Action to resize rectangles in QGIS 3

qgis_resize_rectangle_action.py

layer = QgsProject.instance().mapLayer('[% @layer_id %]') 

from math import sqrt 
from PyQt5.QtWidgets import QDialog, QFormLayout, QLabel, QDoubleSpinBox, QComboBox, QDialogButtonBox 
                
class RectDialog(QDialog): 
        def __init__(self, width, length): 
                QDialog.__init__(self) 
                
                self.layout = QFormLayout(self) 
                self.wLabel = QLabel("largeur") 
                self.lLabel = QLabel("longueur") 
                self.wSpinBox = QDoubleSpinBox(self) 
                self.lSpinBox = QDoubleSpinBox(self) 
                self.wSpinBox.setMinimum(-1000) 
                self.lSpinBox.setMinimum(-1000) 
                self.wSpinBox.setMaximum(1000) 
                self.lSpinBox.setMaximum(1000) 
                self.wSpinBox.setValue(width) 
                self.lSpinBox.setValue(length) 
                self.rCombo = QComboBox(self) 
                self.rCombo.addItem("absolu") 
                self.rCombo.addItem("relatif") 
                
                self.buttonBox = QDialogButtonBox(self) 
                self.buttonBox.setStandardButtons(QDialogButtonBox.Cancel|QDialogButtonBox.Ok) 
                
                self.layout.setWidget(0, QFormLayout.LabelRole, self.wLabel) 
                self.layout.setWidget(0, QFormLayout.FieldRole, self.wSpinBox) 
                self.layout.setWidget(1, QFormLayout.LabelRole, self.lLabel) 
                self.layout.setWidget(1, QFormLayout.FieldRole, self.lSpinBox) 
                self.layout.setWidget(2, QFormLayout.FieldRole, self.rCombo) 
                self.layout.setWidget(3, QFormLayout.SpanningRole, self.buttonBox) 
                
                self.initialWidth = width 
                self.initialLength = length 
                
                self.buttonBox.accepted.connect(self.accept) 
                self.buttonBox.rejected.connect(self.reject) 
                self.rCombo.currentIndexChanged.connect(self.relativeChanged) 
        
        def relativeChanged(self, idx): 
                if idx == 0: # absolu 
                        self.lSpinBox.setValue( self.initialLength + self.lSpinBox.value() ) 
                        self.wSpinBox.setValue( self.initialWidth + self.wSpinBox.value() ) 
                else: # relatif 
                        self.lSpinBox.setValue( -self.initialLength + self.lSpinBox.value() ) 
                        self.wSpinBox.setValue( -self.initialWidth + self.wSpinBox.value() ) 
                        
        def width(self): 
                if self.rCombo.currentIndex() == 0: 
                        return self.wSpinBox.value() 
                else: 
                        return self.initialWidth + self.wSpinBox.value() 
        
        def length(self): 
                if self.rCombo.currentIndex() == 0: 
                        return self.lSpinBox.value() 
                else: 
                        return self.initialLength + self.lSpinBox.value() 


# code 
# code 
r = QgsFeatureRequest([% $id %]) 
f = QgsFeature() 
if layer.getFeatures(r).nextFeature(f): 
        geom = f.geometry().asPolygon() 
        if len(geom) != 1 and len(geom[0]) != 4: 
                qgis.utils.iface.messageBar().pushMessage("Geometry is not a 4 points polygon.", Qgis.Warning, 3) 
        else: 
                geom = geom[0] 
                dist = [] 
                geom.append(geom[3]) # re-append first point to calculate distance 
                for p in range(0,4): 
                        dist.append( sqrt(geom[p].sqrDist(geom[p+1])) ) 
                isRectangle = sqrt(geom[0].sqrDist(geom[2])) -sqrt(geom[1].sqrDist(geom[3])) < 0.000001 # check diagonals 
                if not isRectangle: 
                        print("dist: ", dist)
                        print("diag: ", geom[0].sqrDist(geom[2]), geom[1].sqrDist(geom[3]))
                        qgis.utils.iface.messageBar().pushMessage("Geometry is not a rectangle.", Qgis.Warning, 3) 
                        
                else: 
                        if dist[0] < dist[1]: 
                                w = dist[0] 
                                l = dist[1] 
                        else: 
                                w = dist[1] 
                                l = dist[0] 
                        dlg = RectDialog(w, l) 
                        if dlg.exec_(): 
                                if dist[0] < dist[1]: 
                                        d0 = dlg.width()-w 
                                        d1 = dlg.length()-l 
                                else: 
                                        d1 = dlg.width()-w 
                                        d0 = dlg.length()-l 

                                v0 = [geom[1].x()-geom[0].x(), geom[1].y()-geom[0].y()] 
                                v1 = [geom[2].x()-geom[1].x(), geom[2].y()-geom[1].y()] 
                                
                                v0 = [coord / (sqrt(v0[0]*v0[0]+v0[1]*v0[1])) for coord in v0] 
                                v1 = [coord / (sqrt(v1[0]*v1[0]+v1[1]*v1[1])) for coord in v1] 
                                
                                p0 = QgsPointXY( geom[0].x() -d0/2 * v0[0] -d1/2 * v1[0], geom[0].y() -d0/2 * v0[1] -d1/2 * v1[1] ) 
                                p1 = QgsPointXY( geom[1].x() +d0/2 * v0[0] -d1/2 * v1[0], geom[1].y() +d0/2 * v0[1] -d1/2 * v1[1] ) 
                                p2 = QgsPointXY( geom[2].x() +d0/2 * v0[0] +d1/2 * v1[0], geom[2].y() +d0/2 * v0[1] +d1/2 * v1[1] ) 
                                p3 = QgsPointXY( geom[3].x() -d0/2 * v0[0] +d1/2 * v1[0], geom[3].y() -d0/2 * v0[1] +d1/2 * v1[1] ) 
                                
                                geom = [[p0,p1,p2,p3]] 
                                geom = QgsGeometry.fromPolygonXY(geom) 
                                if layer.changeGeometry([% $id %], geom): 
                                        qgis.utils.iface.messageBar().pushMessage("Geométry edited", Qgis.Info, 1) 
                                        qgis.utils.iface.mapCanvas().refresh() 
                                else: 
                                        qgis.utils.iface.messageBar().pushMessage("Geometry could not be edited. Turn on editing.", Qgis.Warning, 3) 
else: 
        qgis.utils.iface.messageBar().pushMessage("Could not fetch feature.", Qgis.Critical, 3)