ensure that child padding stays consistent if ScrollerSize gets updated

CHANGELOG.md

@@ -35,6 +35,7 @@ Improvements
 Fixes
 - Fixed VerticalSpace height parameter being an integer
 - Fixed text not being pasted into a text field at all if it contains characters that don't match the input rule
+- Fixed panels that don't auto-hide their scroll bars ignoring their width for child padding
 
 ### MLEM.Data
 Additions

MLEM.Ui/Elements/Panel.cs

@@ -53,6 +53,7 @@ namespace MLEM.Ui.Elements {
 
         private RenderTarget2D renderTarget;
         private bool relevantChildrenDirty;
+        private float scrollBarChildOffset;
 
         /// <summary>
         /// Creates a new panel with the given settings.
@@ -76,12 +77,6 @@ namespace MLEM.Ui.Elements {
                     AutoHideWhenEmpty = autoHideScrollbar,
                     IsHidden = autoHideScrollbar
                 };
-                if (autoHideScrollbar) {
-                    this.ScrollBar.OnAutoHide += e => {
-                        this.ChildPadding += new Padding(0, this.ScrollerSize.Value.X + this.ScrollBarOffset, 0, 0) * (e.IsHidden ? -1 : 1);
-                        this.SetAreaDirty();
-                    };
-                }
 
                 // handle automatic element selection, the scroller needs to scroll to the right location
                 this.OnSelectedElementChanged += (element, otherElement) => {
@@ -237,6 +232,14 @@ namespace MLEM.Ui.Elements {
             if (!this.ScrollBar.MaxValue.Equals(scrollBarMax, Epsilon)) {
                 this.ScrollBar.MaxValue = scrollBarMax;
                 this.relevantChildrenDirty = true;
+
+                // update child padding based on whether the scroll bar is visible
+                var childOffset = this.ScrollBar.IsHidden ? 0 : this.ScrollerSize.Value.X + this.ScrollBarOffset;
+                if (!this.scrollBarChildOffset.Equals(childOffset, Epsilon)) {
+                    this.ChildPadding += new Padding(0, -this.scrollBarChildOffset + childOffset, 0, 0);
+                    this.scrollBarChildOffset = childOffset;
+                    this.SetAreaDirty();
+                }
             }
 
             // the scroller height has the same relation to the scroll bar height as the visible area has to the total height of the panel's content

Tests/UiTests.cs

@@ -43,7 +43,7 @@ namespace Tests {
         public void TestComplexPanel() {
             var group = new Group(Anchor.TopLeft, Vector2.One, false);
             var panel = group.AddChild(new Panel(Anchor.Center, new Vector2(150, 150), Vector2.Zero, false, true, false) {
-                ChildPadding = new Padding(5, 10, 5, 5)
+                ChildPadding = new Padding(5, 5, 5, 5)
             });
             for (var i = 0; i < 5; i++) {
                 var button = panel.AddChild(new Button(Anchor.AutoLeft, new Vector2(1)) {
@@ -66,10 +66,11 @@ namespace Tests {
             Assert.AreEqual(11, panel.GetChildren(regardGrandchildren: true).Count());
 
             var testBtn = panel.GetChildren<Button>().First();
-            // panel's width is 150, minus child padding of 5 left and 10 right
-            Assert.AreEqual(testBtn.DisplayArea.Width, 150 - 5 - 10);
+            // panel's width is 150, minus child padding of 5 on each side, and scroll bar's width of 5 and gap of 1 
+            const int panelContentWidth = 150 - 5 - 5 - 5 - 1;
+            Assert.AreEqual(testBtn.DisplayArea.Width, panelContentWidth);
             // button's width, minus child padding of 3 left and 3 right, divided by 2 because of group's width
-            Assert.AreEqual(testBtn.GetChildren<Group>().Single().DisplayArea.Width, (150 - 5 - 10 - 3 - 3) * 0.5F);
+            Assert.AreEqual(testBtn.GetChildren<Group>().Single().DisplayArea.Width, (panelContentWidth - 3 - 3) * 0.5F);
         }
 
         [Test]