✅ added alt offset feature (2/2)

Author: softmarshmallow

example/lib/screen/plain_timeline_demo.dart

@@ -2,6 +2,7 @@ import 'dart:math';
 
 import 'package:flutter/material.dart';
 import 'package:flutter_timeline/flutter_timeline.dart';
+import 'package:flutter_timeline/indicator_position.dart';
 import 'package:flutter_timeline/timeline_theme.dart';
 import 'package:flutter_timeline/timeline_theme_data.dart';
 
@@ -80,7 +81,7 @@ class _PlainTimelineDemoScreenState extends State<PlainTimelineDemoScreen> {
   TimelineEventDisplay get plainEventDisplay {
     return TimelineEventDisplay(
         child: TimelineEventCard(
-          title: Text("just now"),
+          title: Text("just \n\n\n\n now"),
           content: Text("someone commented on your timeline ${DateTime.now()}"),
         ),
         indicator: randomIndicator);
@@ -92,6 +93,8 @@ class _PlainTimelineDemoScreenState extends State<PlainTimelineDemoScreen> {
     return TimelineTheme(
         data: TimelineThemeData(lineColor: Colors.blueAccent),
         child: Timeline(
+          indicatorPosition: IndicatorPosition.top,
+          altOffset: Offset(0, -24),
           indicatorSize: 56,
           events: events,
         ));

lib/event_item.dart

@@ -1,11 +1,15 @@
 import 'package:flutter/material.dart';
 
+import 'indicator_position.dart';
+
 class TimelineEventDisplay {
-  TimelineEventDisplay(
-      {@required @required this.child,
-      this.indicator,
-      this.indicatorSize,
-      this.forceLineDrawing = false});
+  TimelineEventDisplay({
+    @required @required this.child,
+    this.indicator,
+    this.indicatorSize,
+    this.forceLineDrawing = false,
+    this.indicatorPosition,
+  });
 
   final Widget child;
 
@@ -16,6 +20,9 @@ class TimelineEventDisplay {
   /// enables indicator line drawing even no indicator is passed.
   final bool forceLineDrawing;
 
+  /// [indicatorPosition] overrides the default IndicatorPosition
+  final IndicatorPosition indicatorPosition;
+
   bool get hasIndicator {
     return indicator != null;
   }

lib/timeline.dart

@@ -4,21 +4,24 @@ import 'package:flutter_timeline/event_item.dart';
 import 'package:flutter_timeline/timeline_theme.dart';
 import 'package:flutter_timeline/timeline_theme_data.dart';
 
+import 'indicator_position.dart';
+
 class Timeline extends StatelessWidget {
-  const Timeline({
-    @required this.events,
-    this.isLeftAligned = true,
-    this.padding = const EdgeInsets.all(8),
-    this.controller,
-    this.physics,
-    this.shrinkWrap = true,
-    this.primary = false,
-    this.reverse = false,
-    this.indicatorSize = 12.0,
-    // item gap will be ignored when custom separatorBuilder is provided
-    this.separatorBuilder,
-    this.altOffset = const Offset(0, 0),
-  }) : itemCount = events.length;
+  const Timeline(
+      {@required this.events,
+      this.isLeftAligned = true,
+      this.padding = const EdgeInsets.all(8),
+      this.controller,
+      this.physics,
+      this.shrinkWrap = true,
+      this.primary = false,
+      this.reverse = false,
+      this.indicatorSize = 12.0,
+      // item gap will be ignored when custom separatorBuilder is provided
+      this.separatorBuilder,
+      this.altOffset = const Offset(0, 0),
+      this.indicatorPosition = IndicatorPosition.center})
+      : itemCount = events.length;
 
   final Offset altOffset;
   final List<TimelineEventDisplay> events;
@@ -32,6 +35,9 @@ class Timeline extends StatelessWidget {
   final bool primary;
   final bool reverse;
 
+  /// [indicatorPosition] describes where the indicator drawing should start. use it with alt offset
+  final IndicatorPosition indicatorPosition;
+
   final IndexedWidgetBuilder separatorBuilder;
 
   @override
@@ -50,13 +56,24 @@ class Timeline extends StatelessWidget {
       primary: primary,
       itemBuilder: (context, index) {
         final event = events[index];
+        // safely get prev, next events
+        TimelineEventDisplay prevEvent;
+        TimelineEventDisplay nextEvent;
+        if (index != 0) {
+          prevEvent = events[index - 1];
+        }
+        if (index != events.length - 1) {
+          nextEvent = events[index + 1];
+        }
         final isFirst = index == 0;
         final isLast = index == itemCount - 1;
         final timelineTile = <Widget>[
           if (event.hasIndicator)
             _buildIndicatorSection(
                 isFirst: isFirst,
                 isLast: isLast,
+                prevHasIndicator: _eventHasIndicator(prevEvent),
+                nextHasIndicator: _eventHasIndicator(nextEvent),
                 event: event,
                 theme: timelineTheme),
           if (event.hasIndicator) SizedBox(width: timelineTheme.gutterSpacing),
@@ -74,6 +91,13 @@ class Timeline extends StatelessWidget {
     );
   }
 
