https://bugs.freedesktop.org/show_bug.cgi?id=85847
Bug ID: 85847
Summary: android: Implement layers of tiles instead of a huge
background image
Product: LibreOffice
Version: 4.4.0.0.alpha0+ Master
Hardware: Other
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: Libreoffice
Assignee: [email protected]
Reporter: [email protected]
At the moment, we use one large background image for the user to see where
about he/she is in the document. This has 2 problems, especially with large
documents:
* The entire document has to be rendered on startup, which eats terrible amount
of time
* The bitmap has so bad resolution, that it looks confusing, and is mostly
unusable.
Instead of one large bitmap, we need several layers that contain tiles of lower
and lower resolution.
Layer 1: The tiles at 1:1 zoom
Layer 2: Tiles at 1:4
Layer 3: Tiles at 1:16
Layer 4: Tiles at 1:64
Layer 5: Tiles at 1:256
...
Layer X: Just 1 tile at 1:4^(X-1)
This is not a huge amount of tiles - we are not supposed to keep all of them,
we can throw away the ones on X-1 layers variously, as in bug 85846.
On startup, the layers should be filled in this way:
* First Layer 1 - the tiles that intersect the visible area (so that the user
gets the view as the first thing).
* Then the some higher layer, like Layer 3, again only the tiles that intersect
the visible area + one tile before + one tile after (so that the scrolling
immediately gives ~something)
* Then (when idle) the higher layers, up to Layer X - so that there is always
something to render, without having to fetch it first
On scroll, always present the highest quality - can happen to be a combination
of various layers, combining the worse and better quality; but fetch the best
ones accordingly.
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