add callback symbol example to gallery

gallery/src/lib.rs

@@ -110,6 +110,7 @@ lazy_static! {
         insert!(m, line, area_pieces);
         insert!(m, line, basic_area);
         insert!(m, line, basic_line);
+        insert!(m, line, different_symbols);
         insert!(m, line, confidence_band);
         insert!(m, line, data_transform_filter);
         insert!(m, line, distribution_of_electricity);

gallery/src/line/different_symbols.rs

@@ -0,0 +1,19 @@
+use charming::{
+    component::Axis,
+    element::{AxisType, Symbol},
+    series::Line,
+    Chart,
+};
+
+pub fn chart() -> Chart {
+    Chart::new()
+        .x_axis(
+            Axis::new()
+                .type_(AxisType::Category)
+                .data(vec!["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]),
+        )
+        .y_axis(Axis::new().type_(AxisType::Value))
+        .series(Line::new().data(vec![150, 230, 224, 218, 135, 147, 260])
+        .symbol_size(20)
+        .symbol(Symbol::Callback("function (value, params) { return params.dataIndex % 2 === 0 ? value > 200 ? 'diamond' : 'circle' : 'triangle'; }".into())))
+}

gallery/src/line/mod.rs

@@ -3,6 +3,7 @@ pub mod basic_area;
 pub mod basic_line;
 pub mod confidence_band;
 pub mod data_transform_filter;
+pub mod different_symbols;
 pub mod distribution_of_electricity;
 pub mod gradient_stacked_area;
 pub mod large_scale_area;