Geometry API

The public types in src/geometry.rs are the single source of truth for virtual-display sizing and pointer-coordinate conversion. A frontend should persist SizingRequest, call SizingRequest::calculate, and pass the request through the existing mapping path. It should not calculate or persist a derived display mode itself.

Sizing

pub struct DisplayGeometry {
    pub native_pixels: PixelSize,
    pub physical: PhysicalMeasurement,
    pub aspect_ratio: Option<AspectRatio>,
    pub rotation: Rotation,
}

pub struct SizingRequest {
    pub reference: DisplayGeometry,
    pub target: DisplayGeometry,
    pub strategy: SizingStrategy,
    pub alignment: u32,
    pub preferred_refresh_millihz: Option<u32>,
}

pub enum SizingStrategy {
    MatchPhysicalSize,
    RoundedScale,
    IntegerScale,
}

reference describes the display whose apparent pixel density should be matched. target describes the physical display that receives the mirror. Physical size may be supplied as width and height in millimetres or as a diagonal; an explicit aspect ratio can be supplied when a diagonal is used.

SizingRequest::calculate() returns:

pub struct SizingResult {
    pub virtual_mode: PixelSize,
    pub oriented_target: PixelSize,
    pub scale_x: f64,
    pub scale_y: f64,
    pub preferred_refresh_millihz: Option<u32>,
}

The alignment must be a power of two from 1 through 256. Measurements must be finite and positive. A preferred refresh rate, when present, must be non-zero. The session gate accepts dimensions from 1 through 16384 and refresh rates up to 1000 Hz.

Mapping path

SizingRequest::calculate
  -> SizingResult.virtual_mode
  -> VirtualMode
  -> protected v5 session gate
  -> IDD monitor and target mode
  -> Windows display source
  -> GPU renderer

The mode is fixed before the software display device is created. Changing it requires stopping and starting the mapping session.

Pointer coordinates

CoordinateTransform::stretch(target, source, rotation) builds the transform shared by the renderer input path. map_target_point maps a physical target point to the corresponding virtual-desktop point and returns None outside the target rectangle.

let transform = CoordinateTransform::stretch(target_rect, source_rect, rotation)?;
let source_point = transform.map_target_point(target_point);

The transform supports 0, 90, 180 and 270 degree rotation.