[gtk/transform-origin] Add a reftest for transform-origin

[Matthias Clasen <matthiasc src gnome org>]

commit 749f1a7c00b215b6c99d2c628868c12c44ff2e78
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jan 24 23:47:10 2021 -0500

    Add a reftest for transform-origin

 testsuite/reftests/transform-origin.css    | 15 +++++++++++++++
 testsuite/reftests/transform-origin.ref.ui | 17 +++++++++++++++++
 testsuite/reftests/transform-origin.ui     | 17 +++++++++++++++++
 3 files changed, 49 insertions(+)
---
diff --git a/testsuite/reftests/transform-origin.css b/testsuite/reftests/transform-origin.css
new file mode 100644
index 0000000000..554321f815
--- /dev/null
+++ b/testsuite/reftests/transform-origin.css
@@ -0,0 +1,15 @@
+@import "reset-to-defaults.css";
+
+window {
+  background: yellow;
+}
+
+#box {
+  transform-origin: top left;
+  transform: rotate(-90deg);
+  background: linear-gradient(to bottom, red 0%, blue 100%);
+}
+
+#reference {
+  background: linear-gradient(to right, red 0%, blue 100%);
+}
diff --git a/testsuite/reftests/transform-origin.ref.ui b/testsuite/reftests/transform-origin.ref.ui
new file mode 100644
index 0000000000..656781692f
--- /dev/null
+++ b/testsuite/reftests/transform-origin.ref.ui
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <object class="GtkWindow" id="window1">
+    <property name="decorated">0</property>
+    <property name="width-request">300</property>
+    <property name="height-request">300</property>
+    <child>
+      <object class="GtkBox">
+        <property name="name">reference</property>
+        <property name="halign">center</property>
+        <property name="valign">start</property>
+        <property name="width-request">100</property>
+        <property name="height-request">100</property>
+      </object>
+    </child>
+  </object>
+</interface>
diff --git a/testsuite/reftests/transform-origin.ui b/testsuite/reftests/transform-origin.ui
new file mode 100644
index 0000000000..889202973f
--- /dev/null
+++ b/testsuite/reftests/transform-origin.ui
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface>
+  <object class="GtkWindow" id="window1">
+    <property name="decorated">0</property>
+    <property name="width-request">300</property>
+    <property name="height-request">300</property>
+    <child>
+      <object class="GtkBox">
+        <property name="name">box</property>
+        <property name="halign">center</property>
+        <property name="valign">center</property>
+        <property name="width-request">100</property>
+        <property name="height-request">100</property>
+      </object>
+    </child>
+  </object>
+</interface>