How to snap to a QGraphicsTextItem grid?

Question

How to snap to a QGraphicsTextItem grid?

Let this little snippet:

import sys from PyQt5 import QtWidgets from PyQt5 import QtCore from PyQt5 import QtGui from PyQt5.QtWidgets import QMenu from PyQt5.QtGui import QKeySequence from PyQt5.QtCore import Qt from PyQt5.QtGui import QCursor from PyQt5.QtWidgets import QGraphicsObject from PyQt5.QtCore import QRectF from PyQt5.QtGui import QBrush from PyQt5.QtCore import QPoint from PyQt5.QtGui import QLinearGradient from PyQt5.QtGui import QColor from PyQt5.QtGui import QPen from PyQt5.QtGui import QPainter from PyQt5.QtWidgets import QGraphicsTextItem from PyQt5.QtWidgets import QGraphicsItem def create_action(parent, text, slot=None, shortcut=None, shortcuts=None, shortcut_context=None, icon=None, tooltip=None, checkable=False, checked=False): action = QtWidgets.QAction(text, parent) if icon is not None: action.setIcon(QIcon(':/%s.png' % icon)) if shortcut is not None: action.setShortcut(shortcut) if shortcuts is not None: action.setShortcuts(shortcuts) if shortcut_context is not None: action.setShortcutContext(shortcut_context) if tooltip is not None: action.setToolTip(tooltip) action.setStatusTip(tooltip) if checkable: action.setCheckable(True) if checked: action.setChecked(True) if slot is not None: action.triggered.connect(slot) return action class Settings(): WIDTH = 20 HEIGHT = 15 NUM_BLOCKS_X = 32 NUM_BLOCKS_Y = 16 class CI(QGraphicsTextItem): def __init__(self, text, pos): QGraphicsTextItem.__init__(self) self.content = text self.setPlainText(text) self.setPos(pos) self.setTextInteractionFlags(Qt.TextEditorInteraction) self.setDefaultTextColor(Qt.black) self.setFlags( self.flags() | QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable) self.setZValue(-1) def paint(self, painter, option, widget): painter.save() painter.setBrush(QBrush(Qt.white)) painter.drawRect(self.boundingRect()) painter.restore() super().paint(painter, option, widget) def keyPressEvent(self, event): super().keyPressEvent(event) self.content = self.toPlainText() def focusInEvent(self, event): self.scene().writing_comment = True # self.setPlainText(self.content) # print("Focusinevent") def focusOutEvent(self, event): self.scene().writing_comment = False # self.setHtml(self.content) # print("FocusOutevent") def contextMenuEvent(self, scme): super().contextMenuEvent(scme) class QS(QtWidgets.QGraphicsScene): def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) width = Settings.NUM_BLOCKS_X * Settings.WIDTH height = Settings.NUM_BLOCKS_Y * Settings.HEIGHT self.setSceneRect(0, 0, width, height) self.setItemIndexMethod(QtWidgets.QGraphicsScene.NoIndex) pos = QPoint( 5 * Settings.WIDTH, 2 * Settings.HEIGHT ) content = """<!DOCTYPE html> <html> <body> <h1>This is heading 1</h1> <h2>This is heading 2</h2> <h3>This is heading 3</h3> <h4>This is heading 4</h4> <h5>This is heading 5</h5> <h6>This is heading 6</h6> </body> </html> """ self.addItem(CI(content, pos)) class QV(QtWidgets.QGraphicsView): def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.view_menu = QMenu(self) self.create_actions() def create_actions(self): act = create_action(self.view_menu, "Zoom in", slot=self.on_zoom_in, shortcut=QKeySequence("+"), shortcut_context=Qt.WidgetShortcut) self.view_menu.addAction(act) act = create_action(self.view_menu, "Zoom out", slot=self.on_zoom_out, shortcut=QKeySequence("-"), shortcut_context=Qt.WidgetShortcut) self.view_menu.addAction(act) self.addActions(self.view_menu.actions()) def on_zoom_in(self): if not self.scene(): return self.scale(1.5, 1.5) def on_zoom_out(self): if not self.scene(): return self.scale(1.0 / 1.5, 1.0 / 1.5) def drawBackground(self, painter, rect): painter.setRenderHint(QPainter.Antialiasing, True) gr = rect.toRect() start_x = gr.left() + Settings.WIDTH - (gr.left() % Settings.WIDTH) start_y = gr.top() + Settings.HEIGHT - (gr.top() % Settings.HEIGHT) painter.save() for index, x in enumerate(range(start_x, gr.right(), Settings.WIDTH)): if index == Settings.NUM_BLOCKS_X: painter.setPen(QtGui.QColor(255, 70, 80).lighter(90)) painter.setOpacity(0.7) else: painter.setPen(QtGui.QColor(60, 70, 80).lighter(90)) painter.setOpacity(0.7) painter.drawLine(x, gr.top(), x, gr.bottom()) for index, y in enumerate(range(start_y, gr.bottom(), Settings.HEIGHT)): if index == Settings.NUM_BLOCKS_Y: painter.setPen(QtGui.QColor(255, 70, 80).lighter(90)) painter.setOpacity(0.7) else: painter.setPen(QtGui.QColor(60, 70, 80).lighter(90)) painter.setOpacity(0.7) painter.drawLine(gr.left(), y, gr.right(), y) painter.restore() super().drawBackground(painter, rect) if __name__ == '__main__': app = QtWidgets.QApplication(sys.argv) a = QS() b = QV() b.setScene(a) print(b.mapToScene(b.rect())) b.show() sys.exit(app.exec_())

