ typedef struct {
   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);
+  // ABI-compat only enabled if vterm_state_callbacks_has_premove() is invoked
+  int (*premove)(VTermRect dest, void *user);
 } VTermStateCallbacks;
 
 typedef struct {
@@ -459,6 +461,8 @@ VTermState *vterm_obtain_state(VTerm *vt);
 void  vterm_state_set_callbacks(VTermState *state, const VTermStateCallbacks *callbacks, void *user);
 void *vterm_state_get_cbdata(VTermState *state);
 
+void vterm_state_callbacks_has_premove(VTermState *state);
+
 void  vterm_state_set_unrecognised_fallbacks(VTermState *state, const VTermStateFallbacks *fallbacks, void *user);
 void *vterm_state_get_unrecognised_fbdata(VTermState *state);
 

src/state.c

@@ -73,6 +73,7 @@ static VTermState *vterm_state_new(VTerm *vt)
 
   state->callbacks = NULL;
   state->cbdata    = NULL;
+  state->callbacks_has_premove = false;
 
   state->selection.callbacks = NULL;
   state->selection.user      = NULL;
@@ -126,6 +127,33 @@ static void scroll(VTermState *state, VTermRect rect, int downward, int rightwar
   else if(rightward < -cols)
     rightward = -cols;
 
+  if(state->callbacks_has_premove && state->callbacks && state->callbacks->premove) {
+    // TODO: technically this logic is wrong if both downward != 0 and rightward != 0
+
+    /* Work out what subsection of the destination area is about to be destroyed */
+    if(downward > 0)
+      /* about to destroy the top */
+      (*state->callbacks->premove)((VTermRect){
+          .start_row = rect.start_row, .end_row = rect.start_row + downward,
+          .start_col = rect.start_col, .end_col = rect.end_col}, state->cbdata);
+    else if(downward < 0)
+      /* about to destroy the bottom */
+      (*state->callbacks->premove)((VTermRect){
+          .start_row = rect.end_row + downward, .end_row = rect.end_row,
+          .start_col = rect.start_col,          .end_col = rect.end_col}, state->cbdata);
+
+    if(rightward > 0)
+      /* about to destroy the left */
+      (*state->callbacks->premove)((VTermRect){
+          .start_row = rect.start_row, .end_row = rect.end_row,
+          .start_col = rect.start_col, .end_col = rect.start_col + rightward}, state->cbdata);
+    else if(rightward < 0)
+      /* about to destroy the right */
+      (*state->callbacks->premove)((VTermRect){
+          .start_row = rect.start_row,           .end_row = rect.end_row,
+          .start_col = rect.end_col + rightward, .end_col = rect.end_col}, state->cbdata);
+  }
+
   // Update lineinfo if full line
   if(rect.start_col == 0 && rect.end_col == state->cols && rightward == 0) {
     int height = rect.end_row - rect.start_row - abs(downward);
@@ -2156,6 +2184,11 @@ void vterm_state_set_callbacks(VTermState *state, const VTermStateCallbacks *cal
   }
 }
 
+void vterm_state_callbacks_has_premove(VTermState *state)
+{
+  state->callbacks_has_premove = true;
+}
+
 void *vterm_state_get_cbdata(VTermState *state)
 {
   return state->cbdata;

src/vterm_internal.h

@@ -58,6 +58,7 @@ struct VTermState
 
   const VTermStateCallbacks *callbacks;
   void *cbdata;
+  bool callbacks_has_premove;
 
   const VTermStateFallbacks *fallbacks;
   void *fbdata;

t/12state_scroll.test

@@ -127,24 +127,28 @@ PUSH "\e[100;105r\eD"
 PUSH "\e[5;2r\eD"
 
 RESET
-WANTSTATE -s+me
+WANTSTATE -s+Pme
 
 !Scroll Down move+erase emulation
 PUSH "\e[S"
+  premove 0..1,0..80
   moverect 1..25,0..80 -> 0..24,0..80
   erase 24..25,0..80
   ?cursor = 0,0
 PUSH "\e[2S"
+  premove 0..2,0..80
   moverect 2..25,0..80 -> 0..23,0..80
   erase 23..25,0..80
   ?cursor = 0,0
 
