fix(kline): 稀疏K线数据时居中显示

当K线数量较少（如1分钟图刚开始）时，K线不再拉伸填满屏幕，
而是使用默认宽度并在可用区域内水平居中显示。

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mining-app/lib/presentation/widgets/kline_chart/kline_chart_widget.dart

@@ -79,12 +79,17 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
 
     // 计算让所有 K 线占满屏幕的宽度
     final idealWidth = chartWidth / widget.klines.length;
-    // 限制在合理范围内
+    // 限制在合理范围内，但如果数据太少，使用默认宽度而不是拉伸
-    _candleWidth = idealWidth.clamp(_minCandleWidth, _maxCandleWidth);
+    if (idealWidth > _maxCandleWidth) {
+      // K 线数量少，使用默认宽度（不要拉伸太宽）
+      _candleWidth = 8.0;
+    } else {
+      _candleWidth = idealWidth.clamp(_minCandleWidth, _maxCandleWidth);
+    }
     _prevCandleWidth = _candleWidth;
 
-    // 首次加载时让最新 K 线居中显示
+    // 首次加载时让最新 K 线靠右显示
-    _scrollToCenter();
+    _scrollToEnd();
   }
 
   /// 滚动使最新 K 线居中显示
@@ -390,6 +395,7 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
                           crossLineIndex: _showCrossLine ? _crossLineIndex - visibleData.startIndex : -1,
                           candleWidth: visibleData.candleWidth,
                           isDark: AppColors.isDark(context),
+                          leftOffset: visibleData.leftOffset,
                         ),
                       ),
                       // 十字线信息
@@ -430,6 +436,7 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
                         crossLineIndex: _showCrossLine ? _crossLineIndex - visibleData.startIndex : -1,
                         candleWidth: visibleData.candleWidth,
                         isDark: AppColors.isDark(context),
+                        leftOffset: visibleData.leftOffset,
                       ),
                     ),
                   ),
@@ -570,6 +577,16 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
       return _VisibleData(klines: [], startIndex: 0, candleWidth: _candleWidth);
     }
 
+    // 计算K线总宽度（不包含左右padding）
+    const rightPadding = 50.0;  // 与 painter 中的 rightPadding 保持一致
+    const leftPadding = 8.0;    // 与 painter 中的 leftPadding 保持一致
+    final availableWidth = chartWidth - rightPadding - leftPadding;
+    final totalWidth = widget.klines.length * _candleWidth;
+
+    // 计算左侧偏移量：当K线总宽度小于可用宽度时，将K线居中显示
+    // 居中偏移 = (可用宽度 - K线总宽度) / 2
+    final leftOffset = totalWidth < availableWidth ? (availableWidth - totalWidth) / 2 : 0.0;
+
     // 根据滚动位置计算可见的K线范围
     final int startIndex = (_scrollX / _candleWidth).floor().clamp(0, widget.klines.length - 1);
     final int visibleCount = (chartWidth / _candleWidth).ceil() + 1;  // +1 确保边缘K线可见
@@ -579,6 +596,7 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
       klines: widget.klines.sublist(startIndex, endIndex),
       startIndex: startIndex,
       candleWidth: _candleWidth,
+      leftOffset: leftOffset,
     );
   }
 
@@ -771,6 +789,12 @@ class _VisibleData {
   final List<Kline> klines;
   final int startIndex;
   final double candleWidth;
+  final double leftOffset;  // K线数据稀疏时的左侧偏移，用于右对齐显示
 
-  _VisibleData({required this.klines, required this.startIndex, required this.candleWidth});
+  _VisibleData({
+    required this.klines,
+    required this.startIndex,
+    required this.candleWidth,
+    this.leftOffset = 0.0,
+  });
 }

frontend/mining-app/lib/presentation/widgets/kline_chart/kline_painter.dart

@@ -12,6 +12,7 @@ class KlinePainter extends CustomPainter {
   final int crossLineIndex;
   final double? candleWidth;  // 可选的K线宽度，不传则自动计算
   final bool isDark;  // 深色模式
+  final double leftOffset;  // K线稀疏时的左侧偏移，用于右对齐显示
 
   static const Color _green = Color(0xFF10B981);
   static const Color _red = Color(0xFFEF4444);
@@ -42,6 +43,7 @@ class KlinePainter extends CustomPainter {
     this.crossLineIndex = -1,
     this.candleWidth,
     this.isDark = false,
+    this.leftOffset = 0.0,
   });
 
   @override
@@ -137,7 +139,7 @@ class KlinePainter extends CustomPainter {
       final color = isUp ? _green : _red;
       final paint = Paint()..color = color;
 
