support feature detection for vis ui styling API

In builds of vis packaged without a git tree (such as openSUSE OBS RPM
builds), vis.API defaults to 0. Checking `vis.API > 3215` therefore
fails even when the new vis.ui styling API is present.

Check for the existence of `vis.ui.style_define` and `vis.ui.style_push`
directly, and accept an optional window object in util.style_define for
backward compatibility with older versions.

3 files changed, 37 insertions, 5 deletions

diff --git a/init.lua b/init.lua
index 8002e62..6f46895 100644
--- a/init.lua
+++ b/init.lua
@@ -594,7 +594,7 @@ end
 local function lspc_highlight_server_diagnostics(win, server_diagnostics, style)
   if not style then
     if not lspc.diagnostic_style_id then
-      if vis.API and vis.API > 3215 then
+      if (vis.API and vis.API > 3215) or (vis.ui and vis.ui.style_push) then
         lspc.diagnostic_style_id = vis.ui:style_push()
       else
         lspc.diagnostic_style_id = win.STYLE_LEXER_MAX
@@ -612,7 +612,7 @@ local function lspc_highlight_server_diagnostics(win, server_diagnostics, style)
 
   for _, diagnostic in ipairs(server_diagnostics) do
     local diagnostic_style = level_mapping[diagnostic.severity] or level_mapping[1]
-    assert(util.style_define(style, diagnostic_style))
+    assert(util.style_define(style, diagnostic_style, win))
 
     if lspc.highlight_diagnostics == 'range' then
       local range = diagnostic.vis_range
diff --git a/util.lua b/util.lua
index c4894c8..7b57231 100644
--- a/util.lua
+++ b/util.lua
@@ -412,11 +412,13 @@ end
 --- Wrapper to define a style in vis.
 -- @param id The style id
 -- @param style The style description
-function util.style_define(id, style)
-  if vis.API and vis.API > 3215 then
+-- @param win The optional window object for older vis versions
+function util.style_define(id, style, win)
+  if (vis.API and vis.API > 3215) or (vis.ui and vis.ui.style_define) then
     return vis.ui:style_define(id, style)
   else
-    return vis.win:style_define(id, style)
+    local w = win or vis.win
+    return w and w:style_define(id, style)
   end
 end
 
diff --git a/util_test.lua b/util_test.lua
index 63393b1..99f34f0 100755
--- a/util_test.lua
+++ b/util_test.lua
@@ -73,4 +73,34 @@ function test_table_merge() -- luacheck: ignore 111
   lunatest.assert_equal(t.foo.bar.nose, 'nose')
 end
 
+function test_style_define() -- luacheck: ignore 111
+  -- Modern vis: vis.ui.style_define present
+  vis.API = 0
+  vis.ui = {
+    style_define = function(self, id, style)
+      return id == 1 and style == 'fore:red'
+    end,
+  }
+  lunatest.assert_true(util.style_define(1, 'fore:red'))
+
+  -- Modern vis: vis.API > 3215
+  vis.API = 3216
+  lunatest.assert_true(util.style_define(1, 'fore:red'))
+
+  -- Older vis: fallback with explicit win
+  vis.API = nil
+  vis.ui = nil
+  local win = {
+    style_define = function(self, id, style)
+      return id == 2 and style == 'fore:blue'
+    end,
+  }
+  lunatest.assert_true(util.style_define(2, 'fore:blue', win))
+
+  -- Older vis: fallback with vis.win
+  vis.win = win
+  lunatest.assert_true(util.style_define(2, 'fore:blue'))
+  vis.win = nil
+end
+
 lunatest.run()