CODEWITHSUNDEEP
c++qtqt5.6
Gizmo
Gizmo

Reputation: 2210

QTextEdit inserting inconsistent HTML (when performing the same operation repeatedly / consistently)

I am using QTextEdit widget to display a nicely formatted chat-window to a user. To keep it basic for testing I use the following format for my html:

    QString style = is_message_sent_by_myself ?
        "background-color:rgb(255,255,255);font-size:14px;color:rgb(10,10,10);" :
        "background-color:rgb(249,86,79);font-size:14px;color:rgb(255,255,255);";

    QString format("<div style='%1'> %2 </div> <div style='font-size:3px;'> &zwnj; </div>");
    QString text_to_append = format.arg(style).arg(message.toHtmlEscaped());

    QTextEdit->append(text_to_append)

This works nice when creating the html myself but when generating it with QT 5.6 by using QTextEdit->append(text_to_be_append) I get a different (and even inconsistent) result.

For a start, when running the above snippet once, the following html is generated (got it with QTextEdit->toHtml()):

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html>
    <head>
        <meta name="qrichtext" content="1" />
        <style type="text/css">
            p, li { white-space: pre-wrap; }
        </style>
    </head>
    <body style=" font-family:'MS Shell Dlg 2'; font-size:8.25pt; font-weight:400; font-style:normal;">
        <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; background-color:#ffffff;"><span style=" font-size:14px; color:#0a0a0a; background-color:#ffffff;">Some message </span></p>
        <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span style=" font-size:3px;">&zwnj; </span></p>
    </body>
</html>

(which looks perfect for the first message)

But after executing the code again, an inconsistency occurs:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html>
    <head>
        <meta name="qrichtext" content="1" />
        <style type="text/css">
            p, li { white-space: pre-wrap; }
        </style>
    </head>
    <body style=" font-family:'MS Shell Dlg 2'; font-size:8.25pt; font-weight:400; font-style:normal;">
        <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; background-color:#ffffff;"><span style=" font-size:14px; color:#0a0a0a; background-color:#ffffff;">Some message </span></p>
        <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span style=" font-size:3px;">&zwnj; </span></p>
        <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span style=" font-size:14px; color:#ffffff; background-color:#f9564f;">Some message </span></p>
        <p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span style=" font-size:3px;">&zwnj; </span></p>
    </body>
</html>

(which looks like this, but should look like this)

As you can see, the background color attribute is missing in the third <p> tag. Where as the background-color attribute is present in the first <p> tag. The same code is repeated over and over and subsequent calls keep generating <p> tags without a background-color attribute.

Why is this happening and how could I work around this issue?

I'm using QT 5.6 with the Visual Studio 2015 Add-on (unofficial one) on Windows 10 x64.

This is how I am creating the QTextEdit box (including all other components for a tabPage):

PAChatClientUI::PAChatClientUI(QTabWidget* tabs_container, QObject *parent)
    : QObject(parent), tabs_container_(tabs_container)
{
    QString suffix = QString::number((size_t)this, 16);

    tab_ = new QWidget();
    tab_->setObjectName("tab_" + suffix);

    tab_grid_layout_ = new QGridLayout(tab_);
    tab_grid_layout_->setSpacing(6);
    tab_grid_layout_->setContentsMargins(11, 11, 11, 11);
    tab_grid_layout_->setObjectName("tab_grid_layout_" + suffix);

    chat_container_grid_ = new QGridLayout();
    chat_container_grid_->setSpacing(6);
    chat_container_grid_->setObjectName("chat_container_grid_" + suffix);

    chat_container_button_grid_ = new QHBoxLayout();
    chat_container_button_grid_->setSpacing(6);
    chat_container_button_grid_->setObjectName("chat_container_button_grid_" + suffix);

    chat_manager_bot_remove_ = new QPushButton(tab_);
    chat_manager_bot_remove_->setObjectName("chat_manager_bot_remove_" + suffix);
    chat_manager_bot_remove_->setMinimumSize(QSize(119, 23));

    chat_container_button_grid_->addWidget(chat_manager_bot_remove_);

    chat_manager_keep_chat_ = new QPushButton(tab_);
    chat_manager_keep_chat_->setObjectName("chat_manager_keep_chat_" + suffix);
    chat_manager_keep_chat_->setMinimumSize(QSize(119, 23));

    chat_container_button_grid_->addWidget(chat_manager_keep_chat_);

    chat_manager_end_chat_ = new QPushButton(tab_);
    chat_manager_end_chat_->setObjectName("chat_manager_end_chat_" + suffix);
    chat_manager_end_chat_->setMinimumSize(QSize(118, 23));

    chat_container_button_grid_->addWidget(chat_manager_end_chat_);

    chat_manager_send_ = new QPushButton(tab_);
    chat_manager_send_->setObjectName("chat_manager_send_" + suffix);
    chat_manager_send_->setMinimumSize(QSize(119, 23));

    chat_container_button_grid_->addWidget(chat_manager_send_);

