Screens

A screen shows the records of a file in a particular way: as a list, a board, a calendar, a record page and so on. This page lists every kind of screen and the tiles and charts that go on them. For the terms used here, see Concepts.

How screens work

A screen is data, not code. The file stores each screen as a tree of nodes with stable IDs: a root node for the screen, and child nodes for its fields, filters, sections, tiles and commands. The file never holds HTML, styling, scripts or SQL. Nendo compiles the whole set of screen definitions when it opens the file and each time the definitions change, then draws the result in Use.

The compiler checks every screen before it draws any of them. If one node is wrong, for example a field binding that names a field the record type does not have, Nendo turns off every custom screen and shows the error in Studio’s Surfaces area. It does not draw part of an app. Your data, Studio and recovery are not affected, and no screen can hide Studio.

Most screens belong to one record type. In Use, the breadcrumb at the top names the record type and the screen, and each name is a picker: choose the record type, then the screen. The front page is the exception: it belongs to the file, and Use opens it first when the file has one. Which screen, tab, month or year is open is remembered for the session only and never written to the file.

A calculated field can appear on any screen as a read-only value. It cannot filter, sort or group a screen, place a record on a calendar or timeline, or feed a total.

Screens for one record type

Screen	Per record type	What it shows	Main limits
List	up to 8	Rows of records, one column per bound field, in a chosen order, with Previous and Next.
Board	up to 8	Cards in columns, grouped by one field. Drag a card to another column to change that field.	Groups by a single-choice field or a bound reference field.
Gallery	up to 8	The same records and pages as a list, drawn as cards. A title field leads each card; a single-choice accent field tints it.	Cards are text only; there are no image fields.
Calendar	up to 8	Records on a month grid by one date field, plus an Undated view.	Date fields only. A date-and-time field is refused.
Timeline	up to 8	Records under month headings on a one-year spine, plus an Undated view. An optional end date draws a span.	Date fields only. A record is placed by its start date.
Matrix	up to 8	A grid that crosses two fields, with an exact count and the cards in each cell.	At most 366 cells, so about 19 by 19.
Outline	up to 8	A record type kept as a tree, as rows you open and close, with columns beside each title. Can let people move records.	Only for a record type kept as a tree. No filters.
Custom graph	up to 8	Records as a node-and-edge graph, drawn by a custom view whose code the file carries.	See Custom views.
Custom view	up to 8	One record type, drawn by a custom view whose code the file carries: a Gantt chart, a map. A custom view can also sit on a record page.	See Custom views.
Record page	1	One record: a header, fields in sections and tabs, related lists, tiles and commands.
Form	1	One record as a plain form for entering data.	Used only when there is no record page.
Command	up to 8	A button that sets fields on the open record.

Board

A board groups cards into columns by one field, which you name in groupByFieldId.

• By choice. The columns are the field’s options in their configured order, in the option’s colour. A filter clause eq on the grouping field leaves one column, and each ne removes one. Other clauses change which cards appear, not which columns exist.
• By reference. The columns are every active record of the target record type, ordered by the reference’s label. A board draws at most 24 reference columns. Above that, it draws no columns and states the record type, its record count and the limit. The reference field must be bound to a target type.

Both kinds have an Ungrouped column for records with no value. Dragging a card writes the grouping field. A tile on a board can count the whole board or one column (scope: group).

Calendar and timeline

A calendar shows one month at a time, Monday first. A timeline shows one year at a time, with a heading for every month. Both load records in pages, so until the period is fully loaded an empty day or month reads None loaded yet. Both have an Undated view for records with no date. Neither writes: an entry opens the record page.

On a timeline, an optional end-date field turns an entry into a span, shown in days and as a bar drawn to scale over the year. A span that runs past 31 December is cut there and says so. An end before the start is shown as a data issue.

Matrix

A matrix crosses two single-choice or Boolean fields: one for rows and one for columns. They must be different fields. Nendo computes every cell in one read, so an empty cell still shows 0. When a cell holds more records than the loaded window, it says, for example, showing 4 of 17. A matrix whose rows times columns, plus one unset lane on each axis, exceeds 366 is refused when it is authored. If the option lists grow past that later, the matrix states that it cannot draw the grid. It never draws part of a grid. You cannot drag cards between cells.

Outline

An outline shows a record type that is kept as a tree: each record indented under its parent, with the number of records directly under it. It opens two levels by itself (or between one and four, as the screen says), and remembers on your computer which rows you opened or closed. The find box opens the path to each record whose title matches, up to 20. When the screen allows moving, drag a row onto another row, or select it and press Alt, Shift and an arrow key, or use Move up, Move down, Outdent and Indent. Nendo refuses a move that would put a record under itself and says why. An outline has no filters: a filtered tree would hide the parents that give a record its place. While an outline shows the tree, the tree cannot be removed from the record type.

Record page and form

A record type can have one record page (detailSurface) and one form (recordForm). When both exist, Use opens the record page. When neither exists, a record opens in Studio’s editor.

