PixelPaint: Add `Crop to Selection` Action

In addition to adding the action, this commit also makes the
`did_change_rect()` method take in an optional rect, which
represents the new rect position. By default it is the same as
`rect()`.

When we are cropping an image, we don't want to move the whole
cropped section to the top-left of the original image in the
ImageEditor widget, so this allows us to keep the cropped image's
position fixed.

Userland/Applications/PixelPaint/Image.cpp

@@ -458,10 +458,11 @@ void Image::did_change(Gfx::IntRect const& a_modified_rect)
         client->image_did_change(modified_rect);
 }
 
-void Image::did_change_rect()
+void Image::did_change_rect(Gfx::IntRect const& a_modified_rect)
 {
+    auto modified_rect = a_modified_rect.is_empty() ? this->rect() : a_modified_rect;
     for (auto* client : m_clients)
-        client->image_did_change_rect(rect());
+        client->image_did_change_rect(modified_rect);
 }
 
 ImageUndoCommand::ImageUndoCommand(Image& image)
@@ -518,4 +519,17 @@ void Image::rotate(Gfx::RotationDirection direction)
     did_change_rect();
 }
 
+void Image::crop(Gfx::IntRect const& cropped_rect)
+{
+    for (auto& layer : m_layers) {
+        auto cropped = layer.bitmap().cropped(cropped_rect);
+        VERIFY(cropped);
+        layer.set_bitmap(*cropped);
+        layer.did_modify_bitmap(rect());
+    }
+
+    m_size = { cropped_rect.width(), cropped_rect.height() };
+    did_change_rect(cropped_rect);
+}
+
 }

Userland/Applications/PixelPaint/Image.h

@@ -101,12 +101,13 @@ public:
 
     void flip(Gfx::Orientation orientation);
     void rotate(Gfx::RotationDirection direction);
+    void crop(Gfx::IntRect const& rect);
 
 private:
     explicit Image(Gfx::IntSize const&);
 
     void did_change(Gfx::IntRect const& modified_rect = {});
-    void did_change_rect();
+    void did_change_rect(Gfx::IntRect const& modified_rect = {});
     void did_modify_layer_stack();
 
     String m_path;

Userland/Applications/PixelPaint/MainWidget.cpp

@@ -375,6 +375,17 @@ void MainWidget::initialize_menubar(GUI::Window& window)
                 return;
             editor->image().rotate(Gfx::RotationDirection::Clockwise);
         }));
+    image_menu.add_separator();
+    image_menu.add_action(GUI::Action::create(
+        "&Crop To Selection", [&](auto&) {
+            auto* editor = current_image_editor();
+            // FIXME: disable this action if there is no selection
+            if (!editor || editor->selection().is_empty())
+                return;
+            auto crop_rect = editor->selection().bounding_rect();
+            editor->image().crop(crop_rect);
+            editor->selection().clear();
+        }));
 
     auto& layer_menu = window.add_menu("&Layer");
     layer_menu.add_action(GUI::Action::create(