//! Fixes various issues in merman's SVG output.//!//! Replaces hardcoded white backgrounds with the theme background://! ```xml//! <!-- before --> <svg style="background-color: white">//! <!-- after --> <svg style="background-color: #1e1e2e">//! ```//!//! Removes `<rect>` elements with missing or invalid dimensions://! ```xml//! <!-- before --> <rect width="NaN" height="10"/>//! <!-- after --> (removed)//! ```//!//! Replaces hardcoded text colors with the theme text color://! ```xml//! <!-- before --> <text fill="#333">Hello</text>//! <!-- after --> <text fill="#cdd6f4">Hello</text>//! ``` use std::borrow::Cow;use std::fmt::Write as _; use anyhow::Result;use quick_xml::events::{BytesStart, Event}; use crate::MermaidTheme; struct ElementFixup<I> { inner: I, background_css: String, text_color_css: String, font_family_css: String, svg_seen: bool, skip_rect_depth: usize,} fn rewrite_attr<'a>( e: &BytesStart<'_>, attr_name: &[u8], new_value: &str,) -> Result<BytesStart<'a>> { let name = e.name(); let tag = std::str::from_utf8(name.as_ref())?; let mut new_elem = BytesStart::new(tag.to_owned()); for attr in e.attributes() { let attr = attr?; if attr.key.local_name().as_ref() == attr_name { let local_name = attr.key.local_name(); let key = std::str::from_utf8(local_name.as_ref())?; new_elem.push_attribute((key, new_value)); } else { new_elem.push_attribute(attr); } } Ok(new_elem)} fn rewrap<'a>(event: &Event<'_>, elem: BytesStart<'a>) -> Event<'a> { match event { Event::Start(_) => Event::Start(elem), _ => Event::Empty(elem), }} fn is_bad_rect(e: &BytesStart) -> Result<bool> { for attr_name in ["width", "height"] { match e.try_get_attribute(attr_name)? { None => return Ok(true), Some(attr) => { let val = attr.unescape_value()?; let trimmed = val.trim(); if trimmed.is_empty() { return Ok(true); } if let Ok(n) = trimmed.parse::<f64>() { if !n.is_finite() || n <= 0.0 { return Ok(true); } } } } } Ok(false)} fn is_hardcoded_text_fill(val: &str) -> bool { matches!( val, "" | "#333" | "black" | "#000" | "#000000" | "white" | "#fff" | "#ffffff" )} fn push_font_style(style: &mut String, font_family: &str) { write!(style, "font-family: {font_family};").expect("write to String cannot fail");} fn font_style(font_family: &str) -> String { let mut style = String::with_capacity(font_family.len() + "font-family: ;".len()); push_font_style(&mut style, font_family); style} fn rewrite_background_style<'a>(style: &'a str, background_css: &str) -> Cow<'a, str> { const PROPERTY: &str = "background-color:"; let Some(property_start) = style.find(PROPERTY) else { return Cow::Borrowed(style); }; let value_start = property_start + PROPERTY.len(); let value_end = style[value_start..] .find(';') .map_or(style.len(), |offset| value_start + offset); let value = style[value_start..value_end].trim(); let is_white = value.eq_ignore_ascii_case("white") || value.eq_ignore_ascii_case("#fff") || value.eq_ignore_ascii_case("#ffffff"); if !is_white { return Cow::Borrowed(style); } let value_len = value_end.saturating_sub(value_start); let mut rewritten = String::with_capacity( style .len() .saturating_sub(value_len) .saturating_add(background_css.len()), ); rewritten.push_str(&style[..value_start]); rewritten.push_str(background_css); rewritten.push_str(&style[value_end..]); Cow::Owned(rewritten)} fn font_family_declaration_value(declaration: &str) -> Option<&str> { let (property, value) = declaration.split_once(':')?; property .trim() .eq_ignore_ascii_case("font-family") .then(|| value.trim())} fn rewrite_font_style<'a>(style: &'a str, font_family: &str) -> Cow<'a, str> { let mut font_family_declaration_count = 0; let mut has_target_font_family = false; for declaration in style .split(';') .map(str::trim) .filter(|declaration| !declaration.is_empty()) { if let Some(value) = font_family_declaration_value(declaration) { font_family_declaration_count += 1; has_target_font_family = value == font_family; } } if font_family_declaration_count == 1 && has_target_font_family { return Cow::Borrowed(style); } let