Add ViewportRect to UICanvas for UI placement

Source/Engine/UI/GUI/CanvasRootControl.cs

@@ -197,6 +197,14 @@ namespace FlaxEngine.GUI
                    && (_canvas.TestCanvasIntersection == null || _canvas.TestCanvasIntersection(ref location));
         }
 
+        /// <inheritdoc />
+        public override void GetDesireClientArea(out Rectangle rect)
+        {
+            var size = Size;
+            var viewportRect = _canvas.ViewportRect;
+            rect = new Rectangle(size * new Float2(viewportRect.X, viewportRect.Y), size * new Float2(viewportRect.Z, viewportRect.W));
+        }
+
         /// <inheritdoc />
         public override void Update(float deltaTime)
         {

Source/Engine/UI/GUI/Control.Bounds.cs

@@ -708,5 +708,22 @@ namespace FlaxEngine.GUI
                 }
             }
         }
+
+        /// <summary>
+        /// Sets the anchors for the control.
+        /// </summary>
+        /// <param name="anchorMin">The minimum anchors point to use.</param>
+        /// <param name="anchorMax">The maximum anchors point to use.</param>
+        /// <param name="preserveBounds">True if preserve current control bounds, otherwise will align control position accordingly to the anchor location.</param>
+        public void SetAnchors(Float2 anchorMin, Float2 anchorMax, bool preserveBounds)
+        {
+            var bounds = _bounds;
+            _anchorMin = anchorMin;
+            _anchorMax = anchorMax;
+            if (preserveBounds)
+                Bounds = bounds;
+            else
+                UpdateBounds();
+        }
     }
 }

Source/Engine/UI/UICanvas.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Wojciech Figat. All rights reserved.
 
 using System;
+using System.ComponentModel;
 using System.Globalization;
 using System.IO;
 using System.Text;
@@ -114,6 +115,7 @@ namespace FlaxEngine
         private readonly CanvasRootControl _guiRoot;
         private CanvasRenderer _renderer;
         private bool _isLoading, _isRegisteredForTick, _isRegisteredForOnDraw;
+        private Float4 _viewportRect = new Float4(0, 0, 1, 1);
 
         /// <summary>
         /// Gets or sets the canvas rendering mode.
@@ -222,6 +224,21 @@ namespace FlaxEngine
         [EditorOrder(70), NoSerialize, EditorDisplay("Canvas"), VisibleIf("Editor_IsGPUTexture")]
         public GPUTexture OutputTexture { get; set; }
 
+        /// <summary>
+        /// Four values that define where on the screen this canvas should be drawn. Measured in normalized coordinates (range 0-1). Order: X, Y, Width, Height. For example (0, 0, 1, 1) means full screen, (0, 0, 0.5, 1) means left half of the screen and (0.5, 0, 0.5, 1) means right half of the screen.
+        /// </summary>
+        [EditorOrder(80), EditorDisplay("Canvas"), Limit(0, 1, 0.001f)]
+        [DefaultValue(typeof(Float4), "0,0,1,1")]
+        public Float4 ViewportRect
+        {
+            get => _viewportRect;
+            set
+            {
+                _viewportRect = value;
+                _guiRoot.PerformLayout();
+            }
+        }
+
         /// <summary>
         /// Gets the canvas GUI root control.
         /// </summary>
@@ -688,6 +705,21 @@ namespace FlaxEngine
                     jsonWriter.WriteValue(Distance);
                 }
 
+                if (noOther || _viewportRect != other._viewportRect)
+                {
+                    jsonWriter.WritePropertyName("ViewportRect");
+                    jsonWriter.WriteStartObject();
+                    jsonWriter.WritePropertyName("X");
+                    jsonWriter.WriteValue(_viewportRect.X);
+                    jsonWriter.WritePropertyName("Y");
+                    jsonWriter.WriteValue(_viewportRect.Y);
+                    jsonWriter.WritePropertyName("Z");
+                    jsonWriter.WriteValue(_viewportRect.Z);
+                    jsonWriter.WritePropertyName("W");
+                    jsonWriter.WriteValue(_viewportRect.W);
+                    jsonWriter.WriteEndObject();
+                }
+
                 bool saveSize = RenderMode == CanvasRenderMode.WorldSpace || RenderMode == CanvasRenderMode.WorldSpaceFaceCamera;
                 if (!noOther)
                     saveSize = (saveSize || other.RenderMode == CanvasRenderMode.WorldSpace || other.RenderMode == CanvasRenderMode.WorldSpaceFaceCamera) && Size != other.Size;