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Introduces frame locking for SDL.

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This commit is contained in:
Thomas Harte 2020-02-10 23:07:09 -05:00
parent bf6bc7c684
commit 6147134423
2 changed files with 29 additions and 9 deletions
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2
OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme
View File

@ -67,7 +67,7 @@
</Testables>
</TestAction>
<LaunchAction
buildConfiguration = "Debug"
buildConfiguration = "Release"
selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
enableASanStackUseAfterReturn = "YES"

36
OSBindings/SDL/main.cpp
View File

@ -36,6 +36,10 @@
namespace {
struct MachineRunner {
MachineRunner() {
frame_lock_.clear();
}
~MachineRunner() {
stop();
}
@ -66,6 +70,10 @@ struct MachineRunner {
_frame_period.store((1e9 * 32.0) / double(frame_time_average_));
}
void signal_did_draw() {
frame_lock_.clear();
}
std::mutex *machine_mutex;
Machine::DynamicMachine *machine;
@ -73,6 +81,7 @@ struct MachineRunner {
SDL_TimerID timer_ = 0;
Time::Nanos last_time_ = 0;
std::atomic<Time::Nanos> vsync_time_;
std::atomic_flag frame_lock_;
Time::ScanSynchroniser scan_synchroniser_;
@ -95,7 +104,7 @@ struct MachineRunner {
const auto time_now = Time::nanos_now();
const auto vsync_time = vsync_time_.load();
std::lock_guard<std::mutex> lock_guard(*machine_mutex);
std::unique_lock<std::mutex> lock_guard(*machine_mutex);
const auto crt_machine = machine->crt_machine();
bool split_and_sync = false;
@ -108,6 +117,14 @@ struct MachineRunner {
crt_machine->set_speed_multiplier(
scan_synchroniser_.next_speed_multiplier(crt_machine->get_scan_status())
);
// This is a bit of an SDL ugliness; wait here until the next frame is drawn.
// That is, unless and until I can think of a good way of running background
// updates via a share group — possibly an extra intermediate buffer is needed?
lock_guard.unlock();
while(frame_lock_.test_and_set());
lock_guard.lock();
crt_machine->run_for(double(time_now - vsync_time) / 1e9);
} else {
crt_machine->run_for(double(time_now - last_time_) / 1e9);
@ -129,7 +146,6 @@ struct SpeakerDelegate: public Outputs::Speaker::Speaker::Delegate {
}
void audio_callback(Uint8 *stream, int len) {
// updater->update();
std::lock_guard<std::mutex> lock_guard(audio_buffer_mutex_);
std::size_t sample_length = static_cast<std::size_t>(len) / sizeof(int16_t);
@ -148,7 +164,6 @@ struct SpeakerDelegate: public Outputs::Speaker::Speaker::Delegate {
}
SDL_AudioDeviceID audio_device;
// Concurrency::BestEffortUpdater *updater;
std::mutex audio_buffer_mutex_;
std::vector<int16_t> audio_buffer_;
@ -716,14 +731,19 @@ int main(int argc, char *argv[]) {
Uint32 fullscreen_mode = 0;
machine_runner.start();
while(!should_quit) {
// Wait for vsync, draw a new frame and post a machine update.
// NB: machine_mutex is *not* currently locked, therefore it shouldn't
// be 'most' of the time.
SDL_GL_SwapWindow(window);
machine_runner.signal_vsync();
// Draw a new frame, indicating completion of the draw to the machine runner.
scan_target.update(int(window_width), int(window_height));
scan_target.draw(int(window_width), int(window_height));
if(activity_observer) activity_observer->draw();
machine_runner.signal_did_draw();
// Wait for presentation of that frame, posting a vsync.
SDL_GL_SwapWindow(window);
machine_runner.signal_vsync();
// NB: machine_mutex is *not* currently locked, therefore it shouldn't
// be 'most' of the time — assuming most of the time is spent waiting
// on vsync, anyway.
// Grab the machine lock and process all pending events.
std::lock_guard<std::mutex> lock_guard(machine_mutex);