mut rewritten = String::with_capacity(style.len() + font_family.len() + " font-family: ;".len()); for declaration in style.split(';') { let declaration = declaration.trim(); if declaration.is_empty() || font_family_declaration_value(declaration).is_some() { continue; } if !rewritten.is_empty() { rewritten.push(' '); } rewritten.push_str(declaration); rewritten.push(';'); } if !rewritten.is_empty() { rewritten.push(' '); } push_font_style(&mut rewritten, font_family); Cow::Owned(rewritten)} impl<'a, I: Iterator<Item = Result<Event<'a>>>> ElementFixup<I> { fn rewrite_svg_style(&self, e: &BytesStart<'_>) -> Result<Option<BytesStart<'a>>> { let Some(style) = e .try_get_attribute("style")? .map(|a| a.unescape_value()) .transpose()? else { return Ok(None); }; let new_style = rewrite_background_style(&style, &self.background_css); if matches!(new_style, Cow::Borrowed(_)) { return Ok(None); } Ok(Some(rewrite_attr(e, b"style", &new_style)?)) } fn rewrite_text_element(&self, e: &BytesStart<'_>, fix_fill: bool) -> Result<BytesStart<'a>> { let name = e.name(); let tag = std::str::from_utf8(name.as_ref())?; let mut new_elem = BytesStart::new(tag.to_owned()); let mut has_font_family = false; let mut has_style = false; for attr in e.attributes() { let attr = attr?; match attr.key.local_name().as_ref() { b"fill" if fix_fill => { let val = attr.unescape_value()?; if is_hardcoded_text_fill(&val) { new_elem.push_attribute(("fill", self.text_color_css.as_str())); } else { new_elem.push_attribute(attr); } } b"font-family" => { has_font_family = true; new_elem.push_attribute(("font-family", self.font_family_css.as_str())); } b"style" => { has_style = true; let style = attr.unescape_value()?; let style = rewrite_font_style(&style, &self.font_family_css); new_elem.push_attribute(("style", style.as_ref())); } _ => new_elem.push_attribute(attr), } } if !has_font_family { new_elem.push_attribute(("font-family", self.font_family_css.as_str())); } if !has_style { let style = font_style(&self.font_family_css); new_elem.push_attribute(("style", style.as_str())); } Ok(new_elem) } fn process_event(&mut self, event: Event<'a>) -> Result<Option<Event<'a>>> { match &event { Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"svg" && !self.svg_seen => { self.svg_seen = true; if let Some(new_elem) = self.rewrite_svg_style(e)? { Ok(Some(rewrap(&event, new_elem))) } else { Ok(Some(event)) } } Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"rect" => { if is_bad_rect(e)? { if matches!(event, Event::Start(_)) { self.skip_rect_depth = 1; } Ok(None) } else { Ok(Some(event)) } } Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"text" => { Ok(Some(rewrap(&event, self.rewrite_text_element(e, true)?))) } Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"tspan" => { Ok(Some(rewrap(&event, self.rewrite_text_element(e, false)?))) } _ => Ok(Some(event)), } }} impl<'a, I: Iterator<Item = Result<Event<'a>>>> Iterator for ElementFixup<I> { type Item = Result<Event<'a>>; fn next(&mut self) -> Option<Self::Item> { loop { let event = match self.inner.next()? { Ok(ev) => ev, Err(e) => return Some(Err(e)), }; if self.skip_rect_depth > 0 { match &event { Event::Start(_) => self.skip_rect_depth += 1, Event::End(_) => self.skip_rect_depth -= 1, _ => {} } continue; } match self.process_event(event) { Ok(Some(ev)) => return Some(Ok(ev)), Ok(None) => continue, Err(e) => return Some(Err(e)), } } }} pub(super) fn process<'a>( events: impl Iterator<Item = Result<Event<'a>>>, theme: &MermaidTheme,) -> impl Iterator<Item = Result<Event<'a>>> { ElementFixup { inner: events, background_css: crate::css_color(theme.background), text_color_css: crate::css_color(theme.text_color), font_family_css: theme.font_family.clone(), svg_seen: false, skip_rect_depth: 0, }}
//! Fixes various issues in merman's SVG output.
//!
//! Replaces hardcoded white backgrounds with the theme background:
//! ```xml
//! <!-- before --> <svg style="background-color: white">
//! <!-- after --> <svg style="background-color: #1e1e2e">
//! ```
//!
