Diagnostics

A template or stylesheet can be valid HTML and CSS and still do nothing in RTXUI: a property the engine does not implement, a typo in a bound name, an attribute borrowed from another framework. Rather than ignore these silently, RTXUI reports each one as a diagnostic.

What Is Reported

Mistake	Example	Diagnostic
Unsupported CSS property or value	font-size: small, flex-direction: diagonal	unsupported CSS declaration 'font-size: small'
Interpolating a name that is not bound	{titel}	'{titel}' in <App> is not a bound name
An expression inside {}	{count == 1}	templates do not evaluate expressions; bind a const method computing the value and use its name
A handler that is not bound	onclick="Sumbit", when clicked	handler 'Sumbit' is not bound in any enclosing component
A tag that is not a built-in or an imported component	<View>, <Card/> without Import<Card>()	unknown tag <Card> in <App>: if it is your component, call Import<Card>() in <App>'s constructor
A <style> nested inside an element	<div><style>...</style></div>	<style> inside <div> in <App> is ignored: put <style> at the top level of the view
Another framework's attribute syntax	v-if, *ngFor, className, onClick, for="x in xs"	attribute 'v-if' on <div> in <App> is not RTXUI syntax: use if="{name}" or <if condition="{name}">

Each distinct message is reported once per run, even though styles are re-applied on every frame.

Markup or CSS that does not parse is reported too, with where the error is:

Mistake	kind	line, column
A <style> block that does not parse, such as one built from bound state	CssSyntax	In that <style> block, 0-based
A template that does not parse, on hot reload, or markup built at run time such as a <markdown> component's	XmlSyntax	In that markup, 0-based

A syntax error is reported each time the text fails to parse, not once, so that an app showing live-edited markup hears about every attempt. Without a handler it is printed with the lines around it, and a component's own template that does not parse ends the process: it is usually a literal in the source, and the message is then the last thing on the terminal.

Where They Go

By default each diagnostic is printed to stderr, prefixed with rtxui:.

Set the environment variable RTXUI_STRICT=1 to abort on the first one instead. This is what RTXUI's own example test runs with, and it is a good setting for your tests and CI:

RTXUI_STRICT=1 ./my_app

An application that owns the terminal can route diagnostics through its own interface, since printing to stderr disturbs a running frame:

#include <rtxui/rtxui.hpp>

rtxui::SetDiagnosticHandler([](const rtxui::Diagnostic& d) {
  if (d.kind() == rtxui::Diagnostic::Kind::CssSyntax) {
    log_file << "line " << d.line() + 1 << ": ";
  }
  log_file << d.message() << '\n';
});

Pass nullptr to restore the default.