In hindsight my emscripten-ifdef (70d416a8f63f) is nonsense. As fpcrtl_glShaderSource() would not be defined and lead to compiling issues. So either it's 3 ifdefs (in pas2cRedo, pas2cSystem and misc.c), in order to toggle between fpcrtl_ and the native function, or alternatively have no ifdef for it at all. I'm going with none at all, which means emscripten will compile with the original (const) function prototype, being wrapped by the fpcrtl_ function, same as non-emscripten builds.

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

ApplicationWindow {
  visible: true
  width: 640
  height: 480
  title: qsTr("Hello World")

  SwipeView {
    id: swipeView
    anchors.fill: parent

    Page1 {
    }
  }
}