fix(highlight): prevent duplicate extmarks from two-pass rendering (#145)

## Problem

Two-pass rendering (Pass 1: backgrounds + intra-line; Pass 2:
treesitter) caused Pass 2 to re-apply all extmarks that Pass 1 already
set, doubling the extmark count on affected lines.

## Solution

Add `syntax_only` mode to `highlight_hunk`. When `syntax_only = true`,
only treesitter syntax and content `DiffsClear` extmarks are applied —
backgrounds, intra-line, prefix clears, and per-char prefix highlights
are skipped. Pass 2 now uses `syntax_only = true` and no longer calls
`nvim_buf_clear_namespace`, so Pass 1's extmarks persist while Pass 2
layers syntax on top.

Closes #143
This commit is contained in:
Barrett Ruth 2026-03-05 09:16:04 -05:00 committed by GitHub
parent 7106bcc291
commit 90b312e8df
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
3 changed files with 190 additions and 69 deletions

View file

@ -65,6 +65,7 @@ end
---@field hide_prefix boolean
---@field highlights diffs.Highlights
---@field defer_vim_syntax? boolean
---@field syntax_only? boolean
---@param bufnr integer
---@param ns integer
@ -381,7 +382,13 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
---@type diffs.IntraChanges?
local intra = nil
local intra_cfg = opts.highlights.intra
if intra_cfg and intra_cfg.enabled and pw == 1 and #hunk.lines <= intra_cfg.max_lines then
if
not opts.syntax_only
and intra_cfg
and intra_cfg.enabled
and pw == 1
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
@ -494,28 +501,70 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
or content:match('^|||||||')
end
if opts.hide_prefix then
local virt_hl = (opts.highlights.background and line_hl) or nil
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
virt_text = { { string.rep(' ', pw), virt_hl } },
virt_text_pos = 'overlay',
})
end
if not opts.syntax_only then
if opts.hide_prefix then
local virt_hl = (opts.highlights.background and line_hl) or nil
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
virt_text = { { string.rep(' ', pw), virt_hl } },
virt_text_pos = 'overlay',
})
end
if pw > 1 then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
end_col = pw,
hl_group = 'DiffsClear',
priority = p.clear,
})
for ci = 0, pw - 1 do
local ch = line:sub(ci + 1, ci + 1)
if ch == '+' or ch == '-' then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, ci, {
end_col = ci + 1,
hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
priority = p.syntax,
if pw > 1 then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
end_col = pw,
hl_group = 'DiffsClear',
priority = p.clear,
})
for ci = 0, pw - 1 do
local ch = line:sub(ci + 1, ci + 1)
if ch == '+' or ch == '-' then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, ci, {
end_col = ci + 1,
hl_group = ch == '+' and '@diff.plus' or '@diff.minus',
priority = p.syntax,
})
end
end
end
if opts.highlights.background and is_diff_line then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
line_hl_group = line_hl,
number_hl_group = opts.highlights.gutter and number_hl or nil,
priority = p.line_bg,
})
end
if is_marker and line_len > pw then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
end_col = line_len,
hl_group = 'DiffsConflictMarker',
priority = p.char_bg,
})
end
if char_spans_by_line[i] then
local char_hl = has_add and 'DiffsAddText' or 'DiffsDeleteText'
for _, span in ipairs(char_spans_by_line[i]) do
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 = p.char_bg,
})
if not ok then
dbg('char extmark FAILED: %s', err)
end
extmark_count = extmark_count + 1
end
end
end
@ -527,46 +576,6 @@ function M.highlight_hunk(bufnr, ns, hunk, opts)
priority = p.clear,
})
end
if opts.highlights.background and is_diff_line then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, 0, {
line_hl_group = line_hl,
number_hl_group = opts.highlights.gutter and number_hl or nil,
priority = p.line_bg,
})
end
if is_marker and line_len > pw then
pcall(vim.api.nvim_buf_set_extmark, bufnr, ns, buf_line, pw, {
end_col = line_len,
hl_group = 'DiffsConflictMarker',
priority = p.char_bg,
})
end
if char_spans_by_line[i] then
local char_hl = has_add and 'DiffsAddText' or 'DiffsDeleteText'
for _, span in ipairs(char_spans_by_line[i]) do
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 = p.char_bg,
})
if not ok then
dbg('char extmark FAILED: %s', err)
end
extmark_count = extmark_count + 1
end
end
end
dbg('hunk %s:%d applied %d extmarks', hunk.filename, hunk.start_line, extmark_count)

View file

@ -797,18 +797,13 @@ local function init()
return
end
local t1 = config.debug and vim.uv.hrtime() or nil
local full_opts = {
local syntax_opts = {
hide_prefix = config.hide_prefix,
highlights = config.highlights,
syntax_only = true,
}
for _, hunk in ipairs(deferred_syntax) do
local start_row = hunk.start_line - 1
local end_row = hunk.start_line + #hunk.lines
if hunk.header_start_line then
start_row = hunk.header_start_line - 1
end
vim.api.nvim_buf_clear_namespace(bufnr, ns, start_row, end_row)
highlight.highlight_hunk(bufnr, ns, hunk, full_opts)
highlight.highlight_hunk(bufnr, ns, hunk, syntax_opts)
end
if t1 then
dbg('deferred pass: %d hunks in %.2fms', #deferred_syntax, (vim.uv.hrtime() - t1) / 1e6)