[Feature] added ability to rotate ChartLimitLine label (ChartsOrg#5085)

* added labelRotationAngle to ChartLimitLine

* added limit line label rotation tests

* fixed the code style
labelLineRotated_Width/Height got the same position

* generated test images for apple TV

* add snapshots on x64 arch for tvOS and iOS

---------

Co-authored-by: Xuan <liuxuan30@noreply.github.com>

Source/Charts/Components/ChartLimitLine.swift

@@ -47,6 +47,7 @@ open class ChartLimitLine: ComponentBase
     @objc open var drawLabelEnabled = true
     @objc open var label = ""
     @objc open var labelPosition = LabelPosition.rightTop
+    @objc open var labelRotationAngle = CGFloat(0.0)
 
     public override init()
     {

Source/Charts/Renderers/XAxisRenderer.swift

@@ -449,40 +449,45 @@ open class XAxisRenderer: NSObject, AxisRenderer
         // if drawing the limit-value label is enabled
         guard limitLine.drawLabelEnabled, !label.isEmpty else { return }
 
-        let labelLineHeight = limitLine.valueFont.lineHeight
+        let labelLineSize = label.size(withAttributes: [.font: limitLine.valueFont])
+        let labelLineRotatedSize = labelLineSize.rotatedBy(degrees: limitLine.labelRotationAngle)
+        let labelLineRotatedWidth = labelLineRotatedSize.width
+        let labelLineRotatedHeight = labelLineRotatedSize.height
 
         let xOffset: CGFloat = limitLine.lineWidth + limitLine.xOffset
+        let labelRotationAngleRadians = limitLine.labelRotationAngle.DEG2RAD
 
-        let align: TextAlignment
         let point: CGPoint
+        let anchor = CGPoint(x: 0.0, y: 0.0)
 
-        switch limitLine.labelPosition
-        {
+        switch limitLine.labelPosition {
         case .rightTop:
-            align = .left
-            point = CGPoint(x: position.x + xOffset,
-                            y: viewPortHandler.contentTop + yOffset)
+            point = CGPoint(
+                x: position.x + xOffset,
+                y: viewPortHandler.contentTop + yOffset)
 
         case .rightBottom:
-            align = .left
             point = CGPoint(x: position.x + xOffset,
-                            y: viewPortHandler.contentBottom - labelLineHeight - yOffset)
+                            y: viewPortHandler.contentBottom - labelLineRotatedHeight - yOffset)
 
         case .leftTop:
-            align = .right
-            point = CGPoint(x: position.x - xOffset,
+            point = CGPoint(x: position.x - labelLineRotatedWidth - xOffset,
                             y: viewPortHandler.contentTop + yOffset)
 
         case .leftBottom:
-            align = .right
-            point = CGPoint(x: position.x - xOffset,
-                            y: viewPortHandler.contentBottom - labelLineHeight - yOffset)
+            point = CGPoint(x: position.x - labelLineRotatedWidth - xOffset,
+                            y: viewPortHandler.contentBottom - labelLineRotatedHeight - yOffset)
         }
 
+        let attributes: [NSAttributedString.Key : Any] = [
+            .font: limitLine.valueFont,
+            .foregroundColor: limitLine.valueTextColor
+        ]
+
         context.drawText(label,
                          at: point,
-                         align: align,
-                         attributes: [.font: limitLine.valueFont,
-                                      .foregroundColor: limitLine.valueTextColor])
+                         anchor: anchor,
+                         angleRadians: labelRotationAngleRadians,
+                         attributes: attributes)
     }
 }

Source/Charts/Renderers/XAxisRendererHorizontalBarChart.swift

@@ -249,41 +249,48 @@ open class XAxisRendererHorizontalBarChart: XAxisRenderer
             // if drawing the limit-value label is enabled
             if l.drawLabelEnabled, !label.isEmpty
             {
-                let labelLineHeight = l.valueFont.lineHeight
-
+
+                let labelLineSize = label.size(withAttributes: [.font: l.valueFont])
+                let labelLineRotatedSize = labelLineSize.rotatedBy(degrees: l.labelRotationAngle)
+                let labelLineRotatedWidth = labelLineRotatedSize.width
+                let labelLineRotatedHeight = labelLineRotatedSize.height
+
                 let xOffset = 4.0 + l.xOffset
-                let yOffset = l.lineWidth + labelLineHeight + l.yOffset
+                let yOffset = l.lineWidth + labelLineRotatedHeight + l.yOffset
+                let labelRotationAngleRadians = l.labelRotationAngle.DEG2RAD
 
