simplex-chat/plans/2026-05-08-fix-select-in-reports.md

Fix copying selected text in reports

PR: #6863 · branch nd/fix-select-in-reports · final commit 96d6f3222

1. Problem statement

Report items in desktop render as a red italic reason prefix followed by the user's comment, e.g. Spam: hi @alice. The user reported that selecting Spam: test and pressing Ctrl-C / clicking the copy button placed only test on the clipboard — the Spam: prefix was silently dropped. Selecting only the prefix produced an empty clipboard.

A second symptom existed for any report whose comment contained a transformed segment (mention with localAlias, link with showText): dragging a selection boundary inside that segment snapped to the wrong character on release, then copy emitted the wrong text.

Both symptoms have a single cause and the bug is desktop-only because the touch UI does not use this selection path.

2. Solution summary

MarkdownText builds the on-screen AnnotatedString as [prefix][body] (one composable, one layout). Compose's layout.getOffsetForPosition(...) therefore returns selection offsets in display-text space, which includes the prefix. Pre-PR, selectedItemCopiedText and snapOffset walked ci.formattedText from displayOffset = 0 — i.e. they treated those offsets as prefix-excluded body offsets. Every offset for a report was off by prefix.length.

The fix is one structural realisation: the prefix is the leading display-space segment, so the loop that walks ci.formattedText must start at displayOffset = prefix.length, and any portion of the selection that falls in [0, prefix.length) must be emitted by appending a slice of the prefix string before the loop runs.

To prevent the same silent decoupling from re-emerging, the prefix string itself is extracted into a single source of truth — itemPrefixText(ci) — used by every call site that either renders or measures the prefix.

3. Detailed tech design

3.1 Where the offsets come from

Compose layout
  └─> SelectableText / ClickableText (TextItemView.kt)
       └─> getOffsetForPosition(localPos)   // returns display-space offset
              └─> SelectionManager.setAnchorOffset / updateFocusOffset
                     └─> selectedRange(...) → IntRange in display space
                            └─> selectedItemCopiedText(ci, sel, linkMode)   // FIX site #1
                            └─> snapOffset(ci, off, linkMode, expandRight)  // FIX site #2

MarkdownText (TextItemView.kt) builds the AnnotatedString in this order:

inlineContent                — never present for report items
appendSender(...)            — null for the CIMarkdownText path
prefix (AnnotatedString)     — "${reason}: " for reports, null otherwise
text / formatted segments    — the body
typingIndicator (live only)  — past selectableEnd
reserve (timestamp space)    — past selectableEnd

For non-report items the prefix is null and the existing identity displayOffset = 0 holds. For reports, the body's first character lives at display offset prefix.length.

3.2 The minimal structural change

Pre-PR loop:

var displayOffset = 0
for (ft in formattedText) {
    val segDisplay = itemSegmentDisplayText(ft, ci, linkMode)
    val displayEnd = displayOffset + segDisplay.length
    val overlapStart = maxOf(displayOffset, sel.first)
    val overlapEnd = minOf(displayEnd, sel.last + 1)
    if (overlapStart < overlapEnd) { /* emit */ }
    displayOffset = displayEnd
}

Two changes only:

1. Seed with prefix length. var displayOffset = prefix.length (or itemPrefixText(ci).length for snapOffset). Loop body is otherwise byte-for-byte identical to pre-PR. For non-reports prefix.length == 0, so the non-report path is unchanged.

2. Emit the prefix slice. Before the loop, append the portion of prefix covered by the selection:

   if (sel.first < prefix.length) {
       sb.append(prefix, sel.first, minOf(prefix.length, sel.last + 1))
   }
   

   selectedRange() guarantees sel.first ≥ 0, so no clamping is needed at this site.

3. Handle the formattedText == null branch. Reports with empty body have null formattedText, but the prefix selection still has to be returned. The early-return in the pre-PR null branch is replaced by the same StringBuilder path so prefix-only selections work:

   val formattedText = ci.formattedText ?: run {
       val start = (sel.first - prefix.length).coerceAtLeast(0).coerceAtMost(ci.text.length)
       val end = (sel.last + 1 - prefix.length).coerceAtMost(ci.text.length)
       if (start < end) sb.append(ci.text, start, end)
       return sb.toString()
   }
   

   coerceAtLeast(0) on start is required here because sel.first - prefix.length is negative when the selection lies entirely inside the prefix.

3.3 Single source of truth

Pre-PR, the prefix expression if (mc.text.isEmpty()) mc.reason.text else "${mc.reason.text}: " lived inline at two render sites:

• FramedItemView.kt:368 — the actual report row
• ChatPreviewView.kt:262 — the chat list preview

Re-introducing it inline in TextSelection.kt would have re-created exactly the silent coupling that produced the bug — a future change to the separator (e.g. localised colon) at the renderer would silently break copy/snap. The fix factors the expression into:

// TextItemView.kt
fun itemPrefixText(ci: ChatItem): String = when (val mc = ci.content.msgContent) {
  is MsgContent.MCReport -> if (mc.text.isEmpty()) mc.reason.text else "${mc.reason.text}: "
  else -> ""
}

Both renderers and both selection-side functions now derive the string from this one definition.

