From 1c270abef6f68cf2fea5a6515c5001bd765035cb Mon Sep 17 00:00:00 2001
From: Jonah Williams <jonahwilliams@google.com>
Date: Thu, 26 Jan 2023 19:33:27 -0800
Subject: [PATCH] [Impeller] ensure 1x1 has mipcount of 1 (#39182)

* [Impeller] ensure 1x1 has mipcount of 1

* Update geometry_unittests.cc

* Update size.h
---
 impeller/geometry/geometry_unittests.cc | 2 ++
 impeller/geometry/size.h                | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/impeller/geometry/geometry_unittests.cc b/impeller/geometry/geometry_unittests.cc
index 2d40b7eac8ed7..9b6706ba9a763 100644
--- a/impeller/geometry/geometry_unittests.cc
+++ b/impeller/geometry/geometry_unittests.cc
@@ -646,6 +646,8 @@ TEST(GeometryTest, CanGenerateMipCounts) {
   ASSERT_EQ((Size{128, 0}.MipCount()), 1u);
   ASSERT_EQ((Size{128, -25}.MipCount()), 1u);
   ASSERT_EQ((Size{-128, 25}.MipCount()), 1u);
+  ASSERT_EQ((Size{1, 1}.MipCount()), 1u);
+  ASSERT_EQ((Size{0, 0}.MipCount()), 1u);
 }
 
 TEST(GeometryTest, CanConvertTTypesExplicitly) {
diff --git a/impeller/geometry/size.h b/impeller/geometry/size.h
index 6cb55cab47472..dc6abd4126d6e 100644
--- a/impeller/geometry/size.h
+++ b/impeller/geometry/size.h
@@ -99,10 +99,12 @@ struct TSize {
   }
 
   constexpr size_t MipCount() const {
+    constexpr size_t minimum_mip = 1u;
     if (!IsPositive()) {
-      return 1u;
+      return minimum_mip;
     }
-    return std::max(ceil(log2(width)), ceil(log2(height)));
+    size_t result = std::max(ceil(log2(width)), ceil(log2(height)));
+    return std::max(result, minimum_mip);
   }
 };