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dart: Flutter web gives completely wrong results when decoding polyline #26
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i have same issue, is the problem have fix? |
I have not found a fix using this package. I have switched to a completely different method, specifically, calling a server of mine which is responsible for getting directions/polyline, using google maps, and communicating that result via http. Not my favourite work around, but it works well for my use case |
Sounds a bit like #52 |
The Dart Lib uses int in Dart for the equivalent of long in Java in https://github.com/heremaps/flexible-polyline/blob/master/dart/lib/converter.dart#L84 The issue is caused by Dart itself - as when code is compiled to JavaScript it loses Precision. You need to use precision 5 or need to use the JavaScript lib (Gist with BigInt lib) for decoding instead as recommended here: #52 (comment) |
Theoretically a base-10 big-int would be relatively easy to implement, since the only operations needed are:
At precision 15 we need log2(360 * 10^15) + 1 = 60 bits. That means that if you were to use Dart's 53 bit type only 2 variables are enough. You could e.g. work with 10^9 per variable (31 bits if signed). Addition would only need to take care of the carry (there's enough space to avoid overflow), and division by a power of ten shifts down the remainder (the equivalent of a bit-shift in base-2). This approach could work for JS as well, and might be noticeably faster than base-2 BigInteger generic size BigInt library. What do you think @moo24 / @haifeng2013 ? |
Decoding polylines on flutter web is completely wrong.
Using the provided example from https://pub.dev/packages/flexible_polyline, running on android works just fine and prints out the expected results
results in the following on android/ios
But running the exact same code with flutter web gives the following:
The first address is correct, but subsequent addresses 2-4 are very large
If there are any additional params/options available that fix the decoding scheme based on web vs mobile, that would be an acceptable workaround until a better solution can be found
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