//! Removes `<rect>` elements with missing or invalid dimensions:
//! ```xml
//! <!-- before --> <rect width="NaN" height="10"/>
//! <!-- after --> (removed)
//! ```
//!
//! Replaces hardcoded text colors with the theme text color:
//! ```xml
//! <!-- before --> <text fill="#333">Hello</text>
//! <!-- after --> <text fill="#cdd6f4">Hello</text>
//! ```
use std::borrow::Cow;
use std::fmt::Write as _;
use anyhow::Result;
use quick_xml::events::{BytesStart, Event};
use crate::MermaidTheme;
struct ElementFixup<I> {
inner: I,
background_css: String,
text_color_css: String,
font_family_css: String,
svg_seen: bool,
skip_rect_depth: usize,
}
fn rewrite_attr<'a>(
e: &BytesStart<'_>,
attr_name: &[u8],
new_value: &str,
) -> Result<BytesStart<'a>> {
let name = e.name();
let tag = std::str::from_utf8(name.as_ref())?;
let mut new_elem = BytesStart::new(tag.to_owned());
for attr in e.attributes() {
let attr = attr?;
if attr.key.local_name().as_ref() == attr_name {
let local_name = attr.key.local_name();
let key = std::str::from_utf8(local_name.as_ref())?;
new_elem.push_attribute((key, new_value));
} else {
new_elem.push_attribute(attr);
}
}
Ok(new_elem)
}
fn rewrap<'a>(event: &Event<'_>, elem: BytesStart<'a>) -> Event<'a> {
match event {
Event::Start(_) => Event::Start(elem),
_ => Event::Empty(elem),
}
}
fn is_bad_rect(e: &BytesStart) -> Result<bool> {
for attr_name in ["width", "height"] {
match e.try_get_attribute(attr_name)? {
None => return Ok(true),
Some(attr) => {
let val = attr.unescape_value()?;
let trimmed = val.trim();
if trimmed.is_empty() {
return Ok(true);
}
if let Ok(n) = trimmed.parse::<f64>() {
if !n.is_finite() || n <= 0.0 {
return Ok(true);
}
}
}
}
}
Ok(false)
}
fn is_hardcoded_text_fill(val: &str) -> bool {
matches!(
val,
"" | "#333" | "black" | "#000" | "#000000" | "white" | "#fff" | "#ffffff"
)
}
fn push_font_style(style: &mut String, font_family: &str) {
write!(style, "font-family: {font_family};").expect("write to String cannot fail");
}
fn font_style(font_family: &str) -> String {
let mut style = String::with_capacity(font_family.len() + "font-family: ;".len());
push_font_style(&mut style, font_family);
style
}
fn rewrite_background_style<'a>(style: &'a str, background_css: &str) -> Cow<'a, str> {
const PROPERTY: &str = "background-color:";
let Some(property_start) = style.find(PROPERTY) else {
return Cow::Borrowed(style);
};
let value_start = property_start + PROPERTY.len();
let value_end = style[value_start..]
.find(';')
.map_or(style.len(), |offset| value_start + offset);
let value = style[value_start..value_end].trim();
let is_white = value.eq_ignore_ascii_case("white")
|| value.eq_ignore_ascii_case("#fff")
|| value.eq_ignore_ascii_case("#ffffff");
if !is_white {
return Cow::Borrowed(style);
}
let value_len = value_end.saturating_sub(value_start);
let mut rewritten = String::with_capacity(
style
.len()
.saturating_sub(value_len)
.saturating_add(background_css.len()),
);
rewritten.push_str(&style[..value_start]);
rewritten.push_str(background_css);
rewritten.push_str(&style[value_end..]);
Cow::Owned(rewritten)
}
fn font_family_declaration_value(declaration: &str) -> Option<&str> {
let (property, value) = declaration.split_once(':')?;
property
.trim()
.eq_ignore_ascii_case("font-family")
.then(|| value.trim())
}
fn rewrite_font_style<'a>(style: &'a str, font_family: &str) -> Cow<'a, str> {
let mut font_family_declaration_count = 0;
let mut has_target_font_family = false;
for declaration in style
.split(';')
.map(str::trim)
.filter(|declaration| !declaration.is_empty())
{
if let Some(value) = font_family_declaration_value(declaration) {
font_family_declaration_count += 1;
has_target_font_family = value == font_family;
}
}
if font_family_declaration_count == 1 && has_target_font_family {
return Cow::Borrowed(style);
}
let mut rewritten =
String::with_capacity(style.len() + font_family.len() + " font-family: ;".len());
for declaration in style.split(';') {
let declaration = declaration.trim();
if declaration.is_empty() || font_family_declaration_value(declaration).is_some() {
continue;
}
if !rewritten.is_empty() {
rewritten.push(' ');
}
rewritten.push_str(declaration);
rewritten.push(';');
}
if !rewritten.is_empty() {
rewritten.push(' ');
}
push_font_style(&mut rewritten, font_family);
Cow::Owned(rewritten)
}
impl<'a, I: Iterator<Item = Result<Event<'a>>>> ElementFixup<I> {
fn rewrite_svg_style(&self, e: &BytesStart<'_>) -> Result<Option<BytesStart<'a>>> {
let Some(style) = e
.try_get_attribute("style")?
