gristlabs_grist-core/app/client/components/Cursor.ts

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/**
* The Cursor module contains functionality related to the cell with the cursor, i.e. a single
* currently selected cell.
*/
import BaseView from 'app/client/components/BaseView';
import * as commands from 'app/client/components/commands';
import BaseRowModel from 'app/client/models/BaseRowModel';
import {LazyArrayModel} from 'app/client/models/DataTableModel';
import {CursorPos, UIRowId} from 'app/plugin/GristAPI';
import {Disposable} from 'grainjs';
import * as ko from 'knockout';
function nullAsUndefined<T>(value: T|null|undefined): T|undefined {
return value == null ? undefined : value;
}
// ================ SequenceNum: used to keep track of cursor edits (lastEditedAt)
// Basically just a global auto-incrementing counter, with some types to make intent more clear
// Cursors are constructed at SequenceNEVER (0). After that, changes to their sequenceNum will go through
// NextSequenceNum(), so they'll have unique, monotonically increasing numbers for their lastEditedAt()
// NOTE: (by the time the page loads they'll already be at nonzero numbers, the never is intended to be transient)
export type SequenceNum = number;
export const SequenceNEVER: SequenceNum = 0; // Cursors will start here
let latestGlobalSequenceNum = SequenceNEVER;
function nextSequenceNum() { // First call to this func should return 1
latestGlobalSequenceNum++;
return latestGlobalSequenceNum;
}
// NOTE: If latestGlobalSequenceNum overflows, I think it would stop incrementing because of floating point imprecision
// However, we don't need to worry about overflow because:
// - Number.MAX_SAFE_INTEGER is 9,007,199,254,740,991 (9 * 10^15)
// - even at 1000 cursor-edits per second, it would take ~300,000 yrs to overflow
// - Plus it's client-side, so that's a single continuous 300-millenia-long session, which would be impressive uptime
/**
* Cursor represents the location of the cursor in the viewsection. It is maintained by BaseView,
* and implements the shared functionality related to the cursor cell.
* @param {BaseView} baseView: The BaseView object to which this Cursor belongs.
* @param {Object} optCursorPos: Optional object containing rowId and fieldIndex properties
* to which the cursor should be initialized.
*/
export class Cursor extends Disposable {
/**
* The commands closely tied to the cursor. They are active when the BaseView containing this
* Cursor has focus. Some may need to be overridden by particular views.
*/
public static editorCommands = {
// The cursor up/down commands may need to be a bit different in non-grid views.
cursorUp(this: Cursor) { this.rowIndex(this.rowIndex()! - 1); },
cursorDown(this: Cursor) { this.rowIndex(this.rowIndex()! + 1); },
cursorLeft(this: Cursor) { this.fieldIndex(this.fieldIndex() - 1); },
cursorRight(this: Cursor) { this.fieldIndex(this.fieldIndex() + 1); },
skipUp(this: Cursor) { this.rowIndex(this.rowIndex()! - 5); },
skipDown(this: Cursor) { this.rowIndex(this.rowIndex()! + 5); },
pageUp(this: Cursor) { this.rowIndex(this.rowIndex()! - 20); }, // TODO Not really pageUp
pageDown(this: Cursor) { this.rowIndex(this.rowIndex()! + 20); }, // TODO Not really pageDown
prevField(this: Cursor) { this.fieldIndex(this.fieldIndex() - 1); },
nextField(this: Cursor) { this.fieldIndex(this.fieldIndex() + 1); },
moveToFirstRecord(this: Cursor) { this.rowIndex(0); },
moveToLastRecord(this: Cursor) { this.rowIndex(Infinity); },
moveToFirstField(this: Cursor) { this.fieldIndex(0); },
moveToLastField(this: Cursor) { this.fieldIndex(Infinity); },
};
public viewData: LazyArrayModel<BaseRowModel>;
// observable with current cursor position
public currentPosition: ko.Computed<CursorPos>;
public rowIndex: ko.Computed<number|null>; // May be null when there are no rows.
public fieldIndex: ko.Observable<number>;
private _rowId: ko.Observable<UIRowId|null>; // May be null when there are no rows.
// The cursor's _rowId property is always fixed across data changes. When isLive is true,
// the rowIndex of the cursor is recalculated to match _rowId. When false, they will
// be out of sync.
private _isLive: ko.Observable<boolean> = ko.observable(true);
private _sectionId: ko.Computed<number>;
private _properRowId: ko.Computed<UIRowId|null>;
// lastEditedAt is updated on _properRowId or fieldIndex update (including through setCursorPos)
// Used to determine which section takes priority for cursorLinking (specifically cycles/bidirectional linking)
private _lastEditedAt: ko.Observable<SequenceNum>;
// _silentUpdatesFlag prevents lastEditedAt from being updated, when a change in cursorPos isn't driven by the user.
// It's used when cursor linking calls setCursorPos, so that linked cursor moves don't trample lastEditedAt.
