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This file describes in detail the process of creating a new quest.

For code style and more general info - see CONTRIBUTING file.

If you want to contribute code to StreetComplete, then making a new quest is one of the easiest programming tasks. It is quite easy to implement a quest where the layout design matches an existing quest. For example, one more yes/no quest or where the user taps a displayed image.

Contributions like that are highly welcomed and you would make mapping one more thing in OSM much easier! You can also implement it if you have never used Kotlin or implemented anything for Android. Being a highly experienced programmer is not necessary here.

Reading the text below is not necessary to create a new quest. Duplicating an existing quest and modifying its code may be sufficient - people were creating new quests before this documentation existed. This material simply helps you get a better understanding of it.

Dependencies - initial setup

If you are doing it for the first time, don't worry if there is an error to solve along the way, this is typical for setting up an Android development environment. See CONTRIBUTING file which has some links to information about the setup.

Alternative to Android Studio

  • Instead of installing Android Studio locally, one can use GitHub Actions to build .apk files. Click on Actions > Build debug apk on your GitHub fork, make sure you select the correct branch with your changes when clicking Run workflow, and after about 15 minutes, download the ready-made debug-apk.zip which contains an .apk file to install on your phone manually. This debug build of StreetComplete can be installed alongside the official version.
  • One can also edit files online in the GitHub file view via the pen icon, thus avoiding the need for a local git client, and doing all the changes on the web.

Invent a new quest

Own ideas

To repeat from that documentation file: open an issue discussing the quest, before starting other work. This way it can be confirmed that such a quest can be included. This can be skipped if you are an experienced StreetComplete contributor.

Existing proposals

You can also look at quest proposals waiting for implementation.

Prepare repository for development

That is a good moment to create a branch and switch to it.

It can be done using Android Studio GUI (Git -> New branch...), or in CLI with the following command:

git checkout -b short_branch_name_describing_planned_work

In general, Intellij documentation about git integration is applicable to Android Studio (which is rebranded Intellij with minor modifications).

Learn from existing code

Find a base

Hints for looking around code

Full text search (ctrl+shift+f is always useful.

Use Ctrl+N to go to a certain class. Ctrl+ mouseclick on a function, class, etc. leads to where it is defined.

Use Ctrl+Q (but not on MacOS 😉) after having marked a class, symbol or function to display the documentation for it.

With Ctrl+Shift+A you can find and explore any action you can do in Android Studio (try it by typing for example "go to"). But "Find usages" (alt+F7) is also a very powerful way to find where given function/constant/property/etc. appears, classified by usages.

Base on existing

Base the new quest on one that exists already.

Find one that has the same type of interface as the one that you are trying to implement.

Are you trying to implement a quest that will have a simple yes/no answer? Take the AddBusStopLit quest as a base. Or AddTracktype where the mapper will be selecting from one of some presented images.

If it is going to be asked for POIs and should be disabled by default, then AddWheelchairAccessBusiness may be a good base.

Quests are grouped in one folder.

Implementing a quest by duplicating and modifiying an existing one is the recommended method.

Locating a quest

Search across the code for part of a question or other text specific to this quest. For example "the name of this place?".

You will find an XML file with an entry looking like this:

    <string name="quest_placeName_title">"What’s the name of this place?"</string>

The identifier quest_placeName_title is a string reference, used in the code to allow translations.

Search for this identifier in *.kt files, it should appear in the quest file (in this case AddPlaceName.kt).

This method can often be used to locate relevant code.

Other people

The issue proposing a quest may also contain a hint as to which quests are similar. If you are unsure what would be a good base - you can ask in issue discussion to confirm what you found or ask for help in finding a good base for a given issue.

Pull Requests

One of the better ways to get around a codebase that is new to you is to look at recent accepted proposals to change the code (pull requests).

This is also likely useful here.

Find some recent ones adding a quest.

You can look at what was changed to achieve the goal, where relevant code is located. How much coding was needed to implement something? And what kind of comments are typical, how long one needs to wait for maintainers and so on.

This can be also used to locate relevant code, especially helpful if some change needs to be done in multiple files.

Copying

Duplicate the relevant quest folder from app/src/main/java/de/westnordost/streetcomplete/quests. Some contain multiple quests, in such case delete unnecessary files.

Some quests are entirely defined in a single file, some have additional answer class, custom interface or utility classes.

