Merge slicing into one tab and one button: Generate G-Code slices, Split slices

- The Shapes & Slicing and Generate G-Code tabs are one "Shapes & G-Code"
tab: upload, table, split and preview accordions, then the generation
options, button, downloads, and G-code preview in one flow (the app is
now two tabs: Shapes & G-Code, Visualization)
- The Slice Shapes button is gone. Generate G-Code slices every shape
from the current table settings before writing G-code, and Split
Selected Shape into Grid Pieces slices before splitting (same shared
Z-grid group plans), so the whole workflow is one button - two with a
split. The layer preview and split-source refreshes moved from the old
slice chain onto the generate and split chains
- Status texts that pointed at the removed button/tabs reworded; README
updated

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -33,7 +33,7 @@ uv run gradio app.py
 
 When `app.py` changes, Gradio will automatically rerun the file and refresh the demo.
 
-Then open the local Gradio URL in your browser, upload STL files or load the bundled samples, and slice the shapes.
+Then open the local Gradio URL in your browser, upload STL files or load the bundled samples, and press **Generate G-Code**.
 
 ## What the app does
 
@@ -54,7 +54,7 @@ Then open the local Gradio URL in your browser, upload STL files or load the bun
 - **Infill %** per shape skips dispensing on evenly-distributed raster lines (rings/revolutions for spiral patterns) — at 50% every other line prints — while the motion path stays exactly the same, so parallel shapes with different infill still share one print path
 - Appends a shape outline contour after each enabled shape layer by tracing that layer's polygon boundary
 - Offers a choice of raster pattern for G-code generation; all shapes always share one combined reference outline for motion (one nozzle path; each dispenses only its own geometry), and every move is emitted as `G1` at one constant speed (no `G0` rapid travel)
-- Re-slices shapes automatically during G-code generation when their slices are missing or stale, so "upload, then Generate G-Code" works in one click
+- Slicing is automatic: **Generate G-Code** slices every shape (fresh or stale) before writing G-code, and **Split Selected Shape into Grid Pieces** slices before splitting — "upload, then Generate G-Code" works in one click with no separate slice step
 - Calculates X/Y nozzle spacing from a grid layout (columns/rows plus gaps) in the Visualization tab's Nozzle Spacing accordion, with an optional per-connection Advanced Grid Spacing table, then visualizes the resulting nozzle layout
 - Previews selected generated G-code inline
 - One Visualization tab that defaults to the parallel print of every generated shape (configured nozzle spacing, animated, with a server-side GIF export), and can switch to a single tool path from any generated shape or an uploaded G-code file
@@ -69,7 +69,7 @@ Slicing uses `trimesh` cross-sections composed into shapely polygons (`slice_stl
 
 ### Reference Layer Union
 
-When you click **Slice Shapes**, the app automatically unions the sliced shapes layer-by-layer into a combined reference layer set (used for shared-motion G-code).
+Whenever shapes are sliced (automatically, during G-code generation or a split), the app unions the sliced shapes layer-by-layer into a combined reference layer set (used for shared-motion G-code).
 
 - Shapes are aligned by centering each shape's XY bounding box on a common center before the union.
 - Alignment is centered placement (in exact millimetres), not bottom-left anchoring.
@@ -89,11 +89,11 @@ For a multi-material object exported as separate STLs (one per material), give e
 
 ### Multi-Nozzle Split
 
-The **Multi-Nozzle Split** accordion on the **Shapes & Slicing** tab can split one sliced shape into a grid of print-ready piece stacks. Choose a source shape that has been sliced, set the number of columns and rows, choose the starting nozzle and valve numbers, then click **Split Selected Shape into Grid Pieces**.
+The **Multi-Nozzle Split** accordion on the **Shapes & G-Code** tab can split one shape into a grid of print-ready piece stacks. Choose a source shape, set the number of columns and rows, choose the starting nozzle and valve numbers, then click **Split Selected Shape into Grid Pieces** — the shapes are sliced automatically first if needed.
 
 - Each layer's geometry is clipped against equal-size grid cells, so every piece keeps exact vector outlines.
 - The selected shape is replaced in Shape Settings by one generated record per grid cell, named by row and column.
-- Nozzle and valve numbers are assigned sequentially from the starting values, and the **Generate G-Code** tab can generate separate G-code for each piece.
+- Nozzle and valve numbers are assigned sequentially from the starting values, and **Generate G-Code** produces separate G-code for each piece.
 - **Overlapping Layers** alternates the interior cut lines by one filament width per layer so neighbouring pieces interlock.
 - **Multi-material assemblies split as one shape**: if the selected shape shares its nozzle with other shapes, the whole group is split together — every material is clipped by the same cell grid over the group's combined bounds. Pieces are emitted cell by cell: each cell's pieces share a nozzle (so every cell is itself a multi-material group, keeping the alignment and seam-free contour behavior), each piece gets its own valve, and cells where a material has no geometry are skipped. Auto Align works on the result like any other split.
 

