Feature: custom crosshair labels formatter (#305)

* fix: denormalize value before invert. * feat: add custom formatter. --------- Co-authored-by: dan12411 <dan12411@fugle.tw>
entronad · Jul 26, 2024 · 44fbd01 · 44fbd01
1 parent adfe987
commit 44fbd01
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 5 deletions.
diff --git a/lib/src/guide/interaction/crosshair.dart b/lib/src/guide/interaction/crosshair.dart
@@ -30,6 +30,7 @@ class CrosshairGuide {
     this.labelStyles,
     this.labelBackgroundStyles,
     this.showLabel,
+    this.formatter,
     this.followPointer,
     this.layer,
     this.mark,
@@ -62,6 +63,11 @@ class CrosshairGuide {
   /// If null, a default `[false, false]` is set.
   List<bool>? showLabel;
 
+  /// Convert the value to a [String] on the chart.
+  ///
+  /// If null, a default [Scale.format, Scale.format] is used.
+  List<String? Function(dynamic)?>? formatter;
+
   /// Whether the position for each dimension follows the pointer or stick to selected
   /// points.
   ///
@@ -127,6 +133,7 @@ class CrosshairRenderOp extends Render {
     final labelBackgroundStyles =
         params['labelBackgroundStyles'] as List<PaintStyle?>;
     final showLabel = params['showLabel'] as List<bool>;
+    final formatter = params['formatter'] as List<String? Function(dynamic)?>;
     final followPointer = params['followPointer'] as List<bool>;
     final scales = params['scales'] as Map<String, ScaleConv>;
     final size = params['size'] as Size;
@@ -210,7 +217,10 @@ class CrosshairRenderOp extends Render {
         if (showLabel[0] && !canvasCross.dx.isNaN && labelStyleX != null) {
           final fieldX = coord.transposed ? fields[1] : fields[0];
           final scaleX = scales[fieldX];
-          final text = scaleX?.format(scaleX.invert(cross.dx)) ?? '';
+          final denormalize = scaleX?.denormalize(cross.dx) ?? -1;
+          final invert = scaleX?.invert(denormalize);
+          final text =
+              formatter[0]?.call(invert) ?? scaleX?.format(invert) ?? '';
           final rect = _getLabelBlock(text: text, style: labelStyleX);
 
           double posX = canvasCrossX;
@@ -256,7 +266,10 @@ class CrosshairRenderOp extends Render {
         if (showLabel[1] && !canvasCross.dy.isNaN && labelStyleY != null) {
           final fieldY = coord.transposed ? fields[0] : fields[1];
           final scaleY = scales[fieldY];
-          final text = scaleY?.format(scaleY.invert(cross.dy)) ?? '';
+          final denormalize = scaleY?.denormalize(cross.dy) ?? -1;
+          final invert = scaleY?.invert(denormalize);
+          final text =
+              formatter[1]?.call(invert) ?? scaleY?.format(invert) ?? '';
           final rect = _getLabelBlock(text: text, style: labelStyleY);
 
           double posY = canvasCrossY;
@@ -297,7 +310,8 @@ class CrosshairRenderOp extends Render {
         if (showLabel[0] && labelStyleX != null) {
           final fieldX = coord.transposed ? fields[2] : fields[0];
           final scaleX = scales[fieldX];
-          final text = scaleX?.format(tuple[fieldX]) ?? '';
+          final value = tuple[fieldX];
+          final text = formatter[0]?.call(value) ?? scaleX?.format(value) ?? '';
           final diagonal = _getLabelDiagonal(text: text, style: labelStyleX);
 
           final label = LabelElement(
@@ -330,8 +344,10 @@ class CrosshairRenderOp extends Render {
         if (showLabel[1] && labelStyleY != null) {
           final fieldY = coord.transposed ? fields[0] : fields[2];
           final scaleY = scales[fieldY];
-          final value = scaleY?.invert(abstractRadius);
-          final text = scaleY?.format(value) ?? '';
+          final denormalize = scaleY?.denormalize(abstractRadius) ?? 0;
+          final invert = scaleY?.invert(denormalize);
+          final text =
+              formatter[0]?.call(invert) ?? scaleY?.format(value) ?? '';
           final rect = _getLabelBlock(text: text, style: labelStyleY);
 
           final label = LabelElement(

diff --git a/lib/src/parse/parse.dart b/lib/src/parse/parse.dart
@@ -685,6 +685,7 @@ void parse<D>(
             PaintStyle(fillColor: const Color(0xff000000)),
           ],
       'showLabel': showLabel,
+      'formatter': crosshairSpec.formatter ?? [null, null],
       'followPointer': crosshairSpec.followPointer ?? [false, false],
       'scales': scales,
       'size': size,