feat(luahl): add priority mechanism

Base priority is 0x1000, in order to stay kinda backward compatible.
Also set tree-sitter default highlight to 100 (middle-ish value)

5 files changed, 125 insertions, 15 deletions

diff --git a/runtime/lua/vim/treesitter/highlighter.lua b/runtime/lua/vim/treesitter/highlighter.lua
index 60db7f24cf..275e960e28 100644
--- a/runtime/lua/vim/treesitter/highlighter.lua
+++ b/runtime/lua/vim/treesitter/highlighter.lua
@@ -219,7 +219,8 @@ local function on_line_impl(self, buf, line)
         a.nvim_buf_set_extmark(buf, ns, start_row, start_col,
                                { end_line = end_row, end_col = end_col,
                                  hl_group = hl,
-                                 ephemeral = true
+                                 ephemeral = true,
+                                 priority = 100 -- Low but leaves room below
                                 })
       end
       if start_row > line then
diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 4fc0ee4fdf..1011f050fd 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -1122,6 +1122,8 @@ static Array extmark_to_array(ExtmarkInfo extmark, bool id, bool add_dict)
         }
         PUT(dict, "virt_text", ARRAY_OBJ(chunks));
       }
+
+      PUT(dict, "priority", INTEGER_OBJ(decor->priority));
     }
 
     if (dict.size) {
@@ -1375,6 +1377,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
 
   uint64_t id = 0;
   int line2 = -1, hl_id = 0;
+  DecorPriority priority = DECOR_PRIORITY_BASE;
   colnr_T col2 = 0;
   VirtText virt_text = KV_INITIAL_VALUE;
   for (size_t i = 0; i < opts.size; i++) {
@@ -1446,6 +1449,19 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
       if (ERROR_SET(err)) {
         goto error;
       }
+    } else if (strequal("priority",  k.data)) {
+      if (v->type != kObjectTypeInteger) {
+        api_set_error(err, kErrorTypeValidation,
+                      "priority is not a Number of the correct size");
+        goto error;
+      }
+
+      if (v->data.integer < 0 || v->data.integer > UINT16_MAX) {
+        api_set_error(err, kErrorTypeValidation,
+                      "priority is not a valid value");
+        goto error;
+      }
+      priority = (DecorPriority)v->data.integer;
     } else {
       api_set_error(err, kErrorTypeValidation, "unexpected key: %s", k.data);
       goto error;
@@ -1479,7 +1495,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
       *vt_allocated = virt_text;
     }
     decor_add_ephemeral(attr_id, (int)line, (colnr_T)col,
-                        (int)line2, (colnr_T)col2, vt_allocated);
+                        (int)line2, (colnr_T)col2, priority, vt_allocated);
   } else {
     if (ephemeral) {
       api_set_error(err, kErrorTypeException, "not yet implemented");
@@ -1492,6 +1508,7 @@ Integer nvim_buf_set_extmark(Buffer buffer, Integer ns_id,
       decor->virt_text = virt_text;
     } else if (hl_id) {
       decor = decor_hl(hl_id);
+      decor->priority = priority;
     }
 
     id = extmark_set(buf, (uint64_t)ns_id, id, (int)line, (colnr_T)col,
diff --git a/src/nvim/decoration.c b/src/nvim/decoration.c
index 03ce2a37b5..e6a616c927 100644
--- a/src/nvim/decoration.c
+++ b/src/nvim/decoration.c
@@ -43,6 +43,7 @@ void bufhl_add_hl_pos_offset(buf_T *buf,
   colnr_T hl_end = 0;
   Decoration *decor = decor_hl(hl_id);
 
+  decor->priority = DECOR_PRIORITY_BASE;
   // TODO(bfredl): if decoration had blocky mode, we could avoid this loop
   for (linenr_T lnum = pos_start.lnum; lnum <= pos_end.lnum; lnum ++) {
     int end_off = 0;
@@ -84,6 +85,7 @@ Decoration *decor_hl(int hl_id)
   Decoration *decor = xcalloc(1, sizeof(*decor));
   decor->hl_id = hl_id;
   decor->shared = true;
+  decor->priority = DECOR_PRIORITY_BASE;
   *dp = decor;
   return decor;
 }
@@ -191,12 +193,12 @@ bool decor_redraw_start(buf_T *buf, int top_row, DecorState *state)
     HlRange range;
     if (mark.id&MARKTREE_END_FLAG) {
       range = (HlRange){ altpos.row, altpos.col, mark.row, mark.col,
-                         attr_id, vt, false };
+                         attr_id, decor->priority, vt, false };
     } else {
       range = (HlRange){ mark.row, mark.col, altpos.row,
-                         altpos.col, attr_id, vt, false };
+                         altpos.col, attr_id, decor->priority, vt, false };
     }
-    kv_push(state->active, range);
+    hlrange_activate(range, state);
 
 next_mark:
     if (marktree_itr_node_done(state->itr)) {
@@ -218,6 +220,34 @@ bool decor_redraw_line(buf_T *buf, int row, DecorState *state)
   return true;  // TODO(bfredl): be more precise
 }
 
