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Enforce matching dimensions between render context and pixmap when rasterizing #1193

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Enforce matching dimensions between render context and pixmap when rasterizing #1193

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1 change: 1 addition & 0 deletions Cargo.lock
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1 change: 1 addition & 0 deletions sparse_strips/vello_cpu/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ ordered-channel = { workspace = true, optional = true, features = ["crossbeam-ch
rayon = { workspace = true, optional = true }
smallvec = { workspace = true, optional = true }
thread_local = { workspace = true, optional = true }
log = { workspace = true }


[features]
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25 changes: 25 additions & 0 deletions sparse_strips/vello_cpu/src/render.rs
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Expand Up @@ -15,6 +15,7 @@ use alloc::boxed::Box;
use alloc::sync::Arc;
use alloc::vec;
use alloc::vec::Vec;
use log::warn;
use vello_common::blurred_rounded_rect::BlurredRoundedRectangle;
use vello_common::encode::{EncodeExt, EncodedPaint};
use vello_common::fearless_simd::Level;
Expand Down Expand Up @@ -448,9 +449,19 @@ impl RenderContext {
}

/// Render the current context into a pixmap.
///
/// Note that the pixmap needs to have the same dimensions as the render context.
pub fn render_to_pixmap(&self, pixmap: &mut Pixmap) {
let width = pixmap.width();
let height = pixmap.height();

if width != self.width || height != self.height {
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Elsewhere, when invariants like this aren't obeyed, we typically panic:

https://github.com/linebender/vello/blob/main/sparse_strips%2Fvello_common%2Fsrc%2Fpixmap.rs#L43-L47

I'm wondering whether we should either return an Error or similarly panic (to at least be consistent).

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Good question, I’m not sure.

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I think the best option is allowing the consumer to decide what to do when they break an invariant (i.e. return an Error). Vello hybrid can return an Error type IIRC when spatiotemporal allocation suffers slot exhaustion.

Otherwise, I think it's fine to defer that to a larger review of this question and simply panic here (to be consistent with the rest of the system).

warn!("cannot render a pixmap with the dimensions {width}x{height} into \
a render context with the dimensions {}x{}", self.width, self.height);

return;
}

self.render_to_buffer(
pixmap.data_as_u8_slice_mut(),
width,
Expand Down Expand Up @@ -945,6 +956,7 @@ impl RenderContext {
mod tests {
use crate::RenderContext;
use vello_common::kurbo::{Rect, Shape};
use vello_common::pixmap::Pixmap;
use vello_common::tile::Tile;

#[test]
Expand Down Expand Up @@ -981,4 +993,17 @@ mod tests {
ctx.flush();
ctx.render_to_pixmap(&mut pixmap);
}

#[test]
fn mismatched_dimensions() {
let mut ctx = RenderContext::new(20, 15);
let mut pixmap = Pixmap::new(20, 20);
let rect = Rect::new(0.0, 0.0, 20.0, 20.0);

ctx.push_layer(Some(&rect.to_path(0.1)), None, None, None);
ctx.pop_layer();

ctx.flush();
ctx.render_to_pixmap(&mut pixmap);
}
}
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