Server to Client Communication
- Robert Graebert
- Lukas Kaser (Unlicensed)
- Andrea Hentschke
It is possible to send JavaScript code to be executed on the client browser from a C++ module loaded on server.
Run JS code on client browser in Kudo Editor iframe
The JS code you want to execute on client can be sent from server to client as a string using WApplication’s doJavaScript function (SDK/Headers/wt_inc/Wt/WApplication). Your module needs to link against Wt lib located in SDK (SDK/Libraries/wt_lib/).
Include XeUpdateLock.h from SDK (SDK/Headers/inc/) - it will also include Wt/WApplication
Take XeUpdateLock before getting WApplication object
Get WApplication object and call doJavaScript on WApplication object
Example how to print something to console:
XeUpdateLock lock;
if (lock)
{
Wt::WApplication::instance()->doJavaScript("console.log('This message is printed to console');");
}Note: If you do not take XeUpdateLock, Wt::WApplication::instance() will return a null pointer.
The JS code is evaluated on client by calling window.eval() function before run and an exception will be thrown if it is not valid what will cause a client disconnect.
Post a message from Kudo Editor iframe to Partner Web Application
It is possible to post data from Kudo Editor iframe to the Partner Web Application directly on the client browser. A Partner Web Applications is referred as “parent” in our SDK.
Using our SDK
Our SDK provides two convenient C++ functions for the communication from Kudo Editor loaded in an iframe to a Partner Web Application, see API Reference.
void XeIntegration::postStringToParent( std::string message );
void XeIntegration::postJSONMessageToParent( std::string messageName, std::string messageContent );We also provide a ready-to-go example application “CrossOriginIntegration”, see samples. This example is a custom module that can be loaded by Kudo Server.
Using postMessage
In addition to the helper functions, the Web API function “Window.postMessage()” can be used directly in your module. For that, JavaScript code executing this function must be transferred from Kudo Server to the client browser.
Sending a simple string from the Kudo Server to its iframe and from there to the parent (your web application) looks like this:
XeUpdateLock lock;
if (lock)
{
std::string js = "if (window.parent) {"
"window.parent.postMessage("my message", '*');"
"}";
Wt::WApplication::instance()->doJavaScript(js);
}