MoonWorks/src/Game.cs

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C#
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using System.Collections.Generic;
using SDL2;
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using MoonWorks.Audio;
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using MoonWorks.Graphics;
using MoonWorks.Input;
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using System.Text;
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using System;
using System.Diagnostics;
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namespace MoonWorks
{
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public abstract class Game
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{
public TimeSpan MAX_DELTA_TIME = TimeSpan.FromMilliseconds(100);
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public TimeSpan Timestep { get; private set; }
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private bool quit = false;
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private Stopwatch gameTimer;
private long previousTicks = 0;
TimeSpan accumulatedUpdateTime = TimeSpan.Zero;
TimeSpan accumulatedDrawTime = TimeSpan.Zero;
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// must be a power of 2 so we can do a bitmask optimization when checking worst case
private const int PREVIOUS_SLEEP_TIME_COUNT = 128;
private const int SLEEP_TIME_MASK = PREVIOUS_SLEEP_TIME_COUNT - 1;
private TimeSpan[] previousSleepTimes = new TimeSpan[PREVIOUS_SLEEP_TIME_COUNT];
private int sleepTimeIndex = 0;
private TimeSpan worstCaseSleepPrecision = TimeSpan.FromMilliseconds(1);
private bool FramerateCapped = false;
private TimeSpan FramerateCapTimeSpan = TimeSpan.Zero;
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public GraphicsDevice GraphicsDevice { get; }
public AudioDevice AudioDevice { get; }
public Inputs Inputs { get; }
public Window MainWindow { get; }
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public Game(
WindowCreateInfo windowCreateInfo,
PresentMode presentMode,
FrameLimiterSettings frameLimiterSettings,
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int targetTimestep = 60,
bool debugMode = false
)
{
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Timestep = TimeSpan.FromTicks(TimeSpan.TicksPerSecond / targetTimestep);
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gameTimer = Stopwatch.StartNew();
SetFrameLimiter(frameLimiterSettings);
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for (int i = 0; i < previousSleepTimes.Length; i += 1)
{
previousSleepTimes[i] = TimeSpan.FromMilliseconds(1);
}
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if (SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_TIMER | SDL.SDL_INIT_GAMECONTROLLER) < 0)
{
System.Console.WriteLine("Failed to initialize SDL!");
return;
}
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Logger.Initialize();
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Inputs = new Inputs();
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GraphicsDevice = new GraphicsDevice(
Backend.Vulkan,
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debugMode
);
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MainWindow = new Window(windowCreateInfo, GraphicsDevice.WindowFlags);
if (!GraphicsDevice.ClaimWindow(MainWindow, presentMode))
{
throw new System.SystemException("Could not claim window!");
}
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AudioDevice = new AudioDevice();
}
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public void Run()
{
while (!quit)
{
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Tick();
}
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Destroy();
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AudioDevice.Dispose();
MainWindow.Dispose();
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GraphicsDevice.Dispose();
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SDL.SDL_Quit();
}
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public void SetFrameLimiter(FrameLimiterSettings settings)
{
FramerateCapped = settings.Mode == FrameLimiterMode.Capped;
if (FramerateCapped)
{
FramerateCapTimeSpan = TimeSpan.FromTicks(TimeSpan.TicksPerSecond / settings.Cap);
}
else
{
FramerateCapTimeSpan = TimeSpan.Zero;
}
}
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protected abstract void Update(TimeSpan delta);
protected abstract void Draw(double alpha);
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protected virtual void Destroy() {}
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// Called when a file is dropped on the game window.
protected virtual void DropFile(string filePath) {}
/* Required to distinguish between multiple files dropped at once
* vs multiple files dropped one at a time.
*
* Called once for every multi-file drop.
*/
protected virtual void DropBegin() {}
protected virtual void DropComplete() {}
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private void Tick()
{
AdvanceElapsedTime();
if (FramerateCapped)
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{
/* 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)
{
System.Threading.Thread.Sleep(1);
TimeSpan timeAdvancedSinceSleeping = AdvanceElapsedTime();
UpdateEstimatedSleepPrecision(timeAdvancedSinceSleeping);
}
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/* 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)
{
System.Threading.Thread.SpinWait(1);
AdvanceElapsedTime();
}
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}
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// Now that we are going to perform an update, let's handle SDL events.
