From 9d82f9e4b8c33b429b1c8a5b2a1d5e9636faad93 Mon Sep 17 00:00:00 2001
From: Michael Ludwig <michaelludwig@google.com>
Date: Wed, 29 Jun 2022 14:43:59 -0400
Subject: [PATCH] [graphite] Add more utility and SkM44/SkMatrix interop to
 Transform class

Change-Id: I028bd133778d14edcb22ccef0c35c5a8e3d7d552
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/554516
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
---
 include/core/SkM44.h                       |  1 +
 src/gpu/graphite/geom/Transform.cpp        | 55 ++++++++++++++++++++++
 src/gpu/graphite/geom/Transform_graphite.h | 18 +++++++
 3 files changed, 74 insertions(+)

diff --git a/include/core/SkM44.h b/include/core/SkM44.h
index ae08b4400c..7fdbcb8e82 100644
--- a/include/core/SkM44.h
+++ b/include/core/SkM44.h
@@ -30,6 +30,7 @@ struct SK_API SkV2 {
     friend SkV2 operator*(SkV2 v, SkScalar s) { return {v.x*s, v.y*s}; }
     friend SkV2 operator*(SkScalar s, SkV2 v) { return {v.x*s, v.y*s}; }
     friend SkV2 operator/(SkV2 v, SkScalar s) { return {v.x/s, v.y/s}; }
+    friend SkV2 operator/(SkScalar s, SkV2 v) { return {s/v.x, s/v.y}; }
 
     void operator+=(SkV2 v) { *this = *this + v; }
     void operator-=(SkV2 v) { *this = *this - v; }
diff --git a/src/gpu/graphite/geom/Transform.cpp b/src/gpu/graphite/geom/Transform.cpp
index ac688ba353..6c5de8a059 100644
--- a/src/gpu/graphite/geom/Transform.cpp
+++ b/src/gpu/graphite/geom/Transform.cpp
@@ -93,6 +93,15 @@ Transform::Transform(const SkM44& m) : fM(m) {
     fType = get_matrix_info(m, &fInvM, &fScale);
 }
 
+const Transform& Transform::Identity() {
+    static const Transform kIdentity{SkM44()};
+    return kIdentity;
+}
+const Transform& Transform::Invalid() {
+    static const Transform kInvalid{SkM44(SkM44::kNaN_Constructor)};
+    return kInvalid;
+}
+
 bool Transform::operator==(const Transform& t) const {
     // Checking fM should be sufficient as all other values are computed from it.
     SkASSERT(fM != t.fM || (fInvM == t.fInvM && fType == t.fType && fScale == t.fScale));
@@ -131,4 +140,50 @@ void Transform::inverseMapPoints(const SkV4* deviceIn, SkV4* localOut, int count
     return map_points(fInvM, deviceIn, localOut, count);
 }
 
+Transform Transform::preTranslate(float x, float y) const {
+    Transform t = *this;
+    t.fM.preTranslate(x, y);
+    t.fInvM.postTranslate(-x, -y);
+
+    // Under normal conditions, type and scale won't change, but if we've overflown the translation
+    // components, mark the matrix as invalid.
+    if (!t.fM.isFinite() || !t.fInvM.isFinite()) {
+        t.fType = Type::kInvalid;
+    }
+    return t;
+}
+
+Transform Transform::postTranslate(float x, float y) const {
+    Transform t = *this;
+    t.fM.postTranslate(x, y);
+    t.fInvM.preTranslate(-x, -y);
+    if (!t.fM.isFinite() || !t.fInvM.isFinite()) {
+        t.fType = Type::kInvalid;
+    }
+    return t;
+}
+
+Transform Transform::concat(const Transform& t) const {
+    Transform c = {fM * t.fM, t.fInvM * fInvM, std::max(fType, t.fType), {fScale * t.fScale}};
+    if (!c.fM.isFinite() || !c.fInvM.isFinite()) {
+        c.fType = Type::kInvalid;
+    }
+    return c;
+}
+
+Transform Transform::concatInverse(const Transform& t) const {
+    Transform c = {fM * t.fInvM, t.fM * fInvM, std::max(fType, t.fType), {fScale * (1.f/t.fScale)}};
+    if (!c.fM.isFinite() || !c.fInvM.isFinite()) {
+        c.fType = Type::kInvalid;
+    }
+    return c;
+}
+
+Transform Transform::concatInverse(const SkM44& t) const {
+    // saves a multiply compared to inverting just t and then computing fM*t^-1 and t*fInvM, if we
+    // instead start with (t*fInvM) and swap definition of computed fM and fInvM.
+    Transform inverse{t * fInvM};
+    return {inverse.fInvM, inverse.fM, inverse.fType, 1.f / inverse.fScale};
+}
+
 } // namespace skgpu::graphite
diff --git a/src/gpu/graphite/geom/Transform_graphite.h b/src/gpu/graphite/geom/Transform_graphite.h
index dc1dddea4c..790131f0f2 100644
--- a/src/gpu/graphite/geom/Transform_graphite.h
+++ b/src/gpu/graphite/geom/Transform_graphite.h
@@ -44,6 +44,9 @@ public:
     explicit Transform(const SkM44& m);
     Transform(const Transform& t) = default;
 
+    static const Transform& Identity();
+    static const Transform& Invalid();
+
     Transform& operator=(const Transform& t) = default;
 
     operator const SkM44&() const { return fM; }
@@ -70,7 +73,22 @@ public:
     void mapPoints(const SkV4* localIn, SkV4* deviceOut, int count) const;
     void inverseMapPoints(const SkV4* deviceIn, SkV4* localOut, int count) const;
 
+    // Returns a transform equal to the pre- or post-translating this matrix
+    Transform preTranslate(float x, float y) const;
+    Transform postTranslate(float x, float y) const;
+
+    // Returns a transform equal to (this * t)
+    Transform concat(const Transform& t) const;
+    Transform concat(const SkM44& t) const { return Transform(fM * t); }
+
+    // Returns a transform equal to (this * t^-1)
+    Transform concatInverse(const Transform& t) const;
+    Transform concatInverse(const SkM44& t) const;
+
 private:
+    Transform(const SkM44& m, const SkM44& invM, Type type, const SkV2 scale)
+            : fM(m), fInvM(invM), fType(type), fScale(scale) {}
+
     SkM44 fM;
     SkM44 fInvM; // M^-1
     Type  fType;