+static void hlrange_activate(HlRange range, DecorState *state)
+{
+  // Get size before preparing the push, to have the number of elements
+  size_t s = kv_size(state->active);
+
+  kv_pushp(state->active);
+
+  size_t dest_index = 0;
+
+  // Determine insertion dest_index
+  while (dest_index < s) {
+    HlRange item = kv_A(state->active, dest_index);
+    if (item.priority > range.priority) {
+      break;
+    }
+
+    dest_index++;
+  }
+
+  // Splice
+  for (size_t index = s; index > dest_index; index--) {
+    kv_A(state->active, index) = kv_A(state->active, index-1);
+  }
+
+  // Insert
+  kv_A(state->active, dest_index) = range;
+}
+
 int decor_redraw_col(buf_T *buf, int col, DecorState *state)
 {
   if (col <= state->col_until) {
@@ -257,9 +287,10 @@ int decor_redraw_col(buf_T *buf, int col, DecorState *state)
 
     int attr_id = decor->hl_id > 0 ? syn_id2attr(decor->hl_id) : 0;
     VirtText *vt = kv_size(decor->virt_text) ? &decor->virt_text : NULL;
-    kv_push(state->active, ((HlRange){ mark.row, mark.col,
-                                       endpos.row, endpos.col,
-                                       attr_id, vt, false }));
+    hlrange_activate((HlRange){ mark.row, mark.col,
+                                endpos.row, endpos.col,
+                                attr_id, decor->priority,
+                                vt, false }, state);
 
 next_mark:
     marktree_itr_next(buf->b_marktree, state->itr);
@@ -321,10 +352,10 @@ VirtText *decor_redraw_virt_text(buf_T *buf, DecorState *state)
 }
 
 void decor_add_ephemeral(int attr_id, int start_row, int start_col,
-                         int end_row, int end_col, VirtText *virt_text)
+                         int end_row, int end_col, DecorPriority priority,
+                         VirtText *virt_text)
 {
-  kv_push(decor_state.active,
-          ((HlRange){ start_row, start_col,
-                      end_row, end_col,
-                      attr_id, virt_text, virt_text != NULL }));
+hlrange_activate(((HlRange){ start_row, start_col, end_row, end_col, attr_id,
+                             priority, virt_text, virt_text != NULL }),
+                 &decor_state);
 }
diff --git a/src/nvim/decoration.h b/src/nvim/decoration.h
index c5941ae2fe..2533a641dd 100644
--- a/src/nvim/decoration.h
+++ b/src/nvim/decoration.h
@@ -15,11 +15,15 @@ typedef struct {
 typedef kvec_t(VirtTextChunk) VirtText;
 #define VIRTTEXT_EMPTY ((VirtText)KV_INITIAL_VALUE)
 
+typedef uint16_t DecorPriority;
+#define DECOR_PRIORITY_BASE 0x1000
+
 struct Decoration
 {
   int hl_id;  // highlight group
   VirtText virt_text;
   // TODO(bfredl): style, signs, etc
+  DecorPriority priority;
   bool shared;  // shared decoration, don't free
 };
 
@@ -29,6 +33,7 @@ typedef struct {
   int end_row;
   int end_col;
   int attr_id;
+  DecorPriority priority;
   VirtText *virt_text;
   bool virt_text_owned;
 } HlRange;
diff --git a/test/functional/ui/bufhl_spec.lua b/test/functional/ui/bufhl_spec.lua
index d7269d2c29..af709cd521 100644
--- a/test/functional/ui/bufhl_spec.lua
+++ b/test/functional/ui/bufhl_spec.lua
@@ -534,6 +534,62 @@ describe('Buffer highlighting', function()
     ]]}
   end)
 
+  it('respects priority', function()
+    local set_extmark = curbufmeths.set_extmark
+    local id = meths.create_namespace('')
+    insert [[foobar]]
+
+    set_extmark(id, 0, 0, {
+      end_line = 0,
+      end_col = 5,
+      hl_group = "Statement",
+      priority = 100
+    })
+    set_extmark(id, 0, 0, {
+      end_line = 0,
+      end_col = 6,
+      hl_group = "String",
+      priority = 1
+    })
+
+    screen:expect [[
+      {3:fooba}{2:^r}                                  |
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+                                              |
+    ]]
+
+    clear_namespace(id, 0, -1)
+
+    set_extmark(id, 0, 0, {
+      end_line = 0,
+      end_col = 6,
+      hl_group = "String",
+      priority = 1
+    })
+    set_extmark(id, 0, 0, {
+      end_line = 0,
+      end_col = 5,
+      hl_group = "Statement",
+      priority = 100
+    })
+
+    screen:expect [[
+      {3:fooba}{2:^r}                                  |
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+                                              |
+    ]]
+  end)
+
   it('works with multibyte text', function()
     insert([[
       Ta båten över sjön!]])
@@ -699,12 +755,12 @@ describe('Buffer highlighting', function()
       -- TODO: only a virtual text from the same ns curretly overrides
       -- an existing virtual text. We might add a prioritation system.
       set_virtual_text(id1, 0, s1, {})
-      eq({{1, 0, 0, {virt_text = s1}}}, get_extmarks(id1, {0,0}, {0, -1}, {details=true}))
+      eq({{1, 0, 0, { priority = 0, virt_text = s1}}}, get_extmarks(id1, {0,0}, {0, -1}, {details=true}))
 
       -- TODO: is this really valid? shouldn't the max be line_count()-1?
       local lastline = line_count()
       set_virtual_text(id1, line_count(), s2, {})
-      eq({{3, lastline, 0, {virt_text = s2}}}, get_extmarks(id1, {lastline,0}, {lastline, -1}, {details=true}))
+      eq({{3, lastline, 0, { priority = 0, virt_text = s2}}}, get_extmarks(id1, {lastline,0}, {lastline, -1}, {details=true}))
 
       eq({}, get_extmarks(id1, {lastline+9000,0}, {lastline+9000, -1}, {}))
     end)