HandleSDLEvents();
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// Do not let any step take longer than our maximum.
if (accumulatedUpdateTime > MAX_DELTA_TIME)
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{
accumulatedUpdateTime = MAX_DELTA_TIME;
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}
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if (!quit)
{
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while (accumulatedUpdateTime >= Timestep)
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{
Inputs.Update();
AudioDevice.Update();
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Update(Timestep);
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accumulatedUpdateTime -= Timestep;
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}
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var alpha = accumulatedUpdateTime / Timestep;
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Draw(alpha);
accumulatedDrawTime -= FramerateCapTimeSpan;
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}
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}
private void HandleSDLEvents()
{
while (SDL.SDL_PollEvent(out var _event) == 1)
{
switch (_event.type)
{
case SDL.SDL_EventType.SDL_QUIT:
quit = true;
break;
case SDL.SDL_EventType.SDL_TEXTINPUT:
HandleTextInput(_event);
break;
case SDL.SDL_EventType.SDL_MOUSEWHEEL:
Inputs.Mouse.Wheel += _event.wheel.y;
break;
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case SDL.SDL_EventType.SDL_DROPBEGIN:
DropBegin();
break;
case SDL.SDL_EventType.SDL_DROPCOMPLETE:
DropComplete();
break;
case SDL.SDL_EventType.SDL_DROPFILE:
HandleFileDrop(_event);
break;
case SDL.SDL_EventType.SDL_CONTROLLERDEVICEADDED:
HandleControllerAdded(_event);
break;
case SDL.SDL_EventType.SDL_CONTROLLERDEVICEREMOVED:
HandleControllerRemoved(_event);
break;
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case SDL.SDL_EventType.SDL_WINDOWEVENT:
HandleWindowEvent(_event);
break;
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}
}
}
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private void HandleWindowEvent(SDL.SDL_Event evt)
{
if (evt.window.windowEvent == SDL.SDL_WindowEventID.SDL_WINDOWEVENT_SIZE_CHANGED)
{
var window = Window.Lookup(evt.window.windowID);
window.SizeChanged((uint) evt.window.data1, (uint) evt.window.data2);
}
else if (evt.window.windowEvent == SDL.SDL_WindowEventID.SDL_WINDOWEVENT_CLOSE)
{
var window = Window.Lookup(evt.window.windowID);
GraphicsDevice.UnclaimWindow(window);
window.Dispose();
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}
}
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private void HandleTextInput(SDL.SDL_Event evt)
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{
// Based on the SDL2# LPUtf8StrMarshaler
unsafe
{
int bytes = MeasureStringLength(evt.text.text);
if (bytes > 0)
{
/* UTF8 will never encode more characters
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* than bytes in a string, so bytes is a
* suitable upper estimate of size needed
*/
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char* charsBuffer = stackalloc char[bytes];
int chars = Encoding.UTF8.GetChars(
evt.text.text,
bytes,
charsBuffer,
bytes
);
for (int i = 0; i < chars; i += 1)
{
Inputs.OnTextInput(charsBuffer[i]);
}
}
}
}
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private void HandleFileDrop(SDL.SDL_Event evt)
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{
// Need to do it this way because SDL2 expects you to free the filename string.
string filePath = SDL.UTF8_ToManaged(evt.drop.file, true);
DropFile(filePath);
}
private void HandleControllerAdded(SDL.SDL_Event evt)
{
var index = evt.cdevice.which;
if (SDL.SDL_IsGameController(index) == SDL.SDL_bool.SDL_TRUE)
{
System.Console.WriteLine($"New controller detected!");
Inputs.AddGamepad(index);
}
}
private void HandleControllerRemoved(SDL.SDL_Event evt)
{
System.Console.WriteLine($"Controller removal detected!");
Inputs.RemoveGamepad(evt.cdevice.which);
}
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private TimeSpan AdvanceElapsedTime()
{
long currentTicks = gameTimer.Elapsed.Ticks;
TimeSpan timeAdvanced = TimeSpan.FromTicks(currentTicks - previousTicks);
accumulatedUpdateTime += timeAdvanced;
accumulatedDrawTime += timeAdvanced;
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previousTicks = currentTicks;
return timeAdvanced;
}
/* 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 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.
*/
var 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)
{
var 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) & SLEEP_TIME_MASK;
}
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private unsafe static int MeasureStringLength(byte* ptr)
{
int bytes;
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for (bytes = 0; *ptr != 0; ptr += 1, bytes += 1) ;
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return bytes;
}
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}
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}