Switch to vertical layout automatically as the window is being resized

Prevents ending up in the wrong layout on startup and being unable to fix it
without restarting the emulator.

UI/MainScreen.cpp

@@ -707,6 +707,7 @@ UI::EventReturn GameBrowser::NavigateClick(UI::EventParams &e) {
 MainScreen::MainScreen() : highlightProgress_(0.0f), prevHighlightProgress_(0.0f), backFromStore_(false), lockBackgroundAudio_(false) {
 	System_SendMessage("event", "mainscreen");
 	SetBackgroundAudioGame("");
+	lastVertical_ = UseVerticalLayout();
 }
 
 MainScreen::~MainScreen() {
@@ -721,7 +722,7 @@ void MainScreen::CreateViews() {
 	using namespace UI;
 
 	// Vertical mode is not finished.
-	bool vertical = dp_yres > dp_xres;
+	bool vertical = UseVerticalLayout();
 
 	I18NCategory *m = GetI18NCategory("MainMenu");
 
@@ -906,6 +907,15 @@ void MainScreen::sendMessage(const char *message, const char *value) {
 void MainScreen::update(InputState &input) {
 	UIScreen::update(input);
 	UpdateUIState(UISTATE_MENU);
+	bool vertical = UseVerticalLayout();
+	if (vertical != lastVertical_) {
+		RecreateViews();
+		lastVertical_ = vertical;
+	}
+}
+
+bool MainScreen::UseVerticalLayout() const {
+	return dp_yres > dp_xres * 1.1f;
 }
 
 UI::EventReturn MainScreen::OnLoadFile(UI::EventParams &e) {