chore(client): improve chart rendering

packages/client/src/components/chart.vue

@@ -143,6 +143,7 @@ export default defineComponent({
 			}
 
 			const gridColor = defaultStore.state.darkMode ? 'rgba(255, 255, 255, 0.1)' : 'rgba(0, 0, 0, 0.1)';
+			const vLineColor = defaultStore.state.darkMode ? 'rgba(255, 255, 255, 0.2)' : 'rgba(0, 0, 0, 0.2)';
 
 			// フォントカラー
 			Chart.defaults.color = getComputedStyle(document.documentElement).getPropertyValue('--fg');
@@ -255,6 +256,27 @@ export default defineComponent({
 						},
 					},
 				},
+				plugins: [{
+					id: 'vLine',
+					beforeDraw(chart, args, options) {
+						if (chart.tooltip._active && chart.tooltip._active.length) {
+							const activePoint = chart.tooltip._active[0];
+							const ctx = chart.ctx;
+							const x = activePoint.element.x;
+							const topY = chart.scales.y.top;
+							const bottomY = chart.scales.y.bottom;
+
+							ctx.save();
+							ctx.beginPath();
+							ctx.moveTo(x, bottomY);
+							ctx.lineTo(x, topY);
+							ctx.lineWidth = 1;
+							ctx.strokeStyle = vLineColor;
+							ctx.stroke();
+							ctx.restore();
+						}
+					}
+				}]
 			});
 		};