Skip to content

Support direct scanout with src crop and dst boxes

David Turner requested to merge david.turner/wlroots:letterbox_scale_scanout into master

Enable scene-tree direct scanout of a single buffer with various options for scaling and source crop. This is intended to support direct scanout for fullscreen video with/without scaling, letterboxing/pillarboxing (e.g. 4:3 content on a 16:9 display), and source crop (e.g. when 1920x1088 planes are used for 1920x1080 video).

This works by explicitly specifying the source crop and destination box for the primary buffer in the output state. DRM atomic and libliftoff backends will turn this into a crop and scale of the plane (assuming the hardware supports that). For the Wayland/X11 backends I just reject this so scanout will be disabled.

The previous behaviour is preserved if buffer_src_box and buffer_dst_box are unset: the buffer is displayed at native size at the top-left of the output with no crop.

The change to struct wlr_output_state makes this a binary breaking change (but this works transparently for scene-tree compositors like labwc after a recompile).

Merge request reports