asynchronicity improvements for ui system

- Added UiSystem.EnqueueAction to do work synchronously next time the ui system updates
- Fixed TextField EnterReceiver not allowing element addition or removal in

Author: Ellpeck

CHANGELOG.md

@@ -29,6 +29,7 @@ Additions
 - Added the ability to set a selected texture and color for buttons
 - Added the ability for tooltips to snap to a specified selection-independent element
 - Added Image.UseImagePivot to allow disabling texture region pivot being taken into account
+- Added UiSystem.EnqueueAction to do work synchronously next time the ui system updates
 
 Improvements
 - Explicitly return the element type from Dropdown.AddElement overloads
@@ -41,6 +42,7 @@ Fixes
 - Fixed UiParser ImageExceptionHandler being ignored when an exception occurs during texture construction
 - Fixed images displaying the initial texture when the texture callback starts returning null
 - Fixed UiStyle copy constructor not copying all style properties
+- Fixed TextField EnterReceiver not allowing element addition or removal in OnPressed
 
 Removals
 - Marked RootElement.OnAddedToUi as obsolete in favor of UiSystem.OnRootAdded

MLEM.Ui/Elements/TextField.cs

@@ -209,8 +209,10 @@ public TextField(Anchor anchor, Vector2 size, Rule rule = null, GenericFont font
                 }
             };
             this.OnTextInput += (element, key, character) => {
-                if (this.IsSelectedActive && !this.IsHidden && !this.textInput.OnTextInput(key, character) && key == Keys.Enter && !this.Multiline)
-                    this.InvokeOnEnter();
+                if (this.IsSelectedActive && !this.IsHidden && !this.textInput.OnTextInput(key, character) && key == Keys.Enter && !this.Multiline) {
+                    // enqueue the press to be executed next update since all other presses are executed in the regular update loop
+                    this.System.EnqueueAction((_, t) => ((TextField) t).InvokeOnEnter(), this);
+                }
             };
         }
 

MLEM.Ui/UiSystem.cs

@@ -169,6 +169,8 @@ public UiStyle Style {
         /// </summary>
         public event RootCallback OnRootRemoved;
 
+        private readonly Queue<(Action<UiSystem, object> Action, object ActionObject)> nextUpdateActions = new Queue<(Action<UiSystem, object> Action, object ActionObject)>();
+        private readonly object nextUpdateActionsLock = new object();
         private readonly List<RootElement> rootElements = new List<RootElement>();
         private readonly Stopwatch stopwatch = new Stopwatch();
         private float globalScale = 1;
@@ -249,6 +251,12 @@ public override void Update(GameTime time) {
             this.stopwatch.Restart();
 
             this.Controls.Update();
+            lock (this.nextUpdateActionsLock) {
+                while (this.nextUpdateActions.Count > 0) {
+                    var next = this.nextUpdateActions.Dequeue();
+                    next.Action.Invoke(this, next.ActionObject);
+                }
+            }
             for (var i = this.rootElements.Count - 1; i >= 0; i--)
                 this.rootElements[i].Element.Update(time);
 
@@ -332,6 +340,17 @@ public RootElement Get(string name) {
             return index < 0 ? null : this.rootElements[index];
         }
 
+        /// <summary>
+        /// Enqueues the given <paramref name="action"/> (optionally with the given <paramref name="actionObject"/> attached) to be executed the next time <see cref="Update"/> is called, before all of this ui system's elements are updated.
+        /// This method is thread-safe, meaning actions can be enqueued from other threads (for example, after downloading content to display) and they will be executed on the main thread.
+        /// </summary>
+        /// <param name="action">The action to enqueue.</param>
+        /// <param name="actionObject">An optional object to attach to the action, which will be passed as the second parameter to <paramref name="action"/>.</param>
+        public void EnqueueAction(Action<UiSystem, object> action, object actionObject = null) {
+            lock (this.nextUpdateActionsLock)
+                this.nextUpdateActions.Enqueue((action, actionObject));
+        }
+
         private int IndexOf(string name) {
             return this.rootElements.FindIndex(element => element.Name == name);
         }