LibGfx: Small improvement for DisjointRectSet::shatter

This avoids a call to clone() which would be discarded immediately.
Also, avoid essentially cloning for each hammer rectangle unless
there is actually a need for it.

1 files changed, 7 insertions, 4 deletions

diff --git a/Libraries/LibGfx/DisjointRectSet.cpp b/Libraries/LibGfx/DisjointRectSet.cpp
index b68f4cab05..1ec3d95d90 100644
--- a/Libraries/LibGfx/DisjointRectSet.cpp
+++ b/Libraries/LibGfx/DisjointRectSet.cpp
@@ -173,10 +173,13 @@ DisjointRectSet DisjointRectSet::shatter(const DisjointRectSet& hammer) const
         return clone();
 
     // TODO: This could use some optimization
-    auto shards = clone();
-    for (auto& hammer_rect : hammer.m_rects) {
-        auto shattered = shards.shatter(hammer_rect);
-        shards = move(shattered);
+    DisjointRectSet shards = shatter(hammer.m_rects[0]);
+    auto rects_count = hammer.m_rects.size();
+    for (size_t i = 1; i < rects_count && !shards.is_empty(); i++) {
+        if (hammer.m_rects[i].intersects(shards.m_rects)) {
+            auto shattered = shards.shatter(hammer.m_rects[i]);
+            shards = move(shattered);
+        }
     }
     // Since there should be no overlaps, we don't need to call shatter()
     return shards;