feat: create delegate for project item views

This allows us to define custom painting for list view items. In
particular, this is applied to the mod downloader, in order to allow
displaying both the mod name and mod description, and settings their
effects (like bold or underline) independent of each other.

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

launcher/ui/widgets/ProjectItem.cpp

@@ -0,0 +1,78 @@
+#include "ProjectItem.h"
+
+#include "Common.h"
+
+#include <QIcon>
+#include <QPainter>
+
+ProjectItemDelegate::ProjectItemDelegate(QWidget* parent) : QStyledItemDelegate(parent) {}
+
+void ProjectItemDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
+{
+    painter->save();
+
+    QStyleOptionViewItem opt(option);
+    initStyleOption(&opt, index);
+
+    auto& rect = opt.rect;
+    auto icon_width = rect.height(), icon_height = rect.height();
+    auto remaining_width = rect.width() - icon_width;
+
+    if (opt.state & QStyle::State_Selected) {
+        painter->fillRect(rect, opt.palette.highlight());
+        painter->setPen(opt.palette.highlightedText().color());
+    } else if (opt.state & QStyle::State_MouseOver) {
+        painter->fillRect(rect, opt.palette.window());
+    }
+
+    {  // Icon painting
+        // Square-sized, occupying the left portion
+        opt.icon.paint(painter, rect.x(), rect.y(), icon_width, icon_height);
+    }
+
+    {  // Title painting
+        auto title = index.data(UserDataTypes::TITLE).toString();
+
+        painter->save();
+
+        auto font = opt.font;
+        if (index.data(UserDataTypes::SELECTED).toBool()) {
+            // Set nice font
+            font.setBold(true);
+            font.setUnderline(true);
+        }
+
+        font.setPointSize(font.pointSize() + 2);
+        painter->setFont(font);
+
+        // On the top, aligned to the left after the icon
+        painter->drawText(rect.x() + icon_width, rect.y() + QFontMetrics(font).height(), title);
+
+        painter->restore();
+    }
+
+    {  // Description painting
+        auto description = index.data(UserDataTypes::DESCRIPTION).toString();
+
+        QTextLayout text_layout(description, opt.font);
+
+        qreal height = 0;
+        auto cut_text = viewItemTextLayout(text_layout, remaining_width, height);
+
+        // Get first line unconditionally
+        description = cut_text.first().second;
+        // Get second line, elided if needed
+        if (cut_text.size() > 1) {
+            if (cut_text.size() > 2)
+                description += opt.fontMetrics.elidedText(cut_text.at(1).second, opt.textElideMode, cut_text.at(1).first);
+            else
+                description += cut_text.at(1).second;
+        }
+
+        // On the bottom, aligned to the left after the icon, and featuring at most two lines of text (with some margin space to spare)
+        painter->drawText(rect.x() + icon_width, rect.y() + rect.height() - 2.2 * opt.fontMetrics.height(), remaining_width,
+                          2 * opt.fontMetrics.height(), Qt::TextWordWrap, description);
+    }
+
+    painter->restore();
+}