gui2/tscreenshot_notification: Don't obtain file size from caller

The caller's provided size is notoriously unreliable right now --
especially after the addition of PNG support -- because it's obtained
from display::screenshot(), which just does some math voodoo to
calculate the *expected* size of a BMP file and sticks to that.

stat-ing a file is cheap, and simplifies our constructor's signature.
This also fixes PNG files having the wrong size reported.

src/gui/dialogs/screenshot_notification.cpp

@@ -63,13 +63,19 @@ namespace gui2
 
 REGISTER_DIALOG(screenshot_notification)
 
-tscreenshot_notification::tscreenshot_notification(const std::string& path,
-												   int filesize)
+tscreenshot_notification::tscreenshot_notification(const std::string& path)
 	: path_(path), screenshots_dir_path_(filesystem::get_screenshot_dir())
 {
+	const int filesize = filesystem::file_size(path);
+
+	const std::string sizetext
+			= filesize >= 0
+			? utils::si_string(filesize, true, _("unit_byte^B"))
+			: _("file_size^Unknown");
+
 	register_label("filesize",
 				   false,
-				   utils::si_string(filesize, true, _("unit_byte^B")),
+				   sizetext,
 				   false);
 }
 

src/gui/dialogs/screenshot_notification.hpp

@@ -26,19 +26,20 @@ public:
 	/**
 	 * Constructor.
 	 *
-	 * @param path     Path to the screenshot file created,
-	 * @param filesize Size of the screenshot file.
+	 * @param path     Path to the screenshot file created. The caller should
+	 *                 ensure the file exists, otherwise it will be displayed
+	 *                 with size 0.
 	 */
-	tscreenshot_notification(const std::string& path, int filesize);
+	tscreenshot_notification(const std::string& path);
 
 	/**
 	 * The display function.
 	 *
 	 * See @ref tdialog for more information.
 	 */
-	static void display(const std::string& path, int filesize, CVideo& video)
+	static void display(const std::string& path, CVideo& video)
 	{
-		tscreenshot_notification(path, filesize).show(video);
+		tscreenshot_notification(path).show(video);
 	}
 
 private:

src/hotkey/command_executor.cpp

@@ -651,7 +651,7 @@ void execute_command(display& disp, const hotkey_command& command, command_execu
 			filename = filesystem::get_next_filename(filename, ext);
 			int size = disp.screenshot(filename, map_screenshot);
 			if (size > 0) {
-				gui2::tscreenshot_notification::display(filename, size, disp.video());
+				gui2::tscreenshot_notification::display(filename, disp.video());
 			} else {
 				gui2::show_message(disp.video(), _("Screenshot Done"), "");
 			}

src/tests/gui/test_gui2.cpp

@@ -811,8 +811,7 @@ struct twrapper<gui2::tscreenshot_notification>
 {
 	static gui2::tscreenshot_notification* create()
 	{
-		return new gui2::tscreenshot_notification("path"
-				, 0);
+		return new gui2::tscreenshot_notification("path");
 	}
 };