"""
Demonstrate using QPainter on a subclass of GLGraphicsItem.
"""

import OpenGL.GL as GL

import pyqtgraph as pg
from pyqtgraph.opengl import GLAxisItem, GLGraphicsItem, GLGridItem, GLViewWidget
from pyqtgraph.Qt import QtCore, QtGui

SIZE = 32

class GLPainterItem(GLGraphicsItem.GLGraphicsItem):
    def __init__(self, **kwds):
        super().__init__()
        glopts = kwds.pop('glOptions', 'additive')
        self.setGLOptions(glopts)

    def compute_projection(self):
        modelview = GL.glGetDoublev(GL.GL_MODELVIEW_MATRIX)
        projection = GL.glGetDoublev(GL.GL_PROJECTION_MATRIX)
        mvp = projection.T @ modelview.T
        mvp = QtGui.QMatrix4x4(mvp.ravel().tolist())

        # note that QRectF.bottom() != QRect.bottom()
        rect = QtCore.QRectF(self.view().rect())
        ndc_to_viewport = QtGui.QMatrix4x4()
        ndc_to_viewport.viewport(rect.left(), rect.bottom(), rect.width(), -rect.height())

        return ndc_to_viewport * mvp

    def paint(self):
        self.setupGLState()

        painter = QtGui.QPainter(self.view())
        self.draw(painter)
        painter.end()

    def draw(self, painter):
        painter.setPen(QtCore.Qt.GlobalColor.white)
        painter.setRenderHints(QtGui.QPainter.RenderHint.Antialiasing | QtGui.QPainter.RenderHint.TextAntialiasing)

        rect = self.view().rect()
        af = QtCore.Qt.AlignmentFlag

        painter.drawText(rect, af.AlignTop | af.AlignRight, 'TR')
        painter.drawText(rect, af.AlignBottom | af.AlignLeft, 'BL')
        painter.drawText(rect, af.AlignBottom | af.AlignRight, 'BR')

        opts = self.view().cameraParams()
        lines = []
        center = opts['center']
        lines.append(f"center : ({center.x():.1f}, {center.y():.1f}, {center.z():.1f})")
        for key in ['distance', 'fov', 'elevation', 'azimuth']:
            lines.append(f"{key} : {opts[key]:.1f}")
        xyz = self.view().cameraPosition()
        lines.append(f"xyz : ({xyz.x():.1f}, {xyz.y():.1f}, {xyz.z():.1f})")
        info = "\n".join(lines)
        painter.drawText(rect, af.AlignTop | af.AlignLeft, info)

        project = self.compute_projection()

        hsize = SIZE // 2
        for xi in range(-hsize, hsize+1):
            for yi in range(-hsize, hsize+1):
                if xi == -hsize and yi == -hsize:
                    # skip one corner for visual orientation
                    continue
                vec3 = QtGui.QVector3D(xi, yi, 0)
                pos = project.map(vec3).toPointF()
                painter.drawEllipse(pos, 1, 1)


pg.mkQApp("GLPainterItem Example")
glv = GLViewWidget()
glv.show()
glv.setWindowTitle('pyqtgraph example: GLPainterItem')
glv.setCameraPosition(distance=50, elevation=90, azimuth=0)

griditem = GLGridItem()
griditem.setSize(SIZE, SIZE)
griditem.setSpacing(1, 1)
glv.addItem(griditem)

axisitem = GLAxisItem()
axisitem.setSize(SIZE/2, SIZE/2, 1)
glv.addItem(axisitem)

paintitem = GLPainterItem()
glv.addItem(paintitem)

if __name__ == '__main__':
    pg.exec()