fix: draggable regions exclusively on BrowserViews (#26145)

shell/browser/ui/drag_util.cc

@@ -0,0 +1,42 @@
+// Copyright (c) 2020 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "shell/browser/ui/drag_util.h"
+
+#include <memory>
+
+#include "ui/gfx/skia_util.h"
+
+namespace electron {
+
+// Return a vector of non-draggable regions that fill a window of size
+// |width| by |height|, but leave gaps where the window should be draggable.
+std::vector<gfx::Rect> CalculateNonDraggableRegions(
+    std::unique_ptr<SkRegion> draggable,
+    int width,
+    int height) {
+  std::vector<gfx::Rect> result;
+  SkRegion non_draggable;
+  non_draggable.op({0, 0, width, height}, SkRegion::kUnion_Op);
+  non_draggable.op(*draggable, SkRegion::kDifference_Op);
+  for (SkRegion::Iterator it(non_draggable); !it.done(); it.next()) {
+    result.push_back(gfx::SkIRectToRect(it.rect()));
+  }
+  return result;
+}
+
+// Convert draggable regions in raw format to SkRegion format.
+std::unique_ptr<SkRegion> DraggableRegionsToSkRegion(
+    const std::vector<mojom::DraggableRegionPtr>& regions) {
+  auto sk_region = std::make_unique<SkRegion>();
+  for (const auto& region : regions) {
+    sk_region->op(
+        {region->bounds.x(), region->bounds.y(), region->bounds.right(),
+         region->bounds.bottom()},
+        region->draggable ? SkRegion::kUnion_Op : SkRegion::kDifference_Op);
+  }
+  return sk_region;
+}
+
+}  // namespace electron