As the SpriteCache is used as a one-shot operation in practise, holding on to the capacity of backing collections is not required. Memory usage can be reduced by allowing the capacity to be reset after the SpriteCache has resolved items.
- Once LoadReservations is called, reset the reservation dictionaries so their backing collections can be reclaimed.
- When ResolveSprites is called, shrink the resolved dictionary as resolutions take place.
In a3d0a50f4d, SpriteCache is updated to sort sprites by height before adding them onto the sheet. This improves packing by reducing wasted space as the sprites are packed onto the sheet. D2kSpriteSequence does not fully benefit from this change, as it creates additional sprites afterwards in the ResolveSprites method. These are not sorted, so they often waste space due to height changes between adjacent sprites and cause an inefficient packing. Sorting them in place is insufficient, as each sequence performs the operation independently. So sets of sprites across different sequences end up with poor packing overall. We need all the sprites to be collected together and sorted in one place for best effect.
We restructure SpriteCache to allow a frame mutation function to be provided when reserving sprites. This removes the need for the ReserveFrames and ResolveFrames methods in SpriteCache. D2kSpriteSequence can use this new function to pass in the required modification, and no longer has to add frames to the sheet builder itself. Now the SpriteCache can apply the desired frame mutations, it can batch together these mutated frames with the other frames and sort them all as a single batch. With all frames sorted together the maximum benefit of this packing approach is realised.
This reduces the number of BGRA sheets required for the d2k mod from 3 to 2.
When sheet builders are adding sprites to a sheet, they work left to right along each row. They reserve height for the highest sprite seen along that row, resetting the height reservation when the row runs out of space and it moves down to the next row.
As the SpriteCache adds the sprites in a giant batch, it can optimise this operation by ordering the sprites by their height. This reduces wastage where shorter sprites don't use the the full height reserved within the row. The reduced wastage can help the sheet builder allocate fewer sheets, improving load times and improving GPU memory usage as less texture memory is required.
Multiple layers of Lazy<T>ness are replaced with
an explicit two-part loading scheme.
Sequences are parsed immediately, without the need
for the sprite assets, and tell the SpriteCache
which frames they need. Use-cases that want the
actual sprites can then tell the SpriteCache to
load the frames and the sequences to resolve the
sprites.