If we run it, we will see that it creates a small scene with a grid and QGraphicsTextItem, for example:

What I'm trying to understand here is how to snap a QGraphicsTextItem to the intersections of the grid every time I move it or resize it (when I write some text), how can I guarantee this? Here is a small picture to better explain what I want:

+7

python python-3.x pyqt5 pyqt

Bpl Jan 24 '17 at 9:09

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1 answer

a_manthey_67 · Accepted Answer · 2017-01-29T10:05:19+0000

To set the new width and height of QGraphicsTextItem , you can overwrite boundingRect() , to setPos() , for example, you can use any suitable event, MouseReleaseEvent or MouseMoveEvent , and compute the following upper left set is the intersection from the last pos() :

 class CI(QGraphicsTextItem): def __init__(self, text, pos): QGraphicsTextItem.__init__(self) self.content = text self.setPlainText(text) self.setPos(pos) self.setTextInteractionFlags(Qt.TextEditorInteraction) self.setDefaultTextColor(Qt.black) self.setFlags( self.flags() | QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable) self.setZValue(-1) def boundingRect(self): # get the original width and height of boundingrect br = QGraphicsTextItem.boundingRect(self) brw = br.width() brh = br.height() # new width and height in "blocks" wblocks = int(brw/Settings.WIDTH) + 1 hblocks = int(brh/Settings.HEIGHT) + 1 w = wblocks*Settings.WIDTH h = hblocks*Settings.HEIGHT return QtCore.QRectF(0, 0, w, h) def mouseReleaseEvent(self, event): # QGraphicsItem.mouseReleaseEvent(self, event) QGraphicsTextItem.mouseReleaseEvent(self, event) self.setGridIntersection(self.pos()) def mouseMoveEvent(self, event): QGraphicsTextItem.mouseMoveEvent(self, event) self.setGridIntersection(self.pos()) def setGridIntersection(self, pos): # get the next grid intersection top left of items top-left corner grid_x = int(pos.x()/Settings.WIDTH) grid_y = int(pos.y()/Settings.HEIGHT) self.setPos(grid_x*Settings.WIDTH, grid_y*Settings.HEIGHT) def paint(self, painter, option, widget): painter.save() painter.setBrush(QBrush(Qt.white)) painter.drawRect(self.boundingRect()) painter.restore() super().paint(painter, option, widget) def keyPressEvent(self, event): super().keyPressEvent(event) self.content = self.toPlainText() def focusInEvent(self, event): self.scene().writing_comment = True # self.setPlainText(self.content) # print("Focusinevent") def focusOutEvent(self, event): self.scene().writing_comment = False # self.setHtml(self.content) # print("FocusOutevent") def contextMenuEvent(self, scme): super().contextMenuEvent(scme)

Edit 02/01/17: the above solution is only suitable for single selections, since for single and multi-selections it is used:

 class CI(QGraphicsTextItem): def __init__(self, text, pos): QGraphicsTextItem.__init__(self) self.content = text self.setPlainText(text) self.setPos(pos) self.setTextInteractionFlags(Qt.TextEditorInteraction) self.setDefaultTextColor(Qt.black) self.setFlags( self.flags() | QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable) self.setZValue(-1) self.setAcceptDrops(True) def boundingRect(self): # get the original width and height of boundingrect br = QGraphicsTextItem.boundingRect(self) brw = br.width() brh = br.height() # new width and height in "blocks" wblocks = int(brw / Settings.WIDTH) + 1 hblocks = int(brh / Settings.HEIGHT) + 1 w = wblocks * Settings.WIDTH h = hblocks * Settings.HEIGHT return QtCore.QRectF(0, 0, w, h) def setGridIntersection(self, pos): # get the next grid intersection top left of items top-left corner grid_x = int(pos.x() / Settings.WIDTH) grid_y = int(pos.y() / Settings.HEIGHT) self.setPos(grid_x * Settings.WIDTH, grid_y * Settings.HEIGHT) def paint(self, painter, option, widget): painter.save() painter.setBrush(QBrush(Qt.white)) painter.drawRect(self.boundingRect()) painter.restore() super().paint(painter, option, widget) def keyPressEvent(self, event): super().keyPressEvent(event) self.content = self.toPlainText() def focusInEvent(self, event): self.scene().writing_comment = True # self.setPlainText(self.content) # print("Focusinevent") def focusOutEvent(self, event): self.scene().writing_comment = False # self.setHtml(self.content) # print("FocusOutevent") def contextMenuEvent(self, scme): super().contextMenuEvent(scme)

and in the QS add class:

  def mouseMoveEvent(self, event): QtWidgets.QGraphicsScene.mouseMoveEvent(self, event) for i in self.selectedItems(): if type(i) == CI: i.setGridIntersection(i.pos())

How to snap to a QGraphicsTextItem grid?

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