Nerfed/Nerfed.Runtime/Engine.cs
2024-07-12 16:38:30 +02:00

266 lines
9.2 KiB
C#

using Nerfed.Runtime.Audio;
using Nerfed.Runtime.Graphics;
using SDL2;
using System.Diagnostics;
namespace Nerfed.Runtime;
public static class Engine
{
public static TimeSpan MaxDeltaTime { get; set; } = TimeSpan.FromMilliseconds(100);
public static bool VSync { get; set; }
public static GraphicsDevice GraphicsDevice { get; private set; }
public static AudioDevice AudioDevice { get; private set; }
public static Window MainWindow { get; private set; }
public static TimeSpan Timestep { get; private set; }
private static bool quit;
private static Stopwatch gameTimer;
private static long previousTicks = 0;
private static TimeSpan accumulatedUpdateTime = TimeSpan.Zero;
private static TimeSpan accumulatedDrawTime = TimeSpan.Zero;
// must be a power of 2 so we can do a bitmask optimization when checking worst case
private const int previousSleepTimeCount = 128;
private const int sleepTimeMask = previousSleepTimeCount - 1;
private static readonly TimeSpan[] previousSleepTimes = new TimeSpan[previousSleepTimeCount];
private static int sleepTimeIndex;
private static TimeSpan worstCaseSleepPrecision = TimeSpan.FromMilliseconds(1);
private static bool framerateCapped;
private static TimeSpan framerateCapTimeSpan = TimeSpan.Zero;
//TODO: These are temp
private const int MaxFps = 300;
private const int TargetTimestep = 60;
private const int WindowWidth = 1280;
private const int WindowHeight = 720;
private const string WindowTitle = "Nerfed";
//..
private static Gui.GuiController Controller;
internal static void Run(string[] args)
{
Timestep = TimeSpan.FromTicks(TimeSpan.TicksPerSecond / TargetTimestep);
gameTimer = Stopwatch.StartNew();
SetFrameLimiter(new FrameLimiterSettings(FrameLimiterMode.Capped, MaxFps));
for (int i = 0; i < previousSleepTimes.Length; i += 1)
{
previousSleepTimes[i] = TimeSpan.FromMilliseconds(1);
}
if (SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_TIMER | SDL.SDL_INIT_GAMECONTROLLER) < 0)
{
throw new Exception("Failed to init SDL");
}
GraphicsDevice = new GraphicsDevice(BackendFlags.All);
MainWindow = new Window(GraphicsDevice, new WindowCreateInfo(WindowTitle, WindowWidth, WindowHeight, ScreenMode.Windowed));
if (!GraphicsDevice.ClaimWindow(MainWindow, SwapchainComposition.SDR, VSync ? PresentMode.VSync : PresentMode.Mailbox))
{
throw new Exception("Failed to claim window");
}
MainWindow.OnCloseEvent += (w) => {
Quit();
};
AudioDevice = new AudioDevice();
Controller = new Gui.GuiController(GraphicsDevice, MainWindow, Color.DarkOliveGreen);
Controller.OnGui += () => {
ImGuiNET.ImGui.ShowDemoWindow();
};
while (!quit)
{
Tick();
}
Controller.Dispose();
GraphicsDevice.UnclaimWindow(MainWindow);
MainWindow.Dispose();
GraphicsDevice.Dispose();
AudioDevice.Dispose();
SDL.SDL_Quit();
}
/// <summary>
/// Updates the frame limiter settings.
/// </summary>
public static void SetFrameLimiter(FrameLimiterSettings settings)
{
framerateCapped = settings.Mode == FrameLimiterMode.Capped;
if (framerateCapped)
{
framerateCapTimeSpan = TimeSpan.FromTicks(TimeSpan.TicksPerSecond / settings.Cap);
}
else
{
framerateCapTimeSpan = TimeSpan.Zero;
}
}
public static void Quit()
{
quit = true;
}
private static void Tick()
{
AdvanceElapsedTime();
if (framerateCapped)
{
/* We want to wait until the framerate cap,
* but we don't want to oversleep. Requesting repeated 1ms sleeps and
* seeing how long we actually slept for lets us estimate the worst case
* sleep precision so we don't oversleep the next frame.
*/
while (accumulatedDrawTime + worstCaseSleepPrecision < framerateCapTimeSpan)
{
Thread.Sleep(1);
TimeSpan timeAdvancedSinceSleeping = AdvanceElapsedTime();
UpdateEstimatedSleepPrecision(timeAdvancedSinceSleeping);
}
/* Now that we have slept into the sleep precision threshold, we need to wait
* for just a little bit longer until the target elapsed time has been reached.
