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feat: <sup> and <sub> support (#2131)

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## Summary

* **What is the goal of this PR?** Support for `<sup>` and `<sub>` tags.

## Additional Context

This isn't my work, but @jpirnay 's (missing you here, man!). I migrated
his work from
https://github.com/jpirnay/crosspoint-reader/commit/bcd8c32cf26447ccc792cfedd2fdbfce4fee5210
with some micro-optimizations.

Screenshots: 

[Subscript-and-Superscript-Tests_ch2_p1_10pct_55632.bmp](https://github.com/user-attachments/files/28196936/Subscript-and-Superscript-Tests_ch2_p1_10pct_55632.bmp)

[Subscript-and-Superscript-Tests_ch3_p1_21pct_77473.bmp](https://github.com/user-attachments/files/28196937/Subscript-and-Superscript-Tests_ch3_p1_21pct_77473.bmp)


---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**< YES >**_

---------

Co-authored-by: jpirnay <jens@pirnay.com>
Co-authored-by: Julia <julia@uxj.io>
This commit is contained in:
Uri Tauber
2026-05-26 12:38:40 -04:00
committed by GitHub
co-authored by jpirnay Julia
parent 34e923d722
commit c5e861d71c
11 changed files with 443 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/Epub/Epub/css/CssStyle.h
+16 -4
View File
@@ -57,6 +57,9 @@ enum class CssTextDecoration : uint8_t { None = 0, Underline = 1 };
// Display options - only None and Block are relevant for e-ink rendering
enum class CssDisplay : uint8_t { Block = 0, None = 1 };
// Vertical alignment options for inline elements (e.g. superscript/subscript)
enum class CssVerticalAlign : uint8_t { Baseline = 0, Super = 1, Sub = 2 };
// Bitmask for tracking which properties have been explicitly set
struct CssPropertyFlags {
uint16_t textAlign : 1;
@@ -75,6 +78,7 @@ struct CssPropertyFlags {
uint16_t imageHeight : 1;
uint16_t imageWidth : 1;
uint16_t display : 1;
uint16_t verticalAlign : 1;
CssPropertyFlags()
: textAlign(0),
@@ -92,19 +96,20 @@ struct CssPropertyFlags {
paddingRight(0),
imageHeight(0),
imageWidth(0),
display(0) {}
display(0),
verticalAlign(0) {}
[[nodiscard]] bool anySet() const {
return textAlign || fontStyle || fontWeight || textDecoration || textIndent || marginTop || marginBottom ||
marginLeft || marginRight || paddingTop || paddingBottom || paddingLeft || paddingRight || imageHeight ||
imageWidth || display;
imageWidth || display || verticalAlign;
}
void clearAll() {
textAlign = fontStyle = fontWeight = textDecoration = textIndent = 0;
marginTop = marginBottom = marginLeft = marginRight = 0;
paddingTop = paddingBottom = paddingLeft = paddingRight = 0;
imageHeight = imageWidth = display = 0;
imageHeight = imageWidth = display = verticalAlign = 0;
}
};
@@ -128,7 +133,8 @@ struct CssStyle {
CssLength paddingRight; // Padding right
CssLength imageHeight; // Height for img (e.g. 2em) – width derived from aspect ratio when only height set
CssLength imageWidth; // Width for img when both or only width set
CssDisplay display = CssDisplay::Block; // display property (Block or None)
CssDisplay display = CssDisplay::Block; // display property (Block or None)
CssVerticalAlign verticalAlign = CssVerticalAlign::Baseline; // vertical-align (super/sub positioning)
CssPropertyFlags defined; // Tracks which properties were explicitly set
@@ -199,6 +205,10 @@ struct CssStyle {
display = base.display;
defined.display = 1;
}
if (base.hasVerticalAlign()) {
verticalAlign = base.verticalAlign;
defined.verticalAlign = 1;
}
}
[[nodiscard]] bool hasTextAlign() const { return defined.textAlign; }
@@ -217,6 +227,7 @@ struct CssStyle {
[[nodiscard]] bool hasImageHeight() const { return defined.imageHeight; }
[[nodiscard]] bool hasImageWidth() const { return defined.imageWidth; }
[[nodiscard]] bool hasDisplay() const { return defined.display; }
[[nodiscard]] bool hasVerticalAlign() const { return defined.verticalAlign; }
void reset() {
textAlign = CssTextAlign::Left;
@@ -228,6 +239,7 @@ struct CssStyle {
paddingTop = paddingBottom = paddingLeft = paddingRight = CssLength{};
imageHeight = imageWidth = CssLength{};
display = CssDisplay::Block;
verticalAlign = CssVerticalAlign::Baseline;
defined.clearAll();
}
};