+  bool _eventHasIndicator(TimelineEventDisplay event) {
+    if (event == null) {
+      return false;
+    }
+    return event.hasIndicator;
+  }
+
   Widget buildWrappedIndicator(Widget child, {double width, double height}) {
     return Container(
       width: width,
@@ -86,10 +110,16 @@ class Timeline extends StatelessWidget {
   Widget _buildIndicatorSection(
       {bool isFirst,
       bool isLast,
+      bool prevHasIndicator,
+      bool nextHasIndicator,
       TimelineEventDisplay event,
       TimelineThemeData theme}) {
     var overrideIndicatorSize =
         event.indicatorSize != null ? event.indicatorSize : indicatorSize;
+    var overrideIndicatorPosition = event.indicatorPosition != null
+        ? event.indicatorPosition
+        : indicatorPosition;
+
     var line = CustomPaint(
       painter: _LineIndicatorPainter(
         hideDefaultIndicator: event.child != null,
@@ -104,6 +134,9 @@ class Timeline extends StatelessWidget {
         style: theme.style,
         itemGap: theme.itemGap,
         altOffset: altOffset,
+        prevHasIndicator: prevHasIndicator,
+        nextHasIndicator: nextHasIndicator,
+        indicatorPosition: overrideIndicatorPosition,
       ),
       child: SizedBox(height: double.infinity, width: indicatorSize),
     );
@@ -125,20 +158,23 @@ class Timeline extends StatelessWidget {
 }
 
 class _LineIndicatorPainter extends CustomPainter {
-  _LineIndicatorPainter({
-    @required this.hideDefaultIndicator,
-    @required this.indicatorSize,
-    @required this.altOffset,
-    @required this.maxIndicatorSize,
-    @required this.lineGap,
-    @required this.strokeCap,
-    @required this.strokeWidth,
-    @required this.style,
-    @required this.lineColor,
-    @required this.isFirst,
-    @required this.isLast,
-    @required this.itemGap,
-  }) : linePaint = Paint()
+  _LineIndicatorPainter(
+      {@required this.hideDefaultIndicator,
+      @required this.indicatorSize,
+      @required this.altOffset,
+      @required this.maxIndicatorSize,
+      @required this.lineGap,
+      @required this.strokeCap,
+      @required this.strokeWidth,
+      @required this.style,
+      @required this.lineColor,
+      @required this.isFirst,
+      @required this.isLast,
+      @required this.nextHasIndicator,
+      @required this.prevHasIndicator,
+      @required this.itemGap,
+      @required this.indicatorPosition})
+      : linePaint = Paint()
           ..color = lineColor
           ..strokeCap = strokeCap
           ..strokeWidth = strokeWidth
@@ -156,31 +192,62 @@ class _LineIndicatorPainter extends CustomPainter {
   final Paint linePaint;
   final bool isFirst;
   final bool isLast;
+  final bool nextHasIndicator;
+  final bool prevHasIndicator;
   final double itemGap;
+  final IndicatorPosition indicatorPosition;
+
+  double get altX {
+    return altOffset.dx;
+  }
+
+  double get altY {
+    return altOffset.dy;
+  }
 
   @override
   void paint(Canvas canvas, Size size) {
     final indicatorRadius = indicatorSize / 2;
     final maxIndicatorRadius = maxIndicatorSize / 2;
     final indicatorMargin = indicatorRadius + lineGap;
     final safeItemGap = (indicatorSize / 2) + lineGap;
-    final altY = altOffset.dy;
+    double topStartY = 0.0;
+    // region calculate starting point
+/*
+    switch (indicatorPosition) {
+      case IndicatorPosition.top:
+        topStartY = -size.height / 2;
+        break;
+      case IndicatorPosition.center:
+        topStartY = 0;
+        break;
+      case IndicatorPosition.bottom:
+        //        startY = size.height / 2;
+        break;
+    }*/
+    // endregion
 
-    // todo
-    // calculate starting point
-    // calculate alt point
-    // use alt point as default point
+    // region override top, bottom calculator for filling empty space between events
+    double overrideOffsetYForTop = altY;
+    double overrideOffsetYForBottom = altY;
+    if (!prevHasIndicator) {
+      overrideOffsetYForTop = 0.0;
+    }
+    if (!nextHasIndicator) {
+      overrideOffsetYForBottom = 0.0;
+    }
+    // endregion
 
-    final top =
-        size.topLeft(Offset(maxIndicatorRadius, 0.0 - safeItemGap + altY));
+    final top = size.topLeft(Offset(maxIndicatorRadius + altX,
+        topStartY - safeItemGap + overrideOffsetYForTop));
     final topOfCenter = size.centerLeft(
-      Offset(maxIndicatorRadius, -indicatorMargin + altY),
+      Offset(maxIndicatorRadius + altX, -indicatorMargin + altY),
     );
 
-    final bottom =
-        size.bottomLeft(Offset(maxIndicatorRadius, 0.0 + safeItemGap + altY));
+    final bottom = size.bottomLeft(Offset(maxIndicatorRadius + altX,
+        0.0 + safeItemGap + overrideOffsetYForBottom));
     final bottomOfCenter = size.centerLeft(
-      Offset(maxIndicatorRadius, indicatorMargin + altY),
+      Offset(maxIndicatorRadius + altX, indicatorMargin + altY),
     );
 
     // if not first, draw top-to-center  upper line