From 47e836b2678cb9581fe22a1690315f7e9671ccb5 Mon Sep 17 00:00:00 2001
From: przemyslawpetka <przemek946@gmail.com>
Date: Fri, 13 Jun 2025 11:29:15 +0200
Subject: [PATCH] percentages on pie chart

---
 .../multiplatform/charts/pie/PieChart.kt      | 42 +++++++++++++++++++
 .../charts/pie/PieChartConfig.kt              |  1 +
 2 files changed, 43 insertions(+)

diff --git a/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChart.kt b/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChart.kt
index 9aa1974..210ac47 100644
--- a/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChart.kt
+++ b/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChart.kt
@@ -18,6 +18,10 @@ import androidx.compose.ui.graphics.PathOperation
 import androidx.compose.ui.graphics.drawscope.DrawScope
 import androidx.compose.ui.graphics.drawscope.Stroke
 import androidx.compose.ui.graphics.drawscope.clipPath
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.text.drawText
+import androidx.compose.ui.text.rememberTextMeasurer
 import com.netguru.multiplatform.charts.ChartAnimation
 import com.netguru.multiplatform.charts.StartAnimation
 import com.netguru.multiplatform.charts.mapValueToDifferentRange
@@ -26,6 +30,7 @@ import com.netguru.multiplatform.charts.pie.PieDefaults.START_ANGLE
 import kotlin.math.PI
 import kotlin.math.cos
 import kotlin.math.min
+import kotlin.math.roundToInt
 import kotlin.math.sin
 
 data class PieChartData(val name: String, val value: Double, val color: Color)
@@ -79,6 +84,15 @@ fun PieChart(
             )
         )
     }
+    val textMeasurer = rememberTextMeasurer()
+    val textLayouts = sweepAngles.mapIndexed { index, _ ->
+        val percent = (data[index].value / sumOfData * 100).roundToInt()
+        val text = "$percent%"
+        val layoutResult = textMeasurer.measure(
+            text = AnnotatedString(text),
+        )
+        layoutResult
+    }
 
     Box(
         modifier = modifier
@@ -97,6 +111,13 @@ fun PieChart(
                             sweepAngle = sweepAngle.toFloat(),
                             config = config,
                         )
+                        if (config.showPercentages) {
+                            drawPercentageLabel(
+                                textLayoutResult = textLayouts[index],
+                                startAngle = startAngle,
+                                sweepAngle = sweepAngle
+                            )
+                        }
                         startAngle += sweepAngle
                     }
                 }
@@ -136,6 +157,27 @@ private fun DrawScope.drawArc(
     )
 }
 
+private fun DrawScope.drawPercentageLabel(
+    textLayoutResult: TextLayoutResult,
+    startAngle: Double,
+    sweepAngle: Double,
+) {
+    val midAngle = startAngle + sweepAngle / 2
+    val angleRad = Math.toRadians(midAngle)
+    val radius = size.minDimension / 2f * 0.65f
+
+    val x = center.x + cos(angleRad).toFloat() * radius
+    val y = center.y + sin(angleRad).toFloat() * radius
+
+    drawText(
+        textLayoutResult = textLayoutResult,
+        topLeft = Offset(
+            x - textLayoutResult.size.width / 2f,
+            y - textLayoutResult.size.height / 2f
+        )
+    )
+}
+
 private const val RIGHT_ANGLE = 90f
 private const val HALF_CIRCLE_ANGLE = 180f
 private const val FULL_CIRCLE_ANGLE = 360f
diff --git a/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChartConfig.kt b/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChartConfig.kt
index 55ff2ea..2781eac 100644
--- a/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChartConfig.kt
+++ b/charts/src/commonMain/kotlin/com/netguru/multiplatform/charts/pie/PieChartConfig.kt
@@ -27,6 +27,7 @@ data class PieChartConfig(
     val legendIconSize: Dp = PieDefaults.LEGEND_ICON_SIZE,
     val legendOrientation: LegendOrientation = LegendOrientation.HORIZONTAL,
     val numberOfColsInLegend: Int = PieDefaults.NUMBER_OF_COLS_IN_LEGEND,
+    val showPercentages: Boolean = false
 )
 
 enum class LegendIcon {