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HTML 

              
                <h1>An <code>alt</code> Decision Tree Using Only <code>:has()</code></h1>

<p>
  <a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fcdpn.io%2Faardrian%2Fdebug%2FKKrjEEX" target="_top">Nu Checker results</a>. Used in my post <a href="https://adrianroselli.com/2023/08/an-alt-decision-tree-using-only-has.html" target="_top"><cite>An alt Decision Tree Using Only :has()</cite></a>.
</p>

<!-- Q1 -->

<fieldset id="Start">
  <legend>Does the image contain text?</legend>
  <input type="radio" name="hasText" id="hasTextNo">
  <label for="hasTextNo">No</label>
  <input type="radio" name="hasText" id="hasTextYes">
  <label for="hasTextYes">Yes</label>
</fieldset>

<h2 class="hide">
  If yes, the image contains text…
</h2>
<ul id="YesText">
  <li>… and the text is also present as <em>real</em> text nearby.
    Use an empty <code>alt</code> attribute. See <a href="https://www.w3.org/WAI/tutorials/images/decorative/" target="_top">Decorative Images</a>.
  </li>
  <li>… and the text is only shown for visual effects.
    Use an empty <code>alt</code> attribute. See <a href="https://www.w3.org/WAI/tutorials/images/decorative/" target="_top">Decorative Images</a>.
  </li>
  <li>… and the text has a specific function, for example is an icon.
    Use the <code>alt</code> attribute to communicate the function of the image. See <a href="https://www.w3.org/WAI/tutorials/images/functional/" target="_top">Functional Images</a>.
  </li>
  <li>… and the text in the image is not present otherwise. Use the <code>alt</code> attribute to include the text of the image. See <a href="https://www.w3.org/WAI/tutorials/images/textual/#image-of-styled-text-with-decorative-effect" target="_top">Images of Text</a>.</li>
</ul>

<!-- / Q1 -->
<!-- Q2 -->

<h2 class="hide">
  If no, the image contains no text…
</h2>
<fieldset id="NoText">
  <legend>Is the image used in a link or a button, and would it be hard or impossible to understand what the link or the button does, if the image wasn’t there?</legend>
  <input type="radio" name="asControl" id="asControlNo">
  <label for="asControlNo">No</label>
  <input type="radio" name="asControl" id="asControlYes">
  <label for="asControlYes">Yes</label>
</fieldset>

<h2 class="hide">
  If yes, the image is contained in a control…
</h2>
<ul id="YesControl">
  <li>Use the <code>alt</code> attribute to communicate the destination of the link or action taken. See <a href="https://www.w3.org/WAI/tutorials/images/functional/" target="_top">Functional Images</a>.</li>
</ul>

<!-- / Q2 -->
<!-- Q3 -->

<h2 class="hide">
  If no, the image is not contained in a control…
</h2>
<fieldset id="NoControl">
  <legend>Does the image contribute meaning to the current page or context?</legend>
  <input type="radio" name="addsMeaning" id="addsMeaningNo">
  <label for="addsMeaningNo">No</label>
  <input type="radio" name="addsMeaning" id="addsMeaningYes">
  <label for="addsMeaningYes">Yes</label>
</fieldset>

<h2 class="hide">
  If yes, the image contributes meaning…
</h2>
<ul id="YesMeaning">
  <li>… and it’s a simple graphic or photograph.
    Use a brief description of the image in a way that conveys that meaning in the <code>alt</code> attribute. See <a href="https://www.w3.org/WAI/tutorials/images/informative/" target="_top">Informative Images</a>.
  </li>
  <li>… and it’s a graph or complex piece of information.
    Include the information contained in the image elsewhere on the page. See <a href="https://www.w3.org/WAI/tutorials/images/complex/" target="_top">Complex Images</a>.
  </li>
  <li>… and it shows content that is redundant to <em>real</em> text nearby.
    Use an empty <code>alt</code> attribute. See (redundant) <a href="https://www.w3.org/WAI/tutorials/images/functional/#logo-image-within-link-text" target="_top">Functional Images</a>.
  </li>
</ul>