    chat_container_grid_->addLayout(chat_container_button_grid_, 3, 0, 1, 1);

    chat_box_text_messages_ =
        //new QPlainTextEdit(tab_);
        new QTextEdit(tab_);
    chat_box_text_messages_->setObjectName("chat_box_text_messages_" + suffix);
    chat_box_text_messages_->setMinimumSize(QSize(495, 178));

    chat_container_grid_->addWidget(chat_box_text_messages_, 1, 0, 1, 1);

    chat_box_text_input_message_ = new QLineEdit(tab_);
    chat_box_text_input_message_->setObjectName("chat_box_text_input_message_" + suffix);
    chat_box_text_input_message_->setMinimumSize(QSize(495, 20));
    chat_box_text_input_message_->setMaximumSize(QSize(16777215, 16777215));

    chat_container_grid_->addWidget(chat_box_text_input_message_, 2, 0, 1, 1);

    tab_grid_layout_->addLayout(chat_container_grid_, 0, 0, 1, 1);

    chat_manager_bot_remove_->setText("Remove Bot");
    chat_manager_keep_chat_->setText("Keep Chat");
    chat_manager_end_chat_->setText("End Chat");
    chat_manager_send_->setText("Send");

    QPalette p = chat_box_text_messages_->palette();

    p.setColor(QPalette::Active, QPalette::Base, Qt::black);
    p.setColor(QPalette::Inactive, QPalette::Base, Qt::black);
    chat_box_text_messages_->setPalette(p);

    chat_box_text_messages_->setWordWrapMode(QTextOption::WordWrap);
    chat_box_text_messages_->setReadOnly(true);

    //Add nice html messages:
    AddMessage(true, "Some message");

    AddMessage(false, "Some message");

    AddMessage(true, "Some message");

    AddMessage(false, "Some message");

    tabs_container_->addTab(tab_, " 6");
}

void PAChatClientUI::AddMessage(bool me, const QString& message)
{
    QString style = me ?
        "background-color:rgb(255,255,255);font-size:14px;color:rgb(10,10,10);" :
        "background-color:rgb(249,86,79);font-size:14px;color:rgb(255,255,255);";

    QString format("<div style='%1'> %2 </div> <div style='font-size:3px;'> &zwnj; </div>");
    QString safe_msg = format.arg(style).arg(message.toHtmlEscaped());
    qDebug() << "Writing: " << safe_msg;
    chat_box_text_messages_->append(safe_msg);
    qDebug() << "HTML: " << chat_box_text_messages_->toHtml();
}

Edit:

I have tried to edit the code according to the answers and also to one of my thoughts, yielding the following two results for the code:

void PAChatClientUI::AddMessage(bool me, const QString& message)
{
    QString style = me ?
        "background-color:rgb(255,255,255);font-size:14px;color:rgb(10,10,10);" :
        "background-color:rgb(249,86,79);font-size:14px;color:rgb(255,255,255);";

    QString format("<div style='%1'> %2 </div> <div style='font-size:3px;'> &zwnj; </div>");
    QString safe_msg = format.arg(style).arg(message.toHtmlEscaped());
    qDebug() << "Writing: " << safe_msg;
    QTextCursor cursor = chat_box_text_messages_->textCursor();

    if (!cursor.atStart())
        cursor.insertBlock();
    cursor.insertHtml(safe_msg);
    qDebug() << "HTML: " << chat_box_text_messages_->toHtml();
}

This produced exactly the same effect, so to avoid QT "converting" the HTML, I tought I can just write what QT writes, but exactly the same issue happens:

void PAChatClientUI::AddMessage(bool me, const QString& message)
{
    QString bgColor  = me ? "ffffff" : "f9564f";
    QString txtColor = me ? "0a0a0a" : "ffffff";

    QString to_append("\
        <p style=\" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; background-color:#" + bgColor + ";\"><span style=\" font-size:14px; color:#" + txtColor + "; background-color:#" + bgColor + ";\">" + message.toHtmlEscaped() + " </span></p>\
        <p style=\" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;\"><span style=\" font-size:3px;\">&zwnj; </span></p>\
    ");

    chat_box_text_messages_->append(to_append);
}

Upvotes: 1

Views: 2061

Answers (2)

Murphy
Murphy

Reputation: 3999

I was able to reproduce this behaviour when packing two <div> into a common call to append(); splitting them into two calls results in the expected appearance (using Qt 4.7 here).

Upvotes: 0

Murphy
Murphy

Reputation: 3999

Edit: This suggestion doesn't solve the issue; it's left here for completeness.

QTextEdit does some RichText magic to the underlying QTextDocument when appending text blocks. Try explicitely creating a block and use QTextCursor::insertHtml() instead of QTextEdit::append():

QTextCursor cursor = m_ui.entryText->textCursor();

if(!cursor.atStart())
    cursor.insertBlock();
cursor.insertHtml(htmlText);

This should also improve performance for large amounts of text.

Upvotes: 1

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