LibGUI: Add and use Window::center_on_screen()

Various applications were using the same slightly verbose code to center
themselves on the screen/desktop:

Gfx::IntRect window_rect { 0, 0, width, height };
window_rect.center_within(GUI::Desktop::the().rect());
window->set_rect(window_rect);

Which now becomes:

window->resize(width, height);
window->center_on_screen();

3 files changed, 12 insertions, 4 deletions

diff --git a/Libraries/LibGUI/ProcessChooser.cpp b/Libraries/LibGUI/ProcessChooser.cpp
index 413b3b9888..ad47f4b293 100644
--- a/Libraries/LibGUI/ProcessChooser.cpp
+++ b/Libraries/LibGUI/ProcessChooser.cpp
@@ -26,7 +26,6 @@
 
 #include <LibGUI/BoxLayout.h>
 #include <LibGUI/Button.h>
-#include <LibGUI/Desktop.h>
 #include <LibGUI/MessageBox.h>
 #include <LibGUI/ProcessChooser.h>
 #include <LibGUI/RunningProcessesModel.h>
@@ -48,9 +47,8 @@ ProcessChooser::ProcessChooser(const StringView& window_title, const StringView&
     else if (parent_window)
         set_icon(parent_window->icon());
 
-    Gfx::IntRect window_rect { 0, 0, 300, 340 };
-    window_rect.center_within(GUI::Desktop::the().rect());
-    set_rect(window_rect);
+    resize(300, 340);
+    center_on_screen();
 
     auto& widget = set_main_widget<GUI::Widget>();
     widget.set_fill_with_background_color(true);
diff --git a/Libraries/LibGUI/Window.cpp b/Libraries/LibGUI/Window.cpp
index a58b04d898..de1206b918 100644
--- a/Libraries/LibGUI/Window.cpp
+++ b/Libraries/LibGUI/Window.cpp
@@ -32,6 +32,7 @@
 #include <LibCore/MimeData.h>
 #include <LibGUI/Action.h>
 #include <LibGUI/Application.h>
+#include <LibGUI/Desktop.h>
 #include <LibGUI/Event.h>
 #include <LibGUI/Painter.h>
 #include <LibGUI/Widget.h>
@@ -212,6 +213,13 @@ void Window::set_rect(const Gfx::IntRect& a_rect)
         m_main_widget->resize(window_rect.size());
 }
 
+void Window::center_on_screen()
+{
+    auto window_rect = rect();
+    window_rect.center_within(Desktop::the().rect());
+    set_rect(window_rect);
+}
+
 void Window::set_window_type(WindowType window_type)
 {
     m_window_type = window_type;
diff --git a/Libraries/LibGUI/Window.h b/Libraries/LibGUI/Window.h
index 3284a15644..4d8f96e4ce 100644
--- a/Libraries/LibGUI/Window.h
+++ b/Libraries/LibGUI/Window.h
@@ -123,6 +123,8 @@ public:
     void resize(int width, int height) { resize({ width, height }); }
     void resize(const Gfx::IntSize& size) { set_rect({ position(), size }); }
 
+    void center_on_screen();
+
     virtual void event(Core::Event&) override;
 
     bool is_visible() const;