UI: Show warning if starting/stopping broadcast fails

UI/data/locale/en-US.ini

@@ -394,6 +394,8 @@ Output.BadPath.Text="The configured file output path is invalid. Please check yo
 # broadcast setup messages
 Output.NoBroadcast.Title="No Broadcast Configured"
 Output.NoBroadcast.Text="You need to set up a broadcast before you can start streaming."
+Output.BroadcastStartFailed="Failed to start broadcast"
+Output.BroadcastStopFailed="Failed to stop broadcast"
 
 # log upload dialog text and messages
 LogReturnDialog="Log Upload Successful"
@@ -1248,6 +1250,8 @@ YouTube.Actions.Error.BroadcastNotFound="The selected broadcast was not found."
 YouTube.Actions.Error.FileMissing="Selected file does not exist."
 YouTube.Actions.Error.FileOpeningFailed="Failed opening selected file."
 YouTube.Actions.Error.FileTooLarge="Selected file is too large (Limit: 2 MiB)."
+YouTube.Actions.Error.BroadcastTransitionFailed="Transitioning the broadcast failed: %1<br/><br/>If this error persists <a href='https://studio.youtube.com/video/%2/livestreaming'>open the broadcast in YouTube Studio</a> and try manually."
+YouTube.Actions.Error.BroadcastTestStarting="Broadcast is transitioning to the test stage, this can take some time. Please try again in 10-30 seconds."
 
 YouTube.Actions.EventsLoading="Loading list of events..."
 YouTube.Actions.EventCreated.Title="Event Created"
@@ -1268,3 +1272,6 @@ YouTube.Actions.AutoStopStreamingWarning="You will not be able to reconnect.<br>
 # YouTube API errors in format "YouTube.Errors.<error reason>"
 YouTube.Errors.liveStreamingNotEnabled="Live streaming is not enabled on the selected YouTube channel.<br/><br/>See <a href='https://www.youtube.com/features'>youtube.com/features</a> for more information."
 YouTube.Errors.livePermissionBlocked="Live streaming is unavailable on the selected YouTube Channel.<br/>Please note that it may take up to 24 hours for live streaming to become available after enabling it in your channel settings.<br/><br/>See <a href='https://www.youtube.com/features'>youtube.com/features</a> for details."
+YouTube.Errors.errorExecutingTransition="Transition failed due to a backend error. Please try again in a few seconds."
+YouTube.Errors.errorStreamInactive="YouTube is not receiving data for your stream. Please check your configuration and try again."
+YouTube.Errors.invalidTransition="The attempted transition was invalid. This may be due to the stream not having finished a previous transition. Please wait a few seconds and try again."

UI/window-basic-main.cpp

@@ -6364,7 +6364,24 @@ void OBSBasic::BroadcastButtonClicked()
 		std::shared_ptr<YoutubeApiWrappers> ytAuth =
 			dynamic_pointer_cast<YoutubeApiWrappers>(auth);
 		if (ytAuth.get()) {
-			ytAuth->StartLatestBroadcast();
+			if (!ytAuth->StartLatestBroadcast()) {
+				auto last_error = ytAuth->GetLastError();
+				if (last_error.isEmpty())
+					last_error = QTStr(
+						"YouTube.Actions.Error.YouTubeApi");
+				if (!ytAuth->GetTranslatedError(last_error))
+					last_error =
+						QTStr("YouTube.Actions.Error.BroadcastTransitionFailed")
+							.arg(last_error,
+							     ytAuth->GetBroadcastId());
+
+				OBSMessageBox::warning(
+					this,
+					QTStr("Output.BroadcastStartFailed"),
+					last_error, true);
+				ui->broadcastButton->setChecked(false);
+				return;
+			}
 		}
 #endif
 		broadcastActive = true;
@@ -6402,7 +6419,22 @@ void OBSBasic::BroadcastButtonClicked()
 		std::shared_ptr<YoutubeApiWrappers> ytAuth =
 			dynamic_pointer_cast<YoutubeApiWrappers>(auth);
 		if (ytAuth.get()) {
-			ytAuth->StopLatestBroadcast();
+			if (!ytAuth->StopLatestBroadcast()) {
+				auto last_error = ytAuth->GetLastError();
+				if (last_error.isEmpty())
+					last_error = QTStr(
+						"YouTube.Actions.Error.YouTubeApi");
+				if (!ytAuth->GetTranslatedError(last_error))
+					last_error =
+						QTStr("YouTube.Actions.Error.BroadcastTransitionFailed")
+							.arg(last_error,
+							     ytAuth->GetBroadcastId());
+
+				OBSMessageBox::warning(
+					this,
+					QTStr("Output.BroadcastStopFailed"),
+					last_error, true);
+			}
 		}
 #endif
 		broadcastActive = false;