Add <c-g> to cancel current operation

The current implementation only does this during regex operations,
but should be extensible to other operations that might take a long
time by regularly calling EventManager::handle_urgent_events().

src/client.cc

@@ -53,6 +53,12 @@ Client::Client(std::unique_ptr<UserInterface>&& ui,
             killpg(getpgrp(), SIGINT);
             set_signal_handler(SIGINT, prev_handler);
         }
+        else if (key == ctrl('g'))
+        {
+            m_pending_keys.clear();
+            print_status({"operation cancelled", context().faces()["Error"]});
+            throw cancel{};
+        }
         else if (key.modifiers & Key::Modifiers::Resize)
         {
             m_window->set_dimensions(key.coord());

src/event_manager.cc

@@ -161,6 +161,13 @@ void EventManager::force_signal(int fd)
     m_has_forced_fd = true;
 }
 
+void EventManager::handle_urgent_events()
+{
+    if (has_instance())
+        instance().handle_next_events(EventMode::Urgent, nullptr, false);
+}
+
+
 SignalHandler set_signal_handler(int signum, SignalHandler handler)
 {
     struct sigaction new_action, old_action;
@@ -171,4 +178,5 @@ SignalHandler set_signal_handler(int signum, SignalHandler handler)
     sigaction(signum, &new_action, &old_action);
     return old_action.sa_handler;
 }
+
 }

src/event_manager.hh

@@ -96,6 +96,8 @@ public:
     // on next handle_next_events call.
     void force_signal(int fd);
 
+    static void handle_urgent_events();
+
 private:
     friend class FDWatcher;
     friend class Timer;

src/exception.hh

@@ -29,6 +29,11 @@ struct failure : runtime_error
     using runtime_error::runtime_error;
 };
 
+struct cancel : runtime_error
+{
+    cancel() : runtime_error("cancellation requested") {}
+};
+
 struct logic_error : exception
 {
 };

src/main.cc

@@ -894,12 +894,17 @@ int run_server(StringView session, StringView server_init,
             // Loop so that eventual inputs happening during the processing are handled as
             // well, avoiding unneeded redraws.
             bool allow_blocking = not client_manager.has_pending_inputs();
+            try
+            {
                 while (event_manager.handle_next_events(EventMode::Normal, nullptr, allow_blocking))
                 {
                     if (client_manager.process_pending_inputs())
                         break;
                     allow_blocking = false;
                 }
+            }
+            catch (const cancel&) {}
+
             client_manager.process_pending_inputs();
 
             client_manager.clear_client_trash();

src/normal.cc

@@ -1159,7 +1159,7 @@ void keep(Context& context, NormalParams params)
             const auto flags = match_flags(is_bol(begin.coord()), false,
                                            is_bow(buffer, begin.coord()),
                                            is_eow(buffer, end.coord()));
-            if (regex_search(begin, end, begin, end, regex, flags) == matching)
+            if (regex_search(begin, end, begin, end, regex, flags, EventManager::handle_urgent_events) == matching)
                 keep.push_back(sel);
         }
         if (keep.empty())

src/selectors.cc

@@ -2,6 +2,7 @@
 
 #include "buffer_utils.hh"
 #include "context.hh"
+#include "event_manager.hh"
 #include "flags.hh"
 #include "option_types.hh"
 #include "regex.hh"
@@ -287,16 +288,19 @@ find_opening(Iterator pos, const Container& container,
     // When on the token of a non-nestable block, we want to consider it opening
     if (nestable and
         backward_regex_search(container.begin(), pos,
-                              container.begin(), container.end(), res, closing) and
+                              container.begin(), container.end(), res, closing,
+                              RegexExecFlags::None, EventManager::handle_urgent_events) and
         res[0].second == pos)
         pos = res[0].first;
 
-    using RegexIt = RegexIterator<Iterator, RegexMode::Backward>;
+    using RegexIt = RegexIterator<Iterator, RegexMode::Backward, const Regex, void (*)()>;
-    for (auto&& match : RegexIt{container.begin(), pos, container.begin(), container.end(), opening})
+    for (auto&& match : RegexIt{container.begin(), pos, container.begin(), container.end(), opening,
+                                RegexExecFlags::None, EventManager::handle_urgent_events})
     {
         if (nestable)
         {
-            for (auto m [[maybe_unused]] : RegexIt{match[0].second, pos, container.begin(), container.end(), closing})
+            for (auto m [[maybe_unused]] : RegexIt{match[0].second, pos, container.begin(), container.end(), closing,
+                                                   RegexExecFlags::None, EventManager::handle_urgent_events})
                 ++level;
         }
 