3.4 Edge cases verified

Case	Pre-PR	Post-PR
Non-report, fmt non-null (markdown)	works	byte-identical loop, works
Non-report, fmt null (plain text)	substring fast path	StringBuilder path, value-equivalent
Non-report, sel out of bounds	clamped to [L, L] → ""	same
Report, full sel Spam: test	returns test (BUG)	returns Spam: test
Report, prefix-only sel	returns "" (BUG)	returns prefix slice
Report, body-only sel	returns body (offset shift was hidden by Int.MAX_VALUE clamp at sel.last+1)	returns body
Report, sel.first == prefix.length	works coincidentally	works
Report, empty body, prefix-only sel	returns ""	returns prefix
Report with mention having localAlias (transformed)	snap snapped to wrong char (BUG)	snaps correctly
Multi-item interior sel (sel.last = MAX-1)	works	no overflow on +1 - prefix.length

3.5 What was deliberately not done

• Performance restoration of the non-report null-fmt path. Pre-PR returned ci.text.substring(...) directly (1 allocation). Post-PR uses StringBuilder (3 allocations). selectedItemCopiedText runs once per selected item per copy action — never on a hot path. Restoring the pre-PR fast path with an if (prefix.isEmpty() && formattedText == null) early return adds 4 lines of branching for negligible gain. Not worth it.

• Migrating ChatPreviewView.kt was kept because it crossed the 3-site extraction threshold (FramedItemView + ChatPreviewView + 2× TextSelection) and the bug we are fixing is exactly the failure mode of duplicating this expression. ChatPreviewView is not a selection site, so no behaviour change — it shifts to the same single source of truth.

4. Detailed implementation plan

4.1 Files touched (final state)

File	Δ	Purpose
apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/chat/item/TextItemView.kt	+7 / 0	new itemPrefixText(ci) helper next to itemDisplayText
apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/chat/item/FramedItemView.kt	+1 / −1	report branch delegates to itemPrefixText(ci)
apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/chatlist/ChatPreviewView.kt	+2 / −2	preview row delegates; drops unused val mc =
apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/views/chat/TextSelection.kt	+16 / −8	the actual fix in selectedItemCopiedText and snapOffset, plus import

Total: 4 files, +26 / −11.

4.2 Step-by-step (final commit 96d6f3222)

1. Add itemPrefixText(ci) in TextItemView.kt next to itemDisplayText / itemSegmentDisplayText. Returns "" for non-reports.

2. FramedItemView.kt:365-372 (MCReport branch): replace inline expression with append(itemPrefixText(ci)). The surrounding withStyle(SpanStyle(color = Red, italic)) is preserved — visual rendering unchanged.

3. ChatPreviewView.kt:258-264: replace inline expression with append(itemPrefixText(ci)). Drop the now-unused val mc = from when (val mc = ci.content.msgContent) (the discriminator becomes when (ci.content.msgContent)).

4. TextSelection.kt:

   • Add import chat.simplex.common.views.chat.item.itemPrefixText.
   • In selectedItemCopiedText:
     • Compute val prefix = itemPrefixText(ci) and val sb = StringBuilder() first.
     • Emit prefix slice if sel.first < prefix.length.
     • Modify the formattedText ?: ... early-return to a ?: run { … } block that adds the body slice (offsets shifted by -prefix.length, clamped) to sb and returns sb.toString().
     • Seed the formattedText loop with var displayOffset = prefix.length. Loop body unchanged.
   • In snapOffset: change var displayOffset = 0 to var displayOffset = itemPrefixText(ci).length. Loop body unchanged.
   • Update the docstring on selectedItemCopiedText to note that display-text space includes any leading itemPrefixText.

4.3 Verification

• ./gradlew :common:compileKotlinDesktop — passes (warnings are pre-existing).
• bash /home/user/build/linux.sh — full Linux x86_64 AppImage produced (SimpleX_Chat-x86_64-fix-select-in-reports.AppImage).
• Manual test plan, all in desktop:
  1. Open a chat with a report whose rendered form is Spam: test. Select across the whole line + Ctrl-C → clipboard reads Spam: test.
  2. Select only the red prefix → clipboard reads the prefix.
  3. Select only the comment → clipboard reads the comment.
  4. Report comment containing @alice (Bob) (mention with localAlias). Drag a selection boundary into the mention → on release, highlight snaps to mention boundaries.
  5. Plain (non-report) messages: full-line, partial, mention, link selections — clipboard contents unchanged from pre-PR.
  6. Multi-item selection across non-report and report rows — prefixes appear inline at the correct positions.

4.4 Risk and rollback

• Blast radius is the desktop selection-copy code path. iOS / Android use separate selection mechanisms and are unaffected.
• The non-report selection path's inner loop body is byte-for-byte identical to pre-PR (the displayOffset = 0 initialisation is unchanged when prefix.length == 0), so regressions on non-reports would require the prefix expression itself to fail — which is impossible because itemPrefixText returns "" for any msgContent other than MCReport.
• Rollback is git revert 96d6f3222 e97dd7bf4 6aacfa4d2 (three commits) and a force-push, restoring the pre-PR copy behaviour with the original bug.

5. Why this specific shape

• Recognising the prefix as the first display-space segment turns the bug into a one-line seed change. No special-cased report branch in copy/snap; the existing loop handles both.
• The inner loop of selectedItemCopiedText and snapOffset is byte-for-byte identical to pre-PR. Only the seed value of displayOffset and the pre-/post-amble change.
• Four sites need the prefix string (FramedItemView, ChatPreviewView, and two in TextSelection). itemPrefixText becomes their single point of change, closing the silent-coupling gap that produced the bug.
• selectedRange() guarantees sel.first ≥ 0, so no coerceAtLeast(0) is added at the prefix-slice append. The one coerceAtLeast(0) that survives (on the formattedText == null body branch) is reachable when the selection lies entirely inside the prefix and is needed.
• Final PR is 4 files, +26 / −11. The inner loop body changes by zero lines.