Use UIFlexItem for Widgets

With the full release of UIFlexItems out of Beta and available to clients, widgets can start using UIFlexItems.

There are two places where UIFlexItems can be used:
1. Window child containers to fill the full window height after the title and menu bar.
2. Window title bar text to fill the full width and clip properly with the collapse and close buttons.

Closes #46

lib/widgets/Window.lua

@@ -449,7 +449,6 @@ return function(Iris: Types.Internal, widgets: Types.WidgetUtility)
 
             local ChildContainer: ScrollingFrame = Instance.new("ScrollingFrame")
             ChildContainer.Name = "ChildContainer"
-            ChildContainer.AutomaticSize = Enum.AutomaticSize.None
             ChildContainer.Size = UDim2.fromScale(1, 1)
             ChildContainer.Position = UDim2.fromOffset(0, 0)
             ChildContainer.BackgroundColor3 = Iris._config.WindowBgColor
@@ -509,6 +508,8 @@ return function(Iris: Types.Internal, widgets: Types.WidgetUtility)
 
             TitleBar.Parent = Content
 
+            widgets.UIPadding(TitleBar, Vector2.xAxis * Iris._config.FramePadding.X)
+            widgets.UIListLayout(TitleBar, Enum.FillDirection.Horizontal, UDim.new(0, Iris._config.FramePadding.X)).VerticalAlignment = Enum.VerticalAlignment.Center
             widgets.applyInputBegan(thisWidget, TitleBar, function(input: InputObject)
                 if input.UserInputType == Enum.UserInputType.Touch then
                     if not thisWidget.arguments.NoMove then
@@ -526,7 +527,7 @@ return function(Iris: Types.Internal, widgets: Types.WidgetUtility)
             CollapseButton.Name = "CollapseButton"
             CollapseButton.AnchorPoint = Vector2.new(0, 0.5)
             CollapseButton.Size = UDim2.fromOffset(TitleButtonSize, TitleButtonSize)
-            CollapseButton.Position = UDim2.new(0, Iris._config.FramePadding.X + 1, 0.5, 0)
+            CollapseButton.Position = UDim2.new(0, 0, 0.5, 0)
             CollapseButton.AutomaticSize = Enum.AutomaticSize.None
             CollapseButton.BackgroundTransparency = 1
             CollapseButton.BorderSizePixel = 0
@@ -566,13 +567,12 @@ return function(Iris: Types.Internal, widgets: Types.WidgetUtility)
             CloseButton.Name = "CloseButton"
             CloseButton.AnchorPoint = Vector2.new(1, 0.5)
             CloseButton.Size = UDim2.fromOffset(TitleButtonSize, TitleButtonSize)
-            CloseButton.Position = UDim2.new(1, -(Iris._config.FramePadding.X + 1), 0.5, 0)
+            CloseButton.Position = UDim2.new(1, 0, 0.5, 0)
             CloseButton.AutomaticSize = Enum.AutomaticSize.None
             CloseButton.BackgroundTransparency = 1
             CloseButton.BorderSizePixel = 0
             CloseButton.Text = ""
-
-            CloseButton.ZIndex = thisWidget.ZIndex + 4
+            CloseButton.LayoutOrder = 2
             CloseButton.AutoButtonColor = false
 
             widgets.UICorner(CloseButton)
@@ -606,25 +606,23 @@ return function(Iris: Types.Internal, widgets: Types.WidgetUtility)
 
             -- allowing fractional titlebar title location dosent seem useful, as opposed to Enum.LeftRight.
 
-            local titleAlign: number
-            if Iris._config.WindowTitleAlign == Enum.LeftRight.Left then
-                titleAlign = 0
-            elseif Iris._config.WindowTitleAlign == Enum.LeftRight.Center then
-                titleAlign = 0.5
-            else
-                titleAlign = 1
-            end
-
             local Title: TextLabel = Instance.new("TextLabel")
             Title.Name = "Title"
-            Title.AnchorPoint = Vector2.new(titleAlign, 0)
-            Title.Position = UDim2.fromScale(titleAlign, 0)
             Title.AutomaticSize = Enum.AutomaticSize.XY
             Title.BorderSizePixel = 0
             Title.BackgroundTransparency = 1
-
+            Title.LayoutOrder = 1
+            Title.ClipsDescendants = true
+
+            widgets.UIPadding(Title, Vector2.yAxis * Iris._config.FramePadding.Y)
             widgets.applyTextStyle(Title)
-            widgets.UIPadding(Title, Iris._config.FramePadding)
+            Title.TextXAlignment = Enum.TextXAlignment[Iris._config.WindowTitleAlign.Name] :: Enum.TextXAlignment
+
+            local TitleFlexItem: UIFlexItem = Instance.new("UIFlexItem")
+            TitleFlexItem.FlexMode = Enum.UIFlexMode.Fill
+            TitleFlexItem.ItemLineAlignment = Enum.ItemLineAlignment.Center
+
+            TitleFlexItem.Parent = Title
 
             Title.Parent = TitleBar
 
@@ -740,20 +738,15 @@ return function(Iris: Types.Internal, widgets: Types.WidgetUtility)
             end
 
             -- TitleBar buttons
-            local TitleButtonPaddingSize = Iris._config.FramePadding.X + Iris._config.TextSize + Iris._config.FramePadding.X * 2
             if thisWidget.arguments.NoCollapse then
                 TitleBar.CollapseButton.Visible = false
-                TitleBar.Title.UIPadding.PaddingLeft = UDim.new(0, Iris._config.FramePadding.X)
             else
                 TitleBar.CollapseButton.Visible = true
-                TitleBar.Title.UIPadding.PaddingLeft = UDim.new(0, TitleButtonPaddingSize)
             end
             if thisWidget.arguments.NoClose then
                 TitleBar.CloseButton.Visible = false
-                TitleBar.Title.UIPadding.PaddingRight = UDim.new(0, Iris._config.FramePadding.X)
             else
                 TitleBar.CloseButton.Visible = true
-                TitleBar.Title.UIPadding.PaddingRight = UDim.new(0, TitleButtonPaddingSize)
             end
 
             Title.Text = thisWidget.arguments.Title or ""