mouse.c: Adjust clicked column if chars are concealed (#5087)

syntax.c: Added syn_get_concealed_id()

tests: Added tests for mouse clicks on concealed text.

2 files changed, 94 insertions, 0 deletions

diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index 2f499e477c..5efac2623c 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -6,6 +6,7 @@
 #include "nvim/window.h"
 #include "nvim/strings.h"
 #include "nvim/screen.h"
+#include "nvim/syntax.h"
 #include "nvim/ui.h"
 #include "nvim/os_unix.h"
 #include "nvim/fold.h"
@@ -303,6 +304,10 @@ retnomove:
     mouse_past_bottom = true;
   }
 
+  if (!(flags & MOUSE_RELEASED) && which_button == MOUSE_LEFT) {
+    col = mouse_adjust_click(curwin, row, col);
+  }
+
   // Start Visual mode before coladvance(), for when 'sel' != "old"
   if ((flags & MOUSE_MAY_VIS) && !VIsual_active) {
     check_visual_highlight();
@@ -597,3 +602,74 @@ bool mouse_scroll_horiz(int dir)
 
   return leftcol_changed();
 }
+
+// Adjust the clicked column position if there are concealed characters
+// before the current column.  But only when it's absolutely necessary.
+static int mouse_adjust_click(win_T *wp, int row, int col)
+{
+  if (!(wp->w_p_cole > 0 && curbuf->b_p_smc > 0
+        && wp->w_leftcol < curbuf->b_p_smc && conceal_cursor_line(wp))) {
+    return col;
+  }
+
+  int end = (colnr_T)STRLEN(ml_get(wp->w_cursor.lnum));
+  int vend = getviscol2(end, 0);
+
+  if (col >= vend) {
+    return col;
+  }
+
+  int i = wp->w_leftcol;
+
+  if (row > 0) {
+    i += row * (wp->w_width - win_col_off(wp) - win_col_off2(wp)
+                - wp->w_leftcol) + wp->w_skipcol;
+  }
+
+  int start_col = i;
+  int matchid;
+  int last_matchid;
+  int bcol = end - (vend - col);
+
+  while (i < bcol) {
+    matchid = syn_get_concealed_id(wp, wp->w_cursor.lnum, i);
+
+    if (matchid != 0) {
+      if (wp->w_p_cole == 3) {
+        bcol++;
+      } else {
+        if (row > 0 && i == start_col) {
+          // Check if the current concealed character is actually part of
+          // the previous wrapped row's conceal group.
+          last_matchid = syn_get_concealed_id(wp, wp->w_cursor.lnum,
+                                              i - 1);
+          if (last_matchid == matchid) {
+            bcol++;
+          }
+        } else if (wp->w_p_cole == 1
+                   || (wp->w_p_cole == 2
+                       && (lcs_conceal != NUL
+                           || syn_get_sub_char() != NUL))) {
+          // At least one placeholder character will be displayed.
+          bcol--;
+        }
+
+        last_matchid = matchid;
+
+        // Adjust for concealed text that spans more than one character.
+        do {
+          i++;
+          bcol++;
+          matchid = syn_get_concealed_id(wp, wp->w_cursor.lnum, i);
+        } while (last_matchid == matchid);
+
+        continue;
+      }
+    }
+
+    i++;
+  }
+
+  return getviscol2(bcol, 0);
+}
+
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 27855184df..3215f7ea14 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -5661,6 +5661,24 @@ int get_syntax_info(int *seqnrp)
   return current_flags;
 }
 
+
+/// Get the sequence number of the concealed file position.
+///
+/// @return seqnr if the file position is concealed, 0 otherwise.
+int syn_get_concealed_id(win_T *wp, linenr_T lnum, colnr_T col)
+{
+  int seqnr;
+  int syntax_flags;
+
+  (void)syn_get_id(wp, lnum, col, false, NULL, false);
+  syntax_flags = get_syntax_info(&seqnr);
+
+  if (syntax_flags & HL_CONCEAL) {
+    return seqnr;
+  }
+  return 0;
+}
+
 /*
  * Return conceal substitution character
  */