// WARNING: the flag approach relies on ko observables being resolved synchronously, may break if changed to grainjs?
private _silentUpdatesFlag: boolean = false;
constructor(baseView: BaseView, optCursorPos?: CursorPos) {
super();
optCursorPos = optCursorPos || {};
this.viewData = baseView.viewData;
this._sectionId = this.autoDispose(ko.computed(() => baseView.viewSection.id()));
this._rowId = ko.observable<UIRowId|null>(optCursorPos.rowId || 0);
this.rowIndex = this.autoDispose(ko.computed({
read: () => {
if (!this._isLive()) { return this.rowIndex.peek(); }
const rowId = this._rowId();
return rowId == null ? null : this.viewData.clampIndex(this.viewData.getRowIndexWithSub(rowId));
},
write: (index) => {
const rowIndex = index === null ? null : this.viewData.clampIndex(index);
this._rowId(rowIndex == null ? null : this.viewData.getRowId(rowIndex));
},
}));
this.fieldIndex = baseView.viewSection.viewFields().makeLiveIndex(optCursorPos.fieldIndex || 0);
this.autoDispose(commands.createGroup(Cursor.editorCommands, this, baseView.viewSection.hasFocus));
// RowId might diverge from the one stored in _rowId when the data changes (it is filtered out). So here
// we will calculate rowId based on rowIndex (so in reverse order), to have a proper value.
this._properRowId = this.autoDispose(ko.computed(() => {
const rowIndex = this.rowIndex();
const rowId = rowIndex === null ? null : this.viewData.getRowId(rowIndex);
return rowId;
}));
this._lastEditedAt = ko.observable(SequenceNEVER);
// update the section's activeRowId and lastCursorEdit when needed
this.autoDispose(this._properRowId.subscribe((rowId) => baseView.viewSection.activeRowId(rowId)));
this.autoDispose(this._lastEditedAt.subscribe((seqNum) => baseView.viewSection.lastCursorEdit(seqNum)));
// Update the cursor edit time if either the row or column change
// IMPORTANT: need to subscribe AFTER the properRowId->activeRowId subscription.
// (Cursor-linking observables depend on lastCursorEdit, but only peek at activeRowId. Therefore, updating the
// edit time triggers a re-read of activeRowId, and swapping the order will read stale values for rowId)
// NOTE: this may update sequence number twice for a single edit, but this shouldn't cause any issues.
// For determining priority, this cursor will become the latest edited whether we call it once or twice.
// For updating observables, the double-update might cause cursor-linking observables in LinkingState to
// double-update, but it should be transient and get resolved immediately.
this.autoDispose(this._properRowId.subscribe(() => { this._cursorEdited(); }));
this.autoDispose(this.fieldIndex.subscribe(() => { this._cursorEdited(); }));
// On dispose, save the current cursor position to the section model.
this.onDispose(() => { baseView.viewSection.lastCursorPos = this.getCursorPos(); });
// calculate current position
this.currentPosition = this.autoDispose(ko.computed(() => this._isLive() ? this.getCursorPos() : {}));
}
// Returns the cursor position with rowId, rowIndex, and fieldIndex.
public getCursorPos(): CursorPos {
return {
rowId: nullAsUndefined(this._properRowId()),
rowIndex: nullAsUndefined(this.rowIndex()),
fieldIndex: this.fieldIndex(),
sectionId: this._sectionId()
};
}
/**
* Moves the cursor to the given position. Only moves the row if rowId or rowIndex is valid,
* preferring rowId.
*
* isFromLink prevents lastEditedAt from being updated, so lastEdit reflects only user-driven edits
* @param cursorPos: Position as { rowId?, rowIndex?, fieldIndex? }, as from getCursorPos().
* @param isFromLink: should be set if this is a cascading update from cursor-linking
*/
public setCursorPos(cursorPos: CursorPos, isFromLink: boolean = false): void {
try {
// If updating as a result of links, we want to NOT update lastEditedAt
if (isFromLink) { this._silentUpdatesFlag = true; }
if (cursorPos.rowId !== undefined && this.viewData.getRowIndex(cursorPos.rowId) >= 0) {
this.rowIndex(this.viewData.getRowIndex(cursorPos.rowId));
} else if (cursorPos.rowIndex !== undefined && cursorPos.rowIndex >= 0) {
this.rowIndex(cursorPos.rowIndex);
} else {
// Write rowIndex to itself to force an update of rowId if needed.
this.rowIndex(this.rowIndex.peek());
}
if (cursorPos.fieldIndex !== undefined) {
this.fieldIndex(cursorPos.fieldIndex);
}
// NOTE: _cursorEdited
// We primarily update cursorEdited counter from a this._properRowId.subscribe(), since that catches updates
// from many sources (setCursorPos, arrowKeys, save/load, filter/sort-changes, etc)
// However, there's some cases where we user touches a section and properRowId doesn't change. Obvious one is
// clicking in a section on the cell the cursor is already on. This doesn't change the cursor position, but it
// SHOULD still update cursors to use that section as most up-to-date (user just clicked on a cell!), so we do
// it here. (normally is minor issue, but can matter when a section has rows filtered out so cursors desync)
// Also a more subtle case: when deleting a row with several sections linked together, properRowId can fail to
// update. When GridView.deleteRows calls setCursorPos to keep cursor from jumping after delete, the observable
// doesn't trigger cursorEdited(), because (I think) _properRowId has already been updated that cycle.
// This caused a bug when several viewSections were cursor-linked to each other and a row was deleted
// NOTE: Calling it explicitly here will cause cursorEdited to be called twice sometimes,
// but that shouldn't cause any problems, since we don't care about edit counts, just who was edited latest.
this._cursorEdited();
} finally { // Make sure we reset this even on error
this._silentUpdatesFlag = false;
}
}
public setLive(isLive: boolean): void {
this._isLive(isLive);
}
// Should be called whenever the cursor is updated
// EXCEPT FOR: when cursor is set by linking
// this is used to determine which widget/cursor has most recently been touched,
// and therefore which one should be used to drive linking if there's a conflict
private _cursorEdited(): void {
// If updating as a result of links, we want to NOT update lastEdited
if (!this._silentUpdatesFlag)
{ this._lastEditedAt(nextSequenceNum()); }
}
}