Add preferUnstableChannel config option

When set, this sets the environment variable WEBVIEW2_RELEASE_CHANNEL_PREFERENCE to 1, which reverses the default channel search order (i.e. starting with canary and working backwards to stable).

Author: AshleyScirra

src/Config.cpp

@@ -10,6 +10,7 @@ ConfigJson LoadConfigJson(const std::string& path)
 	// Set defaults
 	ConfigJson ret;
 	ret.startUrl = "https://github.com/WebView-CG/CanIWebView2";
+	ret.preferUnstableChannel = false;
 
 	// If file does not exist, just use defaults
 	if (!FileExists(path))
@@ -31,5 +32,8 @@ ConfigJson LoadConfigJson(const std::string& path)
 	if (parsedJson.contains("startUrl"))
 		ret.startUrl = parsedJson["startUrl"].get<std::string>();
 
+	if (parsedJson.contains("preferUnstableChannel"))
+		ret.preferUnstableChannel = parsedJson["preferUnstableChannel"].get<bool>();
+
 	return ret;
 }

src/Config.h

@@ -4,6 +4,7 @@
 
 struct ConfigJson {
 	std::string startUrl;
+	bool preferUnstableChannel;
 };
 
 ConfigJson LoadConfigJson(const std::string& path);

src/WebView.cpp

@@ -35,6 +35,14 @@ int CALLBACK WinMain(
 	std::string configJsonPath = FolderFromPath(GetModulePath()) + "config.json";
 	ConfigJson configJson = LoadConfigJson(configJsonPath);
 
+	// The default channel search order is the WebView2 Runtime, Beta, Dev, and Canary (i.e. stable to unstable).
+	// When preferUnstableCannel is true in config.json, set the environment variable WEBVIEW2_RELEASE_CHANNEL_PREFERENCE
+	// to 1 which reverses the channel search order.
+	if (configJson.preferUnstableChannel)
+	{
+		SetEnvironmentVariable(L"WEBVIEW2_RELEASE_CHANNEL_PREFERENCE", L"1");
+	}
+
 	/////////////////////////////////////////////////////
 	// Register window class
 	WNDCLASSEX wcex;