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use crate::Rect;
/// Size of the viewport in whole, physical pixels.
pub struct ViewportInPixels {
/// Physical pixel offset for left side of the viewport.
pub left_px: i32,
/// Physical pixel offset for top side of the viewport.
pub top_px: i32,
/// Physical pixel offset for bottom side of the viewport.
///
/// This is what `glViewport`, `glScissor` etc expects for the y axis.
pub from_bottom_px: i32,
/// Viewport width in physical pixels.
pub width_px: i32,
/// Viewport height in physical pixels.
pub height_px: i32,
}
impl ViewportInPixels {
/// Convert from ui points.
pub fn from_points(rect: &Rect, pixels_per_point: f32, screen_size_px: [u32; 2]) -> Self {
// Fractional pixel values for viewports are generally valid, but may cause sampling issues
// and rounding errors might cause us to get out of bounds.
// Round:
let left_px = (pixels_per_point * rect.min.x).round() as i32; // inclusive
let top_px = (pixels_per_point * rect.min.y).round() as i32; // inclusive
let right_px = (pixels_per_point * rect.max.x).round() as i32; // exclusive
let bottom_px = (pixels_per_point * rect.max.y).round() as i32; // exclusive
// Clamp to screen:
let screen_width = screen_size_px[0] as i32;
let screen_height = screen_size_px[1] as i32;
let left_px = left_px.clamp(0, screen_width);
let right_px = right_px.clamp(left_px, screen_width);
let top_px = top_px.clamp(0, screen_height);
let bottom_px = bottom_px.clamp(top_px, screen_height);
let width_px = right_px - left_px;
let height_px = bottom_px - top_px;
Self {
left_px,
top_px,
from_bottom_px: screen_height - height_px - top_px,
width_px,
height_px,
}
}
}