 !Scroll Up move+erase emulation
 PUSH "\e[T"
+  premove 24..25,0..80
   moverect 0..24,0..80 -> 1..25,0..80
   erase 0..1,0..80
   ?cursor = 0,0
 PUSH "\e[2T"
+  premove 23..25,0..80
   moverect 0..23,0..80 -> 2..25,0..80
   erase 0..2,0..80
   ?cursor = 0,0

t/13state_edit.test

@@ -268,7 +268,7 @@ PUSH "\e[2\"q"
 PUSH "\eP\$q\"q\e\\"
   output "\eP1\$r2\"q\e\\"
 
-WANTSTATE -s+m
+WANTSTATE -s+Pm
 
 !ICH move+erase emuation
 RESET
@@ -278,12 +278,14 @@ PUSH "ACD"
 PUSH "\e[2D"
   ?cursor = 0,1
 PUSH "\e[@"
+  premove 0..1,79..80
   moverect 0..1,1..79 -> 0..1,2..80
   erase 0..1,1..2
   ?cursor = 0,1
 PUSH "B"
   ?cursor = 0,2
 PUSH "\e[3@"
+  premove 0..1,77..80
   moverect 0..1,2..77 -> 0..1,5..80
   erase 0..1,2..5
 
@@ -295,10 +297,12 @@ PUSH "ABBC"
 PUSH "\e[3D"
   ?cursor = 0,1
 PUSH "\e[P"
+  premove 0..1,1..2
   moverect 0..1,2..80 -> 0..1,1..79
   erase 0..1,79..80
   ?cursor = 0,1
 PUSH "\e[3P"
+  premove 0..1,1..4
   moverect 0..1,4..80 -> 0..1,1..77
   erase 0..1,77..80
   ?cursor = 0,1

t/harness.c

@@ -318,6 +318,18 @@ static int movecursor(VTermPos pos, VTermPos oldpos, int visible, void *user)
   return 1;
 }
 
+static int want_premove = 0;
+static int premove(VTermRect rect, void *user)
+{
+  if(!want_premove)
+    return 0;
+
+  printf("premove %d..%d,%d..%d\n",
+      rect.start_row, rect.end_row, rect.start_col, rect.end_col);
+
+  return 1;
+}
+
 static int want_scrollrect = 0;
 static int scrollrect(VTermRect rect, int downward, int rightward, void *user)
 {
@@ -489,6 +501,7 @@ static int state_sb_clear(void *user) {
 VTermStateCallbacks state_cbs = {
   .putglyph    = state_putglyph,
   .movecursor  = movecursor,
+  .premove     = premove,
   .scrollrect  = scrollrect,
   .moverect    = moverect,
   .erase       = state_erase,
@@ -657,6 +670,7 @@ int main(int argc, char **argv)
       if(!state) {
         state = vterm_obtain_state(vt);
         vterm_state_set_callbacks(state, &state_cbs, NULL);
+        vterm_state_callbacks_has_premove(state);
         /* In some tests we want to check the behaviour of overflowing the
          * buffer, so make it nicely small
          */
@@ -683,6 +697,9 @@ int main(int argc, char **argv)
         case 's':
           want_scrollrect = sense;
           break;
+        case 'P':
+          want_premove = sense;
+          break;
         case 'm':
           want_moverect = sense;
           break;

t/run-test.pl

@@ -125,7 +125,7 @@ sub do_line
       elsif( $line =~ m/^putglyph (\S+) (.*)$/ ) {
          $line = "putglyph " . join( ",", map sprintf("%x", $_), eval($1) ) . " $2";
       }
-      elsif( $line =~ m/^(?:movecursor|scrollrect|moverect|erase|damage|sb_pushline|sb_popline|sb_clear|settermprop|setmousefunc|selection-query) ?/ ) {
+      elsif( $line =~ m/^(?:movecursor|scrollrect|premove|moverect|erase|damage|sb_pushline|sb_popline|sb_clear|settermprop|setmousefunc|selection-query) ?/ ) {
          # no conversion
       }
       elsif( $line =~ m/^(selection-set) (.*?) (\[?)(.*?)(\]?)$/ ) {