refactor(extmarks): use a more efficient representation

marktree.c was originally constructed as a "generic" datatype,
to make the prototyping of its internal logic as simple as possible
and also as the usecases for various kinds of extmarks/decorations was not yet decided.
As a consequence of this, various extra indirections and allocations was
needed to use marktree to implement extmarks (ns/id pairs) and
decorations of different kinds (some which is just a single highlight
id, other an allocated list of virtual text/lines)

This change removes a lot of indirection, by making Marktree specialized
for the usecase. In particular, the namespace id and mark id is stored
directly, instead of the 64-bit global id particular to the Marktree
struct. This removes the two maps needed to convert between global and
per-ns ids.

Also, "small" decorations are stored inline, i.e. those who
doesn't refer to external heap memory anyway. That is highlights (with
priority+flags) are stored inline, while virtual text, which anyway
occurs a lot of heap allocations, do not. (previously a hack was used
to elide heap allocations for highlights with standard prio+flags)

TODO(bfredl): the functionaltest-lua CI version of gcc is having
severe issues with uint16_t bitfields, so splitting up compound
assignments and redundant casts are needed. Clean this up once we switch
to a working compiler version.

1 files changed, 6 insertions, 5 deletions

diff --git a/src/nvim/api/deprecated.c b/src/nvim/api/deprecated.c
index 76b699800e..18243fec2b 100644
--- a/src/nvim/api/deprecated.c
+++ b/src/nvim/api/deprecated.c
@@ -130,7 +130,7 @@ Integer nvim_buf_set_virtual_text(Buffer buffer, Integer src_id, Integer line, A
     return 0;
   }
 
-  uint64_t ns_id = src2ns(&src_id);
+  uint32_t ns_id = src2ns(&src_id);
   int width;
 
   VirtText virt_text = parse_virt_text(chunks, err, &width);
@@ -148,11 +148,12 @@ Integer nvim_buf_set_virtual_text(Buffer buffer, Integer src_id, Integer line, A
     return src_id;
   }
 
-  Decoration *decor = xcalloc(1, sizeof(*decor));
-  decor->virt_text = virt_text;
-  decor->virt_text_width = width;
+  Decoration decor = DECORATION_INIT;
+  decor.virt_text = virt_text;
+  decor.virt_text_width = width;
+  decor.priority = 0;
 
-  extmark_set(buf, ns_id, NULL, (int)line, 0, -1, -1, decor, true,
+  extmark_set(buf, ns_id, NULL, (int)line, 0, -1, -1, &decor, true,
               false, kExtmarkNoUndo);
   return src_id;
 }