@@ -314,12 +318,13 @@ find_closing(Iterator pos, const Container& container,
              const Regex& opening, const Regex& closing,
              int level, bool nestable)
 {
-    using RegexIt = RegexIterator<Iterator, RegexMode::Forward>;
+    for (auto match : RegexIterator{pos, container.end(), container.begin(), container.end(), closing,
-    for (auto match : RegexIt{pos, container.end(), container.begin(), container.end(), closing})
+                                    RegexExecFlags::None, EventManager::handle_urgent_events})
     {
         if (nestable)
         {
-            for (auto m [[maybe_unused]] : RegexIt{pos, match[0].first, container.begin(), container.end(), opening})
+            for (auto m [[maybe_unused]] : RegexIterator{pos, match[0].first, container.begin(), container.end(), opening,
+                                                         RegexExecFlags::None, EventManager::handle_urgent_events})
                 ++level;
         }
 
@@ -356,7 +361,8 @@ find_surrounding(const Container& container, Iterator pos,
             return {};
     }
     else if (MatchResults<Iterator> res;
-             regex_search(pos, container.end(), container.begin(), container.end(), res, opening) and
+             regex_search(pos, container.end(), container.begin(), container.end(), res, opening,
+                          RegexExecFlags::None, EventManager::handle_urgent_events) and
              res[0].first == pos) // Skip opening match if pos lies on it
         last = empty(res[0]) ? std::next(res[0].second) : res[0].second;
 
@@ -868,11 +874,13 @@ static bool find_next(const Buffer& buffer, const BufferIterator& pos,
 {
     if (pos != buffer.end() and
         regex_search(pos, buffer.end(), buffer.begin(), buffer.end(),
-                     matches, ex, match_flags(buffer, pos, buffer.end())))
+                     matches, ex, match_flags(buffer, pos, buffer.end()),
+                     EventManager::handle_urgent_events))
         return true;
     wrapped = true;
     return regex_search(buffer.begin(), buffer.end(), buffer.begin(), buffer.end(),
-                        matches, ex, match_flags(buffer, buffer.begin(), buffer.end()));
+                        matches, ex, match_flags(buffer, buffer.begin(), buffer.end()),
+                        EventManager::handle_urgent_events);
 }
 
 static bool find_prev(const Buffer& buffer, const BufferIterator& pos,
@@ -883,13 +891,15 @@ static bool find_prev(const Buffer& buffer, const BufferIterator& pos,
         backward_regex_search(buffer.begin(), pos, buffer.begin(), buffer.end(),
                               matches, ex,
                               match_flags(buffer, buffer.begin(), pos) |
-                              RegexExecFlags::NotInitialNull))
+                              RegexExecFlags::NotInitialNull,
+                              EventManager::handle_urgent_events))
         return true;
     wrapped = true;
     return backward_regex_search(buffer.begin(), buffer.end(), buffer.begin(), buffer.end(),
                                  matches, ex,
                                  match_flags(buffer, buffer.begin(), buffer.end()) |
-                                 RegexExecFlags::NotInitialNull);
+                                 RegexExecFlags::NotInitialNull,
+                                 EventManager::handle_urgent_events);
 }
 
 template<RegexMode mode>
@@ -935,7 +945,8 @@ Vector<Selection> select_matches(const Buffer& buffer, ConstArrayView<Selection>
         auto sel_beg = buffer.iterator_at(sel.min());
         auto sel_end = utf8::next(buffer.iterator_at(sel.max()), buffer.end());
 
-        for (auto&& match : RegexIterator{sel_beg, sel_end, vm, match_flags(buffer, sel_beg, sel_end)})
+        for (auto&& match : RegexIterator{sel_beg, sel_end, vm, match_flags(buffer, sel_beg, sel_end),
+                                          EventManager::handle_urgent_events})
         {
             auto capture = match[capture_idx];
             if (not capture.matched or capture.first == sel_end)