From 48a96305c8258e016f445acb681f7bd559612eee Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Wed, 3 Nov 2021 12:32:26 +0100
Subject: [PATCH] io/router: move transform state tracking from
 pointerCollector to Router

We're going to need transform tracking for the upcoming meta ops.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 io/router/pointer.go | 34 +++++++---------------------------
 io/router/router.go  | 29 +++++++++++++++++++++++------
 2 files changed, 30 insertions(+), 33 deletions(-)

diff --git a/io/router/pointer.go b/io/router/pointer.go
index d2bcebea..cf6712ad 100644
--- a/io/router/pointer.go
+++ b/io/router/pointer.go
@@ -82,12 +82,9 @@ type collectState struct {
 // pointerCollector tracks the state needed to update an pointerQueue
 // from pointer ops.
 type pointerCollector struct {
-	q          *pointerQueue
-	state      collectState
-	nodeStack  []int
-	transStack []f32.Affine2D
-	// states holds the storage for save/restore ops.
-	states []f32.Affine2D
+	q         *pointerQueue
+	state     collectState
+	nodeStack []int
 }
 
 const (
@@ -95,15 +92,12 @@ const (
 	areaEllipse
 )
 
-func (c *pointerCollector) save(id int) {
-	if extra := id - len(c.states) + 1; extra > 0 {
-		c.states = append(c.states, make([]f32.Affine2D, extra)...)
-	}
-	c.states[id] = c.state.t
+func (c *pointerCollector) resetState() {
+	c.state = collectState{}
 }
 
-func (c *pointerCollector) load(id int) {
-	c.state = collectState{t: c.states[id]}
+func (c *pointerCollector) setTrans(t f32.Affine2D) {
+	c.state.t = t
 }
 
 func (c *pointerCollector) clip(op ops.ClipOp) {
@@ -155,19 +149,6 @@ func (c *pointerCollector) popPass() {
 	c.state.pass--
 }
 
-func (c *pointerCollector) transform(t f32.Affine2D, push bool) {
-	if push {
-		c.transStack = append(c.transStack, c.state.t)
-	}
-	c.state.t = c.state.t.Mul(t)
-}
-
-func (c *pointerCollector) popTransform() {
-	n := len(c.transStack)
-	c.state.t = c.transStack[n-1]
-	c.transStack = c.transStack[:n-1]
-}
-
 func (c *pointerCollector) inputOp(op pointer.InputOp, events *handlerEvents) {
 	area := -1
 	if i := c.state.nodePlusOne - 1; i != -1 {
@@ -207,7 +188,6 @@ func (c *pointerCollector) reset(q *pointerQueue) {
 	q.reset()
 	c.state = collectState{}
 	c.nodeStack = c.nodeStack[:0]
-	c.transStack = c.transStack[:0]
 	c.q = q
 }
 
diff --git a/io/router/router.go b/io/router/router.go
index 03ba608e..4bc8a49c 100644
--- a/io/router/router.go
+++ b/io/router/router.go
@@ -15,6 +15,7 @@ import (
 	"image"
 	"time"
 
+	"gioui.org/f32"
 	"gioui.org/internal/ops"
 	"gioui.org/io/clipboard"
 	"gioui.org/io/event"
@@ -27,7 +28,9 @@ import (
 // Router is a Queue implementation that routes events
 // to handlers declared in operation lists.
 type Router struct {
-	pointer struct {
+	savedTrans []f32.Affine2D
+	transStack []f32.Affine2D
+	pointer    struct {
 		queue     pointerQueue
 		collector pointerCollector
 	}
@@ -135,11 +138,13 @@ func (q *Router) Cursor() pointer.CursorName {
 }
 
 func (q *Router) collect() {
+	q.transStack = q.transStack[:0]
 	pc := &q.pointer.collector
 	pc.reset(&q.pointer.queue)
 	kc := &q.key.collector
 	*kc = keyCollector{q: &q.key.queue}
 	q.key.queue.Reset()
+	var t f32.Affine2D
 	for encOp, ok := q.reader.Decode(); ok; encOp, ok = q.reader.Decode() {
 		switch ops.OpType(encOp.Data[0]) {
 		case ops.TypeInvalidate:
@@ -160,10 +165,15 @@ func (q *Router) collect() {
 			q.cqueue.ProcessWriteClipboard(encOp.Refs)
 		case ops.TypeSave:
 			id := ops.DecodeSave(encOp.Data)
-			pc.save(id)
+			if extra := id - len(q.savedTrans) + 1; extra > 0 {
+				q.savedTrans = append(q.savedTrans, make([]f32.Affine2D, extra)...)
+			}
+			q.savedTrans[id] = t
 		case ops.TypeLoad:
 			id := ops.DecodeLoad(encOp.Data)
-			pc.load(id)
+			t = q.savedTrans[id]
+			pc.resetState()
+			pc.setTrans(t)
 
 		// Pointer ops.
 		case ops.TypeClip:
@@ -177,10 +187,17 @@ func (q *Router) collect() {
 		case ops.TypePopPass:
 			pc.popPass()
 		case ops.TypeTransform:
-			t, push := ops.DecodeTransform(encOp.Data)
-			pc.transform(t, push)
+			t2, push := ops.DecodeTransform(encOp.Data)
+			if push {
+				q.transStack = append(q.transStack, t)
+			}
+			t = t.Mul(t2)
+			pc.setTrans(t)
 		case ops.TypePopTransform:
-			pc.popTransform()
+			n := len(q.transStack)
+			t = q.transStack[n-1]
+			q.transStack = q.transStack[:n-1]
+			pc.setTrans(t)
 		case ops.TypePointerInput:
 			bo := binary.LittleEndian
 			op := pointer.InputOp{