Use Case: Static maps

[prushforth]

This issue is for discussion of the use case “Display a region of map data as a static image”, its examples & list of required capabilities.

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Ironically, sometimes an HTML author wants to provide a simple static map that provides some other mappiness (a pushpin or two, for example). It would be good to be able to 'freeze' a map at a location, perhaps using a CSS property, or possibly, though not preferably, an attribute. Being a map, it would still be "georeferenced" for crawlers' sake only, perhaps. But it could use back-end services like WMS or tile caches to provide visual and non-visual semantic context.

[cmhodgson]

This is typically achieved in existing frameworks by not adding pan and zoom controls to the map. These controls are often added by default to the map and have to be actively disabled. The mechanic in use then is not that the map is "frozen", just that the map has an initial location and zoom level, and the user has no way to change those if no pan or zoom controls are offered.

[prushforth]

So its the pan and zoom controls presence that enables drag-to-pan, for example?

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On Thu, Apr 25, 2019, 1:57 PM Chris Hodgson ***@***.***> wrote: This is typically achieved in existing frameworks by not adding pan and zoom controls to the map. These controls are often added by default to the map and have to be actively disabled. The mechanic in use then is not that the map is "frozen", just that the map has an initial location and zoom level, and the user has no way to change those if no pan or zoom controls are offered. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#17 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AASTBJIRL4UFXL6UJTXVT3LPSHWHZANCNFSM4HIPFOAQ> .

[AmeliaBR]

It's definitely a good use case & it does mean that we have to think more broadly about what it means to provide default "controls": is the control just the visible buttons, or is it the entire functionality?

[cmhodgson]

The pan control provides the drag-to-pan functionality. It may or may not also provide (arrow) button-based click-to-pan, that might be a separate control or an option to the pan control. Also touch-based drag-to-pan uses different events and sometimes requires different handling or to be separately enabled/disabled (depending on how you want the map to behave on touch-based devices).

[prushforth]

OK, well I was thinking about controls being on/off in a similar way to how the <video> element controls attribute works. Turning <video> controls off doesn't disable the feature, you just have to get it via script. Although maybe the user can't play a video that doesn't have controls and for which script is not enabled, which would be the video player analogy of a 'frozen' map.

[cmhodgson]

Ok after reviewing some API docs, I guess it was way back in Openlayers 2 that pan was a control. In the current Openlayers, DragPan is an "interaction" which seems to be anything that receives events from the map and causes things to happen on the map as a result. In Leaflet controls are generally things that put buttons on the map interface. Drag-panning in Leaflet is just an option to the map.
I personally like the idea of an "interaction" or "control" or "behaviour" as a category of "things that do stuff with the map" all of which can be disabled or enabled in a similar way. I think the map "widget" needs to have several basic built-in such controls or behaviours, and there needs to be an API to add new ones. Editing tools are a separate (sub?) category of tool/control as they manipulate features in a layer, not just the map view.

[cmhodgson]

I think the video element controls attribute is a reasonable parallel, just consider how much more complex a map is than a video, and the level of custom interaction that existing map frameworks provide APIs for, and you can see that you need more than a single on/off switch for all controls.

[prushforth]

you need more than a single on/off switch for all controls

I think you're right, and the HTMLMediaElement interface may show us the way that is done for video/audio. If not we may need to invent :-)

[prushforth]

So, getting back to the topic of this issue, which is, the HTML / map author needs a way to enable a static map, or conversely, disable/make static a slippy map, while still retaining some mappyness.