79 lines
2.3 KiB
Dart
79 lines
2.3 KiB
Dart
import 'package:flutter/material.dart';
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import 'package:infinite_lazy_2d_grid/utils/conversions.dart';
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// ------------------------------ Public Types -------------------------------
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typedef WidgetBuilder = Widget Function();
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// ------------------------------ Private Types ------------------------------
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// some simple exceptions
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// ignore: non_constant_identifier_names
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final _ChildNotFoundException = Exception('Child with the given ID does not exist');
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class _CanvasItem {
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Offset gsPosition;
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final WidgetBuilder builder;
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_CanvasItem({required this.gsPosition, required this.builder});
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}
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// ------------------------------ Controller ------------------------------
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/// Every canvas view needs one and this handles the positioning logic
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class CanvasController with ChangeNotifier {
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int _nextId = 0; // surely we won't run out of IDs, Clueless
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Offset _gsTopLeftOffset = Offset.zero;
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final Map<int, _CanvasItem> _children = {}; // int for IDs
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// -------------------- public functions --------------------
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// -------- child manip --------
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int addChild(Offset position, WidgetBuilder builder) {
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_children[_nextId] = _CanvasItem(gsPosition: position, builder: builder);
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return _nextId++;
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}
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void removeChild(int id) {
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_children.remove(id);
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}
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int updatePosition(int id, Offset newPosition) {
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if (_children.containsKey(id)) {
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_children[id]!.gsPosition = newPosition;
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return id;
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} else {
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throw _ChildNotFoundException;
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}
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}
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Offset getPosition(int id) {
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if (_children.containsKey(id)) {
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return _children[id]!.gsPosition;
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} else {
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throw _ChildNotFoundException;
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}
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}
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// -------- gesture handling --------
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void handleGesture(ScaleUpdateDetails details) {
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// handle gestures like pinch to zoom, pan, etc.
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// convention is that if I drag from right to left, dx is negative
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// for top to bottom, dy is postive ( so usual display conventions and final vector postion - initial vector position )
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final delta = details.focalPointDelta;
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_gsTopLeftOffset -= delta;
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notifyListeners();
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}
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List<(Offset, Widget)> widgetsWithScreenPositions() {
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return _children.values.map((item) {
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final ssPosition = gsToSs(item.gsPosition, _gsTopLeftOffset);
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return (ssPosition, item.builder());
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}).toList();
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}
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}
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