app.py

@@ -2947,7 +2947,7 @@ def update_layer_preview(
     if stack is None or not getattr(stack, "layers", None):
         return (
             gr.update(maximum=1, value=1),
-            _layer_preview_message("Slice Shapes to see this shape's layer outlines."),
+            _layer_preview_message("Generate G-Code (or split) to slice this shape and see its layer outlines."),
         )
 
     layer_count = len(stack.layers)
@@ -3291,9 +3291,10 @@ def generate_dynamic_reference_stack(
 
 
 SPLIT_STATUS_DEFAULT = (
-    "Slice a shape, then split it for multi-nozzle printing. Shapes that share "
-    "a nozzle number are one multi-material assembly: selecting any of them "
-    "splits the **whole group** together as one shape."
+    "Pick a shape to split for multi-nozzle printing - shapes are sliced "
+    "automatically when you split. Shapes that share a nozzle number are one "
+    "multi-material assembly: selecting any of them splits the **whole "
+    "group** together as one shape."
 )
 
 
@@ -3353,8 +3354,8 @@ def _split_group_records(
         return _outputs(
             records,
             selected,
-            f"Split failed: shape(s) on nozzle {group_nozzle} have no sliced layers yet - "
-            "press Slice Shapes first so the group shares one Z grid.",
+            f"Split failed: shape(s) on nozzle {group_nozzle} could not be sliced - "
+            "check their STLs.",
         )
     stacks = [member["layer_stack"] for member in group_members]
     layer_counts = {len(stack.layers) for stack in stacks}
@@ -3364,7 +3365,7 @@ def _split_group_records(
             records,
             selected,
             f"Split failed: the shapes on nozzle {group_nozzle} were sliced on different "
-            "Z grids - press Slice Shapes to re-slice the group together.",
+            "Z grids - edit a dimension (or nozzle) so the group re-slices together.",
         )
 
     # Stamp group frames + seam-free contours so pieces inherit contour
@@ -3468,10 +3469,20 @@ def split_selected_shape_for_grid(
     starting_nozzle: float,
     starting_valve: float,
     fil_width: float,
+    layer_height: float = 0.8,
+    scale_mode: str | None = None,
 ) -> tuple:
     records = _apply_shape_settings(records or [], settings_table)
+    # One-button flow: shapes are sliced (or re-sliced when their settings
+    # changed) straight from the table here, so splitting never needs a
+    # separate slicing step.
+    slice_messages: list[str] = []
+    if records:
+        _ensure_records_sliced(records, float(layer_height or 0.8), scale_mode, slice_messages)
 
     def _outputs(next_records: list[dict], selected_value: str | None, status: str) -> tuple:
+        if slice_messages:
+            status = "  \n".join([*slice_messages, status])
         return (
             next_records,
             _shape_settings_rows(next_records),
@@ -3485,7 +3496,7 @@ def split_selected_shape_for_grid(
         )
 
     if not records:
-        return _outputs(records, None, "Slice a shape before splitting it.")
+        return _outputs(records, None, "Add a shape before splitting it.")
 
     pos = _selected_record_index(records, selected)
     if pos < 0:
@@ -3496,7 +3507,7 @@ def split_selected_shape_for_grid(
         return _outputs(
             records,
             selected,
-            f"Split failed: Shape {source.get('idx', pos + 1)} has no sliced layers yet - press Slice Shapes first.",
+            f"Split failed: Shape {source.get('idx', pos + 1)} could not be sliced - check its STL.",
         )
 
     split_column_count = max(1, _coerce_int(columns, 2))
@@ -3781,7 +3792,7 @@ def _parts_from_records(records: list[dict] | None) -> tuple[list[dict], list[st
         path = record.get("gcode_path")
         idx = int(record.get("idx", len(parts) + 1))
         if not path:
-            messages.append(f"Shape {idx}: no G-code (generate it on the Generate G-Code tab).")
+            messages.append(f"Shape {idx}: no G-code (press Generate G-Code on the Shapes & G-Code tab).")
             continue
         try:
             parsed = parse_gcode_path(Path(path).read_text())
@@ -3907,7 +3918,7 @@ def render_dynamic_parallel(
     records = _apply_shape_settings(records or [], settings_table)
     parts, messages = _parts_from_records(records)
     if not parts:
-        return None, "No shape G-code available. Generate G-code on the Generate G-Code tab first."
+        return None, "No shape G-code available. Press Generate G-Code on the Shapes & G-Code tab first."
     offsets, spacings = _resolve_nozzle_grid_layout(
         parts,
         columns,
@@ -3998,11 +4009,11 @@ def build_dynamic_demo() -> gr.Blocks:
         last_shape_delete_at = gr.State(0.0)
         ref_layers = gr.State(None)
 