* SpinWait(1) works by pausing the thread for very short intervals, so it is
* an efficient and time-accurate way to wait out the rest of the time.
*/
while (accumulatedDrawTime < framerateCapTimeSpan)
{
Thread.SpinWait(1);
AdvanceElapsedTime();
}
}
// Do not let any step take longer than our maximum.
if (accumulatedUpdateTime > MaxDeltaTime)
{
accumulatedUpdateTime = MaxDeltaTime;
}
if (!quit)
{
while (accumulatedUpdateTime >= Timestep)
{
Keyboard.Update();
Mouse.Update();
GamePad.Update();
ProcessSDLEvents();
// Tick game here...
Controller.Update((float)Timestep.TotalSeconds);
AudioDevice.WakeThread();
accumulatedUpdateTime -= Timestep;
}
double alpha = accumulatedUpdateTime / Timestep;
// Render here..
Controller.Render();
accumulatedDrawTime -= framerateCapTimeSpan;
}
}
private static TimeSpan AdvanceElapsedTime()
{
long currentTicks = gameTimer.Elapsed.Ticks;
TimeSpan timeAdvanced = TimeSpan.FromTicks(currentTicks - previousTicks);
accumulatedUpdateTime += timeAdvanced;
accumulatedDrawTime += timeAdvanced;
previousTicks = currentTicks;
return timeAdvanced;
}
private static void ProcessSDLEvents()
{
while (SDL.SDL_PollEvent(out SDL.SDL_Event ev) == 1)
{
switch (ev.type)
{
case SDL.SDL_EventType.SDL_QUIT:
Quit();
break;
case SDL.SDL_EventType.SDL_TEXTINPUT:
case SDL.SDL_EventType.SDL_KEYDOWN:
case SDL.SDL_EventType.SDL_KEYUP:
Keyboard.ProcessEvent(ref ev);
break;
case SDL.SDL_EventType.SDL_MOUSEBUTTONDOWN:
case SDL.SDL_EventType.SDL_MOUSEBUTTONUP:
case SDL.SDL_EventType.SDL_MOUSEWHEEL:
case SDL.SDL_EventType.SDL_MOUSEMOTION:
Mouse.ProcessEvent(ref ev);
break;
case SDL.SDL_EventType.SDL_CONTROLLERDEVICEADDED:
case SDL.SDL_EventType.SDL_CONTROLLERDEVICEREMOVED:
case SDL.SDL_EventType.SDL_CONTROLLERBUTTONDOWN:
case SDL.SDL_EventType.SDL_CONTROLLERBUTTONUP:
case SDL.SDL_EventType.SDL_CONTROLLERAXISMOTION:
case SDL.SDL_EventType.SDL_CONTROLLERTOUCHPADDOWN:
case SDL.SDL_EventType.SDL_CONTROLLERTOUCHPADUP:
case SDL.SDL_EventType.SDL_CONTROLLERTOUCHPADMOTION:
case SDL.SDL_EventType.SDL_CONTROLLERSENSORUPDATE:
GamePad.ProcessEvent(ref ev);
break;
case SDL.SDL_EventType.SDL_WINDOWEVENT:
Window.ProcessEvent(ref ev);
break;
}
}
}
/* To calculate the sleep precision of the OS, we take the worst case
* time spent sleeping over the results of previous requests to sleep 1ms.
*/
private static void UpdateEstimatedSleepPrecision(TimeSpan timeSpentSleeping)
{
/* It is unlikely that the scheduler will actually be more imprecise than
* 4ms and we don't want to get wrecked by a single long sleep so we cap this
* value at 4ms for sanity.
*/
TimeSpan upperTimeBound = TimeSpan.FromMilliseconds(4);
if (timeSpentSleeping > upperTimeBound)
{
timeSpentSleeping = upperTimeBound;
}
/* We know the previous worst case - it's saved in worstCaseSleepPrecision.
* We also know the current index. So the only way the worst case changes
* is if we either 1) just got a new worst case, or 2) the worst case was
* the oldest entry on the list.
*/
if (timeSpentSleeping >= worstCaseSleepPrecision)
{
worstCaseSleepPrecision = timeSpentSleeping;
}
else if (previousSleepTimes[sleepTimeIndex] == worstCaseSleepPrecision)
{
TimeSpan maxSleepTime = TimeSpan.MinValue;
for (int i = 0; i < previousSleepTimes.Length; i++)
{
if (previousSleepTimes[i] > maxSleepTime)
{
maxSleepTime = previousSleepTimes[i];
}
}
worstCaseSleepPrecision = maxSleepTime;
}
previousSleepTimes[sleepTimeIndex] = timeSpentSleeping;
sleepTimeIndex = (sleepTimeIndex + 1) & sleepTimeMask;
}
}