.map(|a| a.unescape_value())
.transpose()?
else {
return Ok(None);
};
let new_style = rewrite_background_style(&style, &self.background_css);
if matches!(new_style, Cow::Borrowed(_)) {
return Ok(None);
}
Ok(Some(rewrite_attr(e, b"style", &new_style)?))
}
fn rewrite_text_element(&self, e: &BytesStart<'_>, fix_fill: bool) -> Result<BytesStart<'a>> {
let name = e.name();
let tag = std::str::from_utf8(name.as_ref())?;
let mut new_elem = BytesStart::new(tag.to_owned());
let mut has_font_family = false;
let mut has_style = false;
for attr in e.attributes() {
let attr = attr?;
match attr.key.local_name().as_ref() {
b"fill" if fix_fill => {
let val = attr.unescape_value()?;
if is_hardcoded_text_fill(&val) {
new_elem.push_attribute(("fill", self.text_color_css.as_str()));
} else {
new_elem.push_attribute(attr);
}
}
b"font-family" => {
has_font_family = true;
new_elem.push_attribute(("font-family", self.font_family_css.as_str()));
}
b"style" => {
has_style = true;
let style = attr.unescape_value()?;
let style = rewrite_font_style(&style, &self.font_family_css);
new_elem.push_attribute(("style", style.as_ref()));
}
_ => new_elem.push_attribute(attr),
}
}
if !has_font_family {
new_elem.push_attribute(("font-family", self.font_family_css.as_str()));
}
if !has_style {
let style = font_style(&self.font_family_css);
new_elem.push_attribute(("style", style.as_str()));
}
Ok(new_elem)
}
fn process_event(&mut self, event: Event<'a>) -> Result<Option<Event<'a>>> {
match &event {
Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"svg" && !self.svg_seen => {
self.svg_seen = true;
if let Some(new_elem) = self.rewrite_svg_style(e)? {
Ok(Some(rewrap(&event, new_elem)))
} else {
Ok(Some(event))
}
}
Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"rect" => {
if is_bad_rect(e)? {
if matches!(event, Event::Start(_)) {
self.skip_rect_depth = 1;
}
Ok(None)
} else {
Ok(Some(event))
}
}
Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"text" => {
Ok(Some(rewrap(&event, self.rewrite_text_element(e, true)?)))
}
Event::Start(e) | Event::Empty(e) if e.name().as_ref() == b"tspan" => {
Ok(Some(rewrap(&event, self.rewrite_text_element(e, false)?)))
}
_ => Ok(Some(event)),
}
}
}
impl<'a, I: Iterator<Item = Result<Event<'a>>>> Iterator for ElementFixup<I> {
type Item = Result<Event<'a>>;
fn next(&mut self) -> Option<Self::Item> {
loop {
let event = match self.inner.next()? {
Ok(ev) => ev,
Err(e) => return Some(Err(e)),
};
if self.skip_rect_depth > 0 {
match &event {
Event::Start(_) => self.skip_rect_depth += 1,
Event::End(_) => self.skip_rect_depth -= 1,
_ => {}
}
continue;
}
match self.process_event(event) {
Ok(Some(ev)) => return Some(Ok(ev)),
Ok(None) => continue,
Err(e) => return Some(Err(e)),
}
}
}
}
pub(super) fn process<'a>(
events: impl Iterator<Item = Result<Event<'a>>>,
theme: &MermaidTheme,
) -> impl Iterator<Item = Result<Event<'a>>> {
ElementFixup {
inner: events,
background_css: crate::css_color(theme.background),
text_color_css: crate::css_color(theme.text_color),
font_family_css: theme.font_family.clone(),
svg_seen: false,
skip_rect_depth: 0,
}
}