Userland: Add ability to capture rectangular region in shot

A click and drag selectable, transparent, fullscreen window is
displayed with the command line argument -r for screenshots.

Userland/Utilities/shot.cpp

@@ -1,19 +1,91 @@
 /*
  * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Aziz Berkay Yesilyurt <abyesilyurt@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <AK/Format.h>
+#include <AK/Optional.h>
 #include <LibCore/ArgsParser.h>
 #include <LibCore/DateTime.h>
 #include <LibCore/File.h>
 #include <LibGUI/Application.h>
 #include <LibGUI/Clipboard.h>
+#include <LibGUI/Painter.h>
+#include <LibGUI/Widget.h>
+#include <LibGUI/Window.h>
 #include <LibGUI/WindowServerConnection.h>
 #include <LibGfx/PNGWriter.h>
+#include <LibGfx/Palette.h>
 #include <unistd.h>
 
+class SelectableLayover final : public GUI::Widget {
+    C_OBJECT(SelectableLayover)
+public:
+    SelectableLayover(GUI::Window* window)
+        : m_window(window)
+        , m_background_color(palette().threed_highlight())
+    {
+        set_override_cursor(Gfx::StandardCursor::Crosshair);
+    }
+
+    virtual ~SelectableLayover() override {};
+
+    Gfx::IntRect region() const
+    {
+        return m_region;
+    }
+
+private:
+    virtual void mousedown_event(GUI::MouseEvent& event) override
+    {
+        if (event.button() == GUI::MouseButton::Left)
+            m_anchor_point = event.position();
+    };
+
+    virtual void mousemove_event(GUI::MouseEvent& event) override
+    {
+        if (m_anchor_point.has_value()) {
+            m_region = Gfx::IntRect::from_two_points(*m_anchor_point, event.position());
+            update();
+        }
+    };
+
+    virtual void mouseup_event(GUI::MouseEvent& event) override
+    {
+        if (event.button() == GUI::MouseButton::Left)
+            m_window->close();
+    };
+
+    virtual void paint_event(GUI::PaintEvent&) override
+    {
+        if (m_region.is_empty()) {
+            GUI::Painter painter(*this);
+            painter.fill_rect(m_window->rect(), m_background_color);
+            return;
+        }
+
+        GUI::Painter painter(*this);
+        painter.fill_rect(m_region, Gfx::Color::Transparent);
+        for (auto rect : m_window->rect().shatter(m_region))
+            painter.fill_rect(rect, m_background_color);
+    }
+
+    virtual void keydown_event(GUI::KeyEvent& event) override
+    {
+        if (event.key() == Key_Escape) {
+            m_region = Gfx::IntRect();
+            m_window->close();
+        }
+    }
+
+    Optional<Gfx::IntPoint> m_anchor_point;
+    Gfx::IntRect m_region;
+    GUI::Window* m_window = nullptr;
+    Gfx::Color const m_background_color;
+};
+
 int main(int argc, char** argv)
 {
     Core::ArgsParser args_parser;
@@ -21,12 +93,14 @@ int main(int argc, char** argv)
     String output_path;
     bool output_to_clipboard = false;
     unsigned delay = 0;
+    bool select_region = false;
     int screen = -1;
 
     args_parser.add_positional_argument(output_path, "Output filename", "output", Core::ArgsParser::Required::No);
     args_parser.add_option(output_to_clipboard, "Output to clipboard", "clipboard", 'c');
     args_parser.add_option(delay, "Seconds to wait before taking a screenshot", "delay", 'd', "seconds");
     args_parser.add_option(screen, "The index of the screen (default: -1 for all screens)", "screen", 's', "index");
+    args_parser.add_option(select_region, "Select a region to capture", "region", 'r');
 
     args_parser.parse(argc, argv);
 
@@ -35,6 +109,25 @@ int main(int argc, char** argv)
     }
 
     auto app = GUI::Application::construct(argc, argv);
+    Gfx::IntRect crop_region;
+    if (select_region) {
+        auto window = GUI::Window::construct();
+        auto& container = window->set_main_widget<SelectableLayover>(window);
+        container.set_fill_with_background_color(true);
+
+        window->set_title("shot");
+        window->set_opacity(0.2);
+        window->set_fullscreen(true);
+        window->show();
+        app->exec();
+
+        crop_region = container.region();
+        if (crop_region.is_empty()) {
+            dbgln("cancelled...");
+            return 0;
+        }
+    }
+
     sleep(delay);
     Optional<u32> screen_index;
     if (screen >= 0)
@@ -43,12 +136,16 @@ int main(int argc, char** argv)
     auto shared_bitmap = GUI::WindowServerConnection::the().get_screen_bitmap({}, screen_index);
     dbgln("got screenshot");
 
-    auto* bitmap = shared_bitmap.bitmap();
+    RefPtr<Gfx::Bitmap> bitmap = shared_bitmap.bitmap();
     if (!bitmap) {
         warnln("Failed to grab screenshot");
         return 1;
     }
 
+    if (select_region) {
+        bitmap = bitmap->cropped(crop_region);
+    }
+
     if (output_to_clipboard) {
         GUI::Clipboard::the().set_bitmap(*bitmap);
         return 0;