//! Point projection.
use super::graphics::{CoordAxis, GraphicsState};
use raw::types::{F26Dot6, Point};
impl GraphicsState<'_> {
/// Updates cached state that is derived from projection vectors.
pub fn update_projection_state(&mut self) {
// 1.0 in 2.14 fixed point.
const ONE: i32 = 0x4000;
// Based on Compute_Funcs() at
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2482>.
// FreeType uses function pointers to select between various "modes"
// but we use the CoordAxis type instead.
if self.freedom_vector.x == ONE {
self.fdotp = self.proj_vector.x;
} else if self.freedom_vector.y == ONE {
self.fdotp = self.proj_vector.y;
} else {
let px = self.proj_vector.x;
let py = self.proj_vector.y;
let fx = self.freedom_vector.x;
let fy = self.freedom_vector.y;
self.fdotp = (px * fx + py * fy) >> 14;
}
self.proj_axis = CoordAxis::Both;
if self.proj_vector.x == ONE {
self.proj_axis = CoordAxis::X;
} else if self.proj_vector.y == ONE {
self.proj_axis = CoordAxis::Y;
}
self.dual_proj_axis = CoordAxis::Both;
if self.dual_proj_vector.x == ONE {
self.dual_proj_axis = CoordAxis::X;
} else if self.dual_proj_vector.y == ONE {
self.dual_proj_axis = CoordAxis::Y;
}
self.freedom_axis = CoordAxis::Both;
if self.fdotp == ONE {
if self.freedom_vector.x == ONE {
self.freedom_axis = CoordAxis::X;
} else if self.freedom_vector.y == ONE {
self.freedom_axis = CoordAxis::Y;
}
}
// At small sizes, fdotp can become too small resulting in overflows
// and spikes.
if self.fdotp.abs() < 0x400 {
self.fdotp = ONE;
}
}
/// Computes the projection of vector given by (v1 - v2) along the
/// current projection vector.
#[inline(always)]
pub fn project(&self, v1: Point<F26Dot6>, v2: Point<F26Dot6>) -> F26Dot6 {
match self.proj_axis {
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2431>
CoordAxis::X => v1.x - v2.x,
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2461>
CoordAxis::Y => v1.y - v2.y,
CoordAxis::Both => {
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2373>
let dx = v1.x - v2.x;
let dy = v1.y - v2.y;
F26Dot6::from_bits(dot14(
dx.to_bits(),
dy.to_bits(),
self.proj_vector.x,
self.proj_vector.y,
))
}
}
}
/// Computes the projection of vector given by (v1 - v2) along the
/// current dual projection vector.
#[inline(always)]
pub fn dual_project(&self, v1: Point<F26Dot6>, v2: Point<F26Dot6>) -> F26Dot6 {
match self.dual_proj_axis {
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2431>
CoordAxis::X => v1.x - v2.x,
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2461>
CoordAxis::Y => v1.y - v2.y,
CoordAxis::Both => {
// https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2402
let dx = v1.x - v2.x;
let dy = v1.y - v2.y;
F26Dot6::from_bits(dot14(
dx.to_bits(),
dy.to_bits(),
self.dual_proj_vector.x,
self.dual_proj_vector.y,
))
}
}
}
/// Computes the projection of vector given by (v1 - v2) along the
/// current dual projection vector for unscaled points.
#[inline(always)]
pub fn dual_project_unscaled(&self, v1: Point<i32>, v2: Point<i32>) -> i32 {
match self.dual_proj_axis {
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2431>
CoordAxis::X => v1.x - v2.x,
// <https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2461>
CoordAxis::Y => v1.y - v2.y,
CoordAxis::Both => {
// https://gitlab.freedesktop.org/freetype/freetype/-/blob/57617782464411201ce7bbc93b086c1b4d7d84a5/src/truetype/ttinterp.c#L2402
let dx = v1.x - v2.x;
let dy = v1.y - v2.y;
dot14(dx, dy, self.dual_proj_vector.x, self.dual_proj_vector.y)
}
}
}
}
/// Dot product for vectors in 2.14 fixed point.
fn dot14(ax: i32, ay: i32, bx: i32, by: i32) -> i32 {
let mut v1 = ax as i64 * bx as i64;
let v2 = ay as i64 * by as i64;
v1 += v2;
v1 += 0x2000 + (v1 >> 63);
(v1 >> 14) as i32
}
#[cfg(test)]
mod tests {
use super::{super::math, CoordAxis, F26Dot6, GraphicsState, Point};
#[test]
fn project_one_axis() {
let mut state = GraphicsState {
proj_vector: math::normalize14(1, 0),
..Default::default()
};
state.update_projection_state();
assert_eq!(state.proj_axis, CoordAxis::X);
assert_eq!(state.proj_vector, Point::new(0x4000, 0));
let cases = &[
(Point::new(0, 0), Point::new(0, 0), 0),
(Point::new(100, 100), Point::new(0, 0), 100),
(Point::new(42, 100), Point::new(100, 0), -58),
(Point::new(0, 0), Point::new(100, 100), -100),
];
test_project_cases(&state, cases);
}
#[test]
fn project_both_axes() {
let mut state = GraphicsState {
proj_vector: math::normalize14(0x4000, 0x4000),
..Default::default()
};
state.update_projection_state();
assert_eq!(state.proj_axis, CoordAxis::Both);
let cases = &[
(Point::new(0, 0), Point::new(0, 0), 0),
(Point::new(100, 100), Point::new(0, 0), 141),
(Point::new(42, 100), Point::new(100, 0), 30),
(Point::new(0, 0), Point::new(100, 100), -141),
];
test_project_cases(&state, cases);
}
fn test_project_cases(state: &GraphicsState, cases: &[(Point<i32>, Point<i32>, i32)]) {
for (v1, v2, expected) in cases.iter().copied() {
let v1 = v1.map(F26Dot6::from_bits);
let v2 = v2.map(F26Dot6::from_bits);
let result = state.project(v1, v2).to_bits();
assert_eq!(
result, expected,
"project({v1:?}, {v2:?}) = {result} (expected {expected})"
);
}
}
}
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