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