Polish validation (#311)

* Improve errorbar validation

* Move segment validation from writer to geom layer

- Mark pos1end as Required in segment geom
- Leverage bidirectional validation to enforce "at least one of xend or yend"
- Remove validation logic from SegmentRenderer, keep only transformation
- Add 4 validation tests in segment.rs
- Simplify SegmentRenderer to use entry().or_insert() pattern

The bidirectional validation checks for either:
- Identity: pos1, pos2, pos1end (x, y, xend)
- Flipped: pos1, pos2, pos2end (y, x, yend)

This effectively enforces "at least one endpoint required" without custom logic.

* Add validate_aesthetics hook and move rule validation to geom layer

- Add GeomTrait::validate_aesthetics() method for custom validation
- Mark pos1 as Required in rule geom
- Implement validate_aesthetics() for Rule to enforce XOR (exactly one of x or y)
- Call geom.validate_aesthetics() from Layer::validate_mapping()
- Remove validation logic from RuleRenderer, keep only diagonal rendering
- Add 3 validation tests in rule.rs

Architecture improvement:
- Geoms can now implement custom validation logic beyond Required/Null
- Rule's XOR constraint (pos1 XOR pos2) enforced at geom layer
- Writer only handles rendering, not validation

* Centralize aesthetic-to-encoding channel mapping in writer

Move pos*min/pos*max to x/y/x2/y2 transformation from individual renderers
to the central map_position_to_vegalite() function. This eliminates ad-hoc
transformations scattered across ErrorBarRenderer, RibbonRenderer, and
RectRenderer.

Convention: min → primary channel (x/y), max → secondary channel (x2/y2)

Changes:
- Update map_position_to_vegalite() to map pos*min/pos*max directly to
  Vega-Lite encoding channels (x/y/x2/y2)
- Remove entire RibbonRenderer (now uses DefaultRenderer)
- Remove vestigial modify_encoding() from ErrorBarRenderer and RectRenderer
- Remove 2 redundant tests (test_errorbar_encoding_transformation,
  test_rect_continuous_both_axes)
- Update rect tests to reflect upstream transformation

Result: 155 lines removed, cleaner separation between domain (aesthetics)
and presentation (encoding channels).

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

* rename 'rect' to 'tile' (fix #264)

* appease 1.95.0 clippy

* Make GeomRenderers position-agnostic via RenderContext channels

Add coord_kind to RenderContext with a pre-computed PositionChannels
tuple (pos1, pos1_end, pos1_offset, pos2, pos2_end, pos2_offset) that
resolves to Vega-Lite channel names based on coordinate system. Replaces
hardcoded "x"/"y"/"x2"/"y2" in 8 renderers (Bar, Path, Segment, Rule,
Tile, Violin, ErrorBar, Boxplot) so they work with both Cartesian and
polar coordinates.

Also moves RenderContext from layer.rs to encoding.rs where it belongs,
and adds &RenderContext to the finalize() trait method.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix rect -> tile leftover bug

* Fix horizontal errorbar support and global mapping merge for bidirectional geoms

Add ErrorBar to geom_has_implicit_orientation so the orientation system
correctly detects and flips horizontal errorbars. Fix global mapping merge
to accept flipped position counterparts (e.g., pos2 into a geom declaring
pos1) using flip_position, enabling global aesthetics like `species AS y`
to reach bidirectional geoms.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* cargo fmt

* sneak in small correction

* fix inconsistency

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: teunbrand

CLAUDE.md

@@ -332,7 +332,7 @@ pub struct Layer {
 
 pub enum Geom {
     // Basic geoms
-    Point, Line, Path, Bar, Col, Area, Rect, Polygon, Ribbon,
+    Point, Line, Path, Bar, Col, Area, Tile, Polygon, Ribbon,
     // Statistical geoms
     Histogram, Density, Smooth, Boxplot, Violin,
     // Annotation geoms
@@ -1079,7 +1079,7 @@ All clauses (MAPPING, SETTING, PARTITION BY, FILTER) are optional.
 
 **Geom Types**:
 
-- **Basic**: `point`, `line`, `path`, `bar`, `col`, `area`, `rect`, `polygon`, `ribbon`
+- **Basic**: `point`, `line`, `path`, `bar`, `col`, `area`, `tile`, `polygon`, `ribbon`
 - **Statistical**: `histogram`, `density`, `smooth`, `boxplot`, `violin`
 - **Annotation**: `text`, `label`, `segment`, `arrow`, `rule`, `errorbar`
 

doc/gallery/examples/heatmap.qmd

@@ -1,7 +1,7 @@
 ---
 title: "Heatmap"
 description: "Arranging tiles on a grid"
-image: thumbnails/violin-plot.svg
+image: thumbnails/heatmap.svg
 categories: [basic, heatmap]
 order: 3
 ---
@@ -14,31 +14,31 @@ It works best with discrete or ordinal arrangements.
 
 ```{ggsql}
 VISUALISE Day AS x, Month AS y, Temp AS fill FROM ggsql:airquality
-  DRAW rect
+  DRAW tile
 ```
 
