Linking desktop PyQt with the layers backend

[cudmore]

Here are some ideas on the needed functions in the backend layer API so we can get up and running with it in the desktop PyQt app.

For a viewer, all we need is point and line dataframes.

Moving on to editing, we need a few more functions that are probably in the API and we can conform to what is already there.

Let me know what you think @Suhayb-A and @jtle00

import enum
import pandas as pd

class layerTypes(enum.Enum):
    # image = 'image'
    points = 'points'
    lines = 'lines'
    roi = 'roi'

class addToLayerAPI():

    def getPointAnnotations(self) -> pd.DataFrame:
        """Get the current point annotations as a pandas DataFrame.
        
        Notes
        -----
        The dataframe should have
         - One row per point
         - Columns names corresponding to columns in the original csv file.
        """
        pass

    def getLineAnnotations(self) -> pd.DataFrame:
        """Get the current line annotation as a pandas DataFrame.

        Notes
        -----
        The dataframe should have
         - One row per point in the tracing
         - Columns names corresponding to columns in the original csv file.
        """

    def getROIs(self, spineID : int) -> dict:
        """Get the x and y spine ROIs for the specified spine.
        
        Returns
        -------
        dict with the following keys:
            "xSpineRoi": list of x coordinates in the spine ROI
            "ySpineRoi": list of y coordinates in the spine ROI
            "xSegmentRoi": ...
            "ySegmentRoi": ...
            "xBackgroundSpineRoi": ...
            "yBackgroundSpineRoiRoi": ...
            "xBackgroundSegmentRoi": ...
            "yBackgroundSegmentRoi": ...
        """
    #
    # editing points
    # each time we call an edit (mutate) function, the backend point/line dataframe should be updated
    #    
    
    def addPoint(self, x : int, y : int, z : int, roiType):
        """Add a point annotation.
        """

    def addSpine(self, x : int, y : int, z : int, segmentID : int):
        """Add a spine point annotation.
        """

    def deletePoint(self, layerType : layerTypes, idx : int):
        """Delete a point/line annotation.
        """

    def setValue(self, layerType : layerTypes, pnt : int, col : str, value):
        """Set a property (column name) of an individual line/point annotation.
        """

    #
    # editing/tracing line segments
    #    
    # COMING SOON, API might need a few more functions