For example, lets imagine that new quest will ask whether an AED is placed indoors or outdoors. A very similar in mechanics quest with simple yes/no question is for example quest asking "Is this bicycle parking covered (protected from rain)?".

So, as the first step: lets copy app/src/main/java/de/westnordost/streetcomplete/quests/bike_parking_cover/ folder into app/src/main/java/de/westnordost/streetcomplete/quests/defibrillator/.

This is done in this commit in the demonstration repository.

Adjust the copy

After the quest is copied it is necessary to adjust it a bit so it is not a duplicate anymore.

Change its class name and the file name to the new one.

In the copied code change the package info (things like package de.westnordost.streetcomplete.quests.defibrillator at the top) to match the new folder containing the quest.

When committing changes be careful to not change the already existing quest - only new code (using the built-in refactoring rename will also affect the QuestsModule.kt entry for an existing quest).

See this step in the example repository.

Add the quest to the list of active ones

Adjust QuestsModule.kt file. It contains a big list of active quests, ordered by priority. Read what governs their priority but do not worry too much, it can be tweaked later.

Each quest is associated with a number in this list. These numbers are used to identify the quest uniquely and can be used to save presets as QR codes. When adding a new quest, use the next consecutive number that is not yet in the list. Put the quest in order of priority, even if it means the numbers are not sorted.

Add your quest to the list so that it will be loaded by the app.

At this point you can run the app in the emulator - everything should work and one of the quests will appear twice.

See this step in the example repository.

Modify the template

At this point the prepared template can be modified to achieve the intended effect.

See for example simple yes/no quest asking whether AED is indoor or outdoor.

Element selection

elementFilter property defines nodes, ways and relations which will be selected for a given quest. It is an element selection used by OsmFilterQuestType.

    override val elementFilter = """
        nodes with
         emergency = defibrillator
         and access !~ private|no
         and !indoor
    """

This query will be limited to objects which fulfill some requirements.

  • nodes with
    • nodes only, ways and relations are not eligible
  • emergency = defibrillator
    • this tag must be present
  • and access !~ private|no
    • and access tag must not have values private or no (the ~ indicates it is a regular expression which will be matched against the whole string)
    • this filter excludes objects where the mapper will likely have no access necessary for survey
  • and !indoor
    • and indoor key must not be present at all, to show only ones where this tag is still missing

See the documentation of ElementFilterExpression for a complete documentation of the syntax. You can look around some quests to see more examples of such element filter expressions.

See this step in the example repository.

Prototyping

Overpass Turbo has its own syntax but it is a very useful tool for prototyping filters. It is very useful to verify your own assumptions about how things are tagged. Especially in more complex cases.

Hints

The rules should generate as few false positives as possible. I.e. instead of asking for the surface of any way tagged with highway=*, the surface should instead only be asked for an inclusive list of roads.

In some cases it will be a good idea to limit quests to certain countries.

You can obtain more info about properties by placing the cursor in a property and pressing Ctrl+Q within Android Studio.

changesetComment

override val changesetComment = "Add whether defibrillator is inside a building"

message used as a changeset comment

See this step in the example repository.

wikiLink

override val wikiLink = "Key:indoor"

points to the OSM Wiki page most relevant to the given quest, typically it is an added key. In this case, it is a page about indoor=* tagging.

See this step in the example repository.

icon

override val icon = R.drawable.ic_quest_defibrillator

icon drawable, you can initially use any icon.

Do not worry, submissions with placeholder icons are also welcomed! In many cases the icon itself was not made by the PR author.

More info about icon handling will be given later.

See this step in the example repository.

achievements

override val achievements = listOf(LIFESAVER)

In quest achievements, list what is relevant to the given quest, see the full list of available ones in AchievementsModule.kt

See this step in the example repository.

getTitle

override fun getTitle(tags: Map<String, String>) = R.string.quest_is_defibrillator_inside_title

It is a message displayed to the user, code here passes a reference to the string. You can change it to the new, not yet existing one and use a built in tool to place text.

Actual strings sit in app/src/main/res/values/strings.xml

There are separate files with translated text, but do not worry about it - translations are handled separately.

See this step in the example repository.

Form

override fun createForm() = YesNoQuestForm()

Form defines the interface used by mappers.

In this case, the simplest possible form is used.

