Whether the plot is laid out with a horizontal value axis (bottom) and a vertical category axis (left) instead of the default vertical value axis (left) / horizontal category axis (bottom). Only BarChart opts in via CartesianChart::is_horizontal. When true, y_scale's pixel range spans the plot's horizontal extent (left→right) rather than vertical — it still represents the "value" axis, just rotated.
<insightdock/cartesian_chart.h>
bool horizontal = false;