feat(terminal)!: cursor shape and blink (#31562)

When a terminal application running inside the terminal emulator sets
the cursor shape or blink status of the cursor, update the cursor in the
parent terminal to match.

This removes the "virtual cursor" that has been in use by the terminal
emulator since the beginning. The original rationale for using the
virtual cursor was to avoid having to support additional UI methods to
change the cursor color for other (non-TUI) UIs, instead relying on the
TermCursor and TermCursorNC highlight groups.

The TermCursor highlight group is now used in the default 'guicursor'
value, which has a new entry for Terminal mode. However, the
TermCursorNC highlight group is no longer supported: since terminal
windows now use the real cursor, when the window is not focused there is
no cursor displayed in the window at all, so there is nothing to
highlight. Users can still use the StatusLineTermNC highlight group to
differentiate non-focused terminal windows.

BREAKING CHANGE: The TermCursorNC highlight group is no longer supported.

1 files changed, 151 insertions, 33 deletions

diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index 6d4af0fc57..fa08f3d6ca 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -52,6 +52,7 @@
 #include "nvim/channel.h"
 #include "nvim/channel_defs.h"
 #include "nvim/cursor.h"
+#include "nvim/cursor_shape.h"
 #include "nvim/drawline.h"
 #include "nvim/drawscreen.h"
 #include "nvim/eval.h"
@@ -160,14 +161,18 @@ struct terminal {
   int invalid_start, invalid_end;   // invalid rows in libvterm screen
   struct {
     int row, col;
+    int shape;
     bool visible;
+    bool blink;
   } cursor;
-  bool pending_resize;              // pending width/height
 
-  bool color_set[16];
+  struct {
+    bool resize;          ///< pending width/height
+    bool cursor;          ///< pending cursor shape or blink change
+    StringBuilder *send;  ///< When there is a pending TermRequest autocommand, block and store input.
+  } pending;
 
-  // When there is a pending TermRequest autocommand, block and store input.
-  StringBuilder *pending_send;
+  bool color_set[16];
 
   char *selection_buffer;  /// libvterm selection buffer
   StringBuilder selection;  /// Growable array containing full selection data
@@ -207,24 +212,24 @@ static void emit_termrequest(void **argv)
   apply_autocmds_group(EVENT_TERMREQUEST, NULL, NULL, false, AUGROUP_ALL, buf, NULL, &data);
   xfree(payload);
 
-  StringBuilder *term_pending_send = term->pending_send;
-  term->pending_send = NULL;
+  StringBuilder *term_pending_send = term->pending.send;
+  term->pending.send = NULL;
   if (kv_size(*pending_send)) {
     terminal_send(term, pending_send->items, pending_send->size);
     kv_destroy(*pending_send);
   }
   if (term_pending_send != pending_send) {
-    term->pending_send = term_pending_send;
+    term->pending.send = term_pending_send;
   }
   xfree(pending_send);
 }
 
 static void schedule_termrequest(Terminal *term, char *payload, size_t payload_length)
 {
-  term->pending_send = xmalloc(sizeof(StringBuilder));
-  kv_init(*term->pending_send);
+  term->pending.send = xmalloc(sizeof(StringBuilder));
+  kv_init(*term->pending.send);
   multiqueue_put(main_loop.events, emit_termrequest, term, payload, (void *)payload_length,
-                 term->pending_send);
+                 term->pending.send);
 }
 
 static int parse_osc8(VTermStringFragment frag, int *attr)
@@ -363,7 +368,7 @@ void terminal_open(Terminal **termpp, buf_T *buf, TerminalOptions opts)
   // Create a new terminal instance and configure it
   Terminal *term = *termpp = xcalloc(1, sizeof(Terminal));
   term->opts = opts;
-  term->cursor.visible = true;
+
   // Associate the terminal instance with the new buffer
   term->buf_handle = buf->handle;
   buf->terminal = term;
@@ -387,6 +392,28 @@ void terminal_open(Terminal **termpp, buf_T *buf, TerminalOptions opts)
   vterm_state_set_selection_callbacks(state, &vterm_selection_callbacks, term,
                                       term->selection_buffer, SELECTIONBUF_SIZE);
 
+  VTermValue cursor_shape;
+  switch (shape_table[SHAPE_IDX_TERM].shape) {
+  case SHAPE_BLOCK:
+    cursor_shape.number = VTERM_PROP_CURSORSHAPE_BLOCK;
+    break;
+  case SHAPE_HOR:
+    cursor_shape.number = VTERM_PROP_CURSORSHAPE_UNDERLINE;
+    break;
+  case SHAPE_VER:
+    cursor_shape.number = VTERM_PROP_CURSORSHAPE_BAR_LEFT;
+    break;
+  }
+  vterm_state_set_termprop(state, VTERM_PROP_CURSORSHAPE, &cursor_shape);
+
+  VTermValue cursor_blink;
+  if (shape_table[SHAPE_IDX_TERM].blinkon != 0 && shape_table[SHAPE_IDX_TERM].blinkoff != 0) {
+    cursor_blink.boolean = true;
+  } else {
+    cursor_blink.boolean = false;
+  }
+  vterm_state_set_termprop(state, VTERM_PROP_CURSORBLINK, &cursor_blink);
+
   // force a initial refresh of the screen to ensure the buffer will always
   // have as many lines as screen rows when refresh_scrollback is called
   term->invalid_start = 0;
@@ -565,7 +592,7 @@ void terminal_check_size(Terminal *term)
 
   vterm_set_size(term->vt, height, width);
   vterm_screen_flush_damage(term->vts);
-  term->pending_resize = true;
+  term->pending.resize = true;
   invalidate_terminal(term, -1, -1);
 }
 
