Update and Repaint on resize. (#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.

Author: otac0n

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;
             }