An IntelliJ IDEA Live Plugin to change the window icon to something more useful. (LivePlugin: https://github.com/dkandalov/live-plugin)

icon-changer.groovy

import com.intellij.ide.plugins.PluginUtil

import java.awt.*

import javax.imageio.*

import com.intellij.openapi.project.*
import com.intellij.openapi.wm.*
import com.intellij.openapi.wm.impl.*
import sun.misc.*

import java.awt.image.BufferedImage

import static liveplugin.PluginUtil.invokeLaterOnEDT
import static liveplugin.PluginUtil.registerProjectListener

invokeLaterOnEDT {
    IdeFrameImpl.frames.each { Frame frame ->
        if (frame instanceof IdeFrameImpl) {
            def project = frame.getProject()
            println("frame found $frame $project")
            setIdeaWindowIcon(project, frame, getIdentifyingLetters(project))
        }
    }
    registerProjectListener("icon-changer-live", new ProjectManagerListener() {
        @Override
        void projectOpened(Project project) {
            invokeLaterOnEDT {
                setIdeaWindowIcon(project, getIdentifyingLetters(project))
            }
        }
    })
}

static def setIdeaWindowIcon(Project project, IdeFrameImpl frame = findFrameForProject(project),
                             String overlayText) {
    if (frame == null) {
        return
    }
    def moreThanTwoChars = overlayText.length() > 2
    def img = toBufferedImage(frame.getIconImage())
    def g = img.createGraphics()
    g.color = Color.BLACK
    g.fillRect(5, 5, 20, 16)
    g.color = Color.WHITE
    g.font = new Font("Consolas", Font.BOLD, moreThanTwoChars ? 13 : 15)
    g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_OFF)
    g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON)
    g.drawString(overlayText,
            moreThanTwoChars ? 5 : 6,
            moreThanTwoChars ? 14 : 16)
    frame.setIconImage(img)
}

static String getIdentifyingLetters(Project project, int i = 0) {
    if (project == null) {
        return "???"
    }
    def prjName = project.name
    if (i >= Constants.identLettersSplitRegexes.length) {
        return prjName.substring(0, Math.min(3, prjName.length()))
    }
    def regex = Constants.identLettersSplitRegexes[i]
    def split = prjName.split(regex) - ""
    if (split.length >= 3) {
        return split[0].substring(0, 1) + split[1].substring(0, 1) + split[2].substring(0, 1)
    } else if (split.length == 2) {
        return split[0].substring(0, 1) + split[1].substring(0, 1)
//    } else if (split.length == 1) {
//        return split[0].substring(0, 1)
    } else {
        return getIdentifyingLetters(project, i + 1)
    }
}

static IdeFrame findFrameForProject(Project project) {
    for (Frame frame : IdeFrameImpl.frames) {
        if (frame instanceof IdeFrame && frame.getProject() == project) {
            return frame
        }
    }
    return null
}

/**
 * Converts a given Image into a BufferedImage
 *
 * @param img The Image to be converted
 * @return The converted BufferedImage
 */
public static BufferedImage toBufferedImage(Image img) {
    if (img instanceof BufferedImage) {
        return (BufferedImage) img;
    }

    // Create a buffered image with transparency
    BufferedImage bimage = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_ARGB);

    // Draw the image on to the buffered image
    Graphics2D bGr = bimage.createGraphics();
    bGr.drawImage(img, 0, 0, null);
    bGr.dispose();

    // Return the buffered image
    return bimage;
}

class Constants {
    static String ideaIconWithBar_base64_28px = "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"
    static String[] identLettersSplitRegexes = ["[a-z0-9_-]+", "[0-9_-]+"]

}

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