Add graphics backend selection

tests/gtest/config_test.cpp

@@ -1,6 +1,7 @@
 #include <gtest/gtest.h>
 
 #include "config/config.h"
+#include "render/rendermanager.h"
 
 TEST(Config, DefaultsPresent)
 {
@@ -10,6 +11,8 @@ TEST(Config, DefaultsPresent)
 	EXPECT_TRUE(cfg[QStringLiteral("Style")].isValid());
 	EXPECT_TRUE(cfg[QStringLiteral("TimecodeDisplay")].isValid());
 	EXPECT_TRUE(cfg[QStringLiteral("DefaultStillLength")].isValid());
+	EXPECT_EQ(cfg[QStringLiteral("GraphicsBackend")].toString(),
+			  QStringLiteral("opengl"));
 }
 
 TEST(Config, SetAndGetValues)
@@ -18,3 +21,19 @@ TEST(Config, SetAndGetValues)
 	cfg[QStringLiteral("UnitTestValue")] = 42;
 	EXPECT_EQ(cfg[QStringLiteral("UnitTestValue")].toInt(), 42);
 }
+
+TEST(Config, GraphicsBackendStringConversion)
+{
+	EXPECT_EQ(olive::RenderManager::BackendFromString(QStringLiteral("opengl")),
+			  olive::RenderManager::kOpenGL);
+	EXPECT_EQ(olive::RenderManager::BackendFromString(QStringLiteral("vulkan")),
+			  olive::RenderManager::kVulkan);
+	EXPECT_EQ(olive::RenderManager::BackendToString(
+				  olive::RenderManager::kOpenGL),
+			  QStringLiteral("opengl"));
+	EXPECT_EQ(olive::RenderManager::BackendToString(
+				  olive::RenderManager::kVulkan),
+			  QStringLiteral("vulkan"));
+	EXPECT_EQ(olive::RenderManager::BackendFromString(QStringLiteral("bad")),
+			  olive::RenderManager::kOpenGL);
+}