Use fg as bg for foreground-only highlight groups (#22)

Also drop support for v0.8.0.

.github/workflows/style.yml

@@ -15,4 +15,4 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           version: 0.16.1
-          args: --check lua/ tests/
+          args: --check lua/ tests/ syntax/

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        neovim_version: ['v0.8.0', 'v0.9.0', 'v0.10.0', 'nightly']
+        neovim_version: ['v0.9.0', 'v0.9.5', 'v0.10.0', 'nightly']
 
     steps:
       - uses: actions/checkout@v3

README.md

@@ -41,7 +41,7 @@ https://github.com/user-attachments/assets/417023dd-9d5d-4ae9-891d-514e0f3038d5
 
 ## Requirements
 
-* Neovim 0.8.0+
+* Neovim 0.9.0+
 
 ## Installing
 
@@ -63,6 +63,11 @@ If you are content with the defaults that are shown below, you don't need to
 call the `configure` function. No default keymaps are set other than those
 active during modes.
 
+> [!NOTE]  
+> For mode highlight groups that only have a foreground color, `winmove` will
+> automatically use the foreground color as a background color for the given
+> mode so you do not have to create a custom highlight group yourself.
+
 ```lua
 require('winmove').configure({
     keymaps = {

lua/winmove/compat.lua

@@ -7,10 +7,15 @@ function compat.has(value)
     return vim.fn.has(value) == 1
 end
 
-if compat.has("nvim-0.9.0") then
-    compat.print = vim.print
-else
-    compat.print = vim.pretty_print
+---@param ns_id integer
+---@param opts vim.api.keyset.get_highlight
+---@return vim.api.keyset.hl_info
+function compat.get_hl(ns_id, opts)
+    if opts.create ~= nil and not compat.has("nvim-0.10.0") then
+        opts.create = nil
+    end
+
+    return vim.api.nvim_get_hl(ns_id, opts)
 end
 
 return compat

lua/winmove/health.lua

@@ -3,7 +3,7 @@ local health = {}
 local compat = require("winmove.compat")
 local config = require("winmove.config")
 
-local min_neovim_version = "0.8.0"
+local min_neovim_version = "0.9.0"
 
 local report_start, report_ok, report_error
 

lua/winmove/highlight.lua

@@ -3,13 +3,16 @@
 
 local highlight = {}
 
----@alias winmove.Highlight string
-
+local compat = require("winmove.compat")
 local config = require("winmove.config")
 local str = require("winmove.util.str")
 
 local api = vim.api
 
+---@alias winmove.Highlight string
+
+local global_ns_id = 0
+
 -- Window higlights per mode
 local win_highlights = {
     move = nil,
@@ -39,18 +42,52 @@ local highlight_groups = {
     "SignColumn",
 }
 
+--- If the highlight group only contains a foreground color, return it as
+--- the color to use for the background, otherwise use the background color
+---@param group string
+---@return boolean
+---@return table<string, unknown>
+local function ensure_background_color(group)
+    local colors = compat.get_hl(global_ns_id, { name = group, link = false, create = false })
+
+    if colors.bg or colors.ctermbg then
+        return true, colors
+    end
+
+    colors.bg = colors.fg
+    colors.fg = nil
+
+    ---@diagnostic disable-next-line: inject-field
+    colors.ctermbg = colors.ctermfg
+    ---@diagnostic disable-next-line: inject-field
+    colors.ctermfg = nil
+
+    return false, colors
+end
+
 --- Generate group highlights for a mode
 ---@param mode winmove.Mode
 ---@param groups string[]
 local function generate_highlights(mode, groups)
     local highlights = {}
-    local color = config.modes[mode].highlight
+    local hl_group = config.modes[mode].highlight
+    local titlecase_mode = str.titlecase(mode)
+    local has_bg, colors = ensure_background_color(hl_group)
+
+    if not has_bg then
+        -- Create a new highlight group we can link to
+        hl_group = ("Winmove%sInternal%s"):format(titlecase_mode, hl_group)
+
+        -- nvim_get_hl creates the highlight group if it does not exist on <= v0.9.0
+        if not compat.has("nvim-0.10.0") or vim.fn.hlexists(hl_group) == 0 then
+            vim.api.nvim_set_hl(global_ns_id, hl_group, colors)
