feat(marks): virtual lines support horizontal scrolling (#32497)

Add a new field `virt_lines_overflow` that enables horizontal scrolling
for virtual lines when set to "scroll".

1 files changed, 17 insertions, 3 deletions

diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index 2cf9221e52..ef09dbb0aa 100644
--- a/src/nvim/api/extmark.c
+++ b/src/nvim/api/extmark.c
@@ -448,7 +448,11 @@ Array nvim_buf_get_extmarks(Buffer buffer, Integer ns_id, Object start, Object e
 ///               - virt_lines_leftcol: Place virtual lines in the leftmost
 ///                                     column of the window, bypassing
 ///                                     sign and number columns.
-///
+///               - virt_lines_overflow: controls how to handle virtual lines wider
+///                   than the window. Currently takes the one of the following values:
+///                 - "trunc": truncate virtual lines on the right (default).
+///                 - "scroll": virtual lines can scroll horizontally with 'nowrap',
+///                    otherwise the same as "trunc".
 ///               - ephemeral : for use with |nvim_set_decoration_provider()|
 ///                   callbacks. The mark will only be used for the current
 ///                   redraw cycle, and not be permantently stored in the
@@ -669,7 +673,17 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
     }
   }
 
-  bool virt_lines_leftcol = opts->virt_lines_leftcol;
+  int virt_lines_flags = opts->virt_lines_leftcol ? kVLLeftcol : 0;
+  if (HAS_KEY(opts, set_extmark, virt_lines_overflow)) {
+    String str = opts->virt_lines_overflow;
+    if (strequal("scroll", str.data)) {
+      virt_lines_flags |= kVLScroll;
+    } else if (!strequal("trunc", str.data)) {
+      VALIDATE_S(false, "virt_lines_overflow", str.data, {
+        goto error;
+      });
+    }
+  }
 
   if (HAS_KEY(opts, set_extmark, virt_lines)) {
     Array a = opts->virt_lines;
@@ -679,7 +693,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id, Integer line, Integer
       });
       int dummig;
       VirtText jtem = parse_virt_text(a.items[j].data.array, err, &dummig);
-      kv_push(virt_lines.data.virt_lines, ((struct virt_line){ jtem, virt_lines_leftcol }));
+      kv_push(virt_lines.data.virt_lines, ((struct virt_line){ jtem, virt_lines_flags }));
       if (ERROR_SET(err)) {
         goto error;
       }