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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Dynamically enables and disables styling globally based on `condition`."><title>whenever in yansi - Rust</title><script> if (window.location.protocol !== "file:") document.write(`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2">`)</script><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-e935ef01ae1c1829.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="yansi" data-themes="" data-resource-suffix="" data-rustdoc-version="1.78.0 (9b00956e5 2024-04-29)" data-channel="1.78.0" data-search-js="search-42d8da7a6b9792c2.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-4c98445ec4002617.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-12cf3b4f4f9dc36d.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-04d5337699b92874.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button><a class="logo-container" href="../yansi/index.html"><img src="https://raw.githubusercontent.com/SergioBenitez/yansi/master/.github/yansi-logo.png" alt=""></a></nav><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../yansi/index.html"><img src="https://raw.githubusercontent.com/SergioBenitez/yansi/master/.github/yansi-logo.png" alt="logo"></a><h2><a href="../yansi/index.html">yansi</a><span class="version">1.0.1</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../yansi/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press S to search, ? for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Function <a href="index.html">yansi</a>::<wbr><a class="fn" href="#">whenever</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/yansi/global.rs.html#82-84">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><pre class="rust item-decl"><code>pub fn whenever(condition: <a class="struct" href="struct.Condition.html" title="struct yansi::Condition">Condition</a>)</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Dynamically enables and disables styling globally based on <code>condition</code>.</p>
<p><code>condition</code> is expected to be fast: it is checked dynamically, each time a
<a href="struct.Painted.html" title="struct yansi::Painted"><code>Painted</code></a> value is displayed.</p>
<h2 id="example"><a class="doc-anchor" href="#example">§</a>Example</h2>
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>yansi::Condition;
yansi::whenever(Condition::STDOUT_IS_TTY);
<span class="comment">// On each styling, check if we have TTYs.
</span>yansi::whenever(Condition::STDOUTERR_ARE_TTY_LIVE);
<span class="comment">// Check `NO_COLOR`, `CLICOLOR`, and if we have TTYs.
</span><span class="kw">const </span>HAVE_COLOR: Condition = Condition(|| {
std::env::var_os(<span class="string">"NO_COLOR"</span>).is_none()
&amp;&amp; (Condition::CLICOLOR_LIVE)()
&amp;&amp; Condition::stdouterr_are_tty_live()
});
<span class="comment">// This will call `HAVE_COLOR` every time styling is needed. In this
// example, this means that env vars will be checked on each styling.
</span>yansi::whenever(HAVE_COLOR);
<span class="comment">// This instead caches the value (checking `env()` exactly once, now).
</span>yansi::whenever(Condition::cached((HAVE_COLOR)()));
<span class="comment">// Is identical to this:
</span><span class="kw">match </span>(HAVE_COLOR)() {
<span class="bool-val">true </span>=&gt; yansi::enable(),
<span class="bool-val">false </span>=&gt; yansi::disable(),
}</code></pre></div>
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