vjrj
bfff95fe8d
Chips clipped at the viewport edge with no cue that more filters exist. New reusable EdgeFade widget (ShaderMask + dstIn) fades an edge only while content remains beyond it, driven by scroll metrics; RTL mirrors via Directionality. Applied to the inventory filter bar, market filter bar and calendar month strip.
82 lines
2.8 KiB
Dart
82 lines
2.8 KiB
Dart
import 'package:flutter/material.dart';
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/// Fades the edges of a horizontal scrollable to transparency wherever more
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/// content lies beyond that edge, so it is obvious the row scrolls.
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///
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/// Wrap directly around a horizontal [SingleChildScrollView] or [ListView].
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/// The fade is a [ShaderMask] with [BlendMode.dstIn], so it melts into
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/// whatever background sits behind — no theme colour involved. Edge state is
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/// tracked per logical side (start/end) and mapped to physical left/right via
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/// [Directionality], so RTL mirrors correctly.
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class EdgeFade extends StatefulWidget {
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const EdgeFade({super.key, required this.child, this.fadeWidth = 28});
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/// The horizontal scrollable to mask.
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final Widget child;
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/// Width of each faded edge in logical pixels.
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final double fadeWidth;
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@override
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State<EdgeFade> createState() => EdgeFadeState();
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}
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class EdgeFadeState extends State<EdgeFade> {
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bool _fadeStart = false;
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bool _fadeEnd = false;
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/// Whether the physical left edge is currently faded.
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@visibleForTesting
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bool get fadeLeft => _isRtl ? _fadeEnd : _fadeStart;
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/// Whether the physical right edge is currently faded.
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@visibleForTesting
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bool get fadeRight => _isRtl ? _fadeStart : _fadeEnd;
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bool get _isRtl => Directionality.of(context) == TextDirection.rtl;
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bool _onMetrics(ScrollMetrics metrics) {
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if (metrics.axis != Axis.horizontal) return false;
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final start = metrics.extentBefore > 0.5;
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final end = metrics.extentAfter > 0.5;
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if (start != _fadeStart || end != _fadeEnd) {
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setState(() {
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_fadeStart = start;
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_fadeEnd = end;
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});
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}
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return false;
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}
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@override
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Widget build(BuildContext context) {
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final fadeLeft = this.fadeLeft;
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final fadeRight = this.fadeRight;
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// The mask stays in the tree even when both edges are opaque: swapping it
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// in and out would re-inflate the child and reset its scroll position.
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return NotificationListener<ScrollMetricsNotification>(
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onNotification: (n) => n.depth == 0 ? _onMetrics(n.metrics) : false,
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child: NotificationListener<ScrollNotification>(
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onNotification: (n) => n.depth == 0 ? _onMetrics(n.metrics) : false,
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child: ShaderMask(
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blendMode: BlendMode.dstIn,
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shaderCallback: (bounds) {
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final w = bounds.width > 0
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? (widget.fadeWidth / bounds.width).clamp(0.0, 0.5)
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: 0.0;
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return LinearGradient(
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colors: [
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fadeLeft ? Colors.transparent : Colors.white,
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Colors.white,
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Colors.white,
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fadeRight ? Colors.transparent : Colors.white,
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],
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stops: [0, w, 1 - w, 1],
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).createShader(bounds);
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},
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child: widget.child,
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),
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),
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);
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}
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}
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