(An ezui implementation) Copy glyphs from another source that don't exist in one of your UFOs.

copy_missing_glyphs.py

# menuTitle: Copy Missing Glyphs from Other Source

import ezui
from mojo.UI import PostBannerNotification, getDefault
from mojo.subscriber import Subscriber
import drawBot
import functools


@functools.cache
def colorImage(color, width=20, height=12):
    if color is None:
        return None
    drawBot.newDrawing()
    drawBot.newPage(width, height)    
    drawBot.fill(*color)    
    drawBot.rect(0, 0, width, height)    
    im = drawBot.saveImage("NSImage")
    drawBot.endDrawing()
    return im

class CopyMissingGlyphs(Subscriber, ezui.WindowController):


    def build(self):
        self.default_mark_colors = [value for (value, name) in getDefault("markColors")]
        
        content = """
        * TwoColumnForm @form
        > :Source Font:
        > ( ...) @popUpSrce
        > :Destination Font:
        > ( ...) @popUpDest

        > -----------------
        
        > :Mark Color:
        > (( ...)) @markColors
    
        > :Fit to:
        > (X) Cap-Height @heights
        > ( ) X-Height
        # (Scales contours and anchors, not components)
        
        > -----------------
        
        > :
        > [ ] Only fill template glyphs @templateFill
        
        * HorizontalStack       @bottomRow
        > %%                    @progressSpinner
        > (Copy Missing Glyphs) @commit
        """
        
        title_width = 105
        item_width = 190
        descriptionData = dict(
            form=dict(
                titleColumnWidth=title_width,
                itemColumnWidth=item_width
            ),
            popUpSrce=dict(
                items=[],
                selected=1,
                width=item_width,
            ),
            popUpDest=dict(
                items=[],
                selected=0, # not necessary
                width=item_width,
            ),
            progressSpinner=dict(
                showWhenStopped=False,
                gravity="trailing"
            ),
            commit=dict(
                width=item_width,
                gravity="trailing"
            ),
            bottomRow=dict(
                distribution="gravity",
            )
        )
        
        self.w = ezui.EZPanel(
            content=content,
            descriptionData=descriptionData,
            title="Copy Missing Glyphs",
            controller=self
        )
        
        self.pop_up_srce = self.w.getItem("popUpSrce")
        self.pop_up_dest = self.w.getItem("popUpDest")
        self.mark_colors = self.w.getItem("markColors")
        self.mark_colors.setItemDescriptions(
            [dict(image=colorImage(value), text=name) for (value, name) in getDefault("markColors")]
        )
        
        self.spinner = self.w.getItem("progressSpinner")
    
        self.getAllFonts()
        
        
    def started(self):
        self.w.open()
        

    def getAllFonts(self):
        self.a = AllFonts()
        print("-1")
        self.list_of_fonts = [] # empty field if no fonts
        if self.a:
            for f in self.a:
                if f.info.familyName and f.info.styleName:
                    self.list_of_fonts.append(f.info.familyName + " - " + f.info.styleName)
                else: # show "Untitled #" or whatever the new font display name is
                    self.list_of_fonts.append(f._document._windowTitleDisplayName())
                    
        # set the menu
        self.pop_up_srce.setItems(self.list_of_fonts)
        self.pop_up_dest.setItems(self.list_of_fonts)
        
        self.pop_up_dest.set(0)
        self.pop_up_srce.set(0)
        if len(self.list_of_fonts) > 1:
            self.pop_up_srce.set(1)
        

    def fontDocumentDidOpen(self, info):
        self.getAllFonts()
        
        
    def fontDocumentDidOpenNew(self, info):
        self.getAllFonts()
        
        
    def commitCallback(self, sender):
        self.spinner.start()
    
        srce_f = self.a[self.w.getItem("popUpSrce").get()]
        dest_f = self.a[self.w.getItem("popUpDest").get()]

        scale_by = dest_f.info.capHeight / srce_f.info.capHeight
        if self.w.getItem("heights").get() == 1:
            scale_by = dest_f.info.xHeight / srce_f.info.xHeight
        
        mark_color_index = self.w.getItem("markColors").get()
        r,g,b,a = getDefault("markColors")[mark_color_index][0]
        
        for srce_g_name in srce_f.glyphOrder:
            for layer in srce_f.layers:
                if srce_g_name in layer.keys():
                    srce_g = layer[srce_g_name]
                    # Match the default layers
                    if layer == srce_f.defaultLayer:
                        dest_layer = dest_f.defaultLayer
                    else:
                        if not layer in dest_f.layerOrder:
                            dest_f.newLayer(layer.name)
                        dest_layer = dest_f.getLayer(layer.name)
                    if srce_g.name not in dest_layer.keys():
                    
                        # Skip copying the glyph if it's not a template glyph in the destination font, and you've chosen that option in the window
                        if self.w.getItem("templateFill").get() == True:
                            if not srce_g.name in dest_f.templateGlyphOrder:
                                continue
                        
                        dest_layer.newGlyph(srce_g.name)
                        copied_glyph = srce_g.copy()

                        # Only scale contours + anchors
                        for c in copied_glyph.contours:
                            c.scaleBy(scale_by, origin=(0,0))
                        for anc in copied_glyph.anchors:
                            anc.scaleBy(scale_by, origin=(0,0))
            
                        copied_glyph.width = srce_g.width * scale_by
            
                        dest_layer.insertGlyph(copied_glyph, name=srce_g.name)
                        dest_layer[srce_g.name].markColor = (r,g,b,a)
                        
        dest_f.changed()
                
        self.spinner.stop()
        
        # Notify what just happened
        message = f"Copying glyphs from {srce_f.info.familyName} {srce_f.info.styleName} into empty glyphs slots of {dest_f.info.familyName} {dest_f.info.styleName}."
        print(message)
        PostBannerNotification("Copied Missing Glyphs", message)
        
        

CopyMissingGlyphs()