Fix texture blit off-by-one errors (#2335)

Ryujinx.Graphics.Gpu/Engine/MethodCopyTexture.cs

@@ -24,11 +24,29 @@ namespace Ryujinx.Graphics.Gpu.Engine
 
             var control = state.Get<CopyTextureControl>(MethodOffset.CopyTextureControl);
 
-            int srcX1 = (int)(region.SrcXF >> 32);
-            int srcY1 = (int)(region.SrcYF >> 32);
+            bool originCorner = control.UnpackOriginCorner();
 
-            int srcX2 = (int)((region.SrcXF + region.SrcWidthRF * region.DstWidth) >> 32);
-            int srcY2 = (int)((region.SrcYF + region.SrcHeightRF * region.DstHeight) >> 32);
+            long srcX = region.SrcXF;
+            long srcY = region.SrcYF;
+
+            if (originCorner)
+            {
+                // If the origin is corner, it is assumed that the guest API
+                // is manually centering the origin by adding a offset to the
+                // source region X/Y coordinates.
+                // Here we attempt to remove such offset to ensure we have the correct region.
+                // The offset is calculated as FactorXY / 2.0, where FactorXY = SrcXY / DstXY,
+                // so we do the same here by dividing the fixed point value by 2, while
+                // throwing away the fractional part to avoid rounding errors.
+                srcX -= (region.SrcWidthRF >> 33) << 32;
+                srcY -= (region.SrcHeightRF >> 33) << 32;
+            }
+
+            int srcX1 = (int)(srcX >> 32);
+            int srcY1 = (int)(srcY >> 32);
+
+            int srcX2 = srcX1 + (int)((region.SrcWidthRF * region.DstWidth + uint.MaxValue) >> 32);
+            int srcY2 = srcY1 + (int)((region.SrcHeightRF * region.DstHeight + uint.MaxValue) >> 32);
 
             int dstX1 = region.DstX;
             int dstY1 = region.DstY;

Ryujinx.Graphics.Gpu/State/CopyTextureControl.cs

@@ -9,6 +9,11 @@ namespace Ryujinx.Graphics.Gpu.State
         public uint Packed;
 #pragma warning restore CS0649
 
+        public bool UnpackOriginCorner()
+        {
+            return (Packed & 1u) != 0;
+        }
+
         public bool UnpackLinearFilter()
         {
             return (Packed & (1u << 4)) != 0;