How can I call a C++ function using JavaScript?
For example, I am executing js code in a browser window using the method CefFrame::ExecuteJavaScript like this:
(*frame).GetMainFrame()).ExecuteJavaScript("const elem = document.getElementsByClassName("my_class")[0];const rect = elem.getBoundingClientRect(); alert(rect.x + \":\" + rect.y)", "", 1);
Is it possible to somehow call a C++ function for the place of the JS alert() function?
It can be done in two ways. They are almost equal: you can create several native functions at once with CefRegisterExtension, and you can create a single native function with CefV8Value::CreateFunction. The example bellow is just a sketch, nowhere can test it, small issues are possible, but the idea is clear:
class MyAlertHandler : public CefV8Handler {
public:
bool Execute(const CefString& name,
CefRefPtr<CefV8Value> object,
const CefV8ValueList& arguments,
CefRefPtr<CefV8Value>& retval,
CefString& exception) override {
if (!arguments.empty()) {
// arguments[0]->GetStringValue();
}
return true;
}
};
CefRefPtr<CefV8Handler> handler = new MyAlertHandler;
CefRefPtr<CefV8Context> v8_context = frame->GetMainFrame()->GetV8Context();
if (v8_context.get() && v8_context->Enter()) {
CefRefPtr<CefV8Value> global = v8_context->GetGlobal();
CefRefPtr<CefV8Value> my_alert = CefV8Value::CreateFunction("my_alert", handler);
global->SetValue("my_alert", my_alert, V8_PROPERTY_ATTRIBUTE_READONLY);
v8_context->Exit();
}
Calling Enter() and Exit() on a V8 context can be omitted if CefV8Value::CreateFunction is called from CefRenderProcessHandler functions.
frame->GetMainFrame()->ExecuteJavaScript(R"(
const elem = document.getElementsByClassName("my_class")[0];
const rect = elem.getBoundingClientRect();
my_alert(rect.x + ":" + rect.y);)", "", 1);