Class GameWindow

The GameWindow class contains cross-platform methods to create and render on an OpenGL window, handle input and load resources.

Inheritance
object
NativeWindow
GameWindow
Implements
Inherited Members
Namespace: OpenTK.Windowing.Desktop
Assembly: OpenTK.Windowing.Desktop.dll
Syntax
public class GameWindow : NativeWindow, IDisposable
Remarks

GameWindow contains several events you can hook or override to add your custom logic:

Constructors

GameWindow(GameWindowSettings, NativeWindowSettings)

Initializes a new instance of the GameWindow class with sensible default attributes.

Declaration
public GameWindow(GameWindowSettings gameWindowSettings, NativeWindowSettings nativeWindowSettings)
Parameters
Type Name Description
GameWindowSettings gameWindowSettings

The GameWindow related settings.
NativeWindowSettings nativeWindowSettings

The NativeWindow related settings.
Remarks

Use GameWindowSettings.Default and NativeWindowSettings.Default to get some sensible default attributes.

Properties

ExpectedSchedulerPeriod

The expected scheduler period in milliseconds. Used to provide accurate sleep timings.

On Windows the scheduler period can be set using timeBeginPeriod(), OpenTK sets this value to 8ms by default. See Run() for more details.
On Linux we set this to 1 as it seems like Sleep(int) is able to accurately sleep 1ms.
On macos we set this to 1 aswell as tests imply Sleep(int) can accurately sleep 1ms.

Declaration
public int ExpectedSchedulerPeriod { get; set; }
Property Value
Type Description
int

IsMultiThreaded

Gets a value indicating whether or not the GameWindow should use a separate thread for rendering.

Declaration
[Obsolete("There is not one size fits all multithreading solution, especially for OpenGL. This feature has been removed and will not work.", true)]
public bool IsMultiThreaded { get; }
Property Value
Type Description
bool
Remarks

If this is true, render frames will be processed in a separate thread. Do not enable this unless your code is thread safe.

IsRunningSlowly

Gets a value indicating whether or not UpdatePeriod has consistently failed to reach TargetUpdatePeriod. This can be used to do things such as decreasing visual quality if the user's computer isn't powerful enough to handle the application.

Declaration
protected bool IsRunningSlowly { get; }
Property Value
Type Description
bool

RenderFrequency

Gets or sets a double representing the render frequency, in hertz.

Declaration
[Obsolete("Use UpdateFrequency instead. We no longer separate UpdateFrame and RenderFrame.", true)]
public double RenderFrequency { get; set; }
Property Value
Type Description
double
Remarks

A value of 0.0 indicates that RenderFrame events are generated at the maximum possible frequency (i.e. only limited by the hardware's capabilities).

Values lower than 1.0Hz are clamped to 0.0. Values higher than 500.0Hz are clamped to 500.0Hz.

RenderTime

Gets a double representing the time spent in the RenderFrame function, in seconds.

Declaration
[Obsolete("Use UpdateTime instead. We no longer separate UpdateFrame and RenderFrame.", true)]
public double RenderTime { get; protected set; }
Property Value
Type Description
double

UpdateFrequency

Gets or sets a double representing the update frequency, in hertz.

Declaration
public double UpdateFrequency { get; set; }
Property Value
Type Description
double
Remarks

A value of 0.0 indicates that UpdateFrame events are generated at the maximum possible frequency (i.e. only limited by the hardware's capabilities).

Values lower than 1.0Hz are clamped to 0.0. Values higher than 500.0Hz are clamped to 500.0Hz.

UpdateTime

Gets a double representing the time spent in the UpdateFrame function, in seconds.

Declaration
public double UpdateTime { get; protected set; }
Property Value
Type Description
double

Methods

Close()

Closes this window.

Declaration
public override void Close()
Overrides

Dispose()

Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

Declaration
public override void Dispose()
Overrides

OnLoad()

Run immediately after Run() is called.

Declaration
protected virtual void OnLoad()

OnRenderFrame(FrameEventArgs)

Run when the window is ready to render. This is called after OnUpdateFrame(FrameEventArgs).

Declaration
protected virtual void OnRenderFrame(FrameEventArgs args)
Parameters
Type Name Description
FrameEventArgs args

The event arguments for this frame.

OnRenderThreadStarted()

Run when the update thread is started. This will never run if you set IsMultiThreaded to false.

Declaration
[Obsolete("There is no longer a separate render thread.")]
protected virtual void OnRenderThreadStarted()

OnUnload()

Run when the window is about to close.

Declaration
protected virtual void OnUnload()

OnUpdateFrame(FrameEventArgs)

Run when the window is ready to update. This is called before OnRenderFrame(FrameEventArgs).

Declaration
protected virtual void OnUpdateFrame(FrameEventArgs args)
Parameters
Type Name Description
FrameEventArgs args

The event arguments for this frame.

ResetTimeSinceLastUpdate()

Resets the time since the last update. This function is useful when implementing updates on resize using windows.

Declaration
public void ResetTimeSinceLastUpdate()

Run()

Initialize the update thread (if using a multi-threaded context, and enter the game loop of the GameWindow).

Declaration
public virtual void Run()
Remarks

On windows this function sets the thread affinity mask to 0x0001 to avoid the thread from changing cores.

On windows this function calls timeBeginPeriod(8) to get better sleep timings, which can increase power usage. This can be undone by calling timeEndPeriod(8) in OnLoad() and timeBeginPeriod(8) in OnUnload(). If the expected scheduler time is changed set ExpectedSchedulerPeriod to the appropriate value to keep the accuracy of the update loop.

SwapBuffers()

Swaps the front and back buffers of the current GraphicsContext, presenting the rendered scene to the user.

Declaration
public virtual void SwapBuffers()

TimeSinceLastUpdate()

The current time since the last update. This function is useful when implementing updates on resize using windows.

Declaration
public double TimeSinceLastUpdate()
Returns
Type Description
double

The time since the last update.
Remarks

Don't use this in OnUpdateFrame(FrameEventArgs) or OnRenderFrame(FrameEventArgs), instead use Time.

Events

Load

Occurs before the window is displayed for the first time.

Declaration
public event Action Load
Event Type
Type Description
Action

RenderFrame

Occurs when it is time to render a frame. This is invoked after UpdateFrequency.

Declaration
public event Action<FrameEventArgs> RenderFrame
Event Type
Type Description
Action<FrameEventArgs>

RenderThreadStarted

If game window is configured to run with a dedicated update thread (by passing isSingleThreaded = false in the constructor), occurs when the update thread has started. This would be a good place to initialize thread specific stuff (like setting a synchronization context).

Declaration
[Obsolete("There is no longer a separate render thread.")]
public event Action RenderThreadStarted
Event Type
Type Description
Action

Unload

Occurs before the window is destroyed.

Declaration
public event Action Unload
Event Type
Type Description
Action

UpdateFrame

Occurs when it is time to update a frame. This is invoked before RenderFrame.

Declaration
public event Action<FrameEventArgs> UpdateFrame
Event Type
Type Description
Action<FrameEventArgs>

Implements