Function build_content_stream 

pub(crate) fn build_content_stream(
    page_height_pt: f32,
    page: &Page,
    encodings: &HashMap<Font, DocEncoding>,
    embedded_by_id: &HashMap<EmbeddedFontId, &EmbeddedFontPlan>,
) -> Result<Vec<u8>>

Build the per-page content stream. The layout engine measures baselines from the top of the page; PDF’s coordinate system is bottom-origin, so we flip once here.

Base14 runs encode through the planner’s per-face DocEncoding (WinAnsi byte + /Differences remap; characters outside both tiers silently render as ?). Embedded-font runs encode the shaped glyph stream as big-endian u16 CIDs.

Image placements (raster XObjects) emit outside the text object : BT/ET brackets only permit text operators, so each image placement is wrapped in its own q ... Q save/restore pair before the text block starts. Putting images first means subsequent text can overlay (e.g. a caption beneath the image is unaffected, but in-line annotations atop a figure would land on top).