PixelPaint: Add function to make layer from selection to ImageEditor

Author: https://github.com/tslater2006
Commit: https://github.com/SerenityOS/serenity/commit/e66763c223
Pull-request: https://github.com/SerenityOS/serenity/pull/15117
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/kleinesfilmroellchen

Userland/Applications/PixelPaint/ImageEditor.cpp

@@ -3,6 +3,7 @@
  * Copyright (c) 2021, Tobias Christiansen <tobyase@serenityos.org>
  * Copyright (c) 2021-2022, Mustafa Quraish <mustafa@serenityos.org>
  * Copyright (c) 2021, David Isaksson <davidisaksson93@gmail.com>
+ * Copyright (c) 2022, Timothy Slater <tslater2006@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -427,6 +428,30 @@ void ImageEditor::set_active_layer(Layer* layer)
     }
 }
 
+ErrorOr<void> ImageEditor::add_new_layer_from_selection()
+{
+    auto current_layer_selection = image().selection();
+    if (current_layer_selection.is_empty())
+        return Error::from_string_literal("There is no active selection to create layer from.");
+
+    // save offsets of selection so we know where to place the new layer
+    auto selection_offset = current_layer_selection.bounding_rect().location();
+
+    auto selection_bitmap = active_layer()->try_copy_bitmap(current_layer_selection);
+    if (selection_bitmap.is_null())
+        return Error::from_string_literal("Unable to create bitmap from selection.");
+
+    auto layer_or_error = PixelPaint::Layer::try_create_with_bitmap(image(), selection_bitmap.release_nonnull(), "New Layer"sv);
+    if (layer_or_error.is_error())
+        return Error::from_string_literal("Unable to create layer from selection.");
+
+    auto new_layer = layer_or_error.release_value();
+    new_layer->set_location(selection_offset);
+    image().add_layer(new_layer);
+    layers_did_change();
+    return {};
+}
+
 void ImageEditor::set_active_tool(Tool* tool)
 {
     if (m_active_tool == tool)

Userland/Applications/PixelPaint/ImageEditor.h

@@ -38,6 +38,7 @@ public:
     Layer* active_layer() { return m_active_layer; }
     void set_active_layer(Layer*);
 
+    ErrorOr<void> add_new_layer_from_selection();
     Tool* active_tool() { return m_active_tool; }
     void set_active_tool(Tool*);
     void update_tool_cursor();