highlight: expose builtin highlight groups using hl_group_set event

8 files changed, 89 insertions, 15 deletions

diff --git a/runtime/doc/ui.txt b/runtime/doc/ui.txt
index c56f9467a3..1440e2ac78 100644
--- a/runtime/doc/ui.txt
+++ b/runtime/doc/ui.txt
@@ -316,6 +316,14 @@ numerical highlight ids to the actual attributes.
 	`info` is an empty array by default, and will be used by the
 	|ui-hlstate| extension explained below.
 
+["hl_group_set", name, hl_id]
+	The bulitin highlight group `name` was set to use the attributes `hl_id`
+	defined by a previous `hl_attr_define` call. This event is not needed
+	to render the grids which use attribute ids directly, but is useful
+	for an UI who want to render its own elements with consistent
+	highlighting. For instance an UI using |ui-popupmenu| events, might
+	use the |hl-Pmenu| family of builtin highlights.
+
 							    *ui-event-grid_line*
 ["grid_line", grid, row, col_start, cells]
 	Redraw a continuous part of a `row` on a `grid`, starting at the column
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 4f28ea5af3..20ed77afad 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -123,6 +123,7 @@ void nvim_ui_attach(uint64_t channel_id, Integer width, Integer height,
   ui->mode_change = remote_ui_mode_change;
   ui->grid_scroll = remote_ui_grid_scroll;
   ui->hl_attr_define = remote_ui_hl_attr_define;
+  ui->hl_group_set = remote_ui_hl_group_set;
   ui->raw_line = remote_ui_raw_line;
   ui->bell = remote_ui_bell;
   ui->visual_bell = remote_ui_visual_bell;
diff --git a/src/nvim/api/ui_events.in.h b/src/nvim/api/ui_events.in.h
index a1d25766fe..41bf0af65b 100644
--- a/src/nvim/api/ui_events.in.h
+++ b/src/nvim/api/ui_events.in.h
@@ -73,6 +73,8 @@ void default_colors_set(Integer rgb_fg, Integer rgb_bg, Integer rgb_sp,
 void hl_attr_define(Integer id, HlAttrs rgb_attrs, HlAttrs cterm_attrs,
                     Array info)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_BRIDGE_IMPL;
+void hl_group_set(String name, Integer id)
+  FUNC_API_SINCE(6) FUNC_API_BRIDGE_IMPL;
 void grid_resize(Integer grid, Integer width, Integer height)
   FUNC_API_SINCE(5) FUNC_API_REMOTE_IMPL FUNC_API_COMPOSITOR_IMPL;
 void grid_clear(Integer grid)
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index e5cbb4f944..f11880cb2b 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -106,14 +106,19 @@ static int get_attr_entry(HlEntry entry)
 /// When a UI connects, we need to send it the table of highlights used so far.
 void ui_send_all_hls(UI *ui)
 {
-  if (!ui->hl_attr_define) {
-    return;
+  if (ui->hl_attr_define) {
+    for (size_t i = 1; i < kv_size(attr_entries); i++) {
+      Array inspect = hl_inspect((int)i);
+      ui->hl_attr_define(ui, (Integer)i, kv_A(attr_entries, i).attr,
+                         kv_A(attr_entries, i).attr, inspect);
+      api_free_array(inspect);
+    }
   }
-  for (size_t i = 1; i < kv_size(attr_entries); i++) {
-    Array inspect = hl_inspect((int)i);
-    ui->hl_attr_define(ui, (Integer)i, kv_A(attr_entries, i).attr,
-                       kv_A(attr_entries, i).attr, inspect);
-    api_free_array(inspect);
+  if (ui->hl_group_set) {
+    for (size_t hlf = 0; hlf < HLF_COUNT; hlf++) {
+      ui->hl_group_set(ui, cstr_as_string((char *)hlf_names[hlf]),
+                       highlight_attr[hlf]);
+    }
   }
 }
 
@@ -251,6 +256,7 @@ void clear_hl_tables(bool reinit)
     map_clear(int, int)(combine_attr_entries);
     map_clear(int, int)(blend_attr_entries);
     map_clear(int, int)(blendthrough_attr_entries);
+    memset(highlight_attr_last, -1, sizeof(highlight_attr_last));
     highlight_attr_set_all();
     highlight_changed();
     screen_invalidate_highlights();
diff --git a/src/nvim/highlight_defs.h b/src/nvim/highlight_defs.h
index 25d859c55d..afccf9e6f6 100644
--- a/src/nvim/highlight_defs.h
+++ b/src/nvim/highlight_defs.h
@@ -150,6 +150,7 @@ EXTERN const char *hlf_names[] INIT(= {
 
 
 EXTERN int highlight_attr[HLF_COUNT];       // Highl. attr for each context.
+EXTERN int highlight_attr_last[HLF_COUNT];  // copy for detecting changed groups
 EXTERN int highlight_user[9];                   // User[1-9] attributes
 EXTERN int highlight_stlnc[9];                  // On top of user
 EXTERN int cterm_normal_fg_color INIT(= 0);
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index e39075739c..bcb18b6e67 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -14,6 +14,7 @@
 
