Utilities: Add a simple "shot" utility for grabbing screenshots :^)

This little CLI program grabs the current screen image from
WindowServer and saves it as a PNG file.

Userland/Utilities/CMakeLists.txt

@@ -38,6 +38,7 @@ target_link_libraries(pape LibGUI)
 target_link_libraries(passwd LibCrypt)
 target_link_libraries(paste LibGUI)
 target_link_libraries(pro LibProtocol)
+target_link_libraries(shot LibGUI)
 target_link_libraries(su LibCrypt)
 target_link_libraries(tar LibArchive LibCompress)
 target_link_libraries(test-crypto LibCrypto LibTLS LibLine)

Userland/Utilities/shot.cpp

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Format.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/DateTime.h>
+#include <LibCore/File.h>
+#include <LibGUI/Application.h>
+#include <LibGUI/WindowServerConnection.h>
+#include <LibGfx/PNGWriter.h>
+
+int main(int argc, char** argv)
+{
+    Core::ArgsParser args_parser;
+
+    String output_path;
+    args_parser.add_positional_argument(output_path, "Output filename", "output", Core::ArgsParser::Required::No);
+
+    args_parser.parse(argc, argv);
+
+    if (output_path.is_empty()) {
+        output_path = Core::DateTime::now().to_string("screenshot-%Y-%m-%d-%H-%M-%S.png");
+    }
+
+    auto app = GUI::Application::construct(argc, argv);
+    auto response = GUI::WindowServerConnection::the().send_sync<Messages::WindowServer::GetScreenBitmap>();
+
+    auto* bitmap = response->bitmap().bitmap();
+    if (!bitmap) {
+        warnln("Failed to grab screenshot");
+        return 1;
+    }
+
+    Gfx::PNGWriter writer;
+    auto encoded_bitmap = writer.write(bitmap);
+    if (encoded_bitmap.is_empty()) {
+        warnln("Failed to encode PNG");
+        return 1;
+    }
+
+    auto file_or_error = Core::File::open(output_path, Core::IODevice::ReadWrite);
+    if (file_or_error.is_error()) {
+        warnln("Could not open '{}' for writing: {}", output_path, file_or_error.error());
+        return 1;
+    }
+
+    auto& file = *file_or_error.value();
+    if (!file.write(encoded_bitmap.data(), encoded_bitmap.size())) {
+        warnln("Failed to write PNG");
+        return 1;
+    }
+
+    outln("{}", output_path);
+    return 0;
+}