-                let align: TextAlignment
                 let point: CGPoint
+                let anchor = CGPoint(x: 0.0, y: 0.0)
 
                 switch l.labelPosition
                 {
                 case .rightTop:
-                    align = .right
-                    point = CGPoint(x: viewPortHandler.contentRight - xOffset,
+                    point = CGPoint(x: viewPortHandler.contentRight - labelLineRotatedWidth - xOffset,
                                     y: position.y - yOffset)
 
                 case .rightBottom:
-                    align = .right
-                    point = CGPoint(x: viewPortHandler.contentRight - xOffset,
-                                    y: position.y + yOffset - labelLineHeight)
+                    point = CGPoint(x: viewPortHandler.contentRight - labelLineRotatedWidth - xOffset,
+                                    y: position.y - labelLineRotatedHeight + yOffset)
 
                 case .leftTop:
-                    align = .left
                     point = CGPoint(x: viewPortHandler.contentLeft + xOffset,
                                     y: position.y - yOffset)
 
                 case .leftBottom:
-                    align = .left
                     point = CGPoint(x: viewPortHandler.contentLeft + xOffset,
-                                    y: position.y + yOffset - labelLineHeight)
+                                    y: position.y - labelLineRotatedHeight + yOffset)
                 }
 
+                let attributes: [NSAttributedString.Key : Any] = [
+                    .font: l.valueFont,
+                    .foregroundColor: l.valueTextColor
+                ]
+
                 context.drawText(label,
                                  at: point,
-                                 align: align,
-                                 attributes: [.font: l.valueFont, .foregroundColor: l.valueTextColor])
+                                 anchor: anchor,
+                                 angleRadians: labelRotationAngleRadians,
+                                 attributes: attributes)
             }
         }
     }

Source/Charts/Renderers/YAxisRenderer.swift

@@ -295,41 +295,47 @@ open class YAxisRenderer: NSObject, AxisRenderer
             // if drawing the limit-value label is enabled
             guard l.drawLabelEnabled, !label.isEmpty else { continue }
 
-            let labelLineHeight = l.valueFont.lineHeight
-
+            let labelLineSize = label.size(withAttributes: [.font: l.valueFont])
+            let labelLineRotatedSize = labelLineSize.rotatedBy(degrees: l.labelRotationAngle)
+            let labelLineRotatedWidth = labelLineRotatedSize.width
+            let labelLineRotatedHeight = labelLineRotatedSize.height
+
             let xOffset = 4.0 + l.xOffset
-            let yOffset = l.lineWidth + labelLineHeight + l.yOffset
+            let yOffset = l.lineWidth + labelLineRotatedHeight + l.yOffset
+            let labelRotationAngleRadians = l.labelRotationAngle.DEG2RAD
 
-            let align: TextAlignment
             let point: CGPoint
+            let anchor = CGPoint(x: 0.0, y: 0.0)
 
             switch l.labelPosition
             {
             case .rightTop:
-                align = .right
-                point = CGPoint(x: viewPortHandler.contentRight - xOffset,
+                point = CGPoint(x: viewPortHandler.contentRight - labelLineRotatedWidth - xOffset,
                                 y: position.y - yOffset)
 
             case .rightBottom:
-                align = .right
-                point = CGPoint(x: viewPortHandler.contentRight - xOffset,
-                                y: position.y + yOffset - labelLineHeight)
+                point = CGPoint(x: viewPortHandler.contentRight - labelLineRotatedWidth - xOffset,
+                                y: position.y - labelLineRotatedHeight + yOffset)
 
             case .leftTop:
-                align = .left
                 point = CGPoint(x: viewPortHandler.contentLeft + xOffset,
                                 y: position.y - yOffset)
 
             case .leftBottom:
-                align = .left
                 point = CGPoint(x: viewPortHandler.contentLeft + xOffset,
-                                y: position.y + yOffset - labelLineHeight)
+                                y: position.y - labelLineRotatedHeight + yOffset)
             }
 
+            let attributes: [NSAttributedString.Key : Any] = [
+                .font: l.valueFont,
+                .foregroundColor: l.valueTextColor
+            ]
+
             context.drawText(label,
                              at: point,
-                             align: align,
-                             attributes: [.font: l.valueFont, .foregroundColor: l.valueTextColor])
+                             anchor: anchor,
+                             angleRadians: labelRotationAngleRadians,
+                             attributes: attributes)
         }
     }
 