 ## Explanation
 
 * The `VISUALISE ... FROM ggsql:airquality` loads the built-in air quality dataset.
 * `Day AS x, Month AS y` defines a 2D grid 'map'. The default width and height of each cell is 1. Because these variables are contiguous whole numbers, this creates a grid.
 * `Temp AS fill` declares the 'heat' variable to display as colour intensity.
-* `DRAW rect` gives instructions to draw a rectangle layer.
+* `DRAW tile` gives instructions to draw a tile layer.
 
 ## Variations
 
 As a stylistic choice, you can set the cells to be opaque without borders.
 
 ```{ggsql}
 VISUALISE Month AS y, Day AS x, Temp AS fill FROM ggsql:airquality
-  DRAW rect
+  DRAW tile
     SETTING stroke => null, opacity => 1
 ```
 
 You can change the color by adapting the scale.
 
 ```{ggsql}
 VISUALISE Month AS y, Day AS x, Temp AS fill FROM ggsql:airquality
-  DRAW rect
+  DRAW tile
   SCALE fill TO magma 
     SETTING reverse => true
 ```
@@ -51,6 +51,6 @@ SELECT *,
 FROM ggsql:airquality
 
 VISUALISE Month AS y, Day AS x, centered AS fill
-  DRAW rect
+  DRAW tile
   SCALE fill FROM (-20, 20) TO vik
 ```

doc/ggsql.xml

@@ -128,7 +128,7 @@
       <item>path</item>
       <item>bar</item>
       <item>area</item>
-      <item>rect</item>
+      <item>tile</item>
       <item>polygon</item>
       <item>ribbon</item>
       <item>histogram</item>

doc/syntax/layer/type/errorbar.qmd

@@ -73,3 +73,13 @@ DRAW errorbar
   MAPPING low AS ymax, high AS ymin
   SETTING width => null
 ```
+
+A horizontal errorbar can be rendered by swapping the `x` and `y` directions.
+
+```{ggsql}
+VISUALISE species AS y FROM penguin_summary
+DRAW errorbar 
+  MAPPING low AS xmax, high AS xmin
+DRAW point 
+  MAPPING mean AS x
+```

doc/syntax/layer/type/rect.qmd doc/syntax/layer/type/tile.qmddoc/syntax/layer/type/rect.qmd renamed to doc/syntax/layer/type/tile.qmd

@@ -1,13 +1,13 @@
 ---
-title: "Rectangle"
+title: "Tile"
 ---
 
 > Layers are declared with the [`DRAW` clause](../../clause/draw.qmd). Read the documentation for this clause for a thorough description of how to use it.
 
-Rectangles can be used to draw heatmaps or indicate ranges.
+Tiles can be used to draw rectangles in heatmaps or indicate ranges.
 
 ## Aesthetics
-The following aesthetics are recognised by the rectangle layer.
+The following aesthetics are recognised by the tile layer.
 
 ### Required
 
@@ -43,22 +43,22 @@ When the primary aesthetics are continuous, primary data is reparameterised to {
 When the secondary aesthetics are continuous, secondary data is reparameterised to {start, end}, e.g. `ymin` and `ymax`.
 
 ## Orientation
-The rectangle layer has no orientation. The axes are treated symmetrically.
+The tile layer has no orientation. The axes are treated symmetrically.
 
 ## Examples
 
 Just using `x` and `y`. Note that `width` and `height` are set to 1.
 
 ```{ggsql}
 VISUALISE Day AS x, Month AS y, Temp AS colour FROM ggsql:airquality
-DRAW rect 
+DRAW tile 
 ```
 
 Customising `width` and `height` with either the `MAPPING` or `SETTING` clauses.
 
 ```{ggsql}
 VISUALISE Day AS x, Month AS y, Temp AS colour FROM ggsql:airquality
-DRAW rect 
+DRAW tile 
   MAPPING 0.5 AS width 
   SETTING height => 0.8
 ```
@@ -72,7 +72,7 @@ SELECT
 FROM ggsql:airquality
 
 VISUALISE Day AS x, Month AS y, Temp AS colour
-DRAW rect 
+DRAW tile 
   MAPPING norm_temp AS width, norm_temp AS height
 ```
 
@@ -88,14 +88,14 @@ FROM ggsql:airquality
 GROUP BY Week
 
 VISUALISE start AS xmin, end AS xmax, min AS ymin, max AS ymax
-DRAW rect
+DRAW tile
 ```
 
