captureCoordinate.py

"""
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
"""
from qgis.PyQt.QtCore import Qt, pyqtSignal
from qgis.PyQt.QtGui import QColor
from qgis.PyQt.QtCore import pyqtSlot
from qgis.core import QgsCoordinateTransform, QgsPointXY, QgsProject, QgsSettings
from qgis.gui import QgsMapToolEmitPoint, QgsVertexMarker
from .util import epsg4326

class CaptureCoordinate(QgsMapToolEmitPoint):
    '''Class to interact with the map canvas to capture the coordinate
    when the mouse button is pressed.'''
    capturePoint = pyqtSignal(QgsPointXY)
    captureStopped = pyqtSignal()

    def __init__(self, canvas):
        QgsMapToolEmitPoint.__init__(self, canvas)
        self.canvas = canvas
        self.vertex = None

    def activate(self):
        '''When activated set the cursor to a crosshair.'''
        self.canvas.setCursor(Qt.CrossCursor)
        self.snapcolor = QgsSettings().value( "/qgis/digitizing/snap_color" , QColor( Qt.magenta ) )

    def deactivate(self):
        self.removeVertexMarker()
        self.captureStopped.emit()

    def snappoint(self, qpoint):
        match = self.canvas.snappingUtils().snapToMap(qpoint)
        if match.isValid():
            if self.vertex is None:
                self.vertex = QgsVertexMarker(self.canvas)
                self.vertex.setIconSize(12)
                self.vertex.setPenWidth(2)
                self.vertex.setColor(self.snapcolor)
                self.vertex.setIconType(QgsVertexMarker.ICON_BOX)
            self.vertex.setCenter(match.point())
            return (match.point()) # Returns QgsPointXY
        else:
            self.removeVertexMarker()
            return self.toMapCoordinates(qpoint) # QPoint input, returns QgsPointXY

    def canvasMoveEvent(self, event):
        '''Capture the coordinate as the user moves the mouse over
        the canvas.'''
        self.snappoint(event.originalPixelPoint()) # input is QPoint

    def canvasReleaseEvent(self, event):
        '''Capture the coordinate when the mouse button has been released,
        format it, and copy it to the clipboard. pt is QgsPointXY'''
        pt = self.snappoint(event.originalPixelPoint())
        self.removeVertexMarker()

        try:
            canvasCRS = self.canvas.mapSettings().destinationCrs()
            transform = QgsCoordinateTransform(canvasCRS, epsg4326, QgsProject.instance())
            pt4326 = transform.transform(pt.x(), pt.y())
            self.capturePoint.emit(pt4326)
        except Exception as e:
            pass

    def removeVertexMarker(self):
        if self.vertex is not None:
            self.canvas.scene().removeItem(self.vertex)
            self.vertex = None