z-bar-qt/Plugins/ZShell/Llm/mathtext.cpp

#include "mathtext.hpp"

#include "latinmodern-fonts.hpp"

#include <jkqtmathtext/jkqtmathtext.h>

#include <QBuffer>
#include <QDir>
#include <QFile>
#include <QFontDatabase>

namespace ZShell::llm {

namespace {
// A few px of breathing room around the equation.
constexpr int kRenderMargin = 2;
constexpr unsigned int kResolutionDpi = 96;

// Registers the embedded Latin Modern faces with the font database
// (once per process) and reports which families became available.
struct LatinModern {
	bool roman = false;
	bool math = false;
};

const LatinModern& loadLatinModern() {
	static const LatinModern fonts = [] {
		LatinModern result;
		// addApplicationFont(QByteArray) fails in this environment, so
		// the embedded bytes are staged to a per-process temp file and
		// registered through the (stable) file-based API.
		const auto add = [](const unsigned char* data, size_t size,
		                    const QString& fileName, const QString& family) {
			const QString path = QDir::tempPath() + QLatin1Char('/') + fileName;
			{
				QFile f(path);
				if (!f.open(QIODevice::WriteOnly) ||
				    f.write(reinterpret_cast<const char*>(data),
				          static_cast<qint64>(size)) != static_cast<qint64>(size))
					return false;
			}
			const int key = QFontDatabase::addApplicationFont(path);
			if (key < 0)
				return false;
			return QFontDatabase::applicationFontFamilies(key).contains(family);
		};
		result.roman =
			add(lmfont::lmroman10_regular, sizeof(lmfont::lmroman10_regular),
			    QStringLiteral("lmroman10-regular.otf"), QStringLiteral("LMRoman10"))
			&& add(lmfont::lmroman10_italic, sizeof(lmfont::lmroman10_italic),
			       QStringLiteral("lmroman10-italic.otf"), QStringLiteral("LMRoman10"))
			&& add(lmfont::lmroman10_bold, sizeof(lmfont::lmroman10_bold),
			       QStringLiteral("lmroman10-bold.otf"), QStringLiteral("LMRoman10"))
			&& add(lmfont::lmroman10_bolditalic, sizeof(lmfont::lmroman10_bolditalic),
			       QStringLiteral("lmroman10-bolditalic.otf"),
			       QStringLiteral("LMRoman10"));
		result.math = add(
			lmfont::latinmodern_math, sizeof(lmfont::latinmodern_math),
			QStringLiteral("latinmodern-math.otf"), QStringLiteral("Latin Modern Math"));
		return result;
	}();
	return fonts;
}

} // namespace

LlmMathText::LlmMathText(QObject* parent)
: QObject(parent), m_renderer(parent, /* useFontsForGUI */ true) {
	// Latin Modern is the default font of modern LaTeX; use the embedded
	// faces instead of whatever the system happens to have installed.
	const LatinModern& fonts = loadLatinModern();
	if (fonts.roman)
		m_renderer.setFontRomanAndMath(QStringLiteral("LMRoman10"),
		                               JKQTMathTextFontEncoding::MTFEUnicode);
	if (fonts.math) {
		// Same pattern as JKQTMathText's useXITS(): the OpenType math
		// font supplies the math alphabet and operators from its MATH
		// table.
		m_renderer.setFontMathRoman(QStringLiteral("Latin Modern Math"),
		                            JKQTMathTextFontEncoding::MTFEUnicode);
		m_renderer.setFallbackFontSymbols(
			QStringLiteral("Latin Modern Math"),
			JKQTMathTextFontEncoding::MTFEUnicode);
	}
}

void LlmMathText::setLatex(const QString& value) {
	if (m_latex == value)
		return;
	m_latex = value;
	reRender();
}

void LlmMathText::setColor(const QColor& value) {
	if (m_color == value)
		return;
	m_color = value;
	reRender();
}

void LlmMathText::setFontPointSize(double value) {
	if (qFuzzyCompare(m_fontPointSize, value))
		return;
	m_fontPointSize = value;
	reRender();
}

void LlmMathText::setDevicePixelRatio(qreal value) {
	if (qFuzzyCompare(m_devicePixelRatio, value))
		return;
	m_devicePixelRatio = value;
	reRender();
}

void LlmMathText::reRender() {
	if (m_latex.trimmed().isEmpty()) {
		m_image = QImage();
		m_imageUrl = QUrl();
		m_width = 0;
		m_height = 0;
		m_ok = false;
		Q_EMIT changed();
		return;
	}

	m_renderer.setFontPointSize(m_fontPointSize);
	m_renderer.setFontColor(m_color);

	const bool ok = m_renderer.parse(
		m_latex,
		JKQTMathText::LatexParser,
		JKQTMathText::DefaultParseOptions);
	if (!ok) {
		m_image = QImage();
		m_imageUrl = QUrl();
		m_width = 0;
		m_height = 0;
		m_ok = false;
		Q_EMIT changed();
		return;
	}

	const QImage image = m_renderer.drawIntoImage(
		/* drawBoxes */ false,
		QColor(Qt::transparent),
		kRenderMargin,
		m_devicePixelRatio,
		kResolutionDpi);
	if (image.isNull()) {
		m_image = QImage();
		m_imageUrl = QUrl();
		m_width = 0;
		m_height = 0;
		m_ok = false;
		Q_EMIT changed();
		return;
	}

	m_image = image;
	QByteArray png;
	{
		QBuffer buffer(&png);
		buffer.open(QIODevice::WriteOnly);
		image.save(&buffer, "PNG");
	}
	m_imageUrl = QUrl(
		QStringLiteral("data:image/png;base64,") + QString::fromLatin1(png.toBase64()));
	// drawIntoImage renders at devicePixelRatio; convert back to
	// logical pixels.
	m_width = image.width() / m_devicePixelRatio;
	m_height = image.height() / m_devicePixelRatio;
	m_ok = true;
	Q_EMIT changed();
}

} // namespace ZShell::llm