From 0e16fb05e945c690d8031b8a1c9bd7186278fd5f Mon Sep 17 00:00:00 2001
From: Pascal Sommer <p@pascalsommer.ch>
Date: Sat, 26 Feb 2022 17:37:24 +0100
Subject: [PATCH] fix half-pixel offsets
---
src/canvas.rs | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/src/canvas.rs b/src/canvas.rs
index 216e8fa..55f706b 100644
--- a/src/canvas.rs
+++ b/src/canvas.rs
@@ -76,6 +76,10 @@ fn make_canvas_color(color: BackendColor) -> JsValue {
format!("rgba({},{},{},{})", r, g, b, a).into()
}
+fn to_f64_offset(x: i32) -> f64 {
+ f64::from(x) + 0.5
+}
+
impl DrawingBackend for CanvasBackend {
type ErrorType = CanvasError;
@@ -119,8 +123,11 @@ impl DrawingBackend for CanvasBackend {
self.set_line_style(style);
self.context.begin_path();
- self.context.move_to(f64::from(from.0), f64::from(from.1));
- self.context.line_to(f64::from(to.0), f64::from(to.1));
+ self.context.set_line_cap("square");
+ self.context
+ .move_to(to_f64_offset(from.0), to_f64_offset(from.1));
+ self.context
+ .line_to(to_f64_offset(to.0), to_f64_offset(to.1));
self.context.stroke();
Ok(())
}
@@ -147,10 +154,10 @@ impl DrawingBackend for CanvasBackend {
} else {
self.set_line_style(style);
self.context.stroke_rect(
- f64::from(upper_left.0),
- f64::from(upper_left.1),
- f64::from(bottom_right.0 - upper_left.0),
- f64::from(bottom_right.1 - upper_left.1),
+ to_f64_offset(upper_left.0),
+ to_f64_offset(upper_left.1),
+ to_f64_offset(bottom_right.0 - upper_left.0),
+ to_f64_offset(bottom_right.1 - upper_left.1),
);
}
Ok(())
@@ -166,11 +173,14 @@ impl DrawingBackend for CanvasBackend {
}
let mut path = path.into_iter();
self.context.begin_path();
+ self.context.set_line_cap("square");
if let Some(start) = path.next() {
self.set_line_style(style);
- self.context.move_to(f64::from(start.0), f64::from(start.1));
+ self.context
+ .move_to(to_f64_offset(start.0), to_f64_offset(start.1));
for next in path {
- self.context.line_to(f64::from(next.0), f64::from(next.1));
+ self.context
+ .line_to(to_f64_offset(next.0), to_f64_offset(next.1));
}
}
self.context.stroke();
@@ -190,9 +200,11 @@ impl DrawingBackend for CanvasBackend {
if let Some(start) = path.next() {
self.context
.set_fill_style(&make_canvas_color(style.color()));
- self.context.move_to(f64::from(start.0), f64::from(start.1));
+ self.context
+ .move_to(to_f64_offset(start.0), to_f64_offset(start.1));
for next in path {
- self.context.line_to(f64::from(next.0), f64::from(next.1));
+ self.context
+ .line_to(to_f64_offset(next.0), to_f64_offset(next.1));
}
self.context.close_path();
}
@@ -219,8 +231,8 @@ impl DrawingBackend for CanvasBackend {
self.context.begin_path();
self.context
.arc(
- f64::from(center.0),
- f64::from(center.1),
+ to_f64_offset(center.0),
+ to_f64_offset(center.1),
f64::from(radius),
0.0,
std::f64::consts::PI * 2.0,