Abstract: A computing device generates an initial data visualization according to a visual specification that specifies a data source, a plurality of visual variables, and a plurality of data fields from the data source. The device determines a visualization region based on a display size of the initial data visualization. The device generates a modified data visualization from the initial data visualization according to the determined visualization region, including: (i) identifying a plurality of elements of the initial data visualization, (ii) for each element of the plurality of identified elements, determining a respective semantic weight for the respective element, (iii) grouping the elements into one or more element layers according to the determined semantic weights, (iv) computing spatial metrics for the elements, and (v) executing one or more generalization operations on the elements in accordance with the one or more computed spatial metrics. The computing device displays the modified data visualization.