From 41f3a7e74ee6b2fe379ecee37d2842eb11070967 Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Fri, 24 Sep 2021 15:55:52 +0200
Subject: [PATCH] gpu: [compute] restore relative transformation correctly on
 state load

Fixes gio#277

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 gpu/compute.go | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/gpu/compute.go b/gpu/compute.go
index c72773c8..604ca547 100644
--- a/gpu/compute.go
+++ b/gpu/compute.go
@@ -1818,11 +1818,19 @@ func (c *collector) collect(root *op.Ops, viewport image.Point, texOps *[]textur
 		case opconst.TypeLoad:
 			id, mask := ops.DecodeLoad(encOp.Data)
 			s := c.states[id]
-			if mask&opconst.TransformState != 0 {
-				state.t = s.t
-			}
 			if mask&^opconst.TransformState != 0 {
 				state = s
+			} else if mask&opconst.TransformState != 0 {
+				state.t = s.t
+				state.relTrans = s.t
+				if cl := state.clip; cl != nil {
+					var relTrans f32.Affine2D
+					for cl != nil {
+						relTrans = cl.relTrans.Mul(relTrans)
+						cl = cl.parent
+					}
+					state.relTrans = relTrans.Invert().Mul(state.relTrans)
+				}
 			}
 		}
 	}