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use crate::{PositionI, PositionU, Size};
use std::fmt::{Display, Formatter};
/// The original destination position and source size, and the position and size used for blitting.
#[derive(Copy, Clone, Debug, Default)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct ClippedRect {
/// The original top-left position of the where the source image should blit to.
pub dst_position: PositionI,
/// The clipped top-left position that is actually used for blitting.
pub dst_position_clipped: PositionU,
/// The original size of the source image.
pub src_size: Size,
/// The clipped size of the source image, which is used for blitting.
pub src_size_clipped: Size,
/// A pixel offset in the source bitmap.
pub(crate) src_position: Option<PositionU>,
/// The size of the destination image.
pub dst_size: Size,
}
impl ClippedRect {
/// Clip `src_size` such that it fits within the rectangle defined by `dst_position` and `dst_size`.
///
/// Returns None if the region is beyond the bounds of `dst_size`
/// or if the blittable source size would be `(0, 0)`.
pub const fn new(dst_position: PositionI, dst_size: Size, src_size: Size) -> Option<Self> {
// Check if the source image is totally out of bounds.
if dst_position.x + (src_size.w.cast_signed()) < 0
|| dst_position.y + (src_size.h.cast_signed()) < 0
{
None
} else {
let mut x = 0;
let mut src_size_clipped = src_size;
if dst_position.x < 0 {
src_size_clipped.w = src_size.w.saturating_sub(dst_position.x.unsigned_abs());
} else {
x = dst_position.x.unsigned_abs();
}
let mut y = 0;
if dst_position.y < 0 {
src_size_clipped.h = src_size.h.saturating_sub(dst_position.y.unsigned_abs());
} else {
y = dst_position.y.unsigned_abs();
}
let dst_position_clipped = PositionU { x, y };
// This allows us to do unchecked subtraction.
// The `blit` methods will also check `is_inside`.
if dst_position_clipped.x < dst_size.w && dst_position_clipped.y < dst_size.h {
let w = dst_size.w - dst_position_clipped.x;
if w < src_size.w {
src_size_clipped.w = w;
}
let h = dst_size.h - dst_position_clipped.y;
if h < src_size.h {
src_size_clipped.h = h;
}
if src_size_clipped.w == 0 || src_size_clipped.h == 0 {
None
} else {
Some(Self {
dst_position,
dst_position_clipped,
src_size,
src_size_clipped,
dst_size,
src_position: None,
})
}
} else {
None
}
}
}
/// Returns true if this rect overlaps with `b`.
pub const fn overlaps(&self, b: &ClippedRect) -> bool {
self.dst_position_clipped.x <= b.dst_position_clipped.x + b.src_size_clipped.w
&& self.dst_position_clipped.x + self.src_size_clipped.w > b.dst_position_clipped.x
&& self.dst_position_clipped.y <= b.dst_position_clipped.y + b.src_size_clipped.h
&& self.dst_position_clipped.y + self.src_size_clipped.h > b.dst_position_clipped.y
}
/// Set the rect within the source bitmap to blit.
///
/// By default, the entirety of the source bitmap blits.
/// This sets an internal positional offset. and modifies `self.src_clipped_area`.
/// If the positional offset would be beyond the original clipped area, this function does nothing.
///
/// - `position` is the position offset from the top-level corner of the source bitmap.
/// - `size` is the size of the rect. This will be clipped to `self.src_size_clipped` if needed.
pub const fn set_src_rect(&mut self, position: PositionU, size: Size) {
// Clip the size.
let mut size = Size {
w: if self.src_size_clipped.w < size.w {
self.src_size_clipped.w
} else {
size.w
},
h: if self.src_size_clipped.h < size.h {
self.src_size_clipped.h
} else {
size.h
},
};
// Apply the offset only if it's within the clipped bounds.
if position.x < size.w && position.y < size.h {
// Set the offset.
self.src_position = Some(position);
// Apply the offset.
size.w -= position.x;
size.h -= position.y;
// Set the new clipped size.
self.src_size_clipped = size;
}
}
pub(crate) fn get_src_position(&self) -> PositionU {
self.src_position
.unwrap_or_else(|| PositionU { x: 0, y: 0 })
}
}
impl Display for ClippedRect {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
write!(
f,
"dst position: {}\ndst position (clipped): {}\nsrc size: {}, src size (clipped): {}",
self.dst_position, self.dst_position_clipped, self.src_size, self.src_size_clipped
)
}
}