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Center-priority load #61

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102 changes: 56 additions & 46 deletions polymaps.js
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Original file line number Diff line number Diff line change
Expand Up @@ -840,7 +840,11 @@ po.layer = function(load, unload) {
oldLocks[key].proxyCount = 0;
}

// load the tiles!
// determine visible tiles
var visibleTiles = [];
var z = c0.zoom,
z0 = 2 - tileLevel,
z1 = 4 + tileLevel;
if (visible && tileLevel > -5 && tileLevel < 3) {
var ymax = c0.zoom < 0 ? 1 : 1 << c0.zoom;
if (tile) {
Expand All @@ -855,60 +859,66 @@ po.layer = function(load, unload) {
scanLine(x, x + 1, y);
}
}

// scan-line conversion
function scanLine(x0, x1, y) {
var z = c0.zoom,
z0 = 2 - tileLevel,
z1 = 4 + tileLevel;

for (var x = x0; x < x1; x++) {
var t = cache.load({column: x, row: y, zoom: z}, projection);
if (!t.ready && !(t.key in newLocks)) {
t.proxyRefs = {};
var c, full, proxy;

// downsample high-resolution tiles
for (var dz = 1; dz <= z0; dz++) {
full = true;
for (var dy = 0, k = 1 << dz; dy <= k; dy++) {
for (var dx = 0; dx <= k; dx++) {
proxy = cache.peek(c = {
column: (x << dz) + dx,
row: (y << dz) + dy,
zoom: z + dz
});
if (proxy && proxy.ready) {
newLocks[proxy.key] = cache.load(c);
proxy.proxyCount++;
t.proxyRefs[proxy.key] = proxy;
} else {
full = false;
}
}
}
if (full) break;
}

// upsample low-resolution tiles
if (!full) {
for (var dz = 1; dz <= z1; dz++) {
visibleTiles.push({column: x, row: y, zoom: z});
}
}

// load the tiles, from tileCenter in order of taxicab distance
visibleTiles.sort(function (infoA, infoB) {
var dA = Math.abs(infoA.row - tileCenter.row) + Math.abs(infoA.column - tileCenter.column);
var dB = Math.abs(infoB.row - tileCenter.row) + Math.abs(infoB.column - tileCenter.column);
return dA - dB;
});
for (var tileIdx = 0, tilesLen = visibleTiles.length; tileIdx < tilesLen; tileIdx++) {
var tileInfo = visibleTiles[tileIdx],
t = cache.load(tileInfo, projection);
if (!t.ready && !(t.key in newLocks)) {
var x = tileInfo.column, y = tileInfo.row;
t.proxyRefs = {};
var c, full, proxy;

// downsample high-resolution tiles
for (var dz = 1; dz <= z0; dz++) {
full = true;
for (var dy = 0, k = 1 << dz; dy <= k; dy++) {
for (var dx = 0; dx <= k; dx++) {
proxy = cache.peek(c = {
column: x >> dz,
row: y >> dz,
zoom: z - dz
column: (x << dz) + dx,
row: (y << dz) + dy,
zoom: z + dz
});
if (proxy && proxy.ready) {
newLocks[proxy.key] = cache.load(c);
proxy.proxyCount++;
t.proxyRefs[proxy.key] = proxy;
break;
} else {
full = false;
}
}
}
if (full) break;
}

// upsample low-resolution tiles
if (!full) {
for (var dz = 1; dz <= z1; dz++) {
proxy = cache.peek(c = {
column: x >> dz,
row: y >> dz,
zoom: z - dz
});
if (proxy && proxy.ready) {
newLocks[proxy.key] = cache.load(c);
proxy.proxyCount++;
t.proxyRefs[proxy.key] = proxy;
break;
}
}
}
newLocks[t.key] = t;
}
newLocks[t.key] = t;
}

// position tiles
Expand Down Expand Up @@ -1763,10 +1773,9 @@ po.hash = function() {
lat = 90 - 1e-8, // allowable latitude range
map;

var parser = function(s) {
var parser = function(map, s) {
var args = s.split("/").map(Number);
if (args.length < 3 || args.some(isNaN))
move(); // replace bogus hash
if (args.length < 3 || args.some(isNaN)) return true; // replace bogus hash
else {
var size = map.size();
map.zoomBy(args[0] - map.zoom(),
Expand All @@ -1791,7 +1800,8 @@ po.hash = function() {

function hashchange() {
if (location.hash === s0) return; // ignore spurious hashchange events
parser((s0 = location.hash).substring(1));
if (parser(map, (s0 = location.hash).substring(1)))
move(); // replace bogus hash
}

hash.map = function(x) {
Expand Down
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