Fixed scrolling panels calculating their height incorrectly when their first child is hidden

CHANGELOG.md

@@ -46,10 +46,12 @@ Improvements
 - Allow dropdowns to have scrolling panels
 - Improved Panel performance when adding and removing a lot of children
 - Don't reset the caret position of a text field when selecting or deselecting it
+- Improved UiParser.ParseImage with locks and a callback action
 
 Fixes
 - Fixed panels updating their relevant children too much when the scroll bar is hidden
 - Fixed a stack overflow exception when a panel's scroll bar auto-hiding causes elements to gain height
+- Fixed scrolling panels calculating their height incorrectly when their first child is hidden
 
 ### MLEM.Extended
 Improvements

MLEM.Ui/Elements/Image.cs

@@ -144,6 +144,12 @@ namespace MLEM.Ui.Elements {
                     ret.X = ret.Y * this.Texture.Width / this.Texture.Height + this.ScaledAutoSizeAddedAbsolute.X;
                 if (this.SetHeightBasedOnAspect)
                     ret.Y = ret.X * this.Texture.Height / this.Texture.Width + this.ScaledAutoSizeAddedAbsolute.Y;
+            } else {
+                // if we don't have a texture and we auto-set width or height, calculate as if we had a texture with a size of 0
+                if (this.SetWidthBasedOnAspect)
+                    ret.X = this.ScaledAutoSizeAddedAbsolute.X;
+                if (this.SetHeightBasedOnAspect)
+                    ret.Y = this.ScaledAutoSizeAddedAbsolute.Y;
             }
             return ret;
         }

MLEM.Ui/Elements/Panel.cs

@@ -223,10 +223,10 @@ namespace MLEM.Ui.Elements {
         /// </summary>
         /// <param name="elementY">The y coordinate to scroll to, which should have this element's <see cref="Element.Scale"/> applied.</param>
         public void ScrollToElement(float elementY) {
-            var firstChild = this.Children.FirstOrDefault(c => c != this.ScrollBar);
-            if (firstChild == null)
+            var highestValidChild = this.Children.FirstOrDefault(c => c != this.ScrollBar && !c.IsHidden);
+            if (highestValidChild == null)
                 return;
-            this.ScrollBar.CurrentValue = (elementY - this.Area.Height / 2 - firstChild.Area.Top) / this.Scale + this.ChildPadding.Value.Height / 2;
+            this.ScrollBar.CurrentValue = (elementY - this.Area.Height / 2 - highestValidChild.Area.Top) / this.Scale + this.ChildPadding.Value.Height / 2;
         }
 
         /// <inheritdoc />
@@ -282,9 +282,9 @@ namespace MLEM.Ui.Elements {
 
             float childrenHeight;
             if (this.Children.Count > 1) {
-                var firstChild = this.Children.FirstOrDefault(c => c != this.ScrollBar);
+                var highestValidChild = this.Children.FirstOrDefault(c => c != this.ScrollBar && !c.IsHidden);
                 var lowestChild = this.GetLowestChild(c => c != this.ScrollBar && !c.IsHidden, true);
-                childrenHeight = lowestChild.GetTotalCoveredArea(false).Bottom - firstChild.Area.Top;
+                childrenHeight = lowestChild.GetTotalCoveredArea(false).Bottom - highestValidChild.Area.Top;
             } else {
                 // if we only have one child (the scroll bar), then the children take up no visual height
                 childrenHeight = 0;

MLEM.Ui/Parsers/UiParser.cs

@@ -10,6 +10,7 @@ using MLEM.Ui.Style;
 
 #if NETSTANDARD2_0_OR_GREATER || NET6_0_OR_GREATER
 using System.Net.Http;
+
 #else
 using System.Net;
 #endif
@@ -138,23 +139,33 @@ namespace MLEM.Ui.Parsers {
         /// This method invokes an asynchronouns action, meaning the <see cref="Image"/>'s <see cref="Image.Texture"/> will likely not have loaded in when this method returns.
         /// </summary>
         /// <param name="path">The absolute, relative or web path to the image.</param>
+        /// <param name="onImageFetched">An action that is invoked with the loaded image once it is fetched. Note that this action will be invoked asynchronously.</param>
         /// <returns>The loaded image.</returns>
         /// <exception cref="NullReferenceException">Thrown if <see cref="GraphicsDevice"/> is null, or if there is an <see cref="Exception"/> loading the image and <see cref="ImageExceptionHandler"/> is unset.</exception>
-        protected Image ParseImage(string path) {
+        protected Image ParseImage(string path, Action<TextureRegion> onImageFetched = null) {
             if (this.GraphicsDevice == null)
                 throw new NullReferenceException("A UI parser requires a GraphicsDevice for parsing images");
 
+            var imageLock = new object();
             TextureRegion image = null;
-            return new Image(Anchor.AutoLeft, Vector2.One, _ => image) {
+            return new Image(Anchor.AutoLeft, Vector2.One, _ => {
+                lock (imageLock)
+                    return image;
+            }) {
                 SetHeightBasedOnAspect = true,
                 OnAddedToUi = e => {
-                    if (image == null)
+                    bool imageNull;
+                    lock (imageLock)
+                        imageNull = image == null;
+                    if (imageNull)
                         LoadImageAsync();
                 },
                 OnRemovedFromUi = e => {
+                    lock (imageLock) {
                         image?.Texture.Dispose();
                         image = null;
                     }
+                }
             };
 
             async void LoadImageAsync() {
@@ -178,7 +189,12 @@ namespace MLEM.Ui.Parsers {
                         using (var stream = Path.IsPathRooted(path) ? File.OpenRead(path) : TitleContainer.OpenStream(path))
                             tex = Texture2D.FromStream(this.GraphicsDevice, stream);
                     }
+                    lock (imageLock) {
+                        if (image == null) {
                             image = new TextureRegion(tex);
+                            onImageFetched?.Invoke(image);
+                        }
+                    }
                 } catch (Exception e) {
                     if (this.ImageExceptionHandler != null) {
                         this.ImageExceptionHandler.Invoke(path, e);