Shared object cache

Cache for sharing glyphs, icons, cursors across clients. Lets clients share identical objects. The cache is a global object, advertised at connect time.

Interface cache

Requests

upload(key, visual, bo, stride, width, height)

Events

item(key, bo, x, y, stride)

retire(bo)

• Upload by passing a visual, bo, stride, width, height to the cache.

• Upload returns a bo name, stride, and x, y location of object in the buffer. Clients take a reference on the atlas bo.

• Shared objects are refcounted, freed by client (when purging glyphs from the local cache) or when a client exits.

• Server can't delete individual items from an atlas, but it can throw out an entire atlas bo if it becomes too sparse. The server sends out an retire event when this happens, and clients must throw away any objects from that bo and reupload. Between the server dropping the atlas and the client receiving the retire event, clients can still legally use the old atlas since they have a ref on the bo.

• cairo needs to hook into the glyph cache, and maybe also a way to create a read-only surface based on an object form the cache (icons).

  cairo_wayland_create_cached_surface(surface-data).