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⚡ Bolt: Use write! macro to prevent temporary allocations in canvas #123

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Merged
Tcode-Motion merged 1 commit into from
Sep 9, 2026
Merged

⚡ Bolt: Use write! macro to prevent temporary allocations in canvas #123

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
Expand Up @@ -11,3 +11,6 @@
## 2024-06-25 - Suboptimal Line Search in LSP
**Learning:** Using `chars().nth()` with a byte offset (such as one returned by `.find()`) inside a loop over a string creates an O(N) penalty and may result in an incorrect character lookup if multi-byte unicode characters are present.
**Action:** Use string slicing with the byte index to create a subset string slice, and call `.chars().next_back()` or `.chars().next()` on it for an O(1) and UTF-8 safe boundary lookup.
## 2024-05-24 - Avoid `push_str(&format!(...))` in loops
**Learning:** Using `push_str(&format!(...))` inside loops creates unnecessary temporary String allocations because `format!` allocates a new `String` which is then appended and immediately dropped.
**Action:** Use `std::fmt::Write` and the `write!` macro directly onto the target string buffer instead.
4 changes: 4 additions & 0 deletions fix_journal.py
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@@ -0,0 +1,4 @@
with open('.jules/bolt.md', 'r') as f:
content = f.read()

# I will append the learning at the end if it doesn't exist, but since it currently only contains my previous write, I need to look at git history to restore it.
88 changes: 57 additions & 31 deletions stdlib/src/canvas.rs
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@@ -1,6 +1,11 @@
use crate::{StdFunction, StdlibModule, StdlibRegistry};
use std::cell::RefCell;
use std::collections::HashMap;
// Performance Note:
// This module uses `std::fmt::Write` and the `write!` macro instead of `push_str(&format!(...))`
// to append content to SVG and buffer strings. This prevents the allocation of temporary `String`
// objects during concatenation, significantly reducing memory overhead when rendering complex canvases.
use std::fmt::Write;
use std::rc::Rc;
use techscript_runtime::{
context::{Capability, RuntimeContext},
Expand Down Expand Up @@ -38,10 +43,11 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
.and_then(|p| p.value.as_ref())
.and_then(|v| v.try_into_int().ok())
.unwrap_or(48);
svg.push_str(&format!(
let _ = write!(
svg,
r#"<text x="250" y="440" text-anchor="middle" dominant-baseline="central" font-size="{}" font-weight="800" fill="{}" font-family="system-ui, -apple-system, sans-serif" letter-spacing="3">{}</text>"#,
size, color, text
));
);
}
"rings" => {
// BLUE FLAME / WING (Bottom-Left Swirl)
Expand Down Expand Up @@ -98,10 +104,11 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
.and_then(|p| p.value.as_ref())
.and_then(|v| v.try_into_int().ok())
.unwrap_or(48);
svg.push_str(&format!(
let _ = write!(
svg,
r#"<text x="250" y="380" text-anchor="middle" dominant-baseline="central" font-size="{}" font-weight="800" fill="{}" font-family="system-ui, -apple-system, sans-serif" letter-spacing="3">{}</text>"#,
size, color, text
));
);
}
"rings" => {
let count = dsl
Expand Down Expand Up @@ -135,10 +142,11 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
for i in 0..count {
let r = 80 + i as i64 * (size / 2);
let opacity = 0.4 - (i as f32 * 0.08);
svg.push_str(&format!(
let _ = write!(
svg,
r#"<circle cx="250" cy="180" r="{}" fill="none" stroke="{}" stroke-width="{}" opacity="{}"/>"#,
r, color, thickness, opacity
));
);
}
}
"emblem" => {
Expand All @@ -158,10 +166,16 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
.unwrap_or(120);
let x = 250 - size / 2;
let y = 180 - size / 2;
svg.push_str(&format!(
let _ = write!(
svg,
r#"<rect x="{}" y="{}" width="{}" height="{}" rx="{}" fill="{}" transform="rotate(45 250 180)" filter="url(#glow)"/>"#,
x, y, size, size, size / 4, color
));
x,
y,
size,
size,
size / 4,
color
);
}
"letter" => {
let ch = dsl
Expand All @@ -185,10 +199,11 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
.and_then(|p| p.value.as_ref())
.and_then(|v| v.try_into_int().ok())
.unwrap_or(32);
svg.push_str(&format!(
let _ = write!(
svg,
r#"<text x="250" y="180" text-anchor="middle" dominant-baseline="central" font-size="{}" font-weight="900" fill="{}" font-family="system-ui, -apple-system, sans-serif">{}</text>"#,
