ui: fixed Linux issues

* no outline style for push buttons
* show error when not using Sourcetrail.sh script in console instead of message box, which won't load

bin/app/data/gui/main/main.css

@@ -4,6 +4,10 @@ QToolTip {
 	font-size: <setting:font_size>px;
 }
 
+QPushButton {
+	outline: none;
+}
+
 QMainWindow::separator {
 	background: <color:window/separator>;
 	width: 1px;

src/app/main.cpp

@@ -187,6 +187,13 @@ QCoreApplication* createApplication(int &argc, char *argv[], bool noGUI = false)
 
 int main(int argc, char *argv[])
 {
+#ifdef __linux__
+	if (std::getenv("SOURCETRAIL_VIA_SCRIPT") == nullptr)
+	{
+		std::cout << "ERROR: Please run Sourcetrail via the Sourcetrail.sh script!" << std::endl;
+	}
+#endif
+
 	QApplication::setApplicationName("Sourcetrail");
 	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling, true);
 

src/lib_gui/qt/window/QtMainWindow.cpp

@@ -5,7 +5,6 @@
 #include <QDockWidget>
 #include <QDir>
 #include <QMenuBar>
-#include <QMessageBox>
 #include <QSettings>
 #include <QTimer>
 
@@ -112,13 +111,6 @@ QtMainWindow::QtMainWindow()
 	setWindowIcon(QIcon((ResourcePaths::getGuiPath().str() + "icon/logo_1024_1024.png").c_str()));
 	setWindowFlags(Qt::Widget);
 
-#ifdef __linux__
-	if (std::getenv("SOURCETRAIL_VIA_SCRIPT") == nullptr)
-	{
-	   QMessageBox::warning(this, "Run Sourcetrail via Script", "Please run Sourcetrail via Sourcetrail.sh");
-	}
-#endif
-
 	QApplication* app = dynamic_cast<QApplication*>(QCoreApplication::instance());
 	app->installEventFilter(new MouseReleaseFilter(this));