-        with gr.Tab("Shapes & Slicing"):
+        with gr.Tab("Shapes & G-Code"):
             gr.Markdown(
                 """
-                # Shapes & Slicing
-                Upload any number of STL files, edit per-shape dimensions and print settings in the table, then slice each shape into per-layer outlines.
+                # Shapes & G-Code
+                Upload any number of STL files, edit per-shape dimensions and print settings in the table, then press **Generate G-Code** below - every shape is sliced automatically as part of generation (and before a split).
                 Pick each shape's plot color straight from the dropdown in the **Color** column.
                 """
             )
@@ -4068,7 +4079,6 @@ def build_dynamic_demo() -> gr.Blocks:
             with gr.Row():
                 layer_height = gr.Number(label="Layer Height (mm)", value=0.8, minimum=0.0001, step=0.01)
                 fil_width = gr.Number(label="Filament/Line Width (mm)", value=0.8, minimum=0.0001, step=0.01)
-                generate_button = gr.Button("Slice Shapes", variant="primary")
 
             with gr.Accordion("Multi-Nozzle Split", open=False, elem_classes=["settings-accordion"]):
                 with gr.Row():
@@ -4109,13 +4119,11 @@ def build_dynamic_demo() -> gr.Blocks:
                     with gr.Column(scale=1, min_width=300):
                         model_details = gr.Markdown("No model loaded.")
 
-            slicer_status = gr.Markdown("")
-
-        with gr.Tab("Generate G-Code"):
             gr.Markdown(
                 """
-                # Generate G-Code
-                Generate G-code for every sliced shape. Pressure, valve, nozzle, port, and color come from the Shape Settings table.
+                ---
+                ### Generate G-Code
+                One button slices every shape from the current table settings and writes its G-code. Pressure, valve, nozzle, port, and color come from the Shape Settings table.
                 All shapes share one combined nozzle path (each dispenses only its own geometry), so parallel heads always stay in sync.
                 """
             )
@@ -4380,21 +4388,6 @@ def build_dynamic_demo() -> gr.Blocks:
             outputs=[model_viewer, model_details],
         )
 
-        generate_button.click(
-            fn=generate_dynamic_layer_stacks,
-            inputs=[shape_records, shape_settings, layer_height, scale_mode, fil_width],
-            outputs=[shape_records, slicer_status, ref_layers],
-        ).then(
-            fn=update_layer_preview,
-            inputs=layer_preview_inputs,
-            outputs=layer_preview_outputs,
-        ).then(
-            fn=lambda records: _dropdown_update(records),
-            inputs=[shape_records],
-            outputs=[split_source],
-            queue=False,
-        )
-
         split_refresh_sources.click(fn=lambda records: _dropdown_update(records), inputs=[shape_records], outputs=[split_source], queue=False)
         # .input (user selections only): programmatic dropdown refills after a
         # split must not overwrite the split result message.
@@ -4416,6 +4409,8 @@ def build_dynamic_demo() -> gr.Blocks:
                 split_start_nozzle,
                 split_start_valve,
                 fil_width,
+                layer_height,
+                scale_mode,
             ],
             outputs=[
                 shape_records,
@@ -4432,6 +4427,10 @@ def build_dynamic_demo() -> gr.Blocks:
             fn=generate_dynamic_reference_stack,
             inputs=[shape_records, fil_width],
             outputs=[ref_layers],
+        ).then(
+            fn=update_layer_preview,
+            inputs=layer_preview_inputs,
+            outputs=layer_preview_outputs,
         ).then(
             fn=_grid_spacing_table_update,
             inputs=grid_spacing_refresh_inputs,
@@ -4459,6 +4458,17 @@ def build_dynamic_demo() -> gr.Blocks:
             fn=load_selected_gcode_text,
             inputs=[shape_records, gcode_text_source],
             outputs=[gcode_text],
+        ).then(
+            # Generation slices the shapes, so refresh everything that
+            # depends on the sliced stacks (the Slice Shapes button is gone).
+            fn=update_layer_preview,
+            inputs=layer_preview_inputs,
+            outputs=layer_preview_outputs,
+        ).then(
+            fn=lambda records: _dropdown_update(records),
+            inputs=[shape_records],
+            outputs=[split_source],
+            queue=False,
         )
         gcode_text_source.change(fn=load_selected_gcode_text, inputs=[shape_records, gcode_text_source], outputs=[gcode_text])
         refresh_gcode_text_button.click(fn=load_selected_gcode_text, inputs=[shape_records, gcode_text_source], outputs=[gcode_text])

tests/test_nozzle_spacing.py

@@ -766,6 +766,12 @@ def test_group_split_splits_all_materials_on_one_shared_grid() -> None:
         _record(1, "bottom", _material(box(0.0, 0.0, 20.0, 5.0), "bottom")),
         _record(2, "top", _material(box(0.0, 5.0, 20.0, 10.0), "top")),
     ]
+    # Mark the stacks as freshly sliced for the split's auto-slice step (the
+    # fixture stl paths don't exist, so a re-slice attempt would wipe them).
+    from app import _slice_params_snapshot
+
+    for record in records:
+        record["slice_params"] = _slice_params_snapshot(record, 0.8, None, None)
 
     outputs = split_selected_shape_for_grid(
         records,