QTextDocument::DrawContents skips resources? - c++

Question

I have this setup:
// ...
// variable document is a QTextDocument* which has some 'RichText' + 'Images'
QTextEdit textEdit;
textEdit.setDocument(document);
textEdit.setLineWrapMode(QTextEdit::LineWrapMode::NoWrap);
auto image = QImage(document->size().width(), document->size().height(),
QImage::Format_ARGB32_Premultiplied);
image.fill(Qt::transparent);
QPainter painter(&image);
document->drawContents(&painter);
// ...
I'm doing this to have my text rendered in a long horizontal QImage (hence the "NoWrap" LineWrapMode), so I can select a small part of it at a time with QImage::copy(QRect) and create a scrolling text effect.
The reason I'm doing it this way is that I need to have a QImage at the end which then I would feed its buffer (QImage::bits()) to the hardware that I'm using as my final output.
So it works great, it displays formatted text with fonts and colors and everything except for the images, it seems to skip them, notice the file icon in "result of text with image" picture.
This is text only in editor
This is result of text only
This is text with image in editor
This is result of text with image
This is how I'm inserting images to my QTextDocument:
QImage image(url.toLocalFile());
if (image.isNull())
return;
image = image.scaledToHeight(getDocumentHeight(), Qt::SmoothTransformation);
auto filename = QUrl(url.fileName());
textEdit->document()->addResource(QTextDocument::ImageResource, filename, image);
textEdit->textCursor().insertImage(filename);
So I don't think it's because "DrawContents" fails to find the image resource file or something like this.
What should I do? Is there something that I'm missing? Any kind of help in the matter is highly appreciated! ;)

Answer 1

In the following code I show how an image should be loaded, then save it to a file, probably the error is that you have not finished painting, for this you must call painter.end() or delete painter from memory.
main.cpp
#include <QtWidgets>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QWidget widget;
QVBoxLayout vlayout(&widget);
QTextEdit textEdit;
QPushButton button("save image");
QPushButton loadButton("Load and Insert");
vlayout.addWidget(&loadButton);
vlayout.addWidget(&textEdit);
vlayout.addWidget(&button);
widget.show();
textEdit.append("some text");
QObject::connect(&loadButton, &QPushButton::clicked,[&textEdit](){
QString filename = QFileDialog::getOpenFileName(&textEdit, "Select", "", "*.png");
if(!filename.isEmpty()){
QImage image(filename);
QUrl url = QUrl::fromLocalFile(filename);
image = image.scaledToHeight(100, Qt::SmoothTransformation);
textEdit.document()->addResource(QTextDocument::ImageResource, url, image);
textEdit.textCursor().insertImage(image);
}
});
QObject::connect(&button, &QPushButton::clicked, [&textEdit](){
QImage image(textEdit.document()->size().toSize() , QImage::Format_ARGB32_Premultiplied);
image.fill(Qt::transparent);
QPainter painter(&image);
textEdit.document()->drawContents(&painter);
painter.end();
image.save("image.png");
});
return a.exec();
}