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Sudden disappearing / "blinking" of POI icons #2318

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opened 2022-03-30 07:53:04 +00:00 by AntonM030481 · 6 comments

AntonM030481 commented

2022-03-30 07:53:04 +00:00

(Migrated from github.com)

The same here:
om://8yxfv6swqu/C_Roushas_%26_Co.
During zoom-out "C Roushas..." disappears.
Maybe because of bar "Rolla..." and its text.

For some reason some icons on map disappear. E.g. om://8yx1FR-URb/Maria_Efthimiou During zoom-out Pharmacy "Maria..." icon disappears. Maybe because of bar "Quotes..." and its text. General rule is to prioritise icons compared to text, right? The same here: om://8yxfv6swqu/C_Roushas_%26_Co. During zoom-out "C Roushas..." disappears. Maybe because of bar "Rolla..." and its text.

biodranik commented

2022-03-30 09:15:33 +00:00

(Migrated from github.com)

There are some priority rules for features. What is the expected behavior? Can you please provide screenshots to compare?

AntonM030481 commented

2022-03-30 11:32:58 +00:00

(Migrated from github.com)

In fact, it's even more strange.

Normal state. Bar and pharmacy are visible:
Zoom-out. Bar is visible (with name), but no pharmacy:
Zoom-out more. No bar, but pharmacy is visible again! (without name)

In fact, it's even more strange. 1. Normal state. Bar and pharmacy are visible: ![image](https://user-images.githubusercontent.com/85622715/160824897-07bcf647-29dc-4789-95b6-3ff6cd7f2273.png) 2. Zoom-out. Bar is visible (with name), but no pharmacy: ![image](https://user-images.githubusercontent.com/85622715/160824564-a793b19a-7cbc-4d76-83b4-3e66528686b9.png) 3. Zoom-out more. No bar, but pharmacy is visible again! (without name) ![image](https://user-images.githubusercontent.com/85622715/160824793-4d9a0089-4c33-4b2f-ba29-c0ac3d377234.png)

AntonM030481 commented

2022-03-30 11:51:04 +00:00

(Migrated from github.com)

Expected behaviour (for icons and names).
Draw order (don't draw if intersected with already drawn items):

Top priority icon
... other icons ...
Bottom priority icon
Top priority name
... other names ...
Bottom priority name

Expected behaviour (for icons and names). Draw order (don't draw if intersected with already drawn items): - Top priority icon - ... other icons ... - Bottom priority icon - Top priority name - ... other names ... - Bottom priority name

pastk commented

2022-03-30 11:59:22 +00:00

Owner

A bar has a lower z-index priority compared a pharmacy.
A bar is displayed starting at z15, a pharmacy - from z16.

But it doesn't quite explain the observed behavior, right? :)
ATM OM lacks continuity in displaying features at different zoom levels indeed.

My guess (I didn't see the code yet) is that the z-index is not respected by the algo which chooses which POIs to omit from the display. Probably z-index is used only to determine which type to display when there are multiple types at the same node.

Update: actually a bar is taking priority over pharmacy because the algo prefers POIs with lowest minZoomLevel first and only after that ranks by z-index

A bar has a lower z-index priority compared a pharmacy. A bar is displayed starting at z15, a pharmacy - from z16. But it doesn't quite explain the observed behavior, right? :) ATM OM lacks continuity in displaying features at different zoom levels indeed. My guess (I didn't see the code yet) is that the z-index is not respected by the algo which chooses which POIs to omit from the display. Probably z-index is used only to determine which type to display when there are multiple types at the same node. Update: actually a bar is taking priority over pharmacy because the algo prefers POIs with lowest minZoomLevel first and only after that ranks by z-index

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AntonM030481 commented

2022-03-31 13:53:56 +00:00

(Migrated from github.com)

From user point of view I expect following (according to the screens above):

OK (all visible)
Bar icon is visible, but no name (because of pharmacy icon has more priority over any name). Pharmacy icon and name are visible.
OK (only pharmacy icon is visible because of higher priority).
As a general rule: names of POI always have lower priorities compared to any icons

From user point of view I expect following (according to the screens above): 1. OK (all visible) 2. Bar icon is visible, but no name (because of pharmacy icon has more priority over any name). Pharmacy icon and name are visible. 3. OK (only pharmacy icon is visible because of higher priority). As a general rule: names of POI always have lower priorities compared to any icons

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pastk commented

2022-04-02 17:49:32 +00:00

Owner

And here is why at lower zooms a pharmacy only is displayed and no bar (though it has a higher priority considering its minVisibleScale):

closely placed POIs that likely to "cover" each other are omitted from the scale index at the map generation stage (see displacement_manager.hpp::Displace() which is used in scale_index_builder.hpp::IndexScales()), which makes perfect sense as an optimization, but the issue it uses different POIs priority calculation compared to the runtime POI displacement code, namely the scale index code doesn't use minVisibleScale, but only a z-index derived priority. Hence the pharmacy displaces the bar from the scale index at lower zoom levels and the bar is not rendered.

At higher zoom levels the bar appears in the scale index and contests pharmacy for the screen space and wins because it has a higher priority (which includes minVisibleScale now). At even higher zoom levels the pharmacy is displayed again because there is enough space for both POIs.

Hence the pharmacy "blinks" while zooming in/out which is quite annoying and ruins UX.

The fix is to make scale index displacement code use the same priority calculation as runtime code (i.e. include minVisibleScale into the mix).

Related to another POI priorities issue #2332

And here is why at lower zooms a pharmacy only is displayed and no bar (though it has a higher priority considering its minVisibleScale): closely placed POIs that likely to "cover" each other are omitted from the scale index at the map generation stage (see `displacement_manager.hpp::Displace()` which is used in `scale_index_builder.hpp::IndexScales()`), which makes perfect sense as an optimization, but the issue it uses different POIs priority calculation compared to the runtime POI displacement code, namely the scale index code doesn't use minVisibleScale, but only a z-index derived priority. Hence the pharmacy displaces the bar from the scale index at lower zoom levels and the bar is not rendered. At higher zoom levels the bar appears in the scale index and contests pharmacy for the screen space and wins because it has a higher priority (which includes minVisibleScale now). At even higher zoom levels the pharmacy is displayed again because there is enough space for both POIs. Hence the pharmacy "blinks" while zooming in/out which is quite annoying and ruins UX. The fix is to make scale index displacement code use the same priority calculation as runtime code (i.e. include minVisibleScale into the mix). Related to another POI priorities issue #2332

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