But sometimes more complex ones are needed, see for example AddBridgeStructure.kt

override fun createForm() = AddBridgeStructureForm()

With the form defined in AddBridgeStructureForm

applyAnswerTo

override fun applyAnswerTo(answer: Boolean, tags: Tags, timestampEdited: Long) {
    tags["indoor"] = answer.toYesNo()
}

This code is responsible for modifying tags object (passed by reference).

In this case it would set indoor tag to have either yes or no answer, depending on the selection in the quest interface.

Actions may include (examples from various quests):

  • tags["indoor"] = answer.toYesNo()
    • set indoor tag to have either yes or no answer, based on provided data
  • tags.remove("amenity")
    • remove key if it is present
  • tags.updateWithCheckDate("lit", answer.toYesNo())
    • if the new value differs from existing tag value: new value will be applied
    • in case of value being the same: add survey date tag, it would be check_date:lit= in this case
      • so can be used even if value will stay the same - possible for resurvey quests
      • if the new value is the same as existing tag value: adds survey date tag (check_date:lit= in this example)
    • always update survey tag if present already
    • necessary if given quest includes resurvey of old elements that are already tagged

See this step in the example repository.

Extras

Info listed so far must be supplied by every quest. But there are also several optional fields. This specific quest has

override fun getHighlightedElements(element: Element, getMapData: () -> MapDataWithGeometry) =
    getMapData().filter("nodes with emergency = defibrillator")

which causes nearby emergency = defibrillator nodes to be shown.

Also see other optional properties.

See this step in the example repository.

Note that for this quest one extra property present in the original quest used as a template was removed

Adding quest icon

It is OK to submit a quest without its own icon, using any icon as a placeholder.

But it would be even better to include also icon.

Note that there are some graphics which haven't been used yet, created for proposed or expected quests; maybe you don't even need to create an icon!

A new icon can reuse the content of other quest icons, it can also be based on openly licensed graphics such as ones from svgrepo.com. See the attribution file for what has been used so far.

Keep similar style to existing ones and the app in general. Note that the background color of the icon marks its relation group:

  • magenta: bicycle traffic
  • blue: pedestrian traffic
  • yellow: motor vehicles (car, motorcycles)
  • grey: constructions (building type/height/entrances/roof/address, power poles, bridges, fire hydrants...)
  • light orange: shop related (opening hours, shop types/seating, shop/atm names, shop level, air conditioning, smoking, internet access, payment, surveillance)
  • green: amenities (nature, picnic, sport, religion, recycling, police, postbox, wheelchair, objects on summits, AED, toilets, backrest, is entrance paid...)
  • brown: nature-related (stile type/steps, trees/orchards)

Once the quest icon is ready:

  • when using Inkscape, save as "Optimized SVG" to remove unnecessary cruft or use another tool for that, like svgo or online SVGOMG
  • Put SVG into res/graphics/quest folder
    • SVG is a standard format editable in various software, unlike internal Android Studio XML that will be produced in the next steps.
  • Open Android Studio
  • Right click on the "app" folder in the Project tool window (top left)
  • Select new → vector asset
  • Select your SVG file
  • Name with ic_quest_ prefix (something like ic_quest_traffic_calming)
  • Press "Finish" button to generate drawable
  • Add an entry in the attribution file
  • Modify icon property in the quest definition to use the new drawable
  • Commit modified or created files
  • Compile, test quest in the emulator

The same method also applies to other vector drawables, although they will be placed in other parts of res/graphics/

Inkscape is a typical tool to create and edit SVG files, it is good, free and open-source so is available to all.

Test

Obviously, testing can also be done earlier. But the quest should at least be tested before submitting for review.

Typically it is done using an emulator. Note that you can set location in emulator settings rather than scrolling within StreetComplete itself.

  • Is the quest listed?
    • Look at the quest list in settings - does your quest appear there? If not - see this step.
    • While you are there you can disable all quests except yours for easier testing.
  • Is it shown for expected elements?
    • Note that due to emulator peculiarities you may need to move the map after quests are downloaded to see their markers (gory details for the curious)
  • Is it selected for some unwanted elements?
  • Can you tap on a quest marker to open the quest form?
  • Can you fill in the answer as expected?
  • Can you solve the quest?
  • Is expected tagging being applied?
    • You can look at logs for info of what was applied or use the undo menu in the bottom-left of the app itself.
    • You can freely answer - as long as you are not logged in, nothing will be submitted. Even after logging in you can disable uploading answers in settings.
  • Does the quest disappear after being solved?
    • If no - then either tags are not being applied or element selection filter has some problems.

