implemented exposure pairs list

lib/models/photography_value.dart

@@ -13,10 +13,21 @@ abstract class PhotographyValue<T> {
   T get value;
 }
 
-extension PhotographyValues<T> on List<PhotographyValue<T>> {
+extension PhotographyValues<T extends PhotographyValue> on List<T> {
-  List<PhotographyValue<T>> fullStops() => where((e) => e.stopType == Stop.full).toList();
+  List<T> whereStopType(Stop stopType) {
+    switch (stopType) {
+      case Stop.full:
+        return where((e) => e.stopType == Stop.full).toList();
+      case Stop.half:
+        return where((e) => e.stopType == Stop.full || e.stopType == Stop.half).toList();
+      case Stop.third:
+        return where((e) => e.stopType == Stop.full || e.stopType == Stop.third).toList();
+    }
+  }
 
-  List<PhotographyValue<T>> halfStops() => where((e) => e.stopType == Stop.full || e.stopType == Stop.half).toList();
+  List<T> fullStops() => whereStopType(Stop.full);
 
-  List<PhotographyValue<T>> thirdStops() => where((e) => e.stopType == Stop.full || e.stopType == Stop.third).toList();
+  List<T> halfStops() => whereStopType(Stop.half);
+
+  List<T> thirdStops() => whereStopType(Stop.third);
 }

lib/res/dimens.dart

@@ -7,6 +7,7 @@ class Dimens {
   static const double grid4 = 4;
   static const double grid8 = 8;
   static const double grid16 = 16;
+  static const double grid24 = 24;
 
   static const double paddingM = 16;
 }

lib/screens/metering/components/exposure_pairs_list/components/exposure_pair_item.dart

@@ -0,0 +1,54 @@
+import 'package:flutter/material.dart';
+import 'package:lightmeter/models/photography_value.dart';
+import 'package:lightmeter/res/dimens.dart';
+
+class ExposurePaitListItem<T extends PhotographyValue> extends StatelessWidget {
+  final T value;
+  final bool tickOnTheLeft;
+
+  const ExposurePaitListItem(this.value, {required this.tickOnTheLeft, super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final List<Widget> rowChildren = [
+      Text(
+        value.toString(),
+        style: labelTextStyle(context).copyWith(color: Theme.of(context).colorScheme.onBackground),
+      ),
+      const SizedBox(width: Dimens.grid8),
+      ColoredBox(
+        color: Theme.of(context).colorScheme.onBackground,
+        child: SizedBox(
+          height: 1,
+          width: tickLength(),
+        ),
+      ),
+    ];
+    return Row(
+      mainAxisAlignment: tickOnTheLeft ? MainAxisAlignment.start : MainAxisAlignment.end,
+      children: tickOnTheLeft ? rowChildren.reversed.toList() : rowChildren,
+    );
+  }
+
+  TextStyle labelTextStyle(BuildContext context) {
+    switch (value.stopType) {
+      case Stop.full:
+        return Theme.of(context).textTheme.bodyLarge!;
+      case Stop.half:
+        return Theme.of(context).textTheme.bodyMedium!;
+      case Stop.third:
+        return Theme.of(context).textTheme.bodySmall!;
+    }
+  }
+
+  double tickLength() {
+    switch (value.stopType) {
+      case Stop.full:
+        return Dimens.grid24;
+      case Stop.half:
+        return Dimens.grid16;
+      case Stop.third:
+        return Dimens.grid8;
+    }
+  }
+}

lib/screens/metering/components/exposure_pairs_list/exposure_pairs_list.dart

@@ -0,0 +1,100 @@
+import 'dart:math';
+
+import 'package:flutter/material.dart';
+import 'package:lightmeter/models/photography_value.dart';
+import 'package:lightmeter/res/dimens.dart';
+import 'package:lightmeter/screens/metering/components/exposure_pairs_list/components/exposure_pair_item.dart';
+
+class ExposurePairsList extends StatelessWidget {
+  final double ev;
+  final Stop stopType;
+  final List<ApertureValue> _apertureValuesList;
+  final List<ShutterSpeedValue> _shutterSpeedValuesList;
+  late final int _apertureOffset;
+  late final int _shutterSpeedOffset;
+  late final int _itemsCount;
+
+  ExposurePairsList({
+    required this.ev,
+    required this.stopType,
+    super.key,
+  })  : _apertureValuesList = apertureValues.whereStopType(stopType),
+        _shutterSpeedValuesList = shutterSpeedValues.whereStopType(stopType) {
+    late final int evSteps;
+    switch (stopType) {
+      case Stop.full:
+        evSteps = ev.floor();
+        break;
+      case Stop.half:
+        evSteps = (ev / 0.5).floor();
+        break;
+      case Stop.third:
+        evSteps = (ev / 0.3).floor();
+        break;
+    }
+
+    final evOffset = _shutterSpeedValuesList.indexOf(const ShutterSpeedValue(1, false, Stop.full)) - evSteps;
+    if (evOffset >= 0) {
+      _apertureOffset = 0;
+      _shutterSpeedOffset = evOffset;
+    } else {
+      _apertureOffset = -evOffset;
+      _shutterSpeedOffset = 0;
+    }
+
+    _itemsCount = min(
+          _apertureValuesList.length + _shutterSpeedOffset,
+          _shutterSpeedValuesList.length + _apertureOffset,
+        ) -
+        max(
+          _apertureOffset,
+          _shutterSpeedOffset,
+        );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Stack(
+      alignment: Alignment.center,
+      children: [
+        Positioned.fill(
+          child: ListView.builder(
+            itemCount: _itemsCount,
+            itemBuilder: (_, index) => Row(
+              mainAxisAlignment: MainAxisAlignment.center,
+              children: [
+                Expanded(
+                  child: Align(
+                    alignment: Alignment.centerLeft,
+                    child: ExposurePaitListItem(
+                      _apertureValuesList[index + _apertureOffset],
+                      tickOnTheLeft: false,
+                    ),
+                  ),
+                ),
+                const SizedBox(width: Dimens.grid16),
+                Expanded(
+                  child: Align(
+                    alignment: Alignment.centerLeft,
+                    child: ExposurePaitListItem(
+                      _shutterSpeedValuesList[index + _shutterSpeedOffset],
+                      tickOnTheLeft: true,
+                    ),
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ),
+        Positioned(
+          top: 0,
+          bottom: 0,
+          child: ColoredBox(
+            color: Theme.of(context).colorScheme.onBackground,
+            child: const SizedBox(width: 1),
+          ),
+        ),
+      ],
+    );
+  }
+}

lib/screens/metering/metering_screen.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/material.dart';
+import 'package:lightmeter/models/photography_value.dart';
 
+import 'components/exposure_pairs_list/exposure_pairs_list.dart';
 import 'components/topbar/topbar.dart';
 
 class MeteringScreen extends StatelessWidget {
@@ -7,17 +9,23 @@ class MeteringScreen extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    const ev = 0.3;
     return Scaffold(
       backgroundColor: Theme.of(context).colorScheme.background,
       body: Column(
-        children: const [
+        children: [
-          MeteringTopBar(
+          const MeteringTopBar(
             lux: 283,
-            ev: 2.3,
+            ev: ev,
             iso: 6400,
             nd: 0,
           ),
-          Spacer()
+          Expanded(
+            child: ExposurePairsList(
+              ev: ev,
+              stopType: Stop.third,
+            ),
+          ),
         ],
       ),
     );