1001397 - Generalize parts of TopSitesCursorWrapper into a MultiCursorWrapper base class

Status: RESOLVED INCOMPLETE

(Firefox for Android Graveyard :: Awesomescreen, defect)

Description

[Lucas Rocha (:lucasr)]

So that we can use similar features in other contexts e.g. search UI with asynchronous queries coming from different sources.

Comment 1

[Wesley Johnston (:wesj)]

In my ideal world we'd make this cursor implement "List<Cursor>", although that's overkill I'll admit. I imagined we'll probably need a special interface (SuperCursor I call it) that can (optionally) provide some extra info/special behavior here:

interface SuperCursor {
  boolean hasEntryAt(int position); // For instance, pinned sites might be 6 long,
                                    // but some rows are empty
  int updateCount(int prevCount);   // Needed if we want to make the empty entries a cursor?
  // FUTURE: Do we need a way to rank results here...
  // or does the multicursor do the ranking (based on if something is in history?
}

Cursor emptySites = new EmptySuperCursor(pinnedSites, MAX_SIZE); 
Cursor suggestedSites = new SuggestedSuperCursor(pinnedSites, MAX_SIZE);
Cursor pinnedSites = new PinnedSuperCursor(pinnedSites, MAX_SIZE);
MultiCursor mc = new MultiCursor(pinnedSites, topSites, suggestedSites, emptySites);

class MultiCursor {
  List<Cursor> cursors;
  List<Map<Int, Int>> indiciesMap; // optimization cache mapping columns between
                                   // this cursor and the individual interior cursors 

  // Haven't thought about this all that much, but a rough sketch
  boolean moveTo(int position) {
    int realPosition = position;
    for (int i = 0; i < cursors.length; i++) {
      Cursor c = cursors[i];

      // If this cursor is all used, just remove all its entries...
      if (c.length > realPosition) {
        realPosition -= c.length; // SuperCursors might have a different "real" length?
        continue;
      }

      if (c instanceof SuperCursor) {
         if (c.hasEntryAt(realPosition)) {
           c.moveTo(realPosition);
           continue;
         }
         realPosition -= c.getPosition();
      } else {
        c.moveTo(realPosition);
      }
    }
  }
}

There's probably other methods that would need special work...

Comment 2

[Eric Edens [:eedens]]

Back into the pool...

Comment 3

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