From 2be39a740ef6bd613d9eba5bbd872c5fb89cfe43 Mon Sep 17 00:00:00 2001
From: Ellpeck <me@ellpeck.de>
Date: Thu, 28 Oct 2021 23:26:42 +0200
Subject: [PATCH] improve handling of arbitrary Epsilon values

---
 CHANGELOG.md                  |  2 ++
 MLEM.Ui/Elements/Element.cs   | 14 ++++++++++----
 MLEM.Ui/Elements/ScrollBar.cs |  2 +-
 MLEM/Cameras/Camera.cs        |  8 +++++++-
 4 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2fccb82..8c73a60 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ Additions
 
 Improvements
 - Exposed Camera's RoundPosition
+- Exposed the epsilon value used by Camera
 
 ### MLEM.Ui
 Additions
@@ -23,6 +24,7 @@ Additions
 
 Improvements
 - Cache TokenizedString inner offsets for non-Left text alignments to improve performance
+- Exposed the epsilon value used by Element calculations
 
 Fixes
 - Fixed VerticalSpace height parameter being an integer
diff --git a/MLEM.Ui/Elements/Element.cs b/MLEM.Ui/Elements/Element.cs
index 0dd40ab..e3b79e0 100644
--- a/MLEM.Ui/Elements/Element.cs
+++ b/MLEM.Ui/Elements/Element.cs
@@ -18,6 +18,12 @@ namespace MLEM.Ui.Elements {
     /// </summary>
     public abstract class Element : GenericDataHolder, IDisposable {
 
+        /// <summary>
+        /// This field holds an epsilon value used in element <see cref="Size"/>, position and resulting <see cref="Area"/> calculations to mitigate floating point rounding inaccuracies.
+        /// If ui elements used are extremely small or extremely large, this value can be reduced or increased.
+        /// </summary>
+        public static float Epsilon = 0.01F;
+
         /// <summary>
         /// A list of all of this element's direct children.
         /// Use <see cref="AddChild{T}"/> or <see cref="RemoveChild"/> to manipulate this list while calling all of the necessary callbacks.
@@ -607,9 +613,9 @@ namespace MLEM.Ui.Elements {
                                 break;
                             case Anchor.AutoInline:
                                 var newX = prevArea.Right + this.ScaledOffset.X;
-                                // with awkward ui scale values, floating point rounding can cause an element that would usually be
-                                // positioned correctly to be pushed into the next line due to a very small deviation, so we add 0.01 here
-                                if (newX + newSize.X <= parentArea.Right + 0.01F) {
+                                // with awkward ui scale values, floating point rounding can cause an element that would usually
+                                // be positioned correctly to be pushed into the next line due to a very small deviation
+                                if (newX + newSize.X <= parentArea.Right + Epsilon) {
                                     pos.X = newX;
                                     pos.Y = prevArea.Y + this.ScaledOffset.Y;
                                 } else {
@@ -676,7 +682,7 @@ namespace MLEM.Ui.Elements {
                     }
 
                     // we want to leave some leeway to prevent float rounding causing an infinite loop
-                    if (!autoSize.Equals(this.UnscrolledArea.Size, 0.01F)) {
+                    if (!autoSize.Equals(this.UnscrolledArea.Size, Epsilon)) {
                         recursion++;
                         if (recursion >= 16) {
                             throw new ArithmeticException($"The area of {this} with root {this.Root.Name} has recursively updated too often. Does its child {foundChild} contain any conflicting auto-sizing settings?");
diff --git a/MLEM.Ui/Elements/ScrollBar.cs b/MLEM.Ui/Elements/ScrollBar.cs
index a3b2b06..fd7a048 100644
--- a/MLEM.Ui/Elements/ScrollBar.cs
+++ b/MLEM.Ui/Elements/ScrollBar.cs
@@ -45,7 +45,7 @@ namespace MLEM.Ui.Elements {
                 // force current value to be clamped
                 this.CurrentValue = this.CurrentValue;
                 // auto-hide if necessary
-                var shouldHide = this.maxValue <= 0.01F;
+                var shouldHide = this.maxValue <= Epsilon;
                 if (this.AutoHideWhenEmpty && this.IsHidden != shouldHide) {
                     this.IsHidden = shouldHide;
                     this.OnAutoHide?.Invoke(this);
diff --git a/MLEM/Cameras/Camera.cs b/MLEM/Cameras/Camera.cs
index 7f119ba..a4341b7 100644
--- a/MLEM/Cameras/Camera.cs
+++ b/MLEM/Cameras/Camera.cs
@@ -11,6 +11,12 @@ namespace MLEM.Cameras {
     /// </summary>
     public class Camera {
 
+        /// <summary>
+        /// This field holds an epsilon value used in some camera calculations to mitigate floating point rounding inaccuracies.
+        /// If camera <see cref="Position"/> or <see cref="Viewport"/> size are extremely small or extremely big, this value can be reduced or increased.
+        /// </summary>
+        public static float Epsilon = 0.01F;
+
         /// <summary>
         /// The top-left corner of the camera's viewport.
         /// <seealso cref="LookingPosition"/>
@@ -158,7 +164,7 @@ namespace MLEM.Cameras {
                 if (this.Max.Y > max.Y)
                     this.Max = new Vector2(this.Max.X, max.Y);
             }
-            return !this.Position.Equals(lastPos, 0.001F);
+            return !this.Position.Equals(lastPos, Epsilon);
         }
 
         /// <summary>