LibGUI: Make clipboard-as-bitmap parsing less data-race-y

This encourages the caller to first fetch data and type atomically, and
then parse that, instead of potentially making multiple requests.

Userland/Applications/PixelPaint/MainWidget.cpp

@@ -214,7 +214,7 @@ void MainWidget::initialize_menubar(GUI::Window& window)
         auto* editor = current_image_editor();
         if (!editor)
             return;
-        auto bitmap = GUI::Clipboard::the().bitmap();
+        auto bitmap = GUI::Clipboard::the().data_and_type().as_bitmap();
         if (!bitmap)
             return;
 

Userland/Libraries/LibGUI/Clipboard.cpp

@@ -64,34 +64,34 @@ Clipboard::DataAndType Clipboard::data_and_type() const
     return { data.release_value(), type, metadata };
 }
 
-RefPtr<Gfx::Bitmap> Clipboard::bitmap() const
+RefPtr<Gfx::Bitmap> Clipboard::DataAndType::as_bitmap() const
 {
-    auto clipping = data_and_type();
-
-    if (clipping.mime_type != "image/x-serenityos")
+    if (mime_type != "image/x-serenityos")
         return nullptr;
 
-    auto width = clipping.metadata.get("width").value_or("0").to_uint();
+    auto width = metadata.get("width").value_or("0").to_uint();
     if (!width.has_value() || width.value() == 0)
         return nullptr;
 
-    auto height = clipping.metadata.get("height").value_or("0").to_uint();
+    auto height = metadata.get("height").value_or("0").to_uint();
     if (!height.has_value() || height.value() == 0)
         return nullptr;
 
-    auto scale = clipping.metadata.get("scale").value_or("0").to_uint();
+    auto scale = metadata.get("scale").value_or("0").to_uint();
     if (!scale.has_value() || scale.value() == 0)
         return nullptr;
 
-    auto pitch = clipping.metadata.get("pitch").value_or("0").to_uint();
+    auto pitch = metadata.get("pitch").value_or("0").to_uint();
     if (!pitch.has_value() || pitch.value() == 0)
         return nullptr;
 
-    auto format = clipping.metadata.get("format").value_or("0").to_uint();
+    auto format = metadata.get("format").value_or("0").to_uint();
     if (!format.has_value() || format.value() == 0)
         return nullptr;
 
-    auto clipping_bitmap_or_error = Gfx::Bitmap::try_create_wrapper((Gfx::BitmapFormat)format.value(), { (int)width.value(), (int)height.value() }, scale.value(), pitch.value(), clipping.data.data());
+    // We won't actually write to the clipping_bitmap, so casting away the const is okay.
+    auto clipping_data = const_cast<u8*>(data.data());
+    auto clipping_bitmap_or_error = Gfx::Bitmap::try_create_wrapper((Gfx::BitmapFormat)format.value(), { (int)width.value(), (int)height.value() }, scale.value(), pitch.value(), clipping_data);
     if (clipping_bitmap_or_error.is_error())
         return nullptr;
     auto clipping_bitmap = clipping_bitmap_or_error.release_value_but_fixme_should_propagate_errors();

Userland/Libraries/LibGUI/Clipboard.h

@@ -32,6 +32,8 @@ public:
         ByteBuffer data;
         String mime_type;
         HashMap<String, String> metadata;
+
+        RefPtr<Gfx::Bitmap> as_bitmap() const;
     };
 
     static void initialize(Badge<Application>);
@@ -40,7 +42,6 @@ public:
     DataAndType data_and_type() const;
     ByteBuffer data() const { return data_and_type().data; }
     String mime_type() const { return data_and_type().mime_type; }
-    RefPtr<Gfx::Bitmap> bitmap() const;
 
     void set_data(ReadonlyBytes data, String const& mime_type = "text/plain", HashMap<String, String> const& metadata = {});
     void set_plain_text(String const& text) { set_data(text.bytes()); }