LibGfx: Don't create AnonymousBuffer for each bitmap in BitmapSequence

When decoding a BitmapSequence received over IPC, we were creating an
AnonymousBuffer for each bitmap and then making a Gfx::Bitmap wrapper
around it.

This was unnecessarily using up one file descriptor per bitmap, and also
wasting a lot of memory for small bitmaps since we always allocated at
least one VM page.

This patch changes the BitmapSequence decoder to use malloc memory
instead, saving file descriptors and using less memory overall.

Libraries/LibGfx/Bitmap.cpp

@@ -127,6 +127,16 @@ ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::create_with_anonymous_buffer(BitmapFormat
     return adopt_nonnull_ref_or_enomem(new (nothrow) Bitmap(format, alpha_type, move(buffer), size));
 }
 
+ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::create_with_raw_data(BitmapFormat format, AlphaType alpha_type, ReadonlyBytes raw_data, IntSize size)
+{
+    if (size_would_overflow(format, size))
+        return Error::from_string_literal("Gfx::Bitmap::create_with_raw_data size overflow");
+
+    auto backing_store = TRY(Bitmap::allocate_backing_store(format, size, InitializeBackingStore::No));
+    raw_data.copy_to(Bytes { backing_store.data, backing_store.size_in_bytes });
+    return AK::adopt_nonnull_ref_or_enomem(new (nothrow) Bitmap(format, alpha_type, size, backing_store));
+}
+
 Bitmap::Bitmap(BitmapFormat format, AlphaType alpha_type, Core::AnonymousBuffer buffer, IntSize size)
     : m_size(size)
     , m_data(buffer.data<void>())
@@ -242,7 +252,7 @@ Gfx::ShareableBitmap Bitmap::to_shareable_bitmap() const
     return Gfx::ShareableBitmap { bitmap_or_error.release_value_but_fixme_should_propagate_errors(), Gfx::ShareableBitmap::ConstructWithKnownGoodBitmap };
 }
 
-ErrorOr<BackingStore> Bitmap::allocate_backing_store(BitmapFormat format, IntSize size)
+ErrorOr<BackingStore> Bitmap::allocate_backing_store(BitmapFormat format, IntSize size, InitializeBackingStore initialize_backing_store)
 {
     if (size.is_empty())
         return Error::from_string_literal("Gfx::Bitmap backing store size is empty");
@@ -253,7 +263,11 @@ ErrorOr<BackingStore> Bitmap::allocate_backing_store(BitmapFormat format, IntSiz
     auto const pitch = minimum_pitch(size.width(), format);
     auto const data_size_in_bytes = size_in_bytes(pitch, size.height());
 
-    void* data = kcalloc(1, data_size_in_bytes);
+    void* data;
+    if (initialize_backing_store == InitializeBackingStore::Yes)
+        data = kcalloc(1, data_size_in_bytes);
+    else
+        data = kmalloc(data_size_in_bytes);
     if (data == nullptr)
         return Error::from_errno(errno);
     return BackingStore { data, pitch, data_size_in_bytes };

Libraries/LibGfx/Bitmap.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2024, Andreas Kling <andreas@ladybird.org>
+ * Copyright (c) 2018-2025, Andreas Kling <andreas@ladybird.org>
  * Copyright (c) 2022, Timothy Slater <tslater2006@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
@@ -70,6 +70,7 @@ public:
     [[nodiscard]] static ErrorOr<NonnullRefPtr<Bitmap>> create(BitmapFormat, AlphaType, IntSize);
     [[nodiscard]] static ErrorOr<NonnullRefPtr<Bitmap>> create_shareable(BitmapFormat, AlphaType, IntSize);
     [[nodiscard]] static ErrorOr<NonnullRefPtr<Bitmap>> create_wrapper(BitmapFormat, AlphaType, IntSize, size_t pitch, void*, Function<void()>&& destruction_callback = {});
+    [[nodiscard]] static ErrorOr<NonnullRefPtr<Bitmap>> create_with_raw_data(BitmapFormat, AlphaType, ReadonlyBytes, IntSize);
     [[nodiscard]] static ErrorOr<NonnullRefPtr<Bitmap>> create_with_anonymous_buffer(BitmapFormat, AlphaType, Core::AnonymousBuffer, IntSize);
 
     ErrorOr<NonnullRefPtr<Gfx::Bitmap>> clone() const;
@@ -172,7 +173,11 @@ private:
     Bitmap(BitmapFormat, AlphaType, IntSize, size_t pitch, void*, Function<void()>&& destruction_callback);
     Bitmap(BitmapFormat, AlphaType, Core::AnonymousBuffer, IntSize);
 
-    static ErrorOr<BackingStore> allocate_backing_store(BitmapFormat format, IntSize size);
+    enum class InitializeBackingStore {
+        No,
+        Yes,
+    };
+    static ErrorOr<BackingStore> allocate_backing_store(BitmapFormat format, IntSize size, InitializeBackingStore = InitializeBackingStore::Yes);
 
     IntSize m_size;
     void* m_data { nullptr };

Libraries/LibGfx/BitmapSequence.cpp

@@ -128,14 +128,9 @@ ErrorOr<Gfx::BitmapSequence> decode(Decoder& decoder)
             if (size_check.has_overflow() || size_check.value() > bytes.size())
                 return Error::from_string_literal("IPC: Invalid Gfx::BitmapSequence buffer data");
 
-            auto buffer = TRY(Core::AnonymousBuffer::create_with_size(size_in_bytes));
+            auto slice = bytes.slice(bytes_read, size_in_bytes);
-            auto buffer_bytes = Bytes { buffer.data<u8>(), buffer.size() };
-
-            bytes.slice(bytes_read, size_in_bytes).copy_to(buffer_bytes);
-
             bytes_read += size_in_bytes;
-
+            bitmap = TRY(Gfx::Bitmap::create_with_raw_data(metadata.format, metadata.alpha_type, slice, metadata.size));
-            bitmap = TRY(Gfx::Bitmap::create_with_anonymous_buffer(metadata.format, metadata.alpha_type, move(buffer), metadata.size));
         }
 
         bitmaps.append(bitmap);