Improve group plots

src/tikzfigure/core/axis.py

@@ -449,7 +449,7 @@ def to_tikz(self, output_unit: str | None = None) -> str:
         if isinstance(self._grid, str):
             axis_opts.append(f"grid={self._grid}")
         else:
-            axis_opts.append(f"grid={'true' if self._grid else 'false'}")
+            axis_opts.append(f"grid={'major' if self._grid else 'none'}")
 
         # Add width and height if specified
         if self._width:

src/tikzfigure/core/figure_layout.py

@@ -10,6 +10,9 @@
 
 
 class FigureLayoutMixin:
+    GROUPPLOT_HORIZONTAL_SEP_CM = 1.5
+    GROUPPLOT_VERTICAL_SEP_CM = 2.0
+
     _subfigure_rows: int | None
     _subfigure_cols: int | None
     _subfigure_position: int
@@ -25,10 +28,16 @@ def subfigure_axis(
         grid: bool = True,
         width: float = 0.45,
         height: str | int | float | None = None,
+        axis_width: str | int | float | None = None,
         comment: str | None = None,
         **kwargs: Any,
     ) -> Axis2D:
-        """Create a 2D axis for side-by-side subfigure layout."""
+        """Create a 2D axis for side-by-side subfigure layout.
+
+        The ``width`` argument controls the layout fraction used for subfigure
+        placement. Use ``axis_width`` and ``height`` to set explicit pgfplots
+        dimensions on the rendered axis itself.
+        """
         if not (0 < width <= 1.0):
             raise ValueError(
                 f"subfigure width must be in range (0.0, 1.0], got {width}"
@@ -40,6 +49,7 @@ def subfigure_axis(
             xlim=xlim,
             ylim=ylim,
             grid=grid,
+            width=axis_width,
             height=height,
             label="",
             comment=comment,
@@ -140,8 +150,8 @@ def _render_groupplot_grid(self, num_rows: int, num_cols: int) -> str:
         group_opts = (
             f"group style={{"
             f"group size={num_cols} by {num_rows}, "
-            f"horizontal sep=1.5cm, "
-            f"vertical sep=2cm"
+            f"horizontal sep={self.GROUPPLOT_HORIZONTAL_SEP_CM}cm, "
+            f"vertical sep={self.GROUPPLOT_VERTICAL_SEP_CM}cm"
             f"}}"
         )
         result = f"\\begin{{groupplot}}[{group_opts}]\n"
@@ -158,8 +168,8 @@ def _render_groupplot_grid(self, num_rows: int, num_cols: int) -> str:
 
     def _render_mixed_grid(self, num_rows: int, num_cols: int) -> str:
         textwidth_cm = 14.0
-        h_sep = 2.0
-        v_sep = 2.0
+        h_sep = self.GROUPPLOT_HORIZONTAL_SEP_CM
+        v_sep = self.GROUPPLOT_VERTICAL_SEP_CM
         default_height = 6.0
 
         from tikzfigure.core.figure import TikzFigure

src/tikzfigure/core/figure_render.py

@@ -16,6 +16,8 @@
 
 
 class FigureRenderMixin:
+    GROUPPLOT_HORIZONTAL_SEP_CM: float
+    GROUPPLOT_VERTICAL_SEP_CM: float
     _extra_packages: list[str] | None
     _tikz_libraries: list[str]
     _named_styles: list[dict[str, Any]]
@@ -286,7 +288,10 @@ def generate_tikz(
             else:
                 num_axes = len(self._subfigure_axes)
                 group_opts = (
-                    f"group style={{group size={num_axes} by 1, horizontal sep=1.5cm}}"
+                    "group style={"
+                    f"group size={num_axes} by 1, "
+                    f"horizontal sep={self.GROUPPLOT_HORIZONTAL_SEP_CM}cm"
+                    "}"
                 )
                 subfig_tikz += f"\\begin{{groupplot}}[{group_opts}]\n"
                 for item_tuple in self._subfigure_axes:

src/tikzfigure/tests/test_axis2d.py

@@ -354,12 +354,12 @@ def test_axis2d_to_tikz_with_grid(self):
         axis = Axis2D(grid=True)
         axis.add_plot([0, 1], [0, 1])
         tikz_with_grid = axis.to_tikz()
-        assert "grid=true" in tikz_with_grid
+        assert "grid=major" in tikz_with_grid
 
         axis2 = Axis2D(grid=False)
         axis2.add_plot([0, 1], [0, 1])
         tikz_no_grid = axis2.to_tikz()
-        assert "grid=false" in tikz_no_grid
+        assert "grid=none" in tikz_no_grid
 
     def test_axis2d_to_tikz_with_log_axes(self):
         axis = Axis2D(xlog=True, ylog=True)
@@ -844,9 +844,10 @@ class TestSubfigures:
     def test_subfigure_axis_with_height(self):
         """Test that subfigure_axis() accepts height parameter."""
         fig = TikzFigure()
-        ax1 = fig.subfigure_axis(xlabel="X", width=0.45, height=4)
+        ax1 = fig.subfigure_axis(xlabel="X", width=0.45, axis_width=3, height=4)
         ax2 = fig.subfigure_axis(xlabel="Y", width=0.45, height=6)
 
+        assert ax1.width == "3cm"
         assert ax1.height == "4cm"
         assert ax2.height == "6cm"
 
@@ -971,15 +972,17 @@ def test_subfigure_axis_dimensions_in_output(self):
         """Test that subfigure dimensions appear correctly in TikZ output."""
         fig = TikzFigure()
 
-        ax1 = fig.subfigure_axis(xlabel="Sin", width=0.45, height=4)
+        ax1 = fig.subfigure_axis(xlabel="Sin", width=0.45, axis_width=3, height=4)
         ax1.add_plot(func="sin(x)", label="sin(x)")
 
-        ax2 = fig.subfigure_axis(xlabel="Cos", width=0.45, height=5)
+        ax2 = fig.subfigure_axis(xlabel="Cos", width=0.45, axis_width="5cm", height=5)
         ax2.add_plot(func="cos(x)", label="cos(x)")
 
         tikz = fig.generate_tikz()
 
-        # Verify both subfigures have their heights in output
+        # Verify both subfigures keep explicit dimensions in groupplot output.
+        assert "width=3cm" in tikz
+        assert "width=5cm" in tikz
         assert "height=4cm" in tikz
         assert "height=5cm" in tikz
         assert "\\begin{groupplot}" in tikz
@@ -1103,7 +1106,7 @@ def test_full_workflow(self):
         assert "xmax=10" in tikz
         assert "ymin=-1" in tikz
         assert "ymax=1" in tikz
-        assert "grid=true" in tikz
+        assert "grid=major" in tikz
         assert "legend pos=north east" in tikz
 
         # Verify plots