Struct GlRegion 

pub struct GlRegion { /* private fields */ }

A physical-pixel rectangle in GL bottom-left coordinates (origin at the framebuffer’s bottom-left corner, y increasing upward). The glow backend’s read coordinates, composite rect_origin, SDF, and backdrop_uv_remap all operate in this one consistent system, so a copyTexSubImage2D from the bottom-left framebuffer lines up with rect_uv.y increasing upward and nothing is rendered upside-down (DESIGN §5).

Fields are private: the only way to obtain one is from_bottom_px from already-bottom-left inputs, so the “never flipped” invariant holds by construction.

Implementations

impl GlRegion

pub fn from_bottom_px(origin_bl: [u32; 2], size: [u32; 2], scale: Scale) -> Self

Build from a bottom-left physical-pixel origin and size. Named _bl/from_bottom_px because the input is required to already be GL-origin (egui’s from_bottom_px field); the constructor performs no flip, which is the whole point of the type.

pub fn intersect(&self, other: &GlRegion) -> Option<GlRegion>

Intersect with another region in the same bottom-left space — the clip_rect ∩ viewport step the adapter runs before grabbing. Saturating; returns None when the two are disjoint or touch only at an edge (zero area), the blur no-op. The result keeps self’s Scale; both inputs are expected to share it (same frame, same DPI).

pub fn clip_to(&self, extent: [u32; 2]) -> Option<GlRegion>

Clip to a framebuffer of size extent (the framebuffer ∩ step). Equivalent to intersect with the box origin (0, 0), size extent; None when the region lies fully outside the framebuffer (the no-op).

pub fn origin_bl(self) -> [u32; 2]

The bottom-left origin, physical pixels. Used by the grab to set copyTexSubImage2D / blitFramebuffer read coordinates directly — GL’s read origin is bottom-left, so no flip.

pub fn size(self) -> [u32; 2]

Width and height, physical pixels. The grab texture is sized to this.

pub fn into_region(self) -> Region

Reinterpret as the orientation-free Region the seam speaks. Pure reinterpret — no arithmetic, no flip: the bottom-left numbers pass straight through, and every compute consumer on the glow path (grab_source, the SDF, backdrop_uv_remap, the composite uniforms) treats the resulting Region as bottom-left consistently, so no coordinate is ever double-interpreted. This is the single line a review checks for a hidden height − y.

The one consumer that must not receive an into_region()’d value is a human-facing error: Region’s Display is documented top-left, so a bottom-left number printed through it would mislead a debugger. That is why BlurError::GrabFailed carries a GlRegion directly (which prints with an explicit bottom-left marker), not a reinterpreted Region.

Trait Implementations

impl Clone for GlRegion

fn clone(&self) -> GlRegion

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for GlRegion

impl Debug for GlRegion

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for GlRegion

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Prints with an explicit bottom-left marker so an error message can never be mistaken for the top-left Region convention.

impl PartialEq for GlRegion

fn eq(&self, other: &GlRegion) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for GlRegion