Complete phase two benchmarks, plot previews and static export workflow

backend/app/plot/model.py

@@ -1,7 +1,7 @@
 """Function Plot 内部数据模型。
 
-契约 §12.2 的 FunctionPlot 结构与 §10.4 的 StaticRenderResult 只在导出链路的后端内部
-流转，不进入 HTTP 契约，因此与 Document AST 一样放在独立包内，不进 contracts.py。
+FunctionPlot 供预览和导出共享；StaticRenderResult 同时是交互预览端点的响应内容。
+模型保留在独立包内，由 plot_routes 中的请求与响应类型注册 OpenAPI。
 """
 
 from __future__ import annotations

backend/app/plot/render.py

@@ -413,12 +413,12 @@ def _grid_svg(geo: PlotGeometry) -> str:
     for x in geo.xticks:
         parts.append(
             f'<line x1="{sx(x):.2f}" y1="{sy(geo.ymin):.2f}" x2="{sx(x):.2f}" '
-            f'y2="{sy(geo.ymax):.2f}" stroke="#eaeef2"/>'
+            f'y2="{sy(geo.ymax):.2f}" stroke="#eaeef2" class="plot-grid"/>'
         )
     for y in geo.yticks:
         parts.append(
             f'<line x1="{sx(geo.xmin):.2f}" y1="{sy(y):.2f}" x2="{sx(geo.xmax):.2f}" '
-            f'y2="{sy(y):.2f}" stroke="#eaeef2"/>'
+            f'y2="{sy(y):.2f}" stroke="#eaeef2" class="plot-grid"/>'
         )
     return "".join(parts)
 
@@ -430,11 +430,11 @@ def _axes_svg(geo: PlotGeometry) -> str:
     # 坐标轴：过原点则画在原点，否则贴边，保证始终有参照系
     parts.append(
         f'<line x1="{sx(geo.xmin):.2f}" y1="{sy(geo.x_axis_y):.2f}" x2="{sx(geo.xmax):.2f}" '
-        f'y2="{sy(geo.x_axis_y):.2f}" stroke="#57606a"/>'
+        f'y2="{sy(geo.x_axis_y):.2f}" stroke="#57606a" class="plot-axis"/>'
     )
     parts.append(
         f'<line x1="{sx(geo.y_axis_x):.2f}" y1="{sy(geo.ymin):.2f}" x2="{sx(geo.y_axis_x):.2f}" '
-        f'y2="{sy(geo.ymax):.2f}" stroke="#57606a"/>'
+        f'y2="{sy(geo.ymax):.2f}" stroke="#57606a" class="plot-axis"/>'
     )
     # x 轴刻度数字（画在轴下方）
     for x in geo.xticks:
@@ -453,10 +453,10 @@ def _axes_svg(geo: PlotGeometry) -> str:
 
 def _polylines_svg(geo: PlotGeometry) -> str:
     parts: list[str] = []
-    for segments, color in zip(geo.polylines, geo.colors):
+    for index, (segments, color) in enumerate(zip(geo.polylines, geo.colors)):
         for seg in segments:
             points = " ".join(f"{px:.2f},{py:.2f}" for px, py in seg)
-            parts.append(f'<polyline points="{points}" fill="none" stroke="{color}"/>')
+            parts.append(f'<polyline points="{points}" fill="none" stroke="{color}" class="plot-curve-{index % 6}"/>')
     return "".join(parts)
 
 
@@ -476,22 +476,43 @@ def _labels_svg(geo: PlotGeometry) -> str:
     return "".join(parts)
 
