Custom qlayout base on borderlayout example

main_layout.py

import sys

from PyQt5.QtCore import QRect, QSize
from PyQt5.QtWidgets import QMainWindow, QApplication, QLayout, QHBoxLayout, QFrame, QPushButton, QWidget, \
    QWidgetItem


POSITISON_HEADER = 1
POSITISON_FOOTER = 2
POSITISON_CONTENT = 3
POSITISON_LEFT_SIDE = 4
POSITISON_RIGHT_SIDE = 5

class MainLayout(QLayout):

    def __init__(self):
        super().__init__()
        self.items = []

    def add(self, item, position):
        if isinstance(item, QWidget):
            item = QWidgetItem(item)
        self.items.append((item, position))

    def count(self):
        return len(self.items)

    def itemAt(self, index):
        if index >= len(self.items):
            return
        return self.items[index][0]

    def _sizeHint(self, minimum=False):
        header_size = QSize()
        content_size = QSize()
        footer_size = QSize()
        left_side_size = QSize()
        right_side_size = QSize()

        for (item, position) in self.items:
            item_size = item.sizeHint() if not minimum else item.minimumSize()
            if position == POSITISON_HEADER:
                header_size = item_size
            if position == POSITISON_CONTENT:
                content_size = item_size
            elif position == POSITISON_FOOTER:
                footer_size = item_size
            elif position == POSITISON_LEFT_SIDE:
                left_side_size = item_size
            elif position == POSITISON_RIGHT_SIDE:
                right_side_size = item_size

        height = max(
            content_size.height(),
            header_size.height() + max(footer_size.height(), left_side_size.height(), right_side_size.height()))
        width = max(
            content_size.width(),
            header_size.width(),
            left_side_size.width() + footer_size.width() + right_side_size.width())

        if header_size.isValid():
            height += self.spacing()
        if footer_size.isValid():
            height += self.spacing()

            if left_side_size.isValid():
                width += self.spacing()
            if right_side_size.isValid():
                width += self.spacing()

        return QSize(width, height)

    def sizeHint(self) -> QSize:
        return self._sizeHint()

    def minimumSize(self):
        return self._sizeHint(minimum=True)

    def setGeometry(self, r):
        super().setGeometry(r)
        header_height = 0
        footer_height = 0
        left_side_width = 0
        right_side_width = 0

        for (item, position) in self.items:
            if position == POSITISON_HEADER:
                header_height = item.sizeHint().height()
            elif position == POSITISON_FOOTER:
                footer_height = item.sizeHint().height()
            elif position == POSITISON_LEFT_SIDE:
                left_side_width = item.sizeHint().width()
            elif position == POSITISON_RIGHT_SIDE:
                right_side_width = item.sizeHint().width()

        for (item, position) in self.items:
            if position == POSITISON_HEADER:
                item.setGeometry(QRect(r.left(), r.top(), r.width(), item.sizeHint().height()))
            elif position == POSITISON_CONTENT:
                item.setGeometry(QRect(r.left(), r.top(), r.width(), r.height()))
            elif position == POSITISON_FOOTER:
                item.setGeometry(QRect(left_side_width + self.spacing(),
                                       r.bottom() - item.sizeHint().height(),
                                       max(item.minimumSize().width(), r.width() - left_side_width - right_side_width - self.spacing()*2),
                                       item.sizeHint().height()))
            elif position == POSITISON_LEFT_SIDE:
                item.setGeometry(QRect(r.left(),
                                       header_height + self.spacing(),
                                       item.sizeHint().width(),
                                       r.height() - header_height - self.spacing()))
            elif position == POSITISON_RIGHT_SIDE:
                item.setGeometry(QRect(r.right() - item.sizeHint().width() + 1,
                                       header_height + self.spacing(),
                                       item.sizeHint().width(),
                                       r.height() - header_height - self.spacing()))

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        left_side_bar = create_side_bar()
        left_side_bar.setStyleSheet("QFrame{background-color: #550000ff; border: 1px solid blue;}")
        right_side_bar = create_side_bar()
        right_side_bar.setStyleSheet("QFrame{background-color: #550000ff; border: 1px solid blue;}")

        top_side_bar = create_side_bar()
        top_side_bar.setStyleSheet("QFrame{background-color: #550000ff; border: 1px solid blue;}")

        bottom_side_bar = create_side_bar()
        bottom_side_bar.setStyleSheet("QFrame{background-color: #550000ff; border: 1px solid blue;}")

        center_content = create_side_bar()
        center_content.setStyleSheet("QFrame{background-color: #550000ff; border: 1px solid blue;}")

        lt = MainLayout()
        lt.add(center_content, POSITISON_CONTENT)
        lt.add(top_side_bar, POSITISON_HEADER)
        lt.add(left_side_bar, POSITISON_LEFT_SIDE)
        lt.add(right_side_bar, POSITISON_RIGHT_SIDE)
        lt.add(bottom_side_bar, POSITISON_FOOTER)

        w = QWidget()
        self.setStyleSheet("QMainWindow {background-color: #55ffffff;}")
        w.setLayout(lt)

        self.setCentralWidget(w)


def create_side_bar(parent=None):
    w = QFrame(parent)
    lt = QHBoxLayout()

    btn = QPushButton("toggle")
    lt.addWidget(btn)

    w.setLayout(lt)

    def toggle():
        if w.minimumWidth() != 100:
            w.setMinimumWidth(100)
            w.setMaximumWidth(100)
        else:
            w.setMinimumWidth(200)
            w.setMaximumWidth(200)

        print("toggle btn clicked")

    btn.clicked.connect(toggle)

    return w


if __name__ == '__main__':
    app = QApplication(sys.argv)

    w = MainWindow()
    w.show()

    sys.exit(app.exec())