+        end
+    end
 
     for _, group in ipairs(groups) do
-        local titlecase_mode = str.titlecase(mode)
         local winmove_group = "Winmove" .. titlecase_mode .. group
 
-        vim.cmd(("hi default link %s %s"):format(winmove_group, color))
+        vim.cmd(("hi default link %s %s"):format(winmove_group, hl_group))
         table.insert(highlights, ("%s:%s"):format(group, winmove_group))
     end
 

lua/winmove/winutil.lua

@@ -1,6 +1,5 @@
 local winutil = {}
 
-local compat = require("winmove.compat")
 local message = require("winmove.message")
 
 local events = {
@@ -9,16 +8,13 @@ local events = {
     "WinNew",
     "WinScrolled",
     "WinClosed",
+    "WinResized",
     "BufWinEnter",
     "BufWinLeave",
     "BufEnter",
     "BufLeave",
 }
 
-if compat.has("nvim-0.8.2") then
-    table.insert(events, "WinResized")
-end
-
 function winutil.get_ignored_events()
     return events
 end

tests/custom_highlights_spec.lua

@@ -1,5 +1,4 @@
 local winmove = require("winmove")
-local compat = require("winmove.compat")
 local config = require("winmove.config")
 local highlight = require("winmove.highlight")
 local vader = require("winmove.util.vader")
@@ -9,11 +8,6 @@ local given = vader.given
 local make_layout = test_helpers.make_layout
 
 describe("custom highlights", function()
-    if not compat.has("nvim-0.9.0") then
-        pending("Skipped for versions below 0.9.0")
-        return
-    end
-
     local function get_expected_winhighlight(prefix)
         local template = {
             "CursorLine:%sCursorLine",
@@ -40,7 +34,8 @@ describe("custom highlights", function()
     end
 
     it("uses a custom highlight for move mode", function()
-        vim.cmd(("hi link %s %s"):format("CustomWinmoveMoveMode", "Title"))
+        vim.cmd.colorscheme("desert")
+        vim.cmd(("hi link %s %s"):format("CustomWinmoveMoveMode", "Todo"))
 
         ---@diagnostic disable-next-line: missing-fields
         config.configure({
@@ -82,7 +77,8 @@ describe("custom highlights", function()
     end)
 
     it("uses a custom highlight for swap mode", function()
-        vim.cmd(("hi link %s %s"):format("CustomWinmoveSwapMode", "Repeat"))
+        vim.cmd.colorscheme("desert")
+        vim.cmd(("hi link %s %s"):format("CustomWinmoveSwapMode", "Todo"))
 
         ---@diagnostic disable-next-line: missing-fields
         config.configure({
@@ -124,7 +120,8 @@ describe("custom highlights", function()
     end)
 
     it("uses a custom highlight for resize mode", function()
-        vim.cmd(("hi link %s %s"):format("CustomWinmoveResizeMode", "Repeat"))
+        vim.cmd.colorscheme("desert")
+        vim.cmd(("hi link %s %s"):format("CustomWinmoveResizeMode", "Todo"))
 
         config.configure({
             modes = {

tests/highlight_spec.lua

@@ -0,0 +1,41 @@
+local winmove = require("winmove")
+local compat = require("winmove.compat")
+local config = require("winmove.config")
+
+describe("highlight", function()
+    it("generates internal highlight groups for foreground-only highlights", function()
+        vim.cmd.colorscheme("desert")
+
+        ---@diagnostic disable-next-line: missing-fields
+        config.configure({
+            modes = {
+                move = {
+                    highlight = "Type",
+                },
+            },
+        })
+
+        vim.cmd.vnew()
+
+        local hl_group = "WinmoveMoveInternalType"
+        local opts = { name = hl_group }
+
+        if compat.has("nvim-0.10.0") then
+            opts.create = false
+        end
+
+        assert.are.same(#vim.api.nvim_get_hl(0, opts), 0)
+
+        winmove.start_mode(winmove.Mode.Move)
+        winmove.stop_mode()
+
+        assert.are.same(vim.api.nvim_get_hl(0, opts), {
+            bold = true,
+            cterm = {
+                bold = true,
+            },
+            bg = 12433259,
+            ctermbg = 143,
+        })
+    end)
+end)