 
-def render_svg(plot: FunctionPlot) -> StaticRenderResult:
+def render_svg(plot: FunctionPlot, theme_id: str = 'light') -> StaticRenderResult:
     """把已解析的 FunctionPlot 渲染为内嵌 SVG。"""
     geo = compute_geometry(plot)
+    legend_height = ((len(plot.expressions) + 1) // 2) * 24
+    height = geo.height + legend_height
     parts: list[str] = [
-        f'<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 {geo.width} {geo.height}" role="img">'
+        f'<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 {geo.width} {height}" role="img" class="function-plot-svg">'
     ]
     if geo.grid:
         parts.append(_grid_svg(geo))
     parts.append(_axes_svg(geo))
     parts.append(_polylines_svg(geo))
     parts.append(_labels_svg(geo))
+    for index, expression in enumerate(plot.expressions):
+        x = 24 + (index % 2) * 310
+        y = geo.height + 18 + (index // 2) * 24
+        label = html.escape(expression.label or ('y = ' + expression.expression))
+        parts.append(f'<text x="{x}" y="{y}" font-size="12" fill="{geo.colors[index]}" class="plot-legend-{index % 6}">{label}</text>')
     parts.append("</svg>")
 
     return StaticRenderResult(
-        content="".join(parts),
+        content=theme_svg("".join(parts), theme_id),
         width=geo.width,
-        height=geo.height,
+        height=height,
         warnings=geo.warnings,
     )
+
+
+def theme_svg(svg: str, theme_id: str) -> str:
+    from app.export.themes import PALETTES
+    palette = PALETTES.get(theme_id, PALETTES['light'])
+    for source, target in [('#eaeef2', palette[5]), ('#57606a', palette[3]), ('#1f2328', palette[2])]:
+        svg = svg.replace(source, target)
+    if theme_id in {'dark', 'midnight-purple'}:
+        for source, target in zip(_PALETTE, ['#79c0ff','#ff9b9b','#7ee787','#d2a8ff','#f2cc60','#ffa657']):
+            svg = svg.replace(source, target)
+    background = '<rect width="100%" height="100%" fill="' + palette[1] + '"/>'
+    if re.search(r'<rect width="100%" height="100%" fill="[^"]*"/>', svg):
+        return re.sub(r'<rect width="100%" height="100%" fill="[^"]*"/>', background, svg, count=1)
+    return svg.replace('role="img" class="function-plot-svg">', 'role="img" class="function-plot-svg">' + background)

backend/app/plot/render_reportlab.py

@@ -17,9 +17,7 @@ from reportlab.pdfbase.cidfonts import UnicodeCIDFont
 from app.plot.model import FunctionPlot
 from app.plot.render import PlotGeometry, _fmt_num, _sx, _sy, compute_geometry
 
-_FONT = "STSong-Light"
-if _FONT not in pdfmetrics.getRegisteredFontNames():
-    pdfmetrics.registerFont(UnicodeCIDFont(_FONT))
+from app.export.fonts import FONT as _FONT
 
 _GRID_COLOR = HexColor("#eaeef2")
 _AXIS_COLOR = HexColor("#57606a")
@@ -115,6 +113,11 @@ def render_drawing(plot: FunctionPlot, width: float | None = None) -> Drawing:
     """
     geo = compute_geometry(plot)
     drawing = _build_drawing(geo)
+    legend_height = ((len(plot.expressions)+1)//2)*24
+    drawing.height += legend_height
+    for index, expression in enumerate(plot.expressions):
+        drawing.add(String(24+(index%2)*310,geo.height+legend_height-18-(index//2)*24,
+            expression.label or 'y = '+expression.expression,fontName=_FONT,fontSize=12,fillColor=HexColor(geo.colors[index])))
     if width is not None and width > 0:
         drawing.renderScale = min(1.0, width / geo.width)
     return drawing

backend/app/plot/renderer.py

@@ -47,7 +47,7 @@ class FunctionPlotStaticRenderer:
         parsed = self.parse(request)
         if parsed.plot is None:
             raise ValueError("function-plot source has no valid plot")
-        return self.render_plot(parsed.plot)
+        return render_svg(parsed.plot, request.theme or 'light')
 
     def render_plot(self, plot: FunctionPlot) -> StaticRenderResult:
         return render_svg(plot)