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".

3 files changed, 20 insertions, 5 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;
       }
diff --git a/src/nvim/api/keysets_defs.h b/src/nvim/api/keysets_defs.h
index 6625908cda..b3015911f9 100644
--- a/src/nvim/api/keysets_defs.h
+++ b/src/nvim/api/keysets_defs.h
@@ -45,6 +45,7 @@ typedef struct {
   Array virt_lines;
   Boolean virt_lines_above;
   Boolean virt_lines_leftcol;
+  String virt_lines_overflow;
   Boolean strict;
   String sign_text;
   HLGroupID sign_hl_group;
diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index d581c6bc10..5cf1ca4d34 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -64,7 +64,7 @@
 #define NIL ((Object)OBJECT_INIT)
 #define NULL_STRING ((String)STRING_INIT)
 
-#define HAS_KEY(d, typ, key) (((d)->is_set__##typ##_ & (1 << KEYSET_OPTIDX_##typ##__##key)) != 0)
+#define HAS_KEY(d, typ, key) (((d)->is_set__##typ##_ & (1ULL << KEYSET_OPTIDX_##typ##__##key)) != 0)
 
 #define GET_BOOL_OR_TRUE(d, typ, key) (HAS_KEY(d, typ, key) ? (d)->key : true)
 
@@ -75,7 +75,7 @@
   kv_push_c(dict, ((KeyValuePair) { .key = cstr_as_string(k), .value = v }))
 
 #define PUT_KEY(d, typ, key, v) \
-  do { (d).is_set__##typ##_ |= (1 << KEYSET_OPTIDX_##typ##__##key); (d).key = v; } while (0)
+  do { (d).is_set__##typ##_ |= (1ULL << KEYSET_OPTIDX_##typ##__##key); (d).key = v; } while (0)
 
 #define ADD(array, item) \
   kv_push(array, item)