Default chart legibility

documentation/changelog.rst

@@ -8,6 +8,7 @@ v0.10.0 | April XX, 2022
 
 New features
 -----------
+* Improve legibility of chart axes [see `PR #413 <http://www.github.com/FlexMeasures/flexmeasures/pull/413>`_]
 
 Bugfixes
 -----------

flexmeasures/data/models/charts/defaults.py

@@ -4,6 +4,7 @@
 import altair as alt
 
 
+FONT_SIZE = 16
 HEIGHT = 300
 WIDTH = 600
 REDUCED_HEIGHT = REDUCED_WIDTH = 60
@@ -36,6 +37,29 @@
         title="Time and date",
     ),
 }
+LEGIBILITY_DEFAULTS = dict(
+    config=dict(
+        axis=dict(
+            titleFontSize=FONT_SIZE,
+            labelFontSize=FONT_SIZE,
+        )
+    ),
+    title=dict(fontSize=FONT_SIZE),
+    encoding=dict(
+        color=dict(
+            dict(
+                legend=dict(
+                    titleFontSize=FONT_SIZE,
+                    labelFontSize=FONT_SIZE,
+                )
+            )
+        )
+    ),
+)
+vega_lite_field_mapping = {
+    "title": "text",
+    "mark": "type",
+}
 
 
 def apply_chart_defaults(fn):
@@ -60,6 +84,12 @@ def decorated_chart_specs(*args, **kwargs):
         if "width" not in chart_specs:
             chart_specs["width"] = WIDTH
 
+        # Improve default legibility
+        chart_specs = merge_vega_lite_specs(
+            LEGIBILITY_DEFAULTS,
+            chart_specs,
+        )
+
         # Add transform function to calculate full date
         if "transform" not in chart_specs:
             chart_specs["transform"] = []
@@ -72,3 +102,33 @@ def decorated_chart_specs(*args, **kwargs):
         return chart_specs
 
     return decorated_chart_specs
+
+
+def merge_vega_lite_specs(child: dict, parent: dict) -> dict:
+    """Merge nested dictionaries, with child inheriting values from parent.
+
+    Child values are updated with parent values if they exist.
+    In case a field is a string and that field is updated with some dict,
+    the string is moved inside the dict under a field defined in vega_lite_field_mapping.
+    For example, 'title' becomes 'text' and 'mark' becomes 'type'.
+    """
+    d = {}
+    for k in set().union(child, parent):
+        if k in parent and k in child:
+            if isinstance(child[k], str):
+                child[k] = {vega_lite_field_mapping.get(k, "type"): child[k]}
+            if isinstance(parent[k], str):
+                parent[k] = {vega_lite_field_mapping.get(k, "type"): parent[k]}
+        if (
+            k in parent
+            and isinstance(parent[k], dict)
+            and k in child
+            and isinstance(child[k], dict)
+        ):
+            v = merge_vega_lite_specs(child[k], parent[k])
+        elif k in parent:
+            v = parent[k]
+        else:
+            v = child[k]
+        d[k] = v
+    return d

flexmeasures/data/tests/test_chart_utils.py

@@ -0,0 +1,24 @@
+import pytest
+
+from flexmeasures.data.models.charts.defaults import merge_vega_lite_specs
+
+
+@pytest.mark.parametrize(
+    "default_specs, custom_specs, expected_specs",
+    [
+        (
+            {"legend": {"titleFontSize": 16}},
+            {"title": "foo"},
+            {"legend": {"titleFontSize": 16}, "title": "foo"},
+        ),
+        (
+            {"title": {"fontSize": 16}},
+            {"title": "foo"},
+            {"title": {"fontSize": 16, "text": "foo"}},
+        ),
+    ],
+)
+def test_merge_vega_lite_specs(
+    default_specs: dict, custom_specs: dict, expected_specs: dict
+):
+    assert merge_vega_lite_specs(default_specs, custom_specs) == expected_specs

flexmeasures/ui/static/css/flexmeasures.css

@@ -504,3 +504,5 @@ i.icon-wind:hover:before {
 .icon-buildings:before { content: '\e803'; } /* '' */
 .icon-charging_stations:before { content: '\e805'; } /* '' */
 .icon-bidirectional_charging_stations:before { content: '\e805'; } /* '' */
+
+.litepicker { font-size: 14px;}

flexmeasures/ui/templates/views/sensors.html

@@ -71,7 +71,7 @@
           numberOfMonths: 2,
           numberOfColumns: 2,
           inlineMode: true,
-          switchingMonths: 2,
+          switchingMonths: 1,
           singleMode: false,
           dropdowns: {
               years: true,