refactor(core): optimize `Chunks` memory layout
What the developer wrote
Authored by Roman Zeyde
refactor(core): optimize `Chunks` memory layout
After:
```
print-type-size type: `ui::component::text::layout::Chunks`: 6 bytes, alignment: 2 bytes
print-type-size field `.max_rows`: 2 bytes
print-type-size field `.x_offset`: 2 bytes
print-type-size field `.chunk_size`: 1 bytes
print-type-size end padding: 1 bytes
```
Before:
```
print-type-size type: `ui::component::text::layout::Chunks`: 16 bytes, alignment: 4 bytes
print-type-size field `.max_rows`: 8 bytes
print-type-size field `.chunk_size`: 4 bytes
print-type-size field `.x_offset`: 2 bytes
print-type-size end padding: 2 bytes
```
[no changelog]
What changed, and why it matters
This commit is a straightforward internal code cleanup that reduces the memory footprint of a text-layout helper struct by switching from larger integer types to smaller ones. There is no security-relevant change: it does not alter how data is validated, how memory is allocated, or how user input is handled. It only changes the size of fields used to count characters and rows on screen.
No security action needed. Treat as a normal code-quality/memory-optimization review.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The patch refactors the Chunks struct in core/embed/rust/src/ui/component/text/layout.rs from usize/Option<usize> fields to u8/Option<u8>, shrinking the type from 16 bytes (align 4) to 6 bytes (align 2). Call sites are updated with explicit casts (i16::from, .into(), usize::from). The logic for chunk sizing, pagination ellipsis, and cursor positioning is unchanged; only the storage width of the counters changed.
Changed components
core/embed/rust/src/ui/component/text/layout.rsInspect captured patch +10 / −7
diff --git a/core/embed/rust/src/ui/component/text/layout.rs b/core/embed/rust/src/ui/component/text/layout.rs
index 6567dd0b1..cc2a73ea4 100644
--- a/core/embed/rust/src/ui/component/text/layout.rs
+++ b/core/embed/rust/src/ui/component/text/layout.rs
@@ -57,15 +57,15 @@ pub struct TextLayout {
#[derive(PartialEq, Eq, Copy, Clone)]
pub struct Chunks {
/// How many characters will be grouped in one chunk.
- pub chunk_size: usize,
+ pub chunk_size: u8,
/// How big will be the space between chunks (in pixels).
pub x_offset: i16,
/// Maximum amount of rows on one page, if any.
- pub max_rows: Option<usize>,
+ pub max_rows: Option<u8>,
}
impl Chunks {
- pub const fn new(chunk_size: usize, x_offset: i16) -> Self {
+ pub const fn new(chunk_size: u8, x_offset: i16) -> Self {
Chunks {
chunk_size,
x_offset,
@@ -73,7 +73,7 @@ impl Chunks {
}
}
- pub const fn with_max_rows(mut self, max_rows: usize) -> Self {
+ pub const fn with_max_rows(mut self, max_rows: u8) -> Self {
self.max_rows = Some(max_rows);
self
}
@@ -299,7 +299,7 @@ impl TextLayout {
// Assuming mono-font, so all the letters have the same width
let letter_size = self.style.text_font.text_width("a");
let icon_offset = self.style.prev_page_ellipsis_icon_width() + 2;
- cursor.x += chunk_config.chunk_size as i16 * letter_size - icon_offset;
+ cursor.x += i16::from(chunk_config.chunk_size) * letter_size - icon_offset;
sink.prev_page_ellipsis(*cursor, self);
cursor.x += icon_offset + chunk_config.x_offset;
} else {
@@ -341,7 +341,10 @@ impl TextLayout {
// Last chunk on the page should not be rendered, put just ellipsis there
// Chunks is last when the next chunk would not fit on the page horizontally
let is_last_chunk = (2 * span.advance.x - chunk_config.x_offset) > remaining_width;
- if is_last_line && is_last_chunk && remaining_text.len() > chunk_config.chunk_size {
+ if is_last_line
+ && is_last_chunk
+ && remaining_text.len() > chunk_config.chunk_size.into()
+ {
// Making sure no text is rendered here, and that we force a line break
span.length = 0;
span.advance.x = 2; // To start at the same horizontal line as the chunk itself
@@ -732,7 +735,7 @@ impl Span {
// When there is a set chunk size and we reach it,
// adjust the line advances and return the line.
if let Some(chunkify_config) = chunks {
- if i == chunkify_config.chunk_size {
+ if i == usize::from(chunkify_config.chunk_size) {
line.advance.y = 0;
line.advance.x += chunkify_config.x_offset;
return line;
Why this scored 14/100
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