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Highlighting: invalidate from the edited row, not the whole buffer

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Every edit bumped the buffer version (through SetDirty) and called
InvalidateFrom(0), so all cached spans and line states were discarded
and stateful highlighters re-lexed from row 0 to the viewport on each
keystroke.

Buffer mutators now report the row they changed (edited_at_), which
bumps the version and tells the engine to drop only rows from there
down; a row's highlighting depends only on rows above it. A version
change that arrives without that notice still clears everything, so a
missed path cannot show stale spans. The engine keeps states as a
contiguous vector and caches spans for every row it lexes. SetDirty no
longer touches the version: the edits themselves do, including undo
and redo back to the saved state (D9 still holds; its test now checks
the highlighting itself).

Typing near the end of a 100k-line C++ file: 46.3 ms -> 0.14 ms of
highlighting work per keystroke.

Audit finding P3.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015rcVQiiWyTzoNrsvLSaAfB
This commit is contained in:
Claude
2026-09-24 09:16:04 -07:00
committed by Kyle Isom
parent 4c42761fc0
commit f853fa60b1
5 changed files with 177 additions and 135 deletions
Download Patch File Download Diff File Expand all files Collapse all files
syntax/HighlighterEngine.cc
+66 -107
View File
@@ -2,6 +2,8 @@
#include "../Buffer.h"
#include "LanguageHighlighter.h"
#include <algorithm>
namespace kte {
HighlighterEngine::HighlighterEngine() = default;
@@ -14,109 +16,79 @@ HighlighterEngine::SetHighlighter(std::unique_ptr<LanguageHighlighter> hl)
{
std::lock_guard<std::mutex> lock(mtx_);
hl_ = std::move(hl);
clear_caches_locked();
}
void
HighlighterEngine::clear_caches_locked() const
{
cache_.clear();
state_cache_.clear();
state_last_contig_.clear();
states_.clear();
}
void
HighlighterEngine::invalidate_from_locked(int row) const
{
if (row < 0)
row = 0;
cache_.erase(cache_.lower_bound(row), cache_.end());
if (states_.size() > static_cast<std::size_t>(row))
states_.resize(static_cast<std::size_t>(row));
}
LineHighlight
HighlighterEngine::GetLine(const Buffer &buf, int row, std::uint64_t buf_version) const
{
std::unique_lock<std::mutex> lock(mtx_);
auto it = cache_.find(row);
if (it != cache_.end() && it->second.version == buf_version) {
return it->second; // return by value (copy)
std::lock_guard<std::mutex> lock(mtx_);
if (!have_version_ || buf_version != version_) {
// Content changed without OnEdit: nothing cached can be trusted.
clear_caches_locked();
version_ = buf_version;
have_version_ = true;
}
auto it = cache_.find(row);
if (it != cache_.end())
return it->second; // return by value (copy)
// We'll compute into a local result to avoid exposing references to cache
LineHighlight result;
result.version = buf_version;
result.spans.clear();
if (!hl_) {
// Cache empty result and return it
if (!hl_ || row < 0) {
cache_[row] = result;
return result;
}
// Copy shared_ptr-like raw pointer for use outside critical sections
LanguageHighlighter *hl_ptr = hl_.get();
bool is_stateful = dynamic_cast<StatefulHighlighter *>(hl_ptr) != nullptr;
if (!is_stateful) {
// Stateless fast path: we can release the lock while computing to reduce contention
lock.unlock();
hl_ptr->HighlightLine(buf, row, result.spans);
// Update cache and return
std::lock_guard<std::mutex> gl(mtx_);
auto *stateful = dynamic_cast<StatefulHighlighter *>(hl_.get());
if (!stateful) {
hl_->HighlightLine(buf, row, result.spans);
cache_[row] = result;
return result;
}
// Stateful path: we need to walk from a known previous state. Keep lock while consulting caches,
// but release during heavy computation.
auto *stateful = static_cast<StatefulHighlighter *>(hl_ptr);
StatefulHighlighter::LineState prev_state;
int start_row = -1;