Source/Charts/Renderers/YAxisRendererHorizontalBarChart.swift

@@ -253,41 +253,47 @@ open class YAxisRendererHorizontalBarChart: YAxisRenderer
             // if drawing the limit-value label is enabled
             if l.drawLabelEnabled, !label.isEmpty
             {
-                let labelLineHeight = l.valueFont.lineHeight
-
+                let labelLineSize = label.size(withAttributes: [.font: l.valueFont])
+                let labelLineRotatedSize = labelLineSize.rotatedBy(degrees: l.labelRotationAngle)
+                let labelLineRotatedWidth = labelLineRotatedSize.width
+                let labelLineRotatedHeight = labelLineRotatedSize.height
+
                 let xOffset = l.lineWidth + l.xOffset
                 let yOffset = 2.0 + l.yOffset
+                let labelRotationAngleRadians = l.labelRotationAngle.DEG2RAD
 
-                let align: TextAlignment
                 let point: CGPoint
+                let anchor = CGPoint(x: 0.0, y: 0.0)
 
                 switch l.labelPosition
                 {
                 case .rightTop:
-                    align = .left
                     point = CGPoint(x: position.x + xOffset,
                                     y: viewPortHandler.contentTop + yOffset)
 
                 case .rightBottom:
-                    align = .left
                     point = CGPoint(x: position.x + xOffset,
-                                    y: viewPortHandler.contentBottom - labelLineHeight - yOffset)
+                                    y: viewPortHandler.contentBottom - labelLineRotatedHeight - yOffset)
 
                 case .leftTop:
-                    align = .right
-                    point = CGPoint(x: position.x - xOffset,
+                    point = CGPoint(x: position.x - labelLineRotatedWidth - xOffset,
                                     y: viewPortHandler.contentTop + yOffset)
 
                 case .leftBottom:
-                    align = .right
-                    point = CGPoint(x: position.x - xOffset,
-                                    y: viewPortHandler.contentBottom - labelLineHeight - yOffset)
+                    point = CGPoint(x: position.x - labelLineRotatedWidth - xOffset,
+                                    y: viewPortHandler.contentBottom - labelLineRotatedHeight - yOffset)
                 }
 
+                let attributes: [NSAttributedString.Key : Any] = [
+                    .font: l.valueFont,
+                    .foregroundColor: l.valueTextColor
+                ]
+
                 context.drawText(label,
                                  at: point,
-                                 align: align,
-                                 attributes: [.font: l.valueFont, .foregroundColor: l.valueTextColor])
+                                 anchor: anchor,
+                                 angleRadians: labelRotationAngleRadians,
+                                 attributes: attributes)
             }
         }
     }

Tests/ChartsTests/LineChartTests.swift

@@ -69,4 +69,41 @@ class LineChartTests: XCTestCase {
         dataSet.drawIconsEnabled = true
         assertChartSnapshot(matching: chart)
     }
+
+    func testLimitLineLabelRotatedBy180() {
+        addLimitLineWithRotatedAngle(labelPosition: .rightBottom, labelRotationAngle: 180)
+        assertChartSnapshot(matching: chart)
+    }
+
+    func testLimitLineLabelRotatedBy120() {
+        addLimitLineWithRotatedAngle(labelPosition: .rightTop, labelRotationAngle: 120)
+        assertChartSnapshot(matching: chart)
+    }
+
+    func testLimitLineLabelRotatedBy90() {
+        addLimitLineWithRotatedAngle(labelPosition: .leftTop, labelRotationAngle: 90)
+        assertChartSnapshot(matching: chart)
+    }
+
+    func testLimitLineLabelRotatedBy45() {
+        addLimitLineWithRotatedAngle(labelPosition: .leftBottom, labelRotationAngle: 45)
+        assertChartSnapshot(matching: chart)
+    }
+
+    func testLimitLineLabelRotatedBy30() {
+        addLimitLineWithRotatedAngle(labelPosition: .leftBottom, labelRotationAngle: 30)
+        assertChartSnapshot(matching: chart)
+    }
+
+    func testLimitLineLabelDefaultRotation() {
+        addLimitLineWithRotatedAngle(labelPosition: .rightTop, labelRotationAngle: 0)
+        assertChartSnapshot(matching: chart)
+    }
+
+    private func addLimitLineWithRotatedAngle(labelPosition: ChartLimitLine.LabelPosition, labelRotationAngle: CGFloat) {
+        let limitline = ChartLimitLine(limit: 50, label: "Limit Line")
+        limitline.labelPosition = labelPosition
+        limitline.labelRotationAngle = labelRotationAngle
+        chart.leftAxis.addLimitLine(limitline)
+    }
 }