Adding clickable widgets into a qplaintextedit

[Fuchsiaff]

So basically let's say you have followed this guide: https://doc.qt.io/qt-5/qtwidgets-widgets-codeeditor-example.html

And you modify the width to be a bit bigger: Screenshot 2019-08-20 at 14.56.46

I want to add a little arrow next to line number 1, like QtCreator has, to be clickable so I could fold the text that is on line 2
But I have no idea where to start, how can I add a little widget next to the line number

[Fuchsiaff]

I'm currently trying to find out how QtCreator does it, if anyone knows, please let me know!

[SGaist]

Hi,

I would start by looking at the TextEditor plugin and the CppEditor plugin.

[Fuchsiaff]

Alright so I think the best way to proceed is to have each of the numbers on the number bar clickable
so instead of painting them, they should be widgets

Here's a little Number class:

class Number(QFrame):
    def __init__(self, number):
        super().__init__()
        self.num = QLabel(str(number), self)
        self.layout = QVBoxLayout()
        self.layout.addWidget(self.num)
        self.layout.addStretch()
        self.setLayout(self.layout)
        self.setStyleSheet("background-color: red; color: black")
        self.setContentsMargins(0,0,0,0)

But there is still some annoying spacing around the widget:
How do I remove that?

[Fuchsiaff]

Well after digging, and I mean A LOT of digging I found I could use QStyle to draw those little arrows
and since QStyleOptionViewItem has states, I can choose how the arrow is pointing.

This is a little example of code:

    def paintEvent(self, event: QPaintEvent):

        if self.isVisible():
            block: QTextBlock = self.editor.firstVisibleBlock()
            height: int = self.fontMetrics().height()
            number: int = block.blockNumber()

            painter = QPainter(self)
            painter.fillRect(event.rect(), QColor(53, 53, 53))
            # painter.drawRect(0, 0, event.rect().width() - 1, event.rect().height() - 1)
            font = painter.font()
            font.setPointSize(15)
            currentBlockNumber: int = self.editor.textCursor().block().blockNumber() + 1

            while block.isValid():
                blockGeometry: QRectF = self.editor.blockBoundingGeometry(block)
                offset: QPointF = self.editor.contentOffset()
                blockTop: int = int(blockGeometry.translated(offset).top() + 1)
                number += 1

                if number == currentBlockNumber:
                    font.setBold(True)
                else:
                    font.setBold(False)
                painter.setFont(font)
                rect: QRect = QRect(0, blockTop, self.width() - 5, height)
                painter.drawText(rect, Qt.AlignCenter, str(number))
                if number in self.lines:
                    options = QStyleOptionViewItem()
                    options.rect = QRect(0, blockTop, self.width() + 45, height)
                    options.state = (QStyle.State_Active |
                                 QStyle.State_Item |
                                 QStyle.State_Children |
                                 QStyle.State_Open)
                    self.style().drawPrimitive(QStyle.PE_IndicatorBranch, options,
                                               painter, self)
                    print("drawn")
                if blockTop > event.rect().bottom():
                    break

                block = block.next()

            painter.end()

That is the whole paintEvent function and the magic happens here:

                if number in self.lines:
                    options = QStyleOptionViewItem()
                    options.rect = QRect(0, blockTop, self.width() + 45, height)
                    options.state = (QStyle.State_Active |
                                 QStyle.State_Item |
                                 QStyle.State_Children |
                                 QStyle.State_Open)
                    self.style().drawPrimitive(QStyle.PE_IndicatorBranch, options,
                                               painter, self)
                    print("drawn")

when painting numbers I will check that if the current number is in a list of numbers where the user can fold at (this is done parsing a syntax tree, if anyone is interested in that please let me know!) and if it is in there then it will create a rect and draw a little arrow that points down (this is because QStyle.State_Open) is in the options.state variable
if you remove that, the arrow points right. That will be useful when after folding

Here's a little preview: