Index: gc_lang/fr/build.py
==================================================================
--- gc_lang/fr/build.py
+++ gc_lang/fr/build.py
@@ -70,12 +70,13 @@
     spfZip = "_build/" + dVars['tb_identifier'] + "-v" + dVars['version'] + '.mailext.xpi'
     hZip = zipfile.ZipFile(spfZip, mode='w', compression=zipfile.ZIP_DEFLATED)
     _copyGrammalecteJSPackageInZipFile(hZip, sLang)
     for spf in ["LICENSE.txt", "LICENSE.fr.txt"]:
         hZip.write(spf)
-    helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/gce_worker.js")
     helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/mailext", "", dVars, True)
+    helpers.addFileToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/gce_worker.js", "gce_worker.js", dVars)
+    helpers.addFileToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/README.md", "README.md", dVars)
     helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/3rd", "3rd", dVars, True)
     helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/_locales", "_locales", dVars, True)
     helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/content_scripts", "content_scripts", dVars, True)
     helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/fonts", "fonts", dVars, True)
     helpers.addFolderToZipAndFileFile(hZip, "gc_lang/"+sLang+"/webext/img", "img", dVars, True)

Index: gc_lang/fr/mailext/background.js
==================================================================
--- gc_lang/fr/mailext/background.js
+++ gc_lang/fr/mailext/background.js
@@ -265,18 +265,10 @@
         //browser.tabs.create({url: "http://grammalecte.net"});
     }
 });
 
 
-
-/*
-    Ports from content-scripts
-*/
-
-let dConnx = new Map();
-
-
 /*
     Messages from the extension (not the Worker)
 */
 function handleMessage (oRequest, xSender, sendResponse) {
     // message from panels
@@ -317,10 +309,15 @@
 }
 
 browser.runtime.onMessage.addListener(handleMessage);
 
 
+/*
+    Ports from content-scripts
+*/
+let dConnx = new Map();
+
 function handleConnexion (xPort) {
     // Messages from tabs
     let iPortId = xPort.sender.tab.id; // identifier for the port: each port can be found at dConnx[iPortId]
     dConnx.set(iPortId, xPort);
     xPort.onMessage.addListener(function (oRequest) {
@@ -364,10 +361,26 @@
     xPort.postMessage({sActionDone: "init", sUrl: browser.extension.getURL("")});
 }
 
 browser.runtime.onConnect.addListener(handleConnexion);
 
+
+
+/*
+    ComposeAction
+    (Thunderbird only)
+*/
+if (bThunderbird) {
+    console.log("[Grammalecte] Thunderbird: listening compose action...");
+    browser.composeAction.onClicked.addListener(function (xTab, xData) {
+        console.log("ComposeAction clicked");
+        console.log(xTab);
+        console.log(xData);
+        browser.tabs.sendMessage(xTab.id, {sActionRequest: "grammar_checker_compose_window"});
+    });
+}
+
 
 /*
     Context Menu
     (not for MailExtension)
 */

Index: gc_lang/fr/mailext/manifest.json
==================================================================
--- gc_lang/fr/mailext/manifest.json
+++ gc_lang/fr/mailext/manifest.json
@@ -23,11 +23,11 @@
              "80": "img/logo-80.png",
              "96": "img/logo-96.png" },
 
   "browser_action": {
     "default_icon": "img/logo-32.png",
-    "default_title": "Grammalecte [fr]",
+    "default_title": "Grammalecte",
     "default_popup": "panel/main.html",
     "browser_style": false
   },
 
   "compose_action": {
@@ -58,10 +58,12 @@
       "description": "Ouvre l’éditeur lexical"
     }
   },
 
   "permissions": [
+    "activeTab",
     "compose",
     "downloads",
-    "storage"
+    "storage",
+    "tabs"
   ]
 }

Index: gc_lang/fr/webext/content_scripts/init.js
==================================================================
--- gc_lang/fr/webext/content_scripts/init.js
+++ gc_lang/fr/webext/content_scripts/init.js
@@ -25,12 +25,16 @@
 let bThunderbird = false;
 if (typeof(browser) !== "object") {
     var browser = chrome;
     bChrome = true;
 }
-if (typeof(messenger) === "object") {
+if (typeof(messenger) === "object" || browser.hasOwnProperty("composeAction")) {
+    // JS sucks again.
+    // In Thunderbird, <browser> exists in content-scripts, but not <messenger>
+    // <browner> has property <composeAction> but is undefined...
     bThunderbird = true;
+    //console.log("[Grammalecte] Thunderbird...");
 }
 
 /*
 function loadImage (sContainerClass, sImagePath) {
     let xRequest = new XMLHttpRequest();
@@ -467,10 +471,17 @@
                         oGrammalecte.startGCPanel(document.activeElement);
                     } else {
                         oGrammalecte.showMessage("Erreur. Le cadre sur lequel vous avez cliqué n’a pas pu être identifié. Sélectionnez le texte à corriger et relancez le correcteur via le menu contextuel.");
                     }
                     break;
+                /*
+                    composeAction
+                    (Thunderbird only)
+                */
+                case "grammar_checker_compose_window":
+                    oGrammalecte.startGCPanel("__ThunderbirdComposeWindow__");
+                    break;
                 default:
                     console.log("[Grammalecte] Content-script. Unknown command: ", sActionDone);
             }
         }.bind(this));
     },
@@ -502,28 +513,10 @@
 
 
 oGrammalecteBackgroundPort.start();
 
 
-/*
-    ComposeAction
-    (Thunderbird only)
-*/
-if (bThunderbird) {
-    console.log("Listen...");
-    try {
-        browser.composeAction.onClicked.addListener(function (oTab, oData) {
-            console.log("START");
-            oGrammalecte.startGCPanel("J'en aie mare...");
-        });
-    }
-    catch (e) {
-        showError(e)
-    }
-    console.log("Done.");
-}
-
 
 /*
     Callable API for the webpage.
     (Not for Thunderbird)
 */

Index: helpers.py
==================================================================
--- helpers.py
+++ helpers.py
@@ -119,10 +119,11 @@
     sText = Template(open(spfSrc, "r", encoding="utf-8").read()).safe_substitute(dVars)
     open(spfDst, "w", encoding="utf-8", newline="\n").write(sText)
 
 
 def addFileToZipAndFileFile (hZip, spfSrc, spfDst, dVars):
+    "add a file to zip archive and file it with <dVars>"
     if spfSrc.endswith((".py", ".js", ".json", ".html", ".htm", ".css", ".xcu", ".xul", ".rdf", ".dtd", ".properties")):
         hZip.writestr(spfDst, fileFile(spfSrc, dVars))
     else:
         hZip.write(spfSrc, spfDst)