See "logcat" (bottom left area of the screen) to see stacktrace or logging messages.

Adding logs

import de.westnordost.streetcomplete.util.logs.Log

Log.w("Unique string for easy grepping in logcat", "Message with whatever you need like #${someVariable.itsProperty}")

Open a pull request

A pull request is a submission of proposed changes to the source code.

You can put into the description of the PR something like "fixes #1234" to mark it as fixing this issue. It can go into a commit message or PR description or the tile.

If you are stuck on something, need some help or guidance and you are willing and able to continue after solving the problem - you can open a pull request in an incomplete state and mention the blocker.

You can see already submitted pull requests to see how this process works in practice.

Future

After opening a pull request it will be reviewed and you will be likely asked to make some changes. This is normal and also happens with pull requests submitted by experienced contributors.

Changes typically include improving code style, tweaking phrasing and quest settings.

When you know more about the code, style and quest guidelines and general architecture of StreetComplete, you are also welcome to help with reviewing other PRs - different people have different strengths, there are active reviewers who help with code style, there are some native speakers of English, some with deep knowledge of OSM tagging schemes or deep knowledge of how StreetComplete works.

When the pull request appears to be ready, it will be marked as approved and wait for merge.

After the PR is finished it will be merged before the beta release of the next version. This way it can be additionally tested with a wider audience before release to all and translators have time to translate text into other languages.

After full release it will reach the entire StreetComplete audience who now will be able to more easily contribute to OpenStreetMap. Thanks in advance for that!

Once your code is merged into StreetComplete you will be credited at repository statistics.

Bad documentation is a bug

Unclear documents, including this one, are a bug. Feel free to either submit a pull request with a fix or open an issue describing your confusion.

Note that not everything will be directly described. This document very intentionally doesn't include a step-by-step guide to installing Android Studio, linking to official docs instead.

More complexity

What was described above is an attempt to cover all aspects of quest creation, without describing all the complexity.

Below is some additional info.

Kotlin

Article about null safety related syntax is likely to be very useful, especially if you are confused by ?: Elvis operator.

Designing the form

As mentioned, the user interface must leave no space for misunderstandings, it must be concise and quick and easy to use. Also sounds obvious, but you will quickly find out that a balance must be found between covering all the edge cases and designing the form to be as straightforward and clutterless as possible.

  • Design the main form clutter-free so that it is straightforward for the majority of use cases.
  • Allow to answer popular edge cases, but don't clutter up the main form with that. A good pattern is to move such answers into the "Uh..." (otherAnswers) menu. E.g. look at the opening hours quest. That menu should also be used when user might have doubts on how to answer a specific situation.
  • Don't rely on the "leave a note" fallback too much. It is not intended and does not work as a regular answer but is designed to cover the case that the question was invalid itself because it was based on wrong data like i.e. the place does not exist anymore.
  • The information the user should fill in should be as atomic as possible. Users are impatient, i.e. do not let them fill out a whole address with street name etc. when just the house number is fine too.
  • "A picture is worth a thousand words": Often the term for certain things may not be enough to convey the meaning of certain predefined answers. Do you know what a wheelbender is? You will know if you see the photo.

Considerations about the edge cases to consider, how the design could look and finding good representative photos or icons that match in style is also part of the preparational work that can be done without programming knowledge.

New photos

Some quests will require photos for their interface.

Photos must be available on open license - so not every photo found on the Internet is usable. You can either take your own photo or find an existing freely licensed photo. Licenses acceptable for photos are public domain, CC-0, CC-BY and CC-BY-SA licenses.

Good places to find freely licensed images are Geograph and Wikimedia Commons.

You can also take your own photos, a standard smartphone camera is good enough. And sometimes a highly specific image is needed.

In StreetComplete many images have unusual composition. Often it is necessary to leave space for a label at the bottom.

Images should be free of visual debris, not misleading. Though it is fine to use an image not strictly matching what is depicted, as long as it is clear. For example, a permanent pile of soil blocking road is illustrated by a temporary landslide. This is OK as images are illustrative.

