Add custom image functionality for inline mod buttons. (#5369)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/util/LoadPixmap.cpp

@@ -0,0 +1,48 @@
+#include "util/LoadPixmap.hpp"
+
+#include "common/network/NetworkRequest.hpp"
+#include "common/network/NetworkResult.hpp"
+#include "common/QLogging.hpp"
+
+#include <QBuffer>
+#include <QImageReader>
+#include <QLoggingCategory>
+#include <QPixmap>
+
+namespace chatterino {
+
+void loadPixmapFromUrl(const Url &url, std::function<void(QPixmap)> &&callback)
+{
+    NetworkRequest(url.string)
+        .concurrent()
+        .cache()
+        .onSuccess(
+            [callback = std::move(callback), url](const NetworkResult &result) {
+                auto data = result.getData();
+                QBuffer buffer(&data);
+                buffer.open(QIODevice::ReadOnly);
+                QImageReader reader(&buffer);
+
+                if (!reader.canRead() || reader.size().isEmpty())
+                {
+                    qCWarning(chatterinoImage)
+                        << "Can't read image file at" << url.string << ":"
+                        << reader.errorString();
+                    return;
+                }
+
+                QImage image = reader.read();
+                if (image.isNull())
+                {
+                    qCWarning(chatterinoImage)
+                        << "Failed reading image at" << url.string << ":"
+                        << reader.errorString();
+                    return;
+                }
+
+                callback(QPixmap::fromImage(image));
+            })
+        .execute();
+}
+
+}  // namespace chatterino

src/util/LoadPixmap.hpp

@@ -0,0 +1,15 @@
+#pragma once
+#include "common/Aliases.hpp"
+
+#include <QPixmap>
+
+namespace chatterino {
+
+/**
+ * Loads an image from url into a QPixmap. Allows for file:// protocol links. Uses cacheing.
+ *
+ * @param callback The callback you will get the pixmap by. It will be invoked concurrently with no guarantees on which thread.
+ */
+void loadPixmapFromUrl(const Url &url, std::function<void(QPixmap)> &&callback);
+
+}  // namespace chatterino