-      final x = leftPadding + i * actualCandleWidth + actualCandleWidth / 2;
+      final x = leftPadding + leftOffset + i * actualCandleWidth + actualCandleWidth / 2;
       final yOpen = priceToY(open);
       final yClose = priceToY(close);
       final yHigh = priceToY(high);
@@ -178,7 +180,7 @@ class KlinePainter extends CustomPainter {
           canvas,
           entry.value,
           _maColors[colorIndex % _maColors.length],
-          leftPadding,
+          leftPadding + leftOffset,
           actualCandleWidth,
           priceToY,
         );
@@ -194,7 +196,7 @@ class KlinePainter extends CustomPainter {
           canvas,
           entry.value,
           _maColors[colorIndex % _maColors.length],
-          leftPadding,
+          leftPadding + leftOffset,
           actualCandleWidth,
           priceToY,
         );
@@ -204,14 +206,14 @@ class KlinePainter extends CustomPainter {
 
     // 绘制BOLL线
     if (bollData != null) {
-      _drawLine(canvas, bollData!['middle']!, _bollMiddleColor, leftPadding, actualCandleWidth, priceToY);
+      _drawLine(canvas, bollData!['middle']!, _bollMiddleColor, leftPadding + leftOffset, actualCandleWidth, priceToY);
-      _drawLine(canvas, bollData!['upper']!, _bollUpperColor, leftPadding, actualCandleWidth, priceToY, isDashed: true);
+      _drawLine(canvas, bollData!['upper']!, _bollUpperColor, leftPadding + leftOffset, actualCandleWidth, priceToY, isDashed: true);
-      _drawLine(canvas, bollData!['lower']!, _bollLowerColor, leftPadding, actualCandleWidth, priceToY, isDashed: true);
+      _drawLine(canvas, bollData!['lower']!, _bollLowerColor, leftPadding + leftOffset, actualCandleWidth, priceToY, isDashed: true);
     }
 
     // 绘制十字线
     if (crossLineIndex >= 0 && crossLineIndex < klines.length) {
-      _drawCrossLine(canvas, size, crossLineIndex, leftPadding, actualCandleWidth, priceToY);
+      _drawCrossLine(canvas, size, crossLineIndex, leftPadding + leftOffset, actualCandleWidth, priceToY);
     }
 
     // 绘制MA图例
@@ -452,6 +454,7 @@ class KlinePainter extends CustomPainter {
         oldDelegate.bollData != bollData ||
         oldDelegate.crossLineIndex != crossLineIndex ||
         oldDelegate.candleWidth != candleWidth ||
-        oldDelegate.isDark != isDark;
+        oldDelegate.isDark != isDark ||
+        oldDelegate.leftOffset != leftOffset;
   }
 }

frontend/mining-app/lib/presentation/widgets/kline_chart/kline_volume_painter.dart

@@ -9,6 +9,7 @@ class KlineVolumePainter extends CustomPainter {
   final int crossLineIndex;
   final double? candleWidth;
   final bool isDark;  // 深色模式
+  final double leftOffset;  // K线稀疏时的左侧偏移，用于右对齐显示
 
   static const Color _green = Color(0xFF10B981);
   static const Color _red = Color(0xFFEF4444);
@@ -23,6 +24,7 @@ class KlineVolumePainter extends CustomPainter {
     this.crossLineIndex = -1,
     this.candleWidth,
     this.isDark = false,
+    this.leftOffset = 0.0,
   });
 
   @override
@@ -91,7 +93,7 @@ class KlineVolumePainter extends CustomPainter {
       final isUp = close >= open;
       final color = isUp ? _green : _red;
 
-      final x = leftPadding + i * actualCandleWidth + actualCandleWidth / 2;
+      final x = leftPadding + leftOffset + i * actualCandleWidth + actualCandleWidth / 2;
       final barHeight = (volume / maxVolume) * chartHeight;
       final y = size.height - bottomPadding - barHeight;
 
@@ -106,7 +108,7 @@ class KlineVolumePainter extends CustomPainter {
 
     // 绘制十字线
     if (crossLineIndex >= 0 && crossLineIndex < klines.length) {
-      final x = leftPadding + crossLineIndex * actualCandleWidth + actualCandleWidth / 2;
+      final x = leftPadding + leftOffset + crossLineIndex * actualCandleWidth + actualCandleWidth / 2;
       canvas.drawLine(
         Offset(x, 0),
         Offset(x, size.height),
@@ -141,6 +143,7 @@ class KlineVolumePainter extends CustomPainter {
     return oldDelegate.klines != klines ||
         oldDelegate.crossLineIndex != crossLineIndex ||
         oldDelegate.candleWidth != candleWidth ||
-        oldDelegate.isDark != isDark;
+        oldDelegate.isDark != isDark ||
+        oldDelegate.leftOffset != leftOffset;
   }
 }