Photos go to a different folder than SVGs: they can be used directly by the build process so put them into folders

  • mdpi - 384 pixels for images, with three square images in each row it would be 128 x 128 pixels for each)
  • hdpi - 576 pixels for images (192 x 192 pixels in case of three square images in each row)
  • xhdpi - 768 pixels for images (256 x 256 pixels in case of three square images in each row)
  • xxhdpi - 1152 pixels (384 x 384 pixels in case of three square images in each row)

Each of these folders should hold the same image resized to a different resolution. While testing various images it is enough to put one into any of the folders.

The rescaling script may be useful, but you can also do this manually with Gimp or similar software.

Please make sure that the images do not take too much disk space. Most useful way to do that is by lowering JPEG quality, which can make images noticeably smaller. Play with settings to see which is the smallest size which does not degrade image quality visibly.

GIMP allows such previews while saving JPG files, and there are also online tools like squoosh which allow for quick visual comparison if you prefer that.

After adding a photo, remember to update the credits file (different to the one for icons).

Resurvey

Some quests are asked not only when a tag is missing but also when it is likely to be outdated. To achieve this elementFilter needs to query not only elements missing some tags.

Typical code is in quest asking about motorcycle parking capacity:

override val elementFilter = """
    nodes, ways with amenity = motorcycle_parking
      and access !~ private|no
      and (!capacity or capacity older today -4 years)
"""

This quest will be triggered when:

  • nodes, ways with
    • on nodes or ways (relations not eligible)
  • amenity = motorcycle_parking
    • where amenity = motorcycle_parking tag is present
  • and access !~ private|no
    • and access tag neither has the value private nor no
  • and (!capacity or capacity older today -4 years)
    • and one of following is fulfilled:
      • capacity tag is not present at all (!capacity)
      • element was not edited for a long time (base time is 4 years, but it can be influenced by user changing settings)
      • check_date:capacity with a date indicating that it is outdated (the same as above applies)

Custom filters

It is possible to use far more complex filters when querying for eligible elements.

Matches like surface ~ earth|dirt|ground are possible and are evaluated as "surface is any of earth, dirt, ground"

access !~ private|no will be evaluated to "access is neither private nor no"

But using regexp like surface ~ ^(.*)[0-9]$ is also possible.

It is possible to check for age of elements or implement a fully custom tag parsing, still combined with filter syntax.

It is possible to share and reuse information about tagging schemes.

(this info is gathered here)

Even more complex ones using different class bases are possible. Such as what was needed by the address quest or the crossing quest but it is better to start from something simpler.

It allows it to make complex geometry checks, but writing them is also far more complex.

enabledInCountries

Some quests should be enabled only in some countries or disabled in a specific countries.

override val enabledInCountries = NoCountriesExcept("SE") - enabled only in Sweden.

override val enabledInCountries = AllCountriesExcept("US", "CA") - not enabled in USA or Canada

defaultDisabledMessage

Some quests should be disabled by default, for example ones that may require going inside a shop. In such case setting override val defaultDisabledMessage = R.string.default_disabled_msg_go_inside will have two effects:

  • quest will be disabled by default
  • on attempting to enable it user will get message asking are they sure. Exact message in this case would be default_disabled_msg_go_inside - but some quests use more specific ones.

Note that a quest may be both disabled by default and limited to some countries.

isDeleteElementEnabled

This will decode whether the user should have access to direct deletion of elements. Note that ways and relations cannot be deleted by SC users.

For nodes within ways, the node will remain and tags will be removed.

hint & hintImages (info button)

When there are doubts on the question itself (terms used, etc.), how to answer or how to find the answer, more information can be provided via info button text & images. Examples for such info button would be explanation of what is halal, what is tactile paving, what is a sanitary dump station, when a level counts as a roof level and when as a normal level, explanation of the street side puzzle UI, etc.

Instructions for answering the quest should instead be directly visible either in the quest title or a label on the form always shown with the answers. For example, when asked for the name of a road, a label instructs the user to expand abbreviated road names. When asked about whether a restaurant offers vegetarian options, it is clarified that one should only answer "yes" if these are proper options (not just a salad or whatever).

For doubts on how to answer specific situations, like e.g. when asked for the opening hours of a shop that doesn't seem to exist anymore or asked about the house number of a building that instead has a house name, it is better to provide such answer through the "Uh..." menu, see Designing the form.

Per-country quest behaviour modification

While quests should generally be tailored to function in whole world similarly, if really needed one can use countryInfo to modify behaviour of the quest in specific country, see e.g. AddTrafficSignalsVibrationForm.kt for example usage.