// Fast path: state_last_contig_ tracks the highest row we've cached state
// for, per version. If that row is already below our target, it's
// necessarily the best anchor the O(n) scan below would have found, so we
// can skip the scan entirely. Re-validated against state_cache_ before
// use since InvalidateFrom()/SetHighlighter() may have raced/cleared it.
auto contig_it = state_last_contig_.find(buf_version);
if (contig_it != state_last_contig_.end() && contig_it->second < row) {
auto sc_it = state_cache_.find(contig_it->second);
if (sc_it != state_cache_.end() && sc_it->second.version == buf_version) {
start_row = contig_it->second;
prev_state = sc_it->second.state;
}
// Stateful: continue from the last row with a known end state (or the
// row just above the target, if that is known), caching every row's
// spans and state along the way so neighbouring rows are cache hits.
const int known = static_cast<int>(states_.size()) - 1;
const int start = std::min(known, row - 1);
StatefulHighlighter::LineState state = (start >= 0) ? states_[static_cast<std::size_t>(start)]
: StatefulHighlighter::LineState{};
const int nrows = static_cast<int>(buf.Nrows());
for (int r = start + 1; r <= row && r < nrows; ++r) {
LineHighlight lh;
lh.version = buf_version;
state = stateful->HighlightLineStateful(buf, r, state, lh.spans);
if (static_cast<std::size_t>(r) == states_.size())
states_.push_back(state);
else
states_[static_cast<std::size_t>(r)] = state;
if (r == row)
result = lh;
else
cache_.insert_or_assign(r, std::move(lh));
}
if (start_row < 0 && !state_cache_.empty()) {
// linear search over map (unordered), track best candidate
int best = -1;
for (const auto &kv: state_cache_) {
int r = kv.first;
// Only use cached state if it's for the current version and row still exists
if (r <= row - 1 && kv.second.version == buf_version) {
// Validate that the cached row index is still valid in the buffer
if (r >= 0 && static_cast<std::size_t>(r) < buf.Nrows()) {
if (r > best)
best = r;
}
}
}
if (best >= 0) {
start_row = best;
prev_state = state_cache_.at(best).state;
}
}
// We'll compute states and the target line's spans without holding the lock for most of the work.
// Create a local copy of prev_state and iterate rows; we will update caches under lock.
lock.unlock();
StatefulHighlighter::LineState cur_state = prev_state;
for (int r = start_row + 1; r <= row; ++r) {
std::vector<HighlightSpan> tmp;
std::vector<HighlightSpan> &out = (r == row) ? result.spans : tmp;
auto next_state = stateful->HighlightLineStateful(buf, r, cur_state, out);
// Update state cache for r
std::lock_guard<std::mutex> gl(mtx_);
StateEntry se;
se.version = buf_version;
se.state = next_state;
state_cache_[r] = se;
cur_state = next_state;
int &contig = state_last_contig_[buf_version];
if (r > contig)
contig = r;
}
// Store in cache and return by value
lock.lock();
cache_[row] = result;
return result;
}
@@ -126,31 +98,18 @@ void
HighlighterEngine::InvalidateFrom(int row)
{
std::lock_guard<std::mutex> lock(mtx_);
if (cache_.empty())
return;
// Simple implementation: erase all rows >= row
for (auto it = cache_.begin(); it != cache_.end();) {
if (it->first >= row)
it = cache_.erase(it);
else
++it;
}
if (!state_cache_.empty()) {
for (auto it = state_cache_.begin(); it != state_cache_.end();) {
if (it->first >= row)
it = state_cache_.erase(it);
else
++it;
}
}
// A version's tracked contiguous-state row is no longer valid once any
// row at or above it has been evicted from state_cache_ above.
for (auto it = state_last_contig_.begin(); it != state_last_contig_.end();) {
if (it->second >= row)
it = state_last_contig_.erase(it);
else
++it;
}
invalidate_from_locked(row);
}
void
HighlighterEngine::OnEdit(int row, std::uint64_t buf_version)
{
std::lock_guard<std::mutex> lock(mtx_);
if (have_version_)
invalidate_from_locked(row);
version_ = buf_version;
have_version_ = true;
}