@@ -614,16 +641,28 @@ bool terminal_enter(void)
   curwin->w_p_so = 0;
   curwin->w_p_siso = 0;
 
+  // Save the existing cursor entry since it may be modified by the application
+  cursorentry_T save_cursorentry = shape_table[SHAPE_IDX_TERM];
+
+  // Update the cursor shape table and flush changes to the UI
+  s->term->pending.cursor = true;
+  refresh_cursor(s->term);
+
   adjust_topline(s->term, buf, 0);  // scroll to end
-  // erase the unfocused cursor
-  invalidate_terminal(s->term, s->term->cursor.row, s->term->cursor.row + 1);
   showmode();
   curwin->w_redr_status = true;  // For mode() in statusline. #8323
   redraw_custom_title_later();
-  ui_busy_start();
+  if (!s->term->cursor.visible) {
+    // Hide cursor if it should be hidden
+    ui_busy_start();
+  }
+  ui_cursor_shape();
   apply_autocmds(EVENT_TERMENTER, NULL, NULL, false, curbuf);
   may_trigger_modechanged();
 
+  // Tell the terminal it has focus
+  terminal_focus(s->term, true);
+
   s->state.execute = terminal_execute;
   s->state.check = terminal_check;
   state_enter(&s->state);
@@ -635,6 +674,9 @@ bool terminal_enter(void)
   RedrawingDisabled = s->save_rd;
   apply_autocmds(EVENT_TERMLEAVE, NULL, NULL, false, curbuf);
 
+  shape_table[SHAPE_IDX_TERM] = save_cursorentry;
+  ui_mode_info_set();
+
   if (save_curwin == curwin->handle) {  // Else: window was closed.
     curwin->w_p_cul = save_w_p_cul;
     if (save_w_p_culopt) {
@@ -649,8 +691,9 @@ bool terminal_enter(void)
     free_string_option(save_w_p_culopt);
   }
 
-  // draw the unfocused cursor
-  invalidate_terminal(s->term, s->term->cursor.row, s->term->cursor.row + 1);
+  // Tell the terminal it lost focus
+  terminal_focus(s->term, false);
+
   if (curbuf->terminal == s->term && !s->close) {
     terminal_check_cursor();
   }
@@ -659,7 +702,11 @@ bool terminal_enter(void)
   } else {
     unshowmode(true);
   }
-  ui_busy_stop();
+  if (!s->term->cursor.visible) {
+    // If cursor was hidden, show it again
+    ui_busy_stop();
+  }
+  ui_cursor_shape();
   if (s->close) {
     bool wipe = s->term->buf_handle != 0;
     s->term->destroy = true;
@@ -810,6 +857,19 @@ static int terminal_execute(VimState *state, int key)
     return 0;
   }
   if (s->term != curbuf->terminal) {
+    // Active terminal buffer changed, flush terminal's cursor state to the UI
+    curbuf->terminal->pending.cursor = true;
+
+    if (!s->term->cursor.visible) {
+      // If cursor was hidden, show it again
+      ui_busy_stop();
+    }
+
+    if (!curbuf->terminal->cursor.visible) {
+      // Hide cursor if it should be hidden
+      ui_busy_start();
+    }
+
     invalidate_terminal(s->term, s->term->cursor.row, s->term->cursor.row + 1);
     invalidate_terminal(curbuf->terminal,
                         curbuf->terminal->cursor.row,
@@ -857,8 +917,8 @@ static void terminal_send(Terminal *term, const char *data, size_t size)
   if (term->closed) {
     return;
   }
-  if (term->pending_send) {
-    kv_concat_len(*term->pending_send, data, size);
+  if (term->pending.send) {
+    kv_concat_len(*term->pending.send, data, size);
     return;
   }
   term->opts.write_cb(data, size, term->opts.data);
@@ -1063,14 +1123,6 @@ void terminal_get_line_attributes(Terminal *term, win_T *wp, int linenr, int *te
       attr_id = hl_combine_attr(attr_id, cell.uri);
     }
 
