Ensure CCW orientation for indicator segments

src/infrastructure/rendering/gpu_structures.rs

@@ -510,14 +510,14 @@ impl CandleGeometry {
 
             // Create a rectangle as two triangles without gaps
             let segment_vertices = [
-                // First triangle
+                // First triangle (CCW)
                 CandleVertex::indicator_vertex(x1 - perp_x, y1 - perp_y, indicator_type),
-                CandleVertex::indicator_vertex(x1 + perp_x, y1 + perp_y, indicator_type),
                 CandleVertex::indicator_vertex(x2 - perp_x, y2 - perp_y, indicator_type),
-                // Second triangle
                 CandleVertex::indicator_vertex(x1 + perp_x, y1 + perp_y, indicator_type),
-                CandleVertex::indicator_vertex(x2 + perp_x, y2 + perp_y, indicator_type),
+                // Second triangle (CCW)
+                CandleVertex::indicator_vertex(x1 + perp_x, y1 + perp_y, indicator_type),
                 CandleVertex::indicator_vertex(x2 - perp_x, y2 - perp_y, indicator_type),
+                CandleVertex::indicator_vertex(x2 + perp_x, y2 + perp_y, indicator_type),
             ];
 
             vertices.extend_from_slice(&segment_vertices);

tests/indicator_vertices.rs

@@ -23,6 +23,22 @@ fn indicator_line_vertex_count() {
     assert!((verts[0].color_type - 2.0).abs() < f32::EPSILON);
 }
 
+#[wasm_bindgen_test]
+fn indicator_line_segments_are_ccw() {
+    let points = [(-0.5, 0.0), (0.5, 0.0)];
+    let verts = CandleGeometry::create_indicator_line_vertices(&points, IndicatorType::SMA20, 0.1);
+
+    let orient_first = (verts[1].position_x - verts[0].position_x)
+        * (verts[2].position_y - verts[0].position_y)
+        - (verts[1].position_y - verts[0].position_y) * (verts[2].position_x - verts[0].position_x);
+    let orient_second = (verts[4].position_x - verts[3].position_x)
+        * (verts[5].position_y - verts[3].position_y)
+        - (verts[4].position_y - verts[3].position_y) * (verts[5].position_x - verts[3].position_x);
+
+    assert!(orient_first > 0.0);
+    assert!(orient_second > 0.0);
+}
+
 #[wasm_bindgen_test]
 fn indicator_line_color_types() {
     let pts = [(-1.0, 0.0), (1.0, 1.0)];