2 files changed, 67 insertions, 0 deletions
diff --git a/devtools/client/inspector/grids/utils/moz.build b/devtools/client/inspector/grids/utils/moz.build
new file mode 100644
index 0000000000..c74e63e617
--- /dev/null
+++ b/devtools/client/inspector/grids/utils/moz.build
@@ -0,0 +1,9 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "utils.js",
+)
diff --git a/devtools/client/inspector/grids/utils/utils.js b/devtools/client/inspector/grids/utils/utils.js
new file mode 100644
index 0000000000..fc25de8775
--- /dev/null
+++ b/devtools/client/inspector/grids/utils/utils.js
@@ -0,0 +1,58 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/**
+ * Compares 2 sets of grid fragments to each other and checks if they have the same
+ * general geometry.
+ * This means that things like areas, area names or line names are ignored.
+ * This only checks if the 2 sets of fragments have as many fragments, as many lines, and
+ * that those lines are at the same distance.
+ *
+ * @param  {Array} fragments1
+ *         A list of gridFragment objects.
+ * @param  {Array} fragments2
+ *         Another list of gridFragment objects to compare to the first list.
+ * @return {Boolean}
+ *         True if the fragments are the same, false otherwise.
+ */
+function compareFragmentsGeometry(fragments1, fragments2) {
+  // Compare the number of fragments.
+  if (fragments1.length !== fragments2.length) {
+    return false;
+  }
+
+  // Compare the number of areas, rows and columns.
+  for (let i = 0; i < fragments1.length; i++) {
+    if (
+      fragments1[i].cols.lines.length !== fragments2[i].cols.lines.length ||
+      fragments1[i].rows.lines.length !== fragments2[i].rows.lines.length
+    ) {
+      return false;
+    }
+  }
+
+  // Compare the offset of lines.
+  for (let i = 0; i < fragments1.length; i++) {
+    for (let j = 0; j < fragments1[i].cols.lines.length; j++) {
+      if (
+        fragments1[i].cols.lines[j].start !== fragments2[i].cols.lines[j].start
+      ) {
+        return false;
+      }
+    }
+    for (let j = 0; j < fragments1[i].rows.lines.length; j++) {
+      if (
+        fragments1[i].rows.lines[j].start !== fragments2[i].rows.lines[j].start
+      ) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+module.exports.compareFragmentsGeometry = compareFragmentsGeometry;