fix: render <br> between paragraphs as a visible section break (#2548)
Co-authored-by: Brooks Ilg <brooksmilg@gmail.com>
This commit is contained in:
Uri Tauber
@@ -32,6 +32,11 @@ struct BlockStyle {
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bool isRtl = false; // true if resolved direction is RTL
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bool directionDefined = false; // true if direction was explicitly set in CSS/HTML
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// Set when this block was created by a <br> element. Used by startNewTextBlock to inject
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// a full line-height gap when the <br> block stays empty (section-break use case).
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// NOT propagated through getCombinedBlockStyle so it can't leak into sibling blocks.
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bool fromBrElement = false;
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// Combined insets (margin + padding)
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[[nodiscard]] int16_t leftInset() const { return marginLeft + paddingLeft; }
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[[nodiscard]] int16_t rightInset() const { return marginRight + paddingRight; }
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@@ -92,6 +97,9 @@ struct BlockStyle {
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result.directionDefined = true;
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}
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// fromBrElement is consumed by startNewTextBlock when an empty <br> block
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// is merged with the following paragraph; never propagate it further.
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result.fromBrElement = false;
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return result;
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}
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@@ -239,7 +239,16 @@ void ChapterHtmlSlimParser::startNewTextBlock(const BlockStyle& blockStyle) {
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// open. Merge those into the new style so the first child in a container inherits
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// the container's vertical spacing.
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const auto style = currentTextBlock->getBlockStyle();
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currentTextBlock->setBlockStyle(style.getCombinedBlockStyle(blockStyle, BlockStyle::CombineAxis::Vertical));
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BlockStyle incoming = blockStyle;
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if (style.fromBrElement) {
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// The empty block was created by a <br> section separator. Inject a full line of
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// blank space before the following paragraph so the scene/section break is visible.
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// This only fires when the <br> block stayed empty (i.e. no inline text was added).
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const int16_t lineHeight = static_cast<int16_t>(renderer.getLineHeight(fontId) * lineCompression + 0.5f);
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incoming.marginTop = static_cast<int16_t>(incoming.marginTop + lineHeight);
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}
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currentTextBlock->setBlockStyle(style.getCombinedBlockStyle(incoming, BlockStyle::CombineAxis::Vertical));
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flushPendingAnchor();
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return;
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@@ -855,7 +864,14 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
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// flush word preceding <br/> to currentTextBlock before calling startNewTextBlock
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self->flushPartWordBuffer();
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}
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self->startNewTextBlock(self->blockStyleStack.back().withoutBottom());
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// Tag the new block so startNewTextBlock can inject a full line-height gap if
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// the block remains empty (i.e. <br> is a section separator between paragraphs).
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// If the block gets text added before the next block opens it becomes non-empty,
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// goes through makePages() normally, and the flag has no effect (inline <br> case).
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BlockStyle brStyle =
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self->currentTextBlock ? self->currentTextBlock->getBlockStyle() : self->blockStyleStack.back();
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brStyle.fromBrElement = true;
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self->startNewTextBlock(brStyle);
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} else {
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self->currentCssStyle = cssStyle;
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const auto accumulated = self->blockStyleStack.back().getCombinedBlockStyle(userAlignmentBlockStyle,
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@@ -0,0 +1,210 @@
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#!/usr/bin/env python3
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"""
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Generate a test EPUB for <br> section-break rendering.
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Tests that a bare <br> element between paragraphs produces a visible blank-line
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gap (section separator), while a <br> inside a paragraph only produces a line
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break with no extra spacing.
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Cases covered:
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1. Standalone <br> between paragraphs (section break — must show gap).
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2. <br class="..."> with a CSS class (calibre-style section break).
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3. Multiple consecutive <br> elements (each adds one line of spacing).
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4. Inline <br> inside a <p> (line break only — no extra gap).
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5. <br> at start of chapter (no gap before first paragraph).
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6. <br> following a heading.
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Visual verification instructions are embedded as the first paragraph of each
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chapter so a human tester can confirm the expected result on device.
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"""
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import os
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import zipfile
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from pathlib import Path
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OUTPUT_DIR = Path(__file__).parent.parent / "test" / "epubs"
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OUTPUT_PATH = OUTPUT_DIR / "test_br_section_break.epub"
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FILLER = (
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"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod "
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"tempor incididunt ut labore et dolore magna aliqua."
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)
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CSS = """\
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body { margin: 0; padding: 0; }
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p { margin-top: 1pt; margin-bottom: 0; text-indent: 1em; text-align: justify; }
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h1 { text-align: center; margin-top: 0.5em; margin-bottom: 0.5em; }
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h2 { text-align: center; margin-top: 0.5em; margin-bottom: 0.5em; }
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.section-br { display: block; }
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"""
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def xhtml(title, body):
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return f"""\
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html>
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>{title}</title>
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<link rel="stylesheet" type="text/css" href="styles/test.css"/>
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</head>
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<body>
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{body}
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</body>
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</html>"""
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# ---------------------------------------------------------------------------
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# Chapter 1 — standalone <br> between paragraphs
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# ---------------------------------------------------------------------------
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ch1 = xhtml("Ch1: Standalone br", f"""
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<h1>Ch 1: Standalone <br> Section Break</h1>
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<p>PASS: A visible blank-line gap should appear between the two sections below.</p>
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<p>{FILLER}</p>
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<br/>
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<p>{FILLER}</p>
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<p>PASS: The gap above should be roughly one line tall (same as a blank line).</p>
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""")
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# ---------------------------------------------------------------------------
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# Chapter 2 — <br class="..."> CSS-classed section break (calibre style)
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# ---------------------------------------------------------------------------
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ch2 = xhtml("Ch2: Classed br", f"""
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<h1>Ch 2: <br class="section-br"/></h1>
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<p>PASS: A blank-line gap should appear between the two sections below, identical
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to Ch 1, even though the <br> carries a CSS class.</p>
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<p>{FILLER}</p>
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<br class="section-br"/>
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<p>{FILLER}</p>
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""")
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# ---------------------------------------------------------------------------
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# Chapter 3 — multiple consecutive <br> elements
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# ---------------------------------------------------------------------------
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ch3 = xhtml("Ch3: Multiple br", f"""
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<h1>Ch 3: Multiple Consecutive <br> Elements</h1>
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<p>PASS: Two blank lines should appear between the sections (one per <br>).</p>
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<p>{FILLER}</p>
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<br/>
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<br/>
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<p>{FILLER}</p>
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<p>PASS: Three blank lines should appear below.</p>
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<p>{FILLER}</p>
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<br/>
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<br/>
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<br/>
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<p>{FILLER}</p>
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""")
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# ---------------------------------------------------------------------------
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# Chapter 4 — inline <br> inside a paragraph (line break, NOT a gap)
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# ---------------------------------------------------------------------------
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ch4 = xhtml("Ch4: Inline br", """
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<h1>Ch 4: Inline <br> Inside a Paragraph</h1>
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<p>PASS: The two lines below should be adjacent with NO extra gap between them.