 #include "nvim/vim.h"
 #include "nvim/ascii.h"
+#include "nvim/api/private/helpers.h"
 #include "nvim/syntax.h"
 #include "nvim/charset.h"
 #include "nvim/cursor_shape.h"
@@ -7500,6 +7501,12 @@ void highlight_changed(void)
 
     highlight_attr[hlf] = hl_get_ui_attr(hlf, final_id,
                                          hlf == (int)HLF_INACTIVE);
+
+    if (highlight_attr[hlf] != highlight_attr_last[hlf]) {
+      ui_call_hl_group_set(cstr_as_string((char *)hlf_names[hlf]),
+                           highlight_attr[hlf]);
+      highlight_attr_last[hlf] = highlight_attr[hlf];
+    }
   }
 
   /* Setup the user highlights
diff --git a/test/functional/ui/highlight_spec.lua b/test/functional/ui/highlight_spec.lua
index 85b5aed2f8..08566fe493 100644
--- a/test/functional/ui/highlight_spec.lua
+++ b/test/functional/ui/highlight_spec.lua
@@ -311,6 +311,38 @@ describe('highlight defaults', function()
       [1] = {foreground=Screen.colors.Blue},
     })
   end)
+
+  it('are sent to UIs', function()
+    screen:try_resize(53, 4)
+    screen:set_default_attr_ids({
+      [0] = {},
+      [1] = {bold = true, foreground = Screen.colors.Blue1},
+      [2] = {bold = true, reverse = true},
+      [3] = {italic=true}
+    })
+    screen:expect{grid=[[
+      ^                                                     |
+      {1:~                                                    }|
+      {1:~                                                    }|
+                                                           |
+    ]], hl_groups={EndOfBuffer=1, MsgSeparator=2}}
+
+    command('highlight EndOfBuffer gui=italic')
+    screen:expect{grid=[[
+      ^                                                     |
+      {3:~                                                    }|
+      {3:~                                                    }|
+                                                           |
+    ]], hl_groups={EndOfBuffer=3, MsgSeparator=2}}
+
+    command('highlight clear EndOfBuffer')
+    screen:expect{grid=[[
+      ^                                                     |
+      ~                                                    |
+      ~                                                    |
+                                                           |
+    ]], hl_groups={EndOfBuffer=0, MsgSeparator=2}}
+  end)
 end)
 
 describe('highlight', function()
diff --git a/test/functional/ui/screen.lua b/test/functional/ui/screen.lua
index 31669f5578..eb059c38ee 100644
--- a/test/functional/ui/screen.lua
+++ b/test/functional/ui/screen.lua
@@ -165,6 +165,7 @@ function Screen.new(width, height)
     showmode = {},
     showcmd = {},
     ruler = {},
+    hl_groups = {},
     _default_attr_ids = nil,
     _default_attr_ignore = nil,
     _mouse_enabled = true,
@@ -322,7 +323,7 @@ function Screen:expect(expected, attr_ids, attr_ignore)
     assert(not (attr_ids ~= nil or attr_ignore ~= nil))
     local is_key = {grid=true, attr_ids=true, attr_ignore=true, condition=true,
                     any=true, mode=true, unchanged=true, intermediate=true,
-                    reset=true, timeout=true, request_cb=true}
+                    reset=true, timeout=true, request_cb=true, hl_groups=true}
     for _, v in ipairs(ext_keys) do
       is_key[v] = true
     end
@@ -418,9 +419,10 @@ screen:redraw_debug() to show all intermediate screen states.  ]])
     -- (e.g. no external cmdline visible). Some extensions require
     -- preprocessing to represent highlights in a reproducible way.
     local extstate = self:_extstate_repr(attr_state)
-    if expected['mode'] ~= nil then
-      extstate['mode'] = self.mode
+    if expected.mode ~= nil then
+      extstate.mode = self.mode
     end
+
     -- Convert assertion errors into invalid screen state descriptions.
     for _, k in ipairs(concat_tables(ext_keys, {'mode'})) do
       -- Empty states are considered the default and need not be mentioned.
@@ -431,6 +433,17 @@ screen:redraw_debug() to show all intermediate screen states.  ]])
         end
       end
     end
+
+    if expected.hl_groups ~= nil then
+      for name, id in pairs(expected.hl_groups) do
+        local expected_hl = attr_state.ids[id]
+        local actual_hl = self._attr_table[self.hl_groups[name]][(self._options.rgb and 1) or 2]
+        local status, res = pcall(eq, expected_hl, actual_hl, "highlight "..name)
+        if not status then
+          return tostring(res)
+        end
+      end
+    end
   end, expected)
 end
 
@@ -836,6 +849,10 @@ function Screen:_handle_hl_attr_define(id, rgb_attrs, cterm_attrs, info)
   self._new_attrs = true
 end
 
+function Screen:_handle_hl_group_set(name, id)
+  self.hl_groups[name] = id
+end
+
 function Screen:get_hl(val)
   if self._options.ext_newgrid then
     return self._attr_table[val][1]
@@ -1411,17 +1428,17 @@ function Screen:_get_attr_id(attr_state, attrs, hl_id)
     end
     return "UNEXPECTED "..self:_pprint_attrs(self._attr_table[hl_id][1])
   else
-    for id, a in pairs(attr_state.ids) do
-      if self:_equal_attrs(a, attrs) then
-         return id
-       end
-    end
     if self:_equal_attrs(attrs, {}) or
         attr_state.ignore == true or
         self:_attr_index(attr_state.ignore, attrs) ~= nil then
       -- ignore this attrs
       return nil
     end
+    for id, a in pairs(attr_state.ids) do
+      if self:_equal_attrs(a, attrs) then
+         return id
+       end
+    end
     if attr_state.mutable then
       table.insert(attr_state.ids, attrs)
       attr_state.modified = true