Update and Repaint on resize. (dotnet#1979)

* Repaint on resize/drag.

* Remove API changes.

* Use the same `onRender` action for Glfw's refresh events, but prevent reentrancy into DoEvents.

* Move protected _onFrame field into the GlfwWindow class rather than the base ViewImplementationBase class.

src/Windowing/Silk.NET.Windowing.Glfw/GlfwWindow.cs

@@ -23,6 +23,7 @@ internal unsafe class GlfwWindow : WindowImplementationBase, IVkSurface
  private GlfwCallbacks.WindowPosCallback? _onMove;
  private GlfwCallbacks.WindowSizeCallback? _onResize;
  private GlfwCallbacks.FramebufferSizeCallback? _onFramebufferResize;
+ private GlfwCallbacks.WindowRefreshCallback? _onRefresh;
  private GlfwCallbacks.DropCallback? _onFileDrop;
  private GlfwCallbacks.WindowCloseCallback? _onClosing;
  private GlfwCallbacks.WindowFocusCallback? _onFocusChanged;
@@ -37,6 +38,16 @@ internal unsafe class GlfwWindow : WindowImplementationBase, IVkSurface
  private string _localTitleCache; // glfw doesn't let us get the window title.
  private GlfwContext? _glContext;
  private string _windowClass;
+ private bool _inDoEvents;
+
+ /// <summary>
+ /// The action passed to <see cref="Run"/>.
+ /// </summary>
+ /// <remarks>
+ /// May be called on repaint from within <see cref="DoEvents"/>.
+ /// For example, during modal operations such as resizing on Windows.
+ /// </remarks>
+ protected Action? _onFrame;
 
  public GlfwWindow(WindowOptions optionsCache, GlfwWindow? parent, GlfwMonitor? monitor) : base(optionsCache)
  {
@@ -67,6 +78,19 @@ protected override Rectangle<int> CoreBorderSize
 
  protected override nint CoreHandle => (nint) _glfwWindow;
 
+ public override void Run(Action onFrame)
+ {
+ try
+ {
+ _onFrame = onFrame;
+ base.Run(onFrame);
+ }
+ finally
+ {
+ _onFrame = null;
+ }
+ }
+
  protected override void CoreReset()
  {
  if (_glfwWindow == null)
@@ -598,13 +622,24 @@ public override Vector2D<int> FramebufferSize
 
  public override void DoEvents()
  {
- if (IsEventDriven)
+ if (!_inDoEvents)
  {
- _glfw.WaitEvents();
- }
- else
- {
- _glfw.PollEvents();
+ try
+ {
+ _inDoEvents = true;
+ if (IsEventDriven)
+ {
+ _glfw.WaitEvents();
+ }
+ else
+ {
+ _glfw.PollEvents();
+ }
+ }
+ finally
+ {
+ _inDoEvents = false;
+ }
  }
  }
 
@@ -658,6 +693,8 @@ protected override void RegisterCallbacks()
  FramebufferResize?.Invoke(new(width, height));
  };
 
+ _onRefresh = (window) => _onFrame?.Invoke();
+
  _onClosing = window => Closing?.Invoke();
 
  _onFocusChanged = (window, isFocused) => FocusChanged?.Invoke(isFocused);
@@ -744,6 +781,7 @@ protected override void RegisterCallbacks()
  _glfw.SetWindowIconifyCallback(_glfwWindow, _onMinimized);
  _glfw.SetWindowMaximizeCallback(_glfwWindow, _onMaximized);
  _glfw.SetFramebufferSizeCallback(_glfwWindow, _onFramebufferResize);
+ _glfw.SetWindowRefreshCallback(_glfwWindow, _onRefresh);
  _glfw.SetDropCallback(_glfwWindow, _onFileDrop);
  GLFW.Glfw.ThrowExceptions();
  }
@@ -761,6 +799,7 @@ protected override void UnregisterCallbacks()
  _glfw.GcUtility.Unpin(_onMove);
  _glfw.GcUtility.Unpin(_onResize);
  _glfw.GcUtility.Unpin(_onFramebufferResize);
+ _glfw.GcUtility.Unpin(_onRefresh);
  _glfw.GcUtility.Unpin(_onFileDrop);
  _glfw.GcUtility.Unpin(_onFocusChanged);
 
@@ -770,6 +809,7 @@ protected override void UnregisterCallbacks()
  _onMove = null;
  _onResize = null;
  _onFramebufferResize = null;
+ _onRefresh = null;
  _onFileDrop = null;
  _onFocusChanged = null;
  }