Constant RECT_STRIP_FLAG 

pub const RECT_STRIP_FLAG: u32 = _ /* 2_147_483_648u32 */;

Bit 31 of GpuStrip::paint_and_rect_flag, marking an instance as a whole rectangle rather than a strip: the shader then reads GpuStrip::dense_width_or_rect_height as a height and GpuStrip::col_idx_or_rect_frac as a coverage fraction.