From 4bbb29070c46798b97163d13f8cc87b4f83ca5ec Mon Sep 17 00:00:00 2001
From: Brian Salomon <bsalomon@google.com>
Date: Tue, 13 Apr 2021 10:04:20 -0400
Subject: [PATCH] Concatenate matrices when GrMatrixEffect wraps another
 GrMatrixEffect

Bug: skia:11844
Change-Id: I13165fb17b06371854a4911c5d91bf2415d4df2a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/396017
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
---
 src/gpu/effects/GrMatrixEffect.cpp | 17 +++++++++++++++++
 src/gpu/effects/GrMatrixEffect.h   |  7 +------
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/gpu/effects/GrMatrixEffect.cpp b/src/gpu/effects/GrMatrixEffect.cpp
index 2ff4604213..172691e3b0 100644
--- a/src/gpu/effects/GrMatrixEffect.cpp
+++ b/src/gpu/effects/GrMatrixEffect.cpp
@@ -35,6 +35,23 @@ private:
     UniformHandle fMatrixVar;
 };
 
+std::unique_ptr<GrFragmentProcessor> GrMatrixEffect::Make(
+        const SkMatrix& matrix, std::unique_ptr<GrFragmentProcessor> child) {
+    if (matrix.isIdentity()) {
+        return child;
+    }
+    if (child->classID() == kGrMatrixEffect_ClassID) {
+        auto me = static_cast<GrMatrixEffect*>(child.get());
+        // registerChild's sample usage records whether the matrix used has perspective or not,
+        // so we can't add perspective to 'me' if it doesn't already have it.
+        if (me->matrix().hasPerspective() || !matrix.hasPerspective()) {
+            me->fMatrix.preConcat(matrix);
+            return child;
+        }
+    }
+    return std::unique_ptr<GrFragmentProcessor>(new GrMatrixEffect(matrix, std::move(child)));
+}
+
 std::unique_ptr<GrGLSLFragmentProcessor> GrMatrixEffect::onMakeProgramImpl() const {
     return std::make_unique<GrGLSLMatrixEffect>();
 }
diff --git a/src/gpu/effects/GrMatrixEffect.h b/src/gpu/effects/GrMatrixEffect.h
index 5d82750f25..f939a93f7f 100644
--- a/src/gpu/effects/GrMatrixEffect.h
+++ b/src/gpu/effects/GrMatrixEffect.h
@@ -16,12 +16,7 @@
 class GrMatrixEffect : public GrFragmentProcessor {
 public:
     static std::unique_ptr<GrFragmentProcessor> Make(const SkMatrix& matrix,
-                                                     std::unique_ptr<GrFragmentProcessor> child) {
-        if (matrix.isIdentity()) {
-            return child;
-        }
-        return std::unique_ptr<GrFragmentProcessor>(new GrMatrixEffect(matrix, std::move(child)));
-    }
+                                                     std::unique_ptr<GrFragmentProcessor> child);
 
     std::unique_ptr<GrFragmentProcessor> clone() const override;
     const char* name() const override { return "MatrixEffect"; }