<!-- / Q3 -->
<!-- Q4 -->

<h2 class="hide">
  If no, the image contributes no meaning…
</h2>
<fieldset id="NoMeaning">
  <legend>Is the image purely decorative or not intended for the user?</legend>
  <input type="radio" name="isDecorative" id="isDecorativeNo">
  <label for="isDecorativeNo">No</label>
  <input type="radio" name="isDecorative" id="isDecorativeYes">
  <label for="isDecorativeYes">Yes</label>
</fieldset>

<h2 class="hide">
  If yes, the image is purely decorative…
</h2>
<ul id="YesDecorative">
  <li>Use an empty <code>alt</code> attribute. See <a href="https://www.w3.org/WAI/tutorials/images/decorative/" target="_top">Decorative Images</a>.</li>
</ul>

<!-- Q5 -->

<h2 class="hide">
  If no, the image is not purely decorative…
</h2>
<fieldset id="NoDecorative">
  <legend>Is the image’s use not listed above or it’s unclear what <code>alt</code> text to provide?</legend>
  <input type="radio" name="isListed" id="isListedNo">
  <label for="isListedNo">No</label>
  <input type="radio" name="isListed" id="isListedYes">
  <label for="isListedYes">Yes</label>
</fieldset>

<h2 class="hide">
  If yes, the image’s use is not listed above…
</h2>
<ul id="YesUnclear">
  <li class="yes">This decision tree <strong>does not</strong> cover all cases. For detailed information on the provision of text alternatives refer to the <a href="https://www.w3.org/WAI/tutorials/images/" target="_top">Image Concepts Page</a>.</li>
</ul>

<h2 class="hide">
  If no, because the image’s use is listed above…
</h2>
<ul id="NoUnclear">
  <li class="yes">I suggest you <a href="#hasTextNo">start over</a>.</li>
</ul>
!

CSS 

              
                html {
  color-scheme: dark light;
}

body {
  font-family: "Segoe UI", -apple-system, BlinkMacSystemFont, Roboto,
    Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
  line-height: 1.4;
  /*   line-height: 1.5; */
  /*   letter-spacing: 0.12em; */
  /*   word-spacing: 0.16em; */
}

h1, h2 {
  line-height: 1;
}

h2 {
  margin-top: 2em;
}

/* Requires :has() support or entire selector fails */
:focus, input:has(+ label:hover) {
  outline: .2em solid rgba(0,0,255,.25);   
}

/* Redundant to account for lack of :has() support */
:focus {
  outline: .2em solid rgba(0,0,255,.25); 
}

/* Requires :has() support or entire selector fails */
label:hover, input:hover, input:hover + label, input:focus + label, input:has(+ label:hover) {
  background-color: rgba(0,0,255,.05);
}

/* Redundant to account for lack of :has() support */
label:hover, input:hover, input:hover + label, input:focus + label {
  background-color: rgba(0,0,255,.05);
}

label, input {
  padding-block-start: .25em;
  padding-block-end: .25em;
  padding-inline-start: .25em;
}

fieldset {
  margin-block-start: 2em;
  margin-block-end: 2em;
  padding-block-start: 1em;
  padding-block-end: 1em;
  display: grid;
  grid-template-columns: 1.5em auto;
  border-radius: .5em;
}

fieldset:has(input:indeterminate) {
  border-color: #900;  
}

fieldset:has(input:not(:indeterminate)) {
  border-color: #090;  
}

legend {
  font-weight: bold;
/* The following are hacks I tried for dealing */
/* with a Safari bug that compresses the width. */
/*   width: max-content; */
/*   white-space: break-spaces; */
/*   text-wrap: balance; */
/*   text-wrap: pretty; */
/*   grid-column-start: 1; */
/*   grid-column-end: 2; */
/*   justify-self: stretch; */
  min-width: 50vw;
}

li {
  margin-block-end: 1em;
}

/* Convoluted, but hides only if browser */
/* supports :has(), ensuring display parity */
fieldset:has(legend) ~ h2.hide {
  display: none;
}

