Projection and rendering

Much of what Swift Charts draws is derived rather than stated directly. We supply data values and chart content, and the framework turns them into positions, styles, and a layered visual result that adapts to the available space and the complete composition. When we want more control over that result, we need to make each adjustment at the stage where the relevant behavior is resolved.

Changing how values enter visual space has different consequences from applying an effect after chart content has been rendered. This distinction affects how a chart responds when its data or layout changes, how overlapping content is combined, and whether a visual treatment remains connected to the values it represents.

This chapter develops a model for reasoning about the path from projection to rendering. It gives us the basis for creating more deliberate chart presentations while preserving the relationships and framework behavior on which the chart depends.