added percentage sizing based on own data to element

MLEM.Ui/Elements/Element.cs

@@ -87,9 +87,18 @@ namespace MLEM.Ui.Elements {
 
         private Vector2 size;
         /// <summary>
-        /// The size of this element.
+        /// The size of this element, where X represents the width and Y represents the height.
-        /// If the x or y value of the size is lower than or equal to 1, the size will be seen as a percentage of its parent's size.
+        /// If the x or y value of the size is between 0 and 1, the size will be seen as a percentage of its parent's size rather than as an absolute value.
+        /// If the x (or y) value of the size is negative, the width (or height) is seen as a percentage of the element's resulting height (or width). 
+        /// If <see cref="SetWidthBasedOnChildren"/> is true, this property's X value is ignored and overridden. If <see cref="SetHeightBasedOnChildren"/> is true, this property's Y value is ignored and overridden.
         /// </summary>
+        /// <example>
+        /// The following example combines both types of percentage-based sizing.
+        /// If this element is inside of a <see cref="Parent"/> whose width is 20, this element's width will be set to <c>0.5 * 20 = 10</c>, and its height will be set to <c>2.5 * 10 = 25</c>.
+        /// <code>
+        /// element.Size = new Vector2(0.5F, -2.5F);
+        /// </code>
+        /// </example>
         public Vector2 Size {
             get => this.size;
             set {
@@ -587,13 +596,19 @@ namespace MLEM.Ui.Elements {
 
         /// <summary>
         /// Calculates the actual size that this element should take up, based on the area that its parent encompasses.
+        /// By default, this is based on the information specified in <see cref="Size"/>'s documentation.
         /// </summary>
         /// <param name="parentArea">This parent's area, or the ui system's viewport if it has no parent</param>
         /// <returns>The actual size of this element, taking <see cref="Scale"/> into account</returns>
         protected virtual Vector2 CalcActualSize(RectangleF parentArea) {
-            return new Vector2(
+            var ret = new Vector2(
                 this.size.X > 1 ? this.ScaledSize.X : parentArea.Width * this.size.X,
                 this.size.Y > 1 ? this.ScaledSize.Y : parentArea.Height * this.size.Y);
+            if (this.size.X < 0)
+                ret.X = -this.size.X * ret.Y;
+            if (this.size.Y < 0)
+                ret.Y = -this.size.Y * ret.X;
+            return ret;
         }
 
         /// <summary>

Sandbox/GameImpl.cs

@@ -82,7 +82,7 @@ namespace Sandbox {
             var panel = new Panel(Anchor.Center, new Vector2(0, 100), Vector2.Zero) {SetWidthBasedOnChildren = true};
             panel.AddChild(new Button(Anchor.AutoLeft, new Vector2(100, 10)));
             panel.AddChild(new Button(Anchor.AutoCenter, new Vector2(80, 10)));
-            this.UiSystem.Add("Panel", panel);
+            //this.UiSystem.Add("Panel", panel);
 
             panel.SetData("TestKey", new Vector2(10, 2));
             //Console.WriteLine(panel.GetData<Vector2>("TestKey"));
@@ -131,14 +131,14 @@ namespace Sandbox {
             this.tokenized = formatter.Tokenize(font, strg);
             this.tokenized.Split(font, 400, 5);
 
-            this.OnDraw += (g, time) => {
+            /*this.OnDraw += (g, time) => {
                 this.SpriteBatch.Begin(samplerState: SamplerState.PointClamp);
                 this.SpriteBatch.FillRectangle(new RectangleF(400, 20, 400, 1000), Color.Green);
                 font.DrawString(this.SpriteBatch, this.tokenized.DisplayString, new Vector2(400, 20), Color.White * 0.25F, 0, Vector2.Zero, 5, SpriteEffects.None, 0);
                 this.tokenized.Draw(time, this.SpriteBatch, new Vector2(400, 20), font, Color.White, 5, 0);
                 this.SpriteBatch.DrawGrid(new Vector2(30, 30), new Vector2(40, 60), new Point(10, 5), Color.Yellow, 3);
                 this.SpriteBatch.End();
-            };
+            };*/
             this.OnUpdate += (g, time) => {
                 if (this.InputHandler.IsPressed(Keys.W)) {
                     this.tokenized = formatter.Tokenize(font, strg);
@@ -146,6 +146,12 @@ namespace Sandbox {
                 }
                 this.tokenized.Update(time);
             };
+
+            var testPanel = new Panel(Anchor.Center, new Vector2(0.5F, 100), Vector2.Zero);
+            testPanel.AddChild(new Button(Anchor.AutoLeft, new Vector2(0.25F, -1)));
+            testPanel.AddChild(new Button(Anchor.AutoInline, new Vector2(0.25F, -1.5F)));
+            testPanel.AddChild(new Button(Anchor.AutoInline, new Vector2(0.5F, -1)));
+            this.UiSystem.Add("Test", testPanel);
         }
 
         protected override void DoUpdate(GameTime gameTime) {