[issue: #4414 ] Added: minAngleForSlices

Source/Charts/Charts/PieChartView.swift

@@ -72,6 +72,9 @@ open class PieChartView: PieRadarChartViewBase
     /// maximum angle for this pie
     private var _maxAngle: CGFloat = 360.0
 
+    /// mininum angle for slices
+    private var _minAngleForSlices: CGFloat = 0.0
+
     public override init(frame: CGRect)
     {
         super.init(frame: frame)
@@ -249,24 +252,40 @@ open class PieChartView: PieRadarChartViewBase
     {
         _drawAngles = [CGFloat]()
         _absoluteAngles = [CGFloat]()
+        var minAngles = [CGFloat]()
 
         guard let data = data else { return }
 
         let entryCount = data.entryCount
 
         _drawAngles.reserveCapacity(entryCount)
         _absoluteAngles.reserveCapacity(entryCount)
+        minAngles.reserveCapacity(entryCount)
 
         let yValueSum = (data as! PieChartData).yValueSum
+        let hasMinAngle = _minAngleForSlices != .zero && (CGFloat(entryCount) * _minAngleForSlices) <= _maxAngle
 
         var cnt = 0
+        var offset = 0.0
+        var diff = 0.0
 
         for set in data
         {
             for j in 0 ..< set.entryCount
             {
                 guard let e = set.entryForIndex(j) else { continue }
+                let drawAngle = calcAngle(value: abs(e.y), yValueSum: yValueSum)
 
+                if hasMinAngle {
+                    let temp = drawAngle - _minAngleForSlices
+                    if temp <= 0 {
+                        minAngles.append(_minAngleForSlices)
+                        offset += -temp
+                    } else {
+                        minAngles.append(drawAngle)
+                        diff += temp
+                    }
+                }
                 _drawAngles.append(calcAngle(value: abs(e.y), yValueSum: yValueSum))
 
                 if cnt == 0
@@ -281,6 +300,20 @@ open class PieChartView: PieRadarChartViewBase
                 cnt += 1
             }
         }
+
+        if hasMinAngle {
+            for i in 0..<entryCount {
+                minAngles[i] -= (minAngles[i] - _minAngleForSlices) / diff * offset
+
+                if i == 0 {
+                    _absoluteAngles[0] = minAngles[0]
+                } else {
+                    _absoluteAngles[i] = _absoluteAngles[i - 1] + minAngles[i]
+                }
+            }
+
+            _drawAngles = minAngles
+        }
     }
 
     /// Checks if the given index is set to be highlighted.
@@ -665,6 +698,28 @@ open class PieChartView: PieRadarChartViewBase
         }
     }
 
+    /// Minimum angle to draw slices,
+    /// this only works if there is enough space for all slices to have the minimum angel
+    ///
+    /// **default**: 0.0
+    @objc open var minAngleForSlices: CGFloat
+    {
+        get
+        {
+            return _minAngleForSlices
+        }
+        set
+        {
+            _minAngleForSlices = newValue
+
+            if _minAngleForSlices > (_maxAngle / 2) {
+                _minAngleForSlices = _maxAngle / 2
+            } else if _minAngleForSlices < 0 {
+                _minAngleForSlices = .zero
+            }
+        }
+    }
+
     /// smallest pie slice angle that will have a label drawn in degrees, 0 by default
     @objc open var sliceTextDrawingThreshold: CGFloat = 0.0
     {

Tests/ChartsTests/PieChartTests.swift

@@ -76,4 +76,9 @@ class PieChartTests: XCTestCase {
         chart.highlightValue(x: 1.0, dataSetIndex: 0, callDelegate: false)
         assertChartSnapshot(matching: chart)
     }
+
+    func testMinAngleForSlices() {
+        chart.minAngleForSlices = 2
+        assertChartSnapshot(matching: chart)
+    }
 }