Add documentation for non-range layers

Author: thomasp85

doc/syntax/layer/type/bar.qmd

@@ -123,7 +123,7 @@ PROJECT TO polar
 Use a different type of aggregation for the bars through the `aggregate` setting:
 
 ```{ggsql}
-VISUALISE species AS y, body_mass AS y FROM ggsql:penguins
+VISUALISE species AS x, body_mass AS y FROM ggsql:penguins
 DRAW bar
   SETTING aggregate => 'mean', fill => 'steelblue'
 DRAW range

doc/syntax/layer/type/point.qmd

@@ -23,9 +23,10 @@ The following aesthetics are recognised by the point layer.
 
 ## Settings
 * `position`: Position adjustment. One of `'identity'` (default), `'stack'`, `'dodge'`, or `'jitter'`
+* `aggregate`: Aggregation functions to apply per group. Either a single string or an array of strings. See an overview of aggregation function in [the `DRAW` documentation](../../clause/draw.qmd#aggregate) and more information in the *Data transformation* section below.
 
 ## Data transformation
-The point layer does not transform its data but passes it through unchanged
+This layer supports aggregation through the `aggregate` setting. Within each group, defined by `PARTITION BY` and all discrete mappings, aggregates will be calculated and used as the values to plot. Multiple aggregates will give rise to multiple separate groups in the end. These can be distinguished through the added `aggregate` column you can remap to, e.g. `REMAPPING aggregate AS color`
 
 ## Orientation
 The point layer has no orientation. The axes are treated symmetrically.

doc/syntax/layer/type/rule.qmd

@@ -25,8 +25,10 @@ The following aesthetics are recognised by the rule layer.
 
 ## Settings
 * `position`: Position adjustment. One of `'identity'` (default), `'stack'`, `'dodge'`, or `'jitter'`
+* `aggregate`: Aggregation functions to apply per group. Either a single string or an array of strings. See an overview of aggregation function in [the `DRAW` documentation](../../clause/draw.qmd#aggregate) and more information in the *Data transformation* section below.
 
 ## Data transformation
+This layer supports aggregation through the `aggregate` setting. Within each group, defined by `PARTITION BY` and all discrete mappings, aggregates will be calculated and used as the values to plot. Multiple aggregates will give rise to multiple separate groups in the end. These can be distinguished through the added `aggregate` column you can remap to, e.g. `REMAPPING aggregate AS color`
 
 For diagonal lines, the position aesthetic determines the intercept:
 
@@ -110,4 +112,14 @@ VISUALISE FROM ggsql:penguins
       intercept AS y, 
       label AS colour
     FROM lines
-```
+```
+
+Show a max rule for a timeseries
+
+```{ggsql}
+VISUALISE Temp AS y FROM ggsql:airquality
+DRAW line
+  MAPPING Date AS x
+DRAW rule
+  SETTING aggregate => 'max'
+```

doc/syntax/layer/type/segment.qmd

@@ -25,9 +25,10 @@ For axis-aligned intervals where one coordinate is shared between the start and
 
 ## Settings
 * `position`: Position adjustment. One of `'identity'` (default), `'stack'`, `'dodge'`, or `'jitter'`
+* `aggregate`: Aggregation functions to apply per group. Either a single string or an array of strings. See an overview of aggregation function in [the `DRAW` documentation](../../clause/draw.qmd#aggregate) and more information in the *Data transformation* section below.
 
 ## Data transformation
-The segment layer does not transform its data but passes it through unchanged.
+This layer supports aggregation through the `aggregate` setting. Within each group, defined by `PARTITION BY` and all discrete mappings, aggregates will be calculated and used as the values to plot. Multiple aggregates will give rise to multiple separate groups in the end. These can be distinguished through the added `aggregate` column you can remap to, e.g. `REMAPPING aggregate AS color`
 
 ## Orientation
 The segment layer has no orientations. The axes are treated symmetrically.

doc/syntax/layer/type/text.qmd

@@ -35,6 +35,7 @@ The following aesthetics are recognised by the text layer.
     * a 2-element numeric array `[h, v]` where the first number is the horizontal offset and the second number is the vertical offset.
 * `format` Formatting specifier, see explanation below.
 * `position`: Position adjustment. One of `'identity'` (default), `'stack'`, `'dodge'`, or `'jitter'`
+* `aggregate`: Aggregation functions to apply per group. Either a single string or an array of strings. See an overview of aggregation function in [the `DRAW` documentation](../../clause/draw.qmd#aggregate) and more information in the *Data transformation* section below.
 
 ### Format
 The `format` setting can take a string that will be used in formatting the `label` aesthetic. 
@@ -66,7 +67,7 @@ Known formatters are:
     * `x`/`X`: Unsigned hexadecimal
 
 ## Data transformation
-The text layer does not transform its data but passed it through unchanged.
+This layer supports aggregation through the `aggregate` setting. Within each group, defined by `PARTITION BY` and all discrete mappings, aggregates will be calculated and used as the values to plot. Multiple aggregates will give rise to multiple separate groups in the end. These can be distinguished through the added `aggregate` column you can remap to, e.g. `REMAPPING aggregate AS color`
 
 ## Orientation
 The text layer has no orientation. The axes are treated symmetrically.
@@ -146,3 +147,14 @@ PLACE text
     x => (40, 50, 50),
     y => (19, 19, 15)
 ```
+
+Use aggregation to place labels at their centroid
+
+```{ggsql}
+VISUALISE bill_len AS x, bill_dep AS y FROM ggsql:penguins
+DRAW point
+  MAPPING species AS fill
+DRAW text
+  MAPPING species AS label
+  SETTING aggregate => 'mean', stroke => 'white', fontweight => 'bold', fontsize => 20
+```

src/execute/mod.rs

@@ -714,9 +714,14 @@ fn add_discrete_columns_to_partition_by(
         // Build set of excluded aesthetics that should not trigger auto-grouping:
         // - Stat-consumed aesthetics (transformed, not grouped)
         // - 'label' aesthetic (text content to display, not grouping categories)
+        //   — except when `aggregate` is set on the layer, in which case label
+        //   becomes a legitimate grouping key (e.g. "mean per species, place
+        //   species name at the centroid").
         let consumed_aesthetics = layer.geom.stat_consumed_aesthetics();
         let mut excluded_aesthetics: HashSet<&str> = consumed_aesthetics.iter().copied().collect();
-        excluded_aesthetics.insert("label");
+        if !crate::plot::layer::geom::has_aggregate_param(&layer.parameters) {
+            excluded_aesthetics.insert("label");
+        }
 
         for (aesthetic, value) in &layer.mappings.aesthetics {
             // Skip position aesthetics - these should not trigger auto-grouping.