expandable-and-linkified-text

name	expandable-and-linkified-text
description	Clamp long text to a few lines with a more/less affordance driven by measured overflow instead of a character count, and make timestamps or URLs inside the same text tappable. Use when "more" shows on text that already fits, never shows on text that does not, gets truncated along with the text, or when tapping a link expands the block instead of following the link.

Expandable text, and tappable spans inside it

Two features that read as one and share no parts: clamping to N lines with a more/less affordance is maxLines plus onTextLayout { hasVisualOverflow }; tappable substrings are buildAnnotatedString plus pushStringAnnotation, hit-tested by character offset. They compete for the same tap, so decide what a tap on the body means before writing either.

Clamping on measured overflow

Only the layout pass knows whether the text overflows — the same string wraps differently per width, font, text scale and translation. Ask it, and re-clamp by hand so the affordance is not itself truncated:

// adapted: names shortened; the source's runCatching if/else (which re-called getLineEnd on the
// success branch) folded into getOrDefault, and its Character.isWhitespace(it) into it.isWhitespace()
var isExpanded by remember { mutableStateOf(false) }
var clickable by remember { mutableStateOf(false) }
var lastCharIndex by remember { mutableIntStateOf(0) }

Box(Modifier.clickable { isExpanded = !isExpanded }) {   // the only write to isExpanded
    Text(
        text = buildAnnotatedString {
             (clickable) {
                 (isExpanded) {
                    append(text)
                    withStyle(showLessStyle) { append(showLessText) }
                }  {
                     adjusted = text.substring(startIndex = , endIndex = lastCharIndex)
                        .dropLast(showMoreText.length)
                        .dropLastWhile { it.isWhitespace() || it ==  }
                    append(adjusted)
                    withStyle(showMoreStyle) { append(showMoreText) }
                }
            }  {
                append(text)          
            }
        },
        maxLines =  (isExpanded) .MAX_VALUE  collapsedMaxLine,
        onTextLayout = { result ->
             (!isExpanded && result.hasVisualOverflow) {
                clickable = 
                lastCharIndex = runCatching { result.getLineEnd(collapsedMaxLine - ) }
                    .getOrDefault(text.length - )
            }
        },
    )
}