/* Q1 */

/* If NO not checked, hide the fields */
fieldset#Start:has(#hasTextNo:not(:checked)) ~ fieldset#NoText {
  display: none;
}
/* If YES not checked, hide the list */
fieldset#Start:has(#hasTextYes:not(:checked)) ~ ul#YesText {
  display: none;
}

/* Q2 */

/* If NO not checked, hide the fields */
fieldset#NoText:has(#asControlNo:not(:checked)) ~ fieldset#NoControl {
  display: none;
}
/* If YES not checked, hide the list */
fieldset#NoText:has(#asControlYes:not(:checked)) ~ ul#YesControl {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#Start:has(#hasTextYes:checked) ~ ul#YesControl {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#Start:has(#hasTextYes:checked) ~ fieldset#NoControl {
  display: none;
}

/* Q3 */

/* If NO not checked, hide the fields */
fieldset#NoControl:has(#addsMeaningNo:not(:checked)) ~ fieldset#NoMeaning {
  display: none;
}
/* If YES not checked, hide the list */
fieldset#NoControl:has(#addsMeaningYes:not(:checked)) ~ ul#YesMeaning {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#NoText:has(#asControlYes:checked) ~ ul#YesMeaning {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#NoText:has(#asControlYes:checked) ~ fieldset#NoMeaning {
  display: none;
}
/* If YES checked in prior prior prior question, this cannot show */
fieldset#Start:has(#hasTextYes:checked) ~ fieldset#NoMeaning {
  display: none;
}

/* Q4 */

/* If NO not checked, hide the fields */
fieldset#NoMeaning:has(#isDecorativeNo:not(:checked)) ~ fieldset#NoDecorative {
  display: none;
}
/* If YES not checked, hide the list */
fieldset#NoMeaning:has(#isDecorativeYes:not(:checked)) ~ ul#YesDecorative {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#NoControl:has(#addsMeaningYes:checked) ~ ul#YesDecorative {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#NoControl:has(#addsMeaningYes:checked) ~ fieldset#NoDecorative {
  display: none;
}
/* If YES checked in prior prior question, this cannot show */
fieldset#NoText:has(#asControlYes:checked) ~ fieldset#NoDecorative {
  display: none;
}
/* If YES checked in prior prior prior question, this cannot show */
fieldset#Start:has(#hasTextYes:checked) ~ fieldset#NoDecorative {
  display: none;
}

/* Q5 */

/* If NO not checked, hide the fields */
fieldset#NoDecorative:has(#isListedNo:not(:checked)) ~ ul#NoUnclear {
  display: none;
}
/* If YES not checked, hide the list */
fieldset#NoDecorative:has(#isListedYes:not(:checked)) ~ ul#YesUnclear {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#NoMeaning:has(#isDecorativeYes:checked) ~ ul#YesUnclear {
  display: none;
}
/* If YES checked in prior question, this cannot show */
fieldset#NoMeaning:has(#isDecorativeYes:checked) ~ ul#NoUnclear {
  display: none;
}
/* If YES checked in prior prior question, this cannot show */
fieldset#NoControl:has(#addsMeaningYes:checked) ~ ul#NoUnclear {
  display: none;
}
/* If YES checked in prior prior prior question, this cannot show */
fieldset#NoText:has(#asControlYes:checked) ~ ul#NoUnclear {
  display: none;
}
/* If YES checked in prior prior prior prior question, this cannot show */
fieldset#Start:has(#hasTextYes:checked) ~ ul#NoUnclear {
  display: none;
}

/* Restart */

fieldset#Start:target ~ * {
/*   display: none; */
}
!

JS
!
999px

Console