Enhance image attachment handling by caching loaded images and improving scaling logic

Author: w15eacre

src/gui/entry/PreviewEntryAttachmentsDialog.cpp

@@ -64,6 +64,7 @@ void PreviewEntryAttachmentsDialog::setAttachment(const QString& name, const QBy
 
     m_type = attachmentType(data);
     m_data = data;
+    m_imageCache = QImage();
 
     update();
 }
@@ -86,23 +87,31 @@ void PreviewEntryAttachmentsDialog::updateTextAttachment(const QByteArray& data)
 
 void PreviewEntryAttachmentsDialog::updateImageAttachment(const QByteArray& data)
 {
-    QImage image{};
-    if (!image.loadFromData(data)) {
+    if (m_imageCache.isNull() && !m_imageCache.loadFromData(data)) {
         updateTextAttachment(tr("Image format not supported").toUtf8());
         return;
     }
 
+    updateImageAttachment(m_imageCache);
+}
+
+void PreviewEntryAttachmentsDialog::updateImageAttachment(const QImage& image)
+{
     m_ui->attachmentTextEdit->clear();
     auto cursor = m_ui->attachmentTextEdit->textCursor();
 
+    cursor.insertImage(image.scaled(calculateImageSize(), Qt::KeepAspectRatio, Qt::SmoothTransformation));
+}
+
+QSize PreviewEntryAttachmentsDialog::calculateImageSize()
+{
     // Scale the image to the contents rect minus another set of margins to avoid scrollbars
     auto margins = m_ui->attachmentTextEdit->contentsMargins();
     auto size = m_ui->attachmentTextEdit->contentsRect().size();
     size.setWidth(size.width() - margins.left() - margins.right());
     size.setHeight(size.height() - margins.top() - margins.bottom());
-    image = image.scaled(size, Qt::KeepAspectRatio, Qt::SmoothTransformation);
 
-    cursor.insertImage(image);
+    return size;
 }
 
 Tools::MimeType PreviewEntryAttachmentsDialog::attachmentType(const QByteArray& data) const

src/gui/entry/PreviewEntryAttachmentsDialog.h

@@ -50,10 +50,14 @@ class PreviewEntryAttachmentsDialog : public QDialog
     void update();
     void updateTextAttachment(const QByteArray& data);
     void updateImageAttachment(const QByteArray& data);
+    void updateImageAttachment(const QImage& data);
+
+    QSize calculateImageSize();
 
     QScopedPointer<Ui::EntryAttachmentsDialog> m_ui;
 
     QString m_name;
     QByteArray m_data;
+    QImage m_imageCache;
     Tools::MimeType m_type{Tools::MimeType::Unknown};
 };