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Crosspoint/lib/Epub/Epub/blocks/BlockStyle.h
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2026-03-26 11:05:13 +01:00

105 lines
5.1 KiB
C++

#pragma once
#include <cstdint>
#include "Epub/css/CssStyle.h"
/**
* BlockStyle - Block-level styling properties
*/
struct BlockStyle {
CssTextAlign alignment = CssTextAlign::Justify;
// Spacing (in pixels)
int16_t marginTop = 0;
int16_t marginBottom = 0;
int16_t marginLeft = 0;
int16_t marginRight = 0;
int16_t paddingTop = 0; // treated same as margin for rendering
int16_t paddingBottom = 0; // treated same as margin for rendering
int16_t paddingLeft = 0; // treated same as margin for rendering
int16_t paddingRight = 0; // treated same as margin for rendering
int16_t textIndent = 0;
bool textIndentDefined = false; // true if text-indent was explicitly set in CSS
bool textAlignDefined = false; // true if text-align was explicitly set in CSS
// Set when this block was created by a <br> element. Used by startNewTextBlock to inject
// a full line-height gap when the <br> block stays empty (section-break use case).
// NOT propagated through getCombinedBlockStyle so it can't leak into sibling blocks.
bool fromBrElement = false;
// Combined horizontal insets (margin + padding)
[[nodiscard]] int16_t leftInset() const { return marginLeft + paddingLeft; }
[[nodiscard]] int16_t rightInset() const { return marginRight + paddingRight; }
[[nodiscard]] int16_t totalHorizontalInset() const { return leftInset() + rightInset(); }
// Combine with another block style. Useful for parent -> child styles, where the child style should be
// applied on top of the parent's style to get the combined style.
BlockStyle getCombinedBlockStyle(const BlockStyle& child) const {
BlockStyle combinedBlockStyle;
combinedBlockStyle.marginTop = static_cast<int16_t>(child.marginTop + marginTop);
combinedBlockStyle.marginBottom = static_cast<int16_t>(child.marginBottom + marginBottom);
combinedBlockStyle.marginLeft = static_cast<int16_t>(child.marginLeft + marginLeft);
combinedBlockStyle.marginRight = static_cast<int16_t>(child.marginRight + marginRight);
combinedBlockStyle.paddingTop = static_cast<int16_t>(child.paddingTop + paddingTop);
combinedBlockStyle.paddingBottom = static_cast<int16_t>(child.paddingBottom + paddingBottom);
combinedBlockStyle.paddingLeft = static_cast<int16_t>(child.paddingLeft + paddingLeft);
combinedBlockStyle.paddingRight = static_cast<int16_t>(child.paddingRight + paddingRight);
// Text indent: use child's if defined
if (child.textIndentDefined) {
combinedBlockStyle.textIndent = child.textIndent;
combinedBlockStyle.textIndentDefined = true;
} else {
combinedBlockStyle.textIndent = textIndent;
combinedBlockStyle.textIndentDefined = textIndentDefined;
}
// Text align: use child's if defined
if (child.textAlignDefined) {
combinedBlockStyle.alignment = child.alignment;
combinedBlockStyle.textAlignDefined = true;
} else {
combinedBlockStyle.alignment = alignment;
combinedBlockStyle.textAlignDefined = textAlignDefined;
}
// fromBrElement is never propagated — it is consumed by startNewTextBlock
// when the empty <br> block is merged with the following paragraph.
combinedBlockStyle.fromBrElement = false;
return combinedBlockStyle;
}
// Create a BlockStyle from CSS style properties, resolving CssLength values to pixels
// emSize is the current font line height, used for em/rem unit conversion
// paragraphAlignment is the user's paragraphAlignment setting preference
static BlockStyle fromCssStyle(const CssStyle& cssStyle, const float emSize, const CssTextAlign paragraphAlignment,
const uint16_t viewportWidth = 0) {
BlockStyle blockStyle;
const float vw = viewportWidth;
// Resolve all CssLength values to pixels using the current font's em size and viewport width
blockStyle.marginTop = cssStyle.marginTop.toPixelsInt16(emSize, vw);
blockStyle.marginBottom = cssStyle.marginBottom.toPixelsInt16(emSize, vw);
blockStyle.marginLeft = cssStyle.marginLeft.toPixelsInt16(emSize, vw);
blockStyle.marginRight = cssStyle.marginRight.toPixelsInt16(emSize, vw);
blockStyle.paddingTop = cssStyle.paddingTop.toPixelsInt16(emSize, vw);
blockStyle.paddingBottom = cssStyle.paddingBottom.toPixelsInt16(emSize, vw);
blockStyle.paddingLeft = cssStyle.paddingLeft.toPixelsInt16(emSize, vw);
blockStyle.paddingRight = cssStyle.paddingRight.toPixelsInt16(emSize, vw);
// For textIndent: if it's a percentage we can't resolve (no viewport width),
// leave textIndentDefined=false so the EmSpace fallback in applyParagraphIndent() is used
if (cssStyle.hasTextIndent() && cssStyle.textIndent.isResolvable(vw)) {
blockStyle.textIndent = cssStyle.textIndent.toPixelsInt16(emSize, vw);
blockStyle.textIndentDefined = true;
}
blockStyle.textAlignDefined = cssStyle.hasTextAlign();
// User setting overrides CSS, unless "Book's Style" alignment setting is selected
if (paragraphAlignment == CssTextAlign::None) {
blockStyle.alignment = blockStyle.textAlignDefined ? cssStyle.textAlign : CssTextAlign::Justify;
} else {
blockStyle.alignment = paragraphAlignment;
}
return blockStyle;
}
};