Multiple updates aimed at improving the Webview part of dump1090 #24
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Let the user control the json history by adjusting interval and size. Change the json history to be allocated on the heap instead of the stack as it's no longer static in size. Also change Webview history loading timeout to scale with the history size so it does not time out when using large history sizes.
The color of the plane track is changed according to its altitude. For every change a new OpenLayer Linestring object is created. Improve performance by only changing color if the altitude changed by more than 200 feet compared to the color being displayed. According to my eyes even 500 feet difference does not create a visible discontinuity in the color of the plane track. As the altitude readout varies slightly even if a plane is flying level this reduces the number of linestring objects quite a bit improving performance.
This actually improves performance as the updateTrack function is not carried out wrongly when there is no new position. Also due to this bug the other bug fixed appending the old position was never reached with the first bug still there.
Intermittent positions are displayed as estimated (dotted) track. The handling of that feature was confusing and differed significantly between history and live data. Clean it up so it works as intended.
The "tail" that is the latest fixed segment is set to the current position. Therefore tail_update needs to be set to the current time not head_update. head_update is updated whenever a new position is received but at the time of the assignment has not been yet assigned the new value. To compensate for the somewhat reduced frequency of positions being saved set the minimum time after which a new position is save to 4 seconds.
Relies on the airplanes providing correct ground track information. In case they do not they just get updated a little less often so that is acceptable. Most airplanes fly straight so decrease the frequency with which their positions are saved. For airplane with unkown track, MLAT aircraft and track changes < 1 degree keep the previous update interval. For >1 degree track changes update every 2 seconds to produce nice curves. Airplanes with constant track are updated every 16 seconds which should be sufficient and reduces overall lines in memory improving performance.
head_update saves the timestamp of the plane's current position in the linestring segments which makes no sense because the position is not always part of the linestring. Save it as part of the plane object and call it prev_position_time because it's used as the timestamp of the previous position of the airplane.
Whenever a point is appended to the current line segment, tail_update is updated. There is no reason this should stick around after moving on to the next segment, it is only used to decide if the current point is to be appended. For consistency add an append_time update when drawing estimated segments even if it's not needed.
Only draw the new state after the new point, don't assume the new state for the line to the previous point.
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So after some consideration replacing tail_update and head_update with some other name does not improve things. Detecting track_change seems to work in practice but i want it to be consistent so i need to change old_track only when changing append_time/tail_update. Up to commit 0b8f923 "Webview: fix append handling" i'm ok with this branch but after that it's no good. |
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I'm closing this pull request and will send a new one when i'm done cleaning the stuff up in a new branch. |
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I've written quite extensive commit logs, please feel free to squash them if they are too much.
The patch using the ground track to decide appending positions to the line segments might be a bit strange but it should work great in practice. At least it does for me. If "show all tracks" is on i can now move the map and scroll when before it was very slow.
The third patch commit log claims a performance improvement which is probably not measurable in practice, i'm not practiced in git enough to change it though.
Regards