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The <br> is inside the paragraph and must only break the line.</p>
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<p>First line of the paragraph.<br/>Second line of the paragraph — directly below, no gap.</p>
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<p>PASS: Above should look like two closely-spaced lines, not like two paragraphs
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separated by a blank line.</p>
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""")
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# ---------------------------------------------------------------------------
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# Chapter 5 — <br> following a heading
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# ---------------------------------------------------------------------------
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ch5 = xhtml("Ch5: br after heading", f"""
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<h1>Ch 5: <br> After a Heading</h1>
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<br/>
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<p>PASS: There should be a blank-line gap between the heading above and this paragraph.</p>
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<p>{FILLER}</p>
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<h2>Section heading</h2>
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<br/>
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<p>PASS: There should be a blank-line gap between the section heading and this paragraph.</p>
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""")
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# ---------------------------------------------------------------------------
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# Chapter 6 — <br> at very start of chapter (no spurious leading gap)
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# ---------------------------------------------------------------------------
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ch6 = xhtml("Ch6: br at chapter start", f"""<br/>
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<h1>Ch 6: <br> at Chapter Start</h1>
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<p>PASS: This heading should appear near the top of the page with no large blank
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area above it despite the <br> being the very first element.</p>
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<p>{FILLER}</p>
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""")
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CHAPTERS = [
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("ch1", "chapter1.xhtml", "Chapter 1: Standalone br", ch1),
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("ch2", "chapter2.xhtml", "Chapter 2: Classed br", ch2),
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("ch3", "chapter3.xhtml", "Chapter 3: Multiple br", ch3),
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("ch4", "chapter4.xhtml", "Chapter 4: Inline br", ch4),
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("ch5", "chapter5.xhtml", "Chapter 5: br after heading", ch5),
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("ch6", "chapter6.xhtml", "Chapter 6: br at start", ch6),
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]
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def build_epub(path):
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os.makedirs(os.path.dirname(path), exist_ok=True)
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with zipfile.ZipFile(path, "w", zipfile.ZIP_DEFLATED) as epub:
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# mimetype must be first and uncompressed
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epub.writestr("mimetype", "application/epub+zip",
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compress_type=zipfile.ZIP_STORED)
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epub.writestr("META-INF/container.xml", """\
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<?xml version="1.0" encoding="UTF-8"?>
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<container xmlns="urn:oasis:names:tc:opendocument:xmlns:container" version="1.0">
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<rootfiles>
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<rootfile full-path="OEBPS/content.opf"
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media-type="application/oebps-package+xml"/>
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</rootfiles>
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</container>""")
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epub.writestr("OEBPS/styles/test.css", CSS)
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manifest_items = []
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spine_items = []
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nav_items = []
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for (chid, chfile, chtitle, chcontent) in CHAPTERS:
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epub.writestr(f"OEBPS/{chfile}", chcontent)
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manifest_items.append(
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f' <item id="{chid}" href="{chfile}" media-type="application/xhtml+xml"/>')
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spine_items.append(f' <itemref idref="{chid}"/>')
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nav_items.append(f' <li><a href="{chfile}">{chtitle}</a></li>')
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manifest_items.append(
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' <item id="nav" href="nav.xhtml" '
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'media-type="application/xhtml+xml" properties="nav"/>')
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content_opf = f"""\
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<?xml version="1.0" encoding="UTF-8"?>
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<package xmlns="http://www.idpf.org/2007/opf" version="3.0" unique-identifier="uid">
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<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
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<dc:identifier id="uid">test-epub-br-section-break</dc:identifier>
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<dc:title>Test: br Section Break</dc:title>
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<dc:language>en</dc:language>
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</metadata>
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<manifest>
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{chr(10).join(manifest_items)}
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</manifest>
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<spine>
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{chr(10).join(spine_items)}
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</spine>
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</package>"""
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epub.writestr("OEBPS/content.opf", content_opf)
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nav_xhtml = f"""\
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<?xml version="1.0" encoding="UTF-8"?>
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<html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idpf.org/2007/ops">
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<head><title>Table of Contents</title></head>
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<body>
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<nav epub:type="toc">
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<ol>
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{chr(10).join(nav_items)}
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</ol>
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</nav>
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</body>
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</html>"""
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epub.writestr("OEBPS/nav.xhtml", nav_xhtml)
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print(f"Generated: {path}")
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if __name__ == "__main__":
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build_epub(OUTPUT_PATH)
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