feat: add widget for a text browser with image support

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/ui/widgets/VariableSizedImageObject.cpp

@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-3.0-only
+/*
+ *  PolyMC - Minecraft Launcher
+ *  Copyright (c) 2022 flowln <flowlnlnln@gmail.com>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, version 3.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "VariableSizedImageObject.h"
+
+#include <QAbstractTextDocumentLayout>
+#include <QDebug>
+#include <QPainter>
+#include <QTextObject>
+
+#include "Application.h"
+
+#include "net/NetJob.h"
+
+enum FormatProperties { ImageData = QTextFormat::UserProperty + 1 };
+
+QSizeF VariableSizedImageObject::intrinsicSize(QTextDocument* doc, int posInDocument, const QTextFormat& format)
+{
+    Q_UNUSED(posInDocument);
+
+    auto image = qvariant_cast<QImage>(format.property(ImageData));
+    auto size = image.size();
+
+    // Get the width of the text content to make the image similar sized.
+    // doc->textWidth() includes the margin, so we need to remove it.
+    auto doc_width = doc->textWidth() - 2 * doc->documentMargin();
+
+    if (size.width() > doc_width)
+        size *= doc_width / (double)size.width();
+
+    return { size };
+}
+void VariableSizedImageObject::drawObject(QPainter* painter,
+                                          const QRectF& rect,
+                                          QTextDocument* doc,
+                                          int posInDocument,
+                                          const QTextFormat& format)
+{
+    if (!format.hasProperty(ImageData)) {
+        QUrl image_url{ qvariant_cast<QString>(format.property(QTextFormat::ImageName)) };
+        if (m_fetching_images.contains(image_url))
+            return;
+
+        loadImage(doc, image_url, posInDocument);
+        return;
+    }
+
+    auto image = qvariant_cast<QImage>(format.property(ImageData));
+
+    painter->setRenderHint(QPainter::RenderHint::SmoothPixmapTransform);
+    painter->drawImage(rect, image);
+}
+
+void VariableSizedImageObject::parseImage(QTextDocument* doc, QImage image, int posInDocument)
+{
+    QTextCursor cursor(doc);
+    cursor.setPosition(posInDocument);
+    cursor.setKeepPositionOnInsert(true);
+
+    auto image_char_format = cursor.charFormat();
+
+    image_char_format.setObjectType(QTextFormat::ImageObject);
+    image_char_format.setProperty(ImageData, image);
+
+    // Qt doesn't allow us to modify the properties of an existing object in the document.
+    // So we remove the old one and add the new one with the ImageData property set.
+    cursor.deleteChar();
+    cursor.insertText(QString(QChar::ObjectReplacementCharacter), image_char_format);
+}
+
+void VariableSizedImageObject::loadImage(QTextDocument* doc, const QUrl& source, int posInDocument)
+{
+    m_fetching_images.append(source);
+
+    MetaEntryPtr entry = APPLICATION->metacache()->resolveEntry(
+        m_meta_entry,
+        QString("images/%1").arg(QString(QCryptographicHash::hash(source.toEncoded(), QCryptographicHash::Algorithm::Sha1).toHex())));
+
+    auto job = new NetJob(QString("Load Image: %1").arg(source.fileName()), APPLICATION->network());
+    job->addNetAction(Net::Download::makeCached(source, entry));
+
+    auto full_entry_path = entry->getFullPath();
+    auto source_url = source;
+    connect(job, &NetJob::succeeded, [this, doc, full_entry_path, source_url, posInDocument] {
+        qDebug() << "Loaded resource at" << full_entry_path;
+
+        QImage image(full_entry_path);
+        doc->addResource(QTextDocument::ImageResource, source_url, image);
+
+        parseImage(doc, image, posInDocument);
+
+        // This size hack is needed to prevent the content from being laid out in an area smaller
+        // than the total width available (weird).
+        auto size = doc->pageSize();
+        doc->adjustSize();
+        doc->setPageSize(size);
+
+        m_fetching_images.removeOne(source_url);
+    });
+    connect(job, &NetJob::finished, job, &NetJob::deleteLater);
+
+    job->start();
+}