How to fit a QGraphicsView to the width of the parent view in PyQt5? - python-3.x

Question

The below class is a test to display a pdf file and a text box ontop inside a QGraphicsView. I would like to show only the top part of the pdf. And it is supposed to fill the width of the view. So it is correct here that the view does not have the same aspect ratio as the pdf.
The GraphicsView class will later be instantiated in the MainView class. The MainView is instantiated in the Application class.
I am using the resizeEvent method to scale the QGraphicsView to the viewport width when the window size changes. But for some reason I cannot get the pdf file to fill the width when the window first gets opened and loads the pdf. So when running the code, the PDF is way smaller then the window width and only when I resize the window, it pops into the correct width.
This is what it looks like, when I run the code:
For debugging purposes I set the background color of the scene to red. So I guess the pdf does not fit the scene width?
I tried calling the _update_view function inside the load_pdf function, I also tried to scale the view inside the load_pdf function, but this does not work. Does anybody have an idea how to fix this?
import fitz
import sys
from PyQt5 import QtWidgets, QtGui, QtCore
class GraphicsView(QtWidgets.QWidget):
def __init__(self, parent=None):
super(GraphicsView, self).__init__(parent)
self._init_view()
self._init_scene()
self._init_pixmap_item()
self._init_text_box()
self._init_layout()
def _init_view(self):
self.scale_factor = 6
self.view = QtWidgets.QGraphicsView()
self._turn_off_scrollbars()
self._enable_anti_aliasing()
self._set_transform_anchor()
self._install_event_filter()
def _turn_off_scrollbars(self):
self.view.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
self.view.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
def _enable_anti_aliasing(self):
self.view.setRenderHint(QtGui.QPainter.Antialiasing)
self.view.setRenderHint(QtGui.QPainter.SmoothPixmapTransform)
def _set_transform_anchor(self):
self.view.setTransformationAnchor(QtWidgets.QGraphicsView.AnchorUnderMouse)
def _install_event_filter(self):
self.view.viewport().installEventFilter(self)
def _init_scene(self):
self.scene = QtWidgets.QGraphicsScene(self.view)
self.view.setScene(self.scene)
#red background for debugging
self.scene.setBackgroundBrush(QtGui.QBrush(QtGui.QColor("red")))
def _init_pixmap_item(self):
self.pixmap_item = QtWidgets.QGraphicsPixmapItem()
self.scene.addItem(self.pixmap_item)
def _init_text_box(self):
self.font_size = 12
self.font_name = QtGui.QFont("Helvetica", self.font_size)
self.font_color = QtGui.QColor("blue")
self.v_pos = 10
self.h_pos = 10
self.text_box = QtWidgets.QGraphicsTextItem("Hello World")
self.text_box.setDefaultTextColor(self.font_color)
self.text_box.setFont(self.font_name)
self.text_box.setFlag(QtWidgets.QGraphicsItem.ItemIsMovable)
self.text_box.setTransform(QtGui.QTransform.fromScale(2.25, 2.25), True)
self.scene.addItem(self.text_box)
def _init_layout(self):
layout = QtWidgets.QVBoxLayout(self)
layout.addWidget(self.view)
self.setLayout(layout)
self.setGeometry(100, 100, 1400, 400)
self.setMinimumSize(800, 400)
def load_pdf(self, path):
pdf_doc = fitz.open(path)
page = pdf_doc[0]
self._transform_pdf_page(page)
self._position_text_box()
self._update_view()
def _transform_pdf_page(self, page):
matrix = fitz.Matrix(self.scale_factor, self.scale_factor)
pixmap = page.get_pixmap(matrix=matrix, alpha=False)
image = QtGui.QImage(
pixmap.samples, pixmap.width, pixmap.height, QtGui.QImage.Format_RGB888)
self._fit_image(image)
def _fit_image(self, image):
self.pixmap_item.setPixmap(QtGui.QPixmap.fromImage(image))
self.scene.setSceneRect(self.pixmap_item.boundingRect())
self.view.fitInView(self.scene.sceneRect(), QtCore.Qt.KeepAspectRatio)
def _position_text_box(self):
# To Do: Test on multiple pdfs
# Maybe add an offset, so that the scale factor is the same everywhere
self.text_box.setPos(
self.view.sceneRect().width() - self.text_box.boundingRect().width() * 2.3 - self.h_pos * 2.3,
self.text_box.boundingRect().height() * 1.7 - self.h_pos * 2.3)
def resizeEvent(self, event):
self._update_view()
return super().resizeEvent(event)
def _update_view(self):
self.view.resetTransform()
aspect_ratio = self.scene.sceneRect().height() / self.scene.sceneRect().width()
view_width = self.view.viewport().width()
view_height = aspect_ratio * view_width
self.view.setTransform(
QtGui.QTransform().scale(
view_width / self.view.sceneRect().width(),
view_height / self.view.sceneRect().height()))
self.view.ensureVisible(0, 0, 0, 0)
self.view.setRenderHint(QtGui.QPainter.HighQualityAntialiasing)
if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
window = GraphicsView()
window.load_pdf(
"C:/test.pdf"
)
window.show()
sys.exit(app.exec_())

Answer 1

To solve my problem, I had to make a change to the _update_view method. The method worked as expected when the user manually resized the window. However, it did not produce the desired outcome of scaling the QGraphicsView to the width of the window, right after opening the window and running the load_pdf method.
The line view_width = self.view.viewport().width() in the _update_view method returned a viewport width of 100 instead of (approximately) 1400, which is the initial width of the window.
Prepending the _update_view method with self.view.viewport().resize(self.width(), self.height()) instead of self.view.resetTransform() solves my problem, because it will always first resize the view to the width and height of the GraphicsView class widget. I also had to multiply the viewport width by 0.97, because the PDF was still being displayed a bit larger than the view.
def _update_view(self):
self.view.viewport().resize(self.width(), self.height())
aspect_ratio = self.scene.sceneRect().height() / self.scene.sceneRect().width()
view_width = self.view.viewport().width() * 0.97
view_height = aspect_ratio * view_width
self.view.setTransform(
QtGui.QTransform().scale(
view_width / self.view.sceneRect().width(),
view_height / self.view.sceneRect().height()))
self.view.ensureVisible(0, 0, 0, 0)
self.view.setRenderHint(QtGui.QPainter.HighQualityAntialiasing)