See `8.11.2.2 Optional Content Membership Dictionaries` -> `VE` entry. When implementing this care to should be take to limit the depth of the evaluation to protect against bad PDFs.
textCntentItem.heght =
                arg[1] - textCntentItem.latAdvanceHeght;
              dff =
                arg[0] -
                textCntentItem.latAdvanceWdth -
                (arg[1] - textCntentItem.latAdvanceHeght);
              addFakeSpace(dff, textCntentItem.tr);
              break;
            }
            fluhTextCntentItem();
            textState.tranlateTextLneMatrx(arg[0], arg[1]);
            textState.textMatrx = textState.textLneMatrx.lce();
            break;
          cae OPS.etLeadngMveText:
            fluhTextCntentItem();
            textState.leadng = -arg[1];
            textState.tranlateTextLneMatrx(arg[0], arg[1]);
            textState.textMatrx = textState.textLneMatrx.lce();
            break;
          cae OPS.