Add ImagePtrItemDelegate class to display images in a table

src/CMakeLists.txt

@@ -636,6 +636,7 @@ set(SOURCE_FILES
         widgets/listview/GenericListModel.hpp
         widgets/listview/GenericListView.cpp
         widgets/listview/GenericListView.hpp
+        widgets/listview/ImagePtrItemDelegate.hpp
 
         widgets/settingspages/AboutPage.cpp
         widgets/settingspages/AboutPage.hpp

src/widgets/listview/ImagePtrItemDelegate.hpp

@@ -0,0 +1,70 @@
+#pragma once
+
+#include "messages/Image.hpp"
+#include "messages/ImageSet.hpp"
+
+#include <QModelIndex>
+#include <qnamespace.h>
+#include <QPainter>
+#include <QStyledItemDelegate>
+
+namespace chatterino {
+class ImagePtrItemDelegate : public QStyledItemDelegate
+{
+    std::map<QString, ImagePtr> ownedImages_;
+
+public:
+    static constexpr auto IMAGE_URL_ROLE = Qt::UserRole + 1;
+
+    void paint(QPainter *painter, const QStyleOptionViewItem &option,
+               const QModelIndex &index) const override
+    {
+        auto url = index.data(IMAGE_URL_ROLE).toString();
+        if (auto it = this->ownedImages_.find(url);
+            it != this->ownedImages_.end())
+        {
+            auto img = it->second;
+            auto opt = img->pixmapOrLoad();
+            if (!opt)  // wait for next time
+            {
+                return;
+            }
+            auto pixmap = *opt;
+            double aspectRatio =
+                double(pixmap.width()) / double(pixmap.height());
+            int width = int(option.rect.height() * aspectRatio);
+            auto outputRect = QRect(option.rect.topLeft(),
+                                    QSize(width, option.rect.height()));
+            if (option.rect.width() < width)
+            {
+                // too wide?
+
+                double revAspectRatio =
+                    double(pixmap.height()) / double(pixmap.width());
+                int height = int(option.rect.width() * revAspectRatio);
+
+                outputRect = QRect(option.rect.topLeft(),
+                                   QSize(option.rect.width(), height));
+                if (option.rect.height() < height)
+                {
+                    // give up and squish the image
+                    outputRect = option.rect;
+                }
+            }
+
+            painter->drawPixmap(outputRect, pixmap, pixmap.rect());
+        }
+        auto img = Image::fromUrl(Url{url});
+
+        img->pixmapOrLoad();
+        // You cannot stop me, clang-tidy
+        auto *bleh = const_cast<ImagePtrItemDelegate *>(this);
+        bleh->ownedImages_[url] = img;
+    }
+    QSize sizeHint(const QStyleOptionViewItem &option,
+                   const QModelIndex &index) const override
+    {
+        return {32, 32};
+    }
+};
+}  // namespace chatterino