select text of input fields when focused

- the content of input fields of relevant sheets and dialogs
  are now selected upon focus
- autofocus the Gamemaster roll modifier in the roll dialog

src/module/ds4.ts

@@ -133,3 +133,21 @@ Hooks.once("setup", function () {
 Hooks.once("ready", function () {
     migration.migrate();
 });
+
+/**
+ * Select the text of input elements in given sheets via onfocus listener.
+ * The hook names are of the form "render"+sheet_superclassname and are called within
+ * the render() method of the foundry Application class.
+ * Note: The render hooks of all classes in the class hierarchy are called,
+ * so e.g. for a Dialog, both "renderDialog" and "renderApplication" are called
+ * (in this order).
+ */
+["renderApplication", "renderActorSheet", "renderItemSheet"].forEach((hookName: string) => {
+    Hooks.on(hookName, (app: Dialog, html: JQueryStatic, data: any) => {
+        $(html)
+            .find("input")
+            .on("focus", (ev: JQuery.FocusEvent<HTMLInputElement>) => {
+                ev.currentTarget.select();
+            });
+    });
+});