Back widget brings focus back to previous page in history when clicked.
"active" + "inactive" labeled elements can be provided and reflect whether
widget is pressed or not.
shortdesc > Jump to previous page
svg_root.removeEventListener("pointerup", this.bound_onmouseup, true);
this.activity_state = false;
if (jump_history.length > 1) {
jump_history.pop(); // forget current page
if (jump_history.length == 0) return;
[page_name, index] = jump_history[jump_history.length-1];
} while (page_name == "ScreenSaver") // never go back to ScreenSaver
fading_page_switch(page_name, index);
svg_root.addEventListener("pointerup", this.bound_onmouseup, true);
this.activity_state = true;
this.bound_onmouseup = this.onmouseup.bind(this);
this.activity_state = false;
this.element.addEventListener("pointerdown", this.onmousedown.bind(this));