size, color, ch
));
);
}
"core" => {
let color = dsl
Expand All @@ -205,11 +220,12 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
.and_then(|p| p.value.as_ref())
.and_then(|v| v.try_into_int().ok())
.unwrap_or(40);
svg.push_str(&format!(
let _ = write!(
svg,
r#"<circle cx="250" cy="180" r="{}" fill="{}" opacity="0.8"/>"#,
size / 2,
color
));
);
}
"circuits" => {
let color = dsl
Expand All @@ -219,15 +235,16 @@ fn dsl_to_svg(val: &RuntimeValue, is_dragon: bool) -> String {
.and_then(|p| p.value.as_ref())
.map(|v| v.to_string())
.unwrap_or_else(|| "#00d4ff".to_string());
svg.push_str(&format!(
let _ = write!(
svg,
r#"<line x1="50" y1="180" x2="450" y2="180" stroke="{}" stroke-width="1.5" stroke-dasharray="5 5" opacity="0.6"/>
<line x1="250" y1="30" x2="250" y2="330" stroke="{}" stroke-width="1.5" stroke-dasharray="5 5" opacity="0.6"/>
<circle cx="50" cy="180" r="4" fill="{}"/>
<circle cx="450" cy="180" r="4" fill="{}"/>
<circle cx="250" cy="30" r="4" fill="{}"/>
<circle cx="250" cy="330" r="4" fill="{}"/>"#,
color, color, color, color, color, color
));
);
}
_ => {}
}
Expand Down Expand Up @@ -292,10 +309,11 @@ impl Callable for CanvasFn {
let w = parse_width(&buf);
let h = parse_height(&buf);
let fill = args[0].to_string();
buf.push_str(&format!(
let _ = write!(
buf,
r#"<rect x="0" y="0" width="{}" height="{}" fill="{}"/>"#,
w, h, fill
));
);
Ok(RuntimeValue::Null)
}
CanvasOp::Rect => {
Expand All @@ -304,21 +322,23 @@ impl Callable for CanvasFn {
let w = args[2].try_into_int().unwrap_or(100);
let h = args[3].try_into_int().unwrap_or(100);
let fill = args[4].to_string();
buf.push_str(&format!(
let _ = write!(
buf,
r#"<rect x="{}" y="{}" width="{}" height="{}" fill="{}"/>"#,
x, y, w, h, fill
));
);
Ok(RuntimeValue::Null)
}
CanvasOp::Circle => {
let cx = args[0].try_into_int().unwrap_or(50);
let cy = args[1].try_into_int().unwrap_or(50);
let r = args[2].try_into_int().unwrap_or(40);
let fill = args[3].to_string();
buf.push_str(&format!(
let _ = write!(
buf,
r#"<circle cx="{}" cy="{}" r="{}" fill="{}"/>"#,
cx, cy, r, fill
));
);
Ok(RuntimeValue::Null)
}
CanvasOp::Text => {
Expand All @@ -335,16 +355,17 @@ impl Callable for CanvasFn {
} else {
"black".to_string()
};
buf.push_str(&format!(r#"<text x="{}" y="{}" font-size="{}" font-family="Arial,sans-serif" fill="{}">{}</text>"#, x, y, size, color, txt));
let _ = write!(
buf,
r#"<text x="{}" y="{}" font-size="{}" font-family="Arial,sans-serif" fill="{}">{}</text>"#,
x, y, size, color, txt
);
Ok(RuntimeValue::Null)
}
CanvasOp::Polygon => {
let points = args[0].to_string();
let fill = args[1].to_string();
buf.push_str(&format!(
r#"<polygon points="{}" fill="{}"/>"#,
points, fill
));
let _ = write!(buf, r#"<polygon points="{}" fill="{}"/>"#, points, fill);
Ok(RuntimeValue::Null)
}
CanvasOp::Line => {
Expand All @@ -353,10 +374,11 @@ impl Callable for CanvasFn {
let x2 = args[2].try_into_int().unwrap_or(100);
let y2 = args[3].try_into_int().unwrap_or(100);
let stroke = args[4].to_string();
buf.push_str(&format!(
let _ = write!(
buf,
r#"<line x1="{}" y1="{}" x2="{}" y2="{}" stroke="{}" stroke-width="2"/>"#,
x1, y1, x2, y2, stroke
));
);
Ok(RuntimeValue::Null)
}
CanvasOp::Close => {
Expand Down Expand Up @@ -405,7 +427,11 @@ impl Callable for CanvasFn {
} else {
"1".to_string()
};
buf.push_str(&format!(r#"<circle cx="{}" cy="{}" r="{}" fill="none" stroke="{}" stroke-width="{}" opacity="{}"/>"#, cx, cy, r, color, width, opacity));
let _ = write!(
buf,
r#"<circle cx="{}" cy="{}" r="{}" fill="none" stroke="{}" stroke-width="{}" opacity="{}"/>"#,
cx, cy, r, color, width, opacity
);
Ok(RuntimeValue::Null)
}
CanvasOp::Reset => {
Expand Down Expand Up @@ -633,7 +659,7 @@ impl StdlibRegistry {
let bg_color = if is_dragon { "#030408" } else { "#0a0e27" };

let mut svg = String::new();
svg.push_str(&format!(r##"<svg xmlns="http://www.w3.org/2000/svg" width="500" height="500" viewBox="0 0 500 500">
let _ = write!(svg, r##"<svg xmlns="http://www.w3.org/2000/svg" width="500" height="500" viewBox="0 0 500 500">
<defs>
<filter id="glow" x="-20%" y="-20%" width="140%" height="140%">
<feGaussianBlur stdDeviation="6" result="blur" />
Expand All @@ -656,7 +682,7 @@ impl StdlibRegistry {
</linearGradient>
</defs>
<rect width="100%" height="100%" fill="{}"/>
"##, bg_color));
"##, bg_color);
for block in &blocks {
svg.push_str(&dsl_to_svg(block, is_dragon));
}
Expand Down
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