barrett/diffs.nvim
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fix(highlight): use hl_group instead of line_hl_group for diff backgrounds

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line_hl_group bg occupies a separate rendering channel from hl_group in
Neovim's extmark system, causing character-level bg-only highlights to be
invisible regardless of priority. Switching to hl_group + hl_eol ensures
all backgrounds compete in the same channel.

Also reorders priorities (Normal 198 < line bg 199 < syntax 200 < char
bg 201), bumps char-level blend alpha from 0.4 to 0.7 for visibility,
and adds debug logging throughout the intra pipeline.
This commit is contained in:
Barrett Ruth 2026-02-06 18:28:22 -05:00
parent f1c13966ba
commit 3482e25c41
5 changed files with 429 additions and 20 deletions
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45
lua/diffs/highlight.lua
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@ -287,7 +287,17 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
local intra = nil
local intra_cfg = opts.highlights.intra
if intra_cfg and intra_cfg.enabled and #hunk.lines <= intra_cfg.max_lines then
dbg('computing intra for hunk %s:%d (%d lines)', hunk.filename, hunk.start_line, #hunk.lines)
intra = diff.compute_intra_hunks(hunk.lines, intra_cfg.algorithm)
if intra then
dbg('intra result: %d add spans, %d del spans', #intra.add_spans, #intra.del_spans)
else
dbg('intra result: nil (no change groups)')
end
elseif intra_cfg and not intra_cfg.enabled then
dbg('intra disabled by config')
elseif intra_cfg and #hunk.lines > intra_cfg.max_lines then
dbg('intra skipped: %d lines > %d max', #hunk.lines, intra_cfg.max_lines)
end
---@type table<integer, diffs.CharSpan[]>
@ -324,21 +334,20 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
})
end
if opts.highlights.background and is_diff_line then
local extmark_opts = {
line_hl_group = line_hl,
priority = 198,
}
if opts.highlights.gutter then
extmark_opts.number_hl_group = number_hl
end
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, extmark_opts)
end
if line_len > 1 and syntax_applied then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 1, {
end_col = line_len,
hl_group = 'Normal',
priority = 198,
})
end
if opts.highlights.background and is_diff_line then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
end_col = line_len,
hl_group = line_hl,
hl_eol = true,
number_hl_group = opts.highlights.gutter and number_hl or nil,
priority = 199,
})
end
@ -346,11 +355,23 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
if char_spans_by_line[i] then
local char_hl = prefix == '+' and 'DiffsAddText' or 'DiffsDeleteText'
for _, span in ipairs(char_spans_by_line[i]) do
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
dbg(
'char extmark: line=%d buf_line=%d col=%d..%d hl=%s text="%s"',
i,
buf_line,
span.col_start,
span.col_end,
char_hl,
line:sub(span.col_start + 1, span.col_end)
)
local ok, err = pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, span.col_start, {
end_col = span.col_end,
hl_group = char_hl,
priority = 201,
})
if not ok then
dbg('char extmark FAILED: %s', err)
end
extmark_count = extmark_count + 1
end
end