feat: display arrow in SVG export

java/pom.xml

@@ -57,6 +57,12 @@
             <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>

java/src/main/java/io/process/analytics/tools/bpmn/generator/export/SVGExporter.java

@@ -17,9 +17,12 @@
 
 import static io.process.analytics.tools.bpmn.generator.internal.StringUtils.defaultIfNull;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.stream.Collectors;
 
 import io.process.analytics.tools.bpmn.generator.converter.AlgoToDisplayModelConverter;
+import io.process.analytics.tools.bpmn.generator.converter.waypoint.Direction;
 import io.process.analytics.tools.bpmn.generator.model.Diagram;
 import io.process.analytics.tools.bpmn.generator.model.Grid;
 import io.process.analytics.tools.bpmn.generator.model.ShapeType;
@@ -51,6 +54,7 @@ public String export(Grid grid, Diagram diagram) {
         final String colorEgeStroke = "Black";
         final int edgeStrokeWidth = 2;
         final double edgeStrokeOpacity = 0.5;
+        final int edgeArrowHeight = 10;
 
         for (DisplayFlowNode flowNode : model.flowNodes) {
             DisplayDimension flowNodeDimension = flowNode.dimension;
@@ -158,16 +162,41 @@ else if (flowNode.type == ShapeType.GATEWAY) {
                         .append(" fill=\"none\"")
                         .append(" />\n");
 
-                // highlight target point
-                DisplayPoint targetPoint = edge.wayPoints.get(edge.wayPoints.size() - 1);
-                content.append("<circle")
-                        .append(" cx=\"").append(targetPoint.x).append("\"")
-                        .append(" cy=\"").append(targetPoint.y).append("\"")
-                        .append(" r=\"").append("5").append("\"")
+                // edge arrow
+                List<DisplayPoint> wayPoints = edge.wayPoints;
+                Direction lastSegmentDirection = detectLastSegmentDirection(wayPoints);
+                DisplayPoint last = wayPoints.get(wayPoints.size() - 1);
+
+                List<DisplayPoint> arrowPoints = new ArrayList<>();
+
+                if (lastSegmentDirection == Direction.LeftToRight) {
+                    arrowPoints.add(new DisplayPoint(last.x, last.y)); // top of the arrow
+                    arrowPoints.add(new DisplayPoint(last.x - edgeArrowHeight, last.y + edgeArrowHeight / 2));
+                    arrowPoints.add(new DisplayPoint(last.x - edgeArrowHeight, last.y - edgeArrowHeight / 2));
+                } else if (lastSegmentDirection == Direction.RightToLeft) {
+                    arrowPoints.add(new DisplayPoint(last.x, last.y)); // top of the arrow
+                    arrowPoints.add(new DisplayPoint(last.x + edgeArrowHeight, last.y + edgeArrowHeight / 2));
+                    arrowPoints.add(new DisplayPoint(last.x + edgeArrowHeight, last.y - edgeArrowHeight / 2));
+                } else if (lastSegmentDirection == Direction.TopToBottom) {
+                    arrowPoints.add(new DisplayPoint(last.x, last.y)); // top of the arrow
+                    arrowPoints.add(new DisplayPoint(last.x - edgeArrowHeight / 2, last.y - edgeArrowHeight));
+                    arrowPoints.add(new DisplayPoint(last.x + edgeArrowHeight / 2, last.y - edgeArrowHeight));
+                } else if (lastSegmentDirection == Direction.BottomToTop) {
+                    arrowPoints.add(new DisplayPoint(last.x, last.y)); // top of the arrow
+                    arrowPoints.add(new DisplayPoint(last.x - edgeArrowHeight / 2, last.y + edgeArrowHeight));
+                    arrowPoints.add(new DisplayPoint(last.x + edgeArrowHeight / 2, last.y + edgeArrowHeight));
+                }
+
+                content.append("<polygon")
                         .append(" stroke=\"").append(colorEgeStroke).append("\"")
                         .append(" stroke-width=\"").append(edgeStrokeWidth).append("\"")
                         .append(" stroke-opacity=\"").append(edgeStrokeOpacity).append("\"")
                         .append(" fill=\"").append(colorEgeStroke).append("\"")
+                        .append(" points=\"")
+                        .append(arrowPoints.stream()
+                                .map(point -> point.x + "," + point.y)
+                                .collect(Collectors.joining(" ")))
+                        .append("\"")
                         .append(" />\n");
             }
         }
@@ -176,4 +205,16 @@ else if (flowNode.type == ShapeType.GATEWAY) {
         return content.toString();
     }
 
+    // here we assume that we have only vertical and horizontal segments, and we have at least 2 points in the list
+    // visible for testing
+    static Direction detectLastSegmentDirection(List<DisplayPoint> wayPoints) {
+        DisplayPoint last = wayPoints.get(wayPoints.size() - 1);
+        DisplayPoint beforeLast = wayPoints.get(wayPoints.size() - 2);
+        // horizontal
+        if (last.x == beforeLast.x) {
+            return last.y > beforeLast.y ? Direction.TopToBottom : Direction.BottomToTop;
+        }
+        // vertical
+        return last.x > beforeLast.x ? Direction.LeftToRight : Direction.RightToLeft;
+    }
 }

java/src/test/java/io/process/analytics/tools/bpmn/generator/export/SVGExporterTest.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2024 Bonitasoft S.A.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.process.analytics.tools.bpmn.generator.export;
+
+import io.process.analytics.tools.bpmn.generator.converter.waypoint.Direction;
+import io.process.analytics.tools.bpmn.generator.model.display.DisplayPoint;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SVGExporterTest {
+
+    @ParameterizedTest
+    @MethodSource("provideWaypointsForDirectionDetection")
+    void detect_last_segment_direction(List<DisplayPoint> waypoints, Direction expectedDirection) {
+        var direction = SVGExporter.detectLastSegmentDirection(waypoints);
+        assertThat(direction).isEqualTo(expectedDirection);
+    }
+
+    private static Stream<Arguments> provideWaypointsForDirectionDetection() {
+        return Stream.of(
+                Arguments.of(List.of(new DisplayPoint(0, 37), new DisplayPoint(10, 37)), Direction.LeftToRight),
+                Arguments.of(List.of(new DisplayPoint(40, 58), new DisplayPoint(10, 58)), Direction.RightToLeft),
+                Arguments.of(List.of(new DisplayPoint(13, 73), new DisplayPoint(13, 137)), Direction.TopToBottom),
+                Arguments.of(List.of(new DisplayPoint(33, 73), new DisplayPoint(33, 37)), Direction.BottomToTop)
+        );
+    }
+
+}
+