-    if (term->cursor.visible && term->cursor.row == row
-        && term->cursor.col == col) {
-      attr_id = hl_combine_attr(attr_id,
-                                is_focused(term) && wp == curwin
-                                ? win_hl_attr(wp, HLF_TERM)
-                                : win_hl_attr(wp, HLF_TERMNC));
-    }
-
     term_attrs[col] = attr_id;
   }
 }
@@ -1085,6 +1137,17 @@ bool terminal_running(const Terminal *term)
   return !term->closed;
 }
 
+static void terminal_focus(const Terminal *term, bool focus)
+  FUNC_ATTR_NONNULL_ALL
+{
+  VTermState *state = vterm_obtain_state(term->vt);
+  if (focus) {
+    vterm_state_focus_in(state);
+  } else {
+    vterm_state_focus_out(state);
+  }
+}
+
 // }}}
 // libvterm callbacks {{{
 
@@ -1106,8 +1169,7 @@ static int term_movecursor(VTermPos new_pos, VTermPos old_pos, int visible, void
   Terminal *term = data;
   term->cursor.row = new_pos.row;
   term->cursor.col = new_pos.col;
-  invalidate_terminal(term, old_pos.row, old_pos.row + 1);
-  invalidate_terminal(term, new_pos.row, new_pos.row + 1);
+  invalidate_terminal(term, -1, -1);
   return 1;
 }
 
@@ -1135,8 +1197,17 @@ static int term_settermprop(VTermProp prop, VTermValue *val, void *data)
     break;
 
   case VTERM_PROP_CURSORVISIBLE:
+    if (is_focused(term)) {
+      if (!val->boolean && term->cursor.visible) {
+        // Hide the cursor
+        ui_busy_start();
+      } else if (val->boolean && !term->cursor.visible) {
+        // Unhide the cursor
+        ui_busy_stop();
+      }
+      invalidate_terminal(term, -1, -1);
+    }
     term->cursor.visible = val->boolean;
-    invalidate_terminal(term, term->cursor.row, term->cursor.row + 1);
     break;
 
   case VTERM_PROP_TITLE: {
@@ -1172,6 +1243,18 @@ static int term_settermprop(VTermProp prop, VTermValue *val, void *data)
     term->forward_mouse = (bool)val->number;
     break;
 
+  case VTERM_PROP_CURSORBLINK:
+    term->cursor.blink = val->boolean;
+    term->pending.cursor = true;
+    invalidate_terminal(term, -1, -1);
+    break;
+
+  case VTERM_PROP_CURSORSHAPE:
+    term->cursor.shape = val->number;
+    term->pending.cursor = true;
+    invalidate_terminal(term, -1, -1);
+    break;
+
   default:
     return 0;
   }
@@ -1849,12 +1932,47 @@ static void refresh_terminal(Terminal *term)
   refresh_size(term, buf);
   refresh_scrollback(term, buf);
   refresh_screen(term, buf);
+  refresh_cursor(term);
   aucmd_restbuf(&aco);
 
   int ml_added = buf->b_ml.ml_line_count - ml_before;
   adjust_topline(term, buf, ml_added);
 }
 
+static void refresh_cursor(Terminal *term)
+  FUNC_ATTR_NONNULL_ALL
+{
+  if (!is_focused(term) || !term->pending.cursor) {
+    return;
+  }
+  term->pending.cursor = false;
+
+  if (term->cursor.blink) {
+    // For the TUI, this value doesn't actually matter, as long as it's non-zero. The terminal
+    // emulator dictates the blink frequency, not the application.
+    // For GUIs we just pick an arbitrary value, for now.
+    shape_table[SHAPE_IDX_TERM].blinkon = 500;
+    shape_table[SHAPE_IDX_TERM].blinkoff = 500;
+  } else {
+    shape_table[SHAPE_IDX_TERM].blinkon = 0;
+    shape_table[SHAPE_IDX_TERM].blinkoff = 0;
+  }
+
+  switch (term->cursor.shape) {
+  case VTERM_PROP_CURSORSHAPE_BLOCK:
+    shape_table[SHAPE_IDX_TERM].shape = SHAPE_BLOCK;
+    break;
+  case VTERM_PROP_CURSORSHAPE_UNDERLINE:
+    shape_table[SHAPE_IDX_TERM].shape = SHAPE_HOR;
+    break;
+  case VTERM_PROP_CURSORSHAPE_BAR_LEFT:
+    shape_table[SHAPE_IDX_TERM].shape = SHAPE_VER;
+    break;
+  }
+
+  ui_mode_info_set();
+}
+
 /// Calls refresh_terminal() on all invalidated_terminals.
 static void refresh_timer_cb(TimeWatcher *watcher, void *data)
 {
@@ -1875,11 +1993,11 @@ static void refresh_timer_cb(TimeWatcher *watcher, void *data)
 
 static void refresh_size(Terminal *term, buf_T *buf)
 {
-  if (!term->pending_resize || term->closed) {
+  if (!term->pending.resize || term->closed) {
     return;
   }
 
-  term->pending_resize = false;
+  term->pending.resize = false;
   int width, height;
   vterm_get_size(term->vt, &height, &width);
   term->invalid_start = 0;