Compute fixed heatmap device size

Usage

heatmap_fixsize(
  width,
  width_sum,
  height,
  height_sum,
  units,
  ht_list,
  legend_list
)

width: Optional user-provided target width. If NULL, width is estimated from the drawn heatmap layout.
width_sum: Numeric baseline width used when heatmap body size is in npc units.
height: Optional user-provided target height. If NULL, height is estimated from the drawn heatmap layout.
height_sum: Numeric baseline height used when heatmap body size is in npc units.
units: Output unit string passed to grid conversion helpers, such as "in", "cm", or "mm".
ht_list: A ComplexHeatmap::Heatmap or ComplexHeatmap::HeatmapList object.
legend_list: A list of ComplexHeatmap::Legend objects.

A list with two converted units: ht_width and ht_height.