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Add panBuffer feature to include extended tilerange #1405

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merged 3 commits into from
Dec 21, 2022
Merged

Add panBuffer feature to include extended tilerange #1405

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ff86039
formatting
ibrierley Nov 14, 2022
9b56848
added if statement to avoid unneeded work if panBuffer is 0
ibrierley Nov 15, 2022
0d1fde7
added panBuffer to tileBuilder example
ibrierley Nov 15, 2022
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21 changes: 20 additions & 1 deletion lib/src/layer/tile_layer/tile_layer.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -138,6 +138,12 @@ class TileLayer extends StatefulWidget {
/// unloading them.
final int keepBuffer;

/// When panning the map, extend the tilerange by this many tiles in each
/// direction.
/// Will cause extra tile loads, and impact performance.
/// Be careful increasing this beyond 0 or 1.
final int panBuffer;

/// Tile image to show in place of the tile that failed to load.
final ImageProvider? errorImage;

Expand Down Expand Up @@ -254,6 +260,7 @@ class TileLayer extends StatefulWidget {
Map<String, String>? additionalOptions,
this.subdomains = const <String>[],
this.keepBuffer = 2,
this.panBuffer = 0,
this.backgroundColor = const Color(0xFFE0E0E0),
this.errorImage,
TileProvider? tileProvider,
Expand Down Expand Up @@ -584,7 +591,19 @@ class _TileLayerState extends State<TileLayer> with TickerProviderStateMixin {
center ??= map.center;

final pixelBounds = _getTiledPixelBounds(map, center);
final tileRange = _pxBoundsToTileRange(pixelBounds);
Bounds tileRange = _pxBoundsToTileRange(pixelBounds);

final panBuffer = widget.panBuffer;

// Increase the tilerange if we have panBuffer set, but make sure we
// don't use values outside valid tiles, eg (0,-1).
tileRange = tileRange.extend(CustomPoint(
math.max(_globalTileRange.min.x, tileRange.min.x - panBuffer),
math.max(_globalTileRange.min.y, tileRange.min.y - panBuffer)));
tileRange = tileRange.extend(CustomPoint(
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We could use a condition if (panBuffer > 0) to avoid unecessary computation on tileRange 🤔
Otherwise the code looks good to me

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Yes, I think I like that, every little helps!

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Ok, have added an if( panBuffer != 0), maybe it should be > 0, but maybe there is some weird reason for someone to reduce it as well that I can't think of (although maybe there could be bugs if they did that, but there is a bit of caveat emptor or whatever it is)!

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Was thinking about it too but I supposed that it wouldn't make sense to buffer -1 tiles 🤔

math.min(_globalTileRange.max.x, tileRange.max.x + panBuffer),
math.min(_globalTileRange.max.y, tileRange.max.y + panBuffer)));

final tileCenter = tileRange.center;
final queue = <Coords<double>>[];
final margin = widget.keepBuffer;
Expand Down