A record page can contain:

• A header with a title field, a subtitle field and an accent field whose option colours the band. The header only shows values; you edit them in the form below it.
• Field bindings, each one an editor for one field.
• Sections, each with a title. A reader can fold any section. The author sets only how it starts, open or closed. A closed section reads nothing until it opens.
• Tab groups, whose tabs are titled sections. Changing tab keeps unsaved typing.
• Related lists, which show the records whose reference points at this record. Add creates a new related record with the reference already filled in. Selecting a row opens it as its own record page. When the related records are links between two record types, such as a support joining a capability and an application, the list also offers Link followed by the other record type, which opens the form with the picker for the other end already open, and each row offers Remove link, which deletes only the link and keeps it in History.
• Tiles and charts over the whole record type.
• Commands, shown as buttons under the header.

A field binding or a section can be shown only when a Boolean calculated field is true (visibleWhen). Only a definite false hides it. The value stays in the form and is still saved.

A form holds only field bindings, sections, tabs and commands. It has no header, related lists or tiles.

Commands. A command is a labelled button that runs ordered steps on the open record. Each step sets one field to a fixed value, today’s date, the current time or empty. A command can be its own root or sit inside the record page.

The front page

A file can have one front page (overviewSurface). It belongs to the file, so it has no record type of its own. Each tile, chart and list on it names the record type it reads. It never combines two record types in one number. It can have a title, a sentence of description, sections and tabs. It needs at least one tile, chart or list. It cannot hold field bindings or related lists, because there is no current record.

Tiles and charts

Every number is exact. Nendo does not round, and a sum that does not fit reads Unavailable with the reason. There is no average.

Part	What it states	Where it can go
Summary tile	One count, sum, minimum or maximum.	List, board, gallery, matrix, record page, front page, section, related list
Breakdown chart	One number per option of a single-choice field, or per yes and no, as a stacked bar.	List, board, gallery, matrix, record page, front page, section
Progress ring	The records that match its own clauses, out of all records in its scope.	Same as breakdown chart
Range tile	The smallest and largest value of one number or date field.	Same as breakdown chart
Trend chart	One number per month or week over the last 12 months, 6 months, 90 days or 30 days.	Same as breakdown chart
Activity grid	One count per day, as squares, for this year or the last twelve months.	Same as breakdown chart
Recent list	Up to 10 records of one type, in a chosen order.	Front page, or a section on it
Ranked list	Up to 50 records at the top of one number field, with bars against the largest.	Front page, or a section on it

On a list, board, gallery or matrix, a tile covers all records the screen’s filter matches, not only the loaded page. Breakdown and trend charts show an empty group or period as zero; they do not leave it out. A grouped chart has at most 366 groups. Select a chart segment, bucket or matrix cell to open the record type’s first list narrowed to that group.

Filters

A filter clause keeps the records where one stored field compares to a value. The operators are eq, ne, lt, lte, gt, gte, isNull and isNotNull. The value is a fixed value, today, now or empty. All clauses on a node must match. There is no OR and no grouping of clauses.

One read carries at most eight filters in total. Filters that Nendo adds itself count towards the eight:

Context	What Nendo adds	Clauses you can write
List, board, gallery, matrix	nothing	8
Tile on a list, board or gallery	the screen’s clauses	8 minus the screen’s
Tile on one board column	the board’s clauses and 1 for the column	7 minus the board’s
Related list	1 for the reference	7
Calendar or timeline	2 for the date bounds	6
Trend chart or activity grid	2 for the date bounds	6, less its context’s clauses
Ranked list	1 to skip records with no number	7
Tile on a record page or the front page	nothing	8

A definition over the budget is refused with a message that names each clause and where it came from. Nendo never drops a clause to make a screen fit.

Filter while you look

A list, a board and a matrix have a Filter button. It offers every choice field and every reference field of the record type. Pick one value, such as one project on a board of all work, or Not set, and the screen shows only the records that hold it, on top of the screen’s own filters. A pill says what is showing, and its button shows everything again. A reference lists at most 100 records to choose from.

This filter is yours, for as long as the file is open. It is not saved in the file, other people do not see it, and nothing about the screen changes. While it is on, the screen’s own tiles and charts are hidden, because they count the whole screen. A screen whose own filters already use all eight clauses has no Filter button.

How screens get made

There is no visual screen editor. Screens are built as proposals:

1. An agent with the Shape app access level reads the file and the screen vocabulary, then builds a change set of node operations: add a node, set a property, move a node, remove a node. See Agents.
2. Nendo validates the change set on a private copy of the file. A valid change set becomes a proposal under Pending changes.
3. You open Review changes. The review lists each change in plain words, for example Order by Amount, largest first, and draws a preview of the screens over a sample of records from the copy. It describes the front page and progress rings instead of drawing them, because their numbers are live reads of the whole record type.
4. Accept changes applies the same operations to your file. Reject leaves the file unchanged.

Studio’s Surfaces area lists the compiled screens of each record type, with their kind and what they are bound to. When the definition does not compile, it shows each error with a hint. The one screen edit Studio makes itself is renaming a board, which also goes through a proposal and a review.

A file records the lowest Nendo version that can draw its screens. An older Nendo refuses the file instead of drawing part of it.