dblclick_gmail_edit.js

// dblclick_gmail_edit.js -- CONTENT SCRIPT THAT LOADS WITH GMAIL AND ENABLES DOUBLE CLICK EDIT FUNCTIONALITY

localStorage.setItem('prev_title', 'undefined');
localStorage.setItem('cur_title', 'undefined');

document.addEventListener('click', function(e) {
    e = e || window.event;

    // KEEPS TRACK OF PREVIOUS CLICK'S IMAGE TITLE FOR USE WITH DOUBLE CLICK LISTENER
    localStorage.setItem('prev_title', localStorage.getItem('cur_title'));

    // IF TAG <img> WAS CLICKED
    if (e.target.nodeName.toLowerCase() === "img") {
        if (e.target.title == null) {
            localStorage.setItem('cur_title', 'undefined');
        }
        else {
            localStorage.setItem('cur_title', e.target.title);
        }
    }
    else {
        localStorage.setItem('cur_title', 'undefined');
    }
});

document.addEventListener('dblclick', function(e) {
    e = e || window.event;

    let dataGrabbed = false;      // INDICATES IF LATEX METADATA WAS RETRIEVED
    let latex_meta = "";          // STORES LATEX METADATA

    latex_meta = localStorage.getItem('prev_title');

    if (latex_meta != 'undefined') {
        dataGrabbed = true;
    }

    // CODE TO GET THE LATEX BACK INTO THE EXTENSION
    if (dataGrabbed) {
        let Browser;
        // DETECT BROWSER TYPE FOR PROPER API USE
        try {
            // FOR FIREFOX
            Browser = browser;
        } catch(e) {
            try {
                // FOR CHROME
                Browser = chrome;
            } catch(e) {
                console.error('TeX Math Here: dblclick_gmail_edit.js: ERROR BROWSER TYPE NOT DETECTED!');
            }
        }

        // SEND LATEX TO BACKGROUND SCRIPT FOR STORAGE UNTIL POPUP IS OPENED
        Browser.runtime.sendMessage({ type: 'latex_store', latex: latex_meta });
        alert('Any embedded TeX in the image can now be found in the TeX Math Here TeX editor.');
    }
});