| 1 | const COLLAPSE_MAX_HEIGHT_EM = 15; |
| 2 | const UNMEASURABLE_WIDTH_PX = 1; |
| 3 | |
| 4 | function pixels(value) { |
| 5 | const parsed = Number.parseFloat(value || "0"); |
| 6 | return Number.isFinite(parsed) ? parsed : 0; |
| 7 | } |
| 8 | |
| 9 | function hasUsableContentWidth(element, style = getComputedStyle(element)) { |
| 10 | const contentWidth = |
| 11 | element.clientWidth - pixels(style.paddingLeft) - pixels(style.paddingRight); |
| 12 | return contentWidth > UNMEASURABLE_WIDTH_PX; |
| 13 | } |
| 14 | |
| 15 | /** |
| 16 | * Measure whether a message body exceeds its collapsed preview. |
| 17 | * |
| 18 | * Returns null while the surrounding chat has no usable layout. Replay can be |
| 19 | * rendered in a hidden or zero-width staging tree, where ordinary text wraps |
| 20 | * once per character and would otherwise produce a false overflow result. |
| 21 | */ |
| 22 | export function measureMessageCollapseOverflow( |
| 23 | content, |
| 24 | { expanded = false, lazy = false } = {}, |
| 25 | ) { |
| 26 | if (lazy) return true; |
| 27 | if (!content?.isConnected) return null; |
| 28 | |
| 29 | const history = content.closest?.("#chat-history"); |
| 30 | if (history && !hasUsableContentWidth(history)) { |
| 31 | return null; |
| 32 | } |
| 33 | |
| 34 | const style = getComputedStyle(content); |
| 35 | if (!hasUsableContentWidth(content, style)) return null; |
| 36 | |
| 37 | const fontSize = Number.parseFloat(style.fontSize || "16") || 16; |
| 38 | const maxHeight = expanded |
| 39 | ? fontSize * COLLAPSE_MAX_HEIGHT_EM |
| 40 | : content.clientHeight; |
| 41 | |
| 42 | return content.scrollHeight > maxHeight; |
| 43 | } |