This most importantly gets rid of a chain of "String to DeprecatedString
to String" transformations when setting a tooltip from GUI::Widget's
set_tooltip function.
Previously, we would divide the widget width and height by the tile size
and round up, which did not result in enough tiles to cover the entire
widget. Although this calculation is correct if you starting drawing
tiles in the top left corner, we have an additional offset to account
for.
Now, we take the number of tiles that fit in the widget completely and
pad it with 2 tiles to account for the partial left/right and top/bottom
sides. An additional tile is added to account for the iterator
translating by width / 2, which rounds down again.
The resulting tile rects are always intersected with the widget
dimensions, so even if we're generating more tile coordinates than
strictly necessary, we're not performing the actual download or draw
operations.
The `operator++` of the spiraling tile iterator was repeating the first
coordinates (`0, 0`) instead of moving to the next tile on the first
iteration. Swapping the move and check ensures we get to the end of the
iterator, fixing gray tiles that would sometimes pop up in the lower
right.
Since we never return from `operator++` without setting a valid
position, we can drop `current_x` and `current_y` and just use the
`Gfx::Point<T>` directly.
Since we divide the width and height of the downscaled tiles by 2,
bilinear blending is identical to box sampling and should be preferred
since it's the simpler one of the two algorithms.
The information the user is most interested in is usually in the center,
so we should start loading tiles from the center and move outwards.
Since tiles are loaded in draw order, simply drawing them in this order
achieves the desired effect. The current center-outwards loading
algorithm is a basic spiral algorithm, but others may be evaluated
later.
When zooming in or out, if a tile is not yet cached, Maps now also
checks the lower and higher zoom levels for cached tiles and composites
a preview tile that is shown until the actual tile is loaded in.
Previously we would bombard RequestServer with as many requests as it
would take, but when frantically zooming in and out, we would run out of
fd's causing the Maps application to hang.
This implements a tile download queue and limits the amount of parallel
downloads to 8. This fixes the hangs accompanied by this debug console
message:
Peer endpoint error: recvfd: Too many open files (errno=24)
It does not fix other sporadic hangs caused by requests that are never
finished, however.
