cam: Use libevent to implement event loop

To prepare for removal of the EventDispatcher from the libcamera public
API, switch to libevent to handle the event loop.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

1 files changed, 27 insertions, 7 deletions

diff --git a/src/cam/event_loop.cpp b/src/cam/event_loop.cpp
index e8ab8617..13f2583d 100644
--- a/src/cam/event_loop.cpp
+++ b/src/cam/event_loop.cpp
@@ -5,19 +5,34 @@
  * event_loop.cpp - cam - Event loop
  */
 
-#include <libcamera/event_dispatcher.h>
-
 #include "event_loop.h"
 
-using namespace libcamera;
+#include <assert.h>
+#include <event2/event.h>
+#include <event2/thread.h>
+
+EventLoop *EventLoop::instance_ = nullptr;
 
-EventLoop::EventLoop(EventDispatcher *dispatcher)
-	: dispatcher_(dispatcher)
+EventLoop::EventLoop()
 {
+	assert(!instance_);
+
+	evthread_use_pthreads();
+	event_ = event_base_new();
+	instance_ = this;
 }
 
 EventLoop::~EventLoop()
 {
+	instance_ = nullptr;
+
+	event_base_free(event_);
+	libevent_global_shutdown();
+}
+
+EventLoop *EventLoop::instance()
+{
+	return instance_;
 }
 
 int EventLoop::exec()
@@ -26,7 +41,7 @@ int EventLoop::exec()
 	exit_.store(false, std::memory_order_release);
 
 	while (!exit_.load(std::memory_order_acquire))
-		dispatcher_->processEvents();
+		event_base_loop(event_, EVLOOP_NO_EXIT_ON_EMPTY);
 
 	return exitCode_;
 }
@@ -35,5 +50,10 @@ void EventLoop::exit(int code)
 {
 	exitCode_ = code;
 	exit_.store(true, std::memory_order_release);
-	dispatcher_->interrupt();
+	interrupt();
+}
+
+void EventLoop::interrupt()
+{
+	event_base_loopbreak(event_);
 }