-Using a rectangle as an annotation. Note we're using the `PLACE` clause here instead of `DRAW` because we're not mapping from data.
+Using a tile as an annotation. Note we're using the `PLACE` clause here instead of `DRAW` because we're not mapping from data.
 
 ```{ggsql}
 VISUALISE FROM ggsql:airquality
-PLACE rect 
+PLACE tile 
   SETTING
     xmin => '1973-06-01', 
     xmax => '1973-06-30',

ggsql-vscode/syntaxes/ggsql.tmLanguage.json

@@ -334,7 +334,7 @@
       "patterns": [
         {
           "name": "support.type.geom.ggsql",
-          "match": "\\b(point|line|path|bar|col|area|rect|polygon|ribbon|histogram|density|smooth|boxplot|violin|text|label|segment|arrow|rule|errorbar)\\b"
+          "match": "\\b(point|line|path|bar|col|area|tile|polygon|ribbon|histogram|density|smooth|boxplot|violin|text|label|segment|arrow|rule|errorbar)\\b"
         },
         { "include": "#common-clause-patterns" }
       ]

ggsql-wasm/demo/src/quarto/links.ts

@@ -36,7 +36,7 @@ const GEOM_LINKS: Record<string, DocLink> = {
   path: { url: "syntax/layer/type/path", label: "path layer" },
   bar: { url: "syntax/layer/type/bar", label: "bar layer" },
   area: { url: "syntax/layer/type/area", label: "area layer" },
-  rect: { url: "syntax/layer/type/rect", label: "rect layer" },
+  tile: { url: "syntax/layer/type/tile", label: "tile layer" },
   polygon: { url: "syntax/layer/type/polygon", label: "polygon layer" },
   ribbon: { url: "syntax/layer/type/ribbon", label: "ribbon layer" },
   histogram: { url: "syntax/layer/type/histogram", label: "histogram layer" },
@@ -144,7 +144,7 @@ const CLAUSE_RE =
   /\b(VISUALISE|VISUALIZE|DRAW|PLACE|SCALE|FACET|PROJECT|LABEL)\b/gi;
 
 const GEOM_RE =
-  /\b(?:DRAW|PLACE)\s+(point|line|path|bar|area|rect|polygon|ribbon|histogram|density|smooth|boxplot|violin|text|segment|rule|linear|errorbar)\b/gi;
+  /\b(?:DRAW|PLACE)\s+(point|line|path|bar|area|tile|polygon|ribbon|histogram|density|smooth|boxplot|violin|text|segment|rule|linear|errorbar)\b/gi;
 
 const COORD_RE = /\bTO\s+(cartesian|polar)\b/gi;
 

src/execute/layer.rs

@@ -595,7 +595,7 @@ where
                         .or_else(|| {
                             // For variant position aesthetics (e.g., pos1min, pos2max),
                             // fall back to the primary aesthetic's original name (pos1, pos2).
-                            // This ensures rect's expanded min/max aesthetics inherit the
+                            // This ensures tile's expanded min/max aesthetics inherit the
                             // original column name from the user's x/y mapping.
                             aesthetic::parse_position(aesthetic).and_then(|(slot, suffix)| {
                                 if !suffix.is_empty() {

src/execute/mod.rs

@@ -183,9 +183,16 @@ fn merge_global_mappings_into_layers(specs: &mut [Plot], layer_schemas: &[Schema
             // Note: Use all_names (not supported) so that Delayed aesthetics like
             // pos2 on histogram can be targeted by explicit global mappings, matching
             // the behavior of layer-level MAPPING
+            // Note: Also accept flipped position counterparts so bidirectional geoms
+            // (e.g., errorbar: pos1+pos2min+pos2max or pos2+pos1min+pos1max) can
+            // receive globals from either orientation.
             for (aesthetic, value) in &spec.global_mappings.aesthetics {
                 let is_facet_aesthetic = crate::plot::scale::is_facet_aesthetic(aesthetic.as_str());
-                if all_names.contains(&aesthetic.as_str()) || is_facet_aesthetic {
+                let flipped = aesthetic_ctx.flip_position(aesthetic);
+                if all_names.contains(&aesthetic.as_str())
+                    || all_names.contains(&flipped.as_str())
+                    || is_facet_aesthetic
+                {
                     layer
                         .mappings
                         .aesthetics

src/parser/builder.rs

@@ -623,7 +623,7 @@ fn parse_geom_type(text: &str) -> Result<Geom> {
         "path" => Ok(Geom::path()),
         "bar" => Ok(Geom::bar()),
         "area" => Ok(Geom::area()),
-        "rect" => Ok(Geom::rect()),
+        "tile" => Ok(Geom::tile()),
         "polygon" => Ok(Geom::polygon()),
         "ribbon" => Ok(Geom::ribbon()),
         "histogram" => Ok(Geom::histogram()),