scheduleRunTransitionAnimations method

void scheduleRunTransitionAnimations(String propertyName, String? prevValue, String currentValue)

Implementation

void scheduleRunTransitionAnimations(String propertyName, String? prevValue, String currentValue) {
  if (DebugFlags.shouldLogTransitionForProp(propertyName)) {
    cssLogger.info('[transition][queue] ${tagName}.$propertyName prev=${prevValue ?? 'null'} -> curr=$currentValue');
  }
  if (_pendingTransitionProps.contains(propertyName)) {
    // Already scheduled this property in current frame; coalesce by updating
    // the pending item's current (end) value so we run once with the latest
    // destination. For color properties, prefer the most recent, fully
    // resolved previous value (from computed style) instead of the earlier
    // raw serialized text (which may still contain var(...)).
    for (int i = _pendingTransitionQueue.length - 1; i >= 0; i--) {
      final item = _pendingTransitionQueue[i];
      if (item.property == propertyName) {
        String? mergedPrev = item.prev;
        // Color-bearing properties where we want the last, concrete
        // previous value (e.g., 'rgb(...)' or 'rgba(...)') to win
        // over earlier var(...) strings like 'rgb(... / null)'.
        final bool isColorProp = propertyName == COLOR ||
            propertyName == BACKGROUND_COLOR ||
            propertyName == TEXT_DECORATION_COLOR ||
            propertyName == BORDER_LEFT_COLOR ||
            propertyName == BORDER_TOP_COLOR ||
            propertyName == BORDER_RIGHT_COLOR ||
            propertyName == BORDER_BOTTOM_COLOR;
        if (isColorProp && prevValue != null && prevValue.isNotEmpty) {
          mergedPrev = prevValue;
        }
        _pendingTransitionQueue[i] = (property: propertyName, prev: mergedPrev, curr: currentValue);
        if (DebugFlags.shouldLogTransitionForProp(propertyName)) {
          cssLogger.info('[transition][queue] coalesce property=$propertyName prevOld=${item.prev ?? 'null'} prevNew=${prevValue ?? 'null'} mergedPrev=${mergedPrev ?? 'null'} new-curr=$currentValue');
        }

        break;
      }
    }
    return;
  }
  _pendingTransitionProps.add(propertyName);
  _pendingTransitionQueue.add((property: propertyName, prev: prevValue, curr: currentValue));

  if (_queuedTransitionBatch) return;
  _queuedTransitionBatch = true;
  SchedulerBinding.instance.addPostFrameCallback((_) {
    // Drain queue in insertion order so related properties (e.g., width, left, transform)
    // start in the same frame, improving sync.
    final items = List<({String property, String? prev, String curr})>.from(_pendingTransitionQueue);
    _pendingTransitionQueue.clear();
    _queuedTransitionBatch = false;
    for (final item in items) {
    if (DebugFlags.shouldLogTransitionForProp(item.property)) {
      cssLogger.info('[transition][drain] run property=${item.property} prev=${item.prev ?? 'null'} curr=${item.curr}');
    }
    renderStyle.runTransition(item.property, item.prev, item.curr);
    _pendingTransitionProps.remove(item.property);
    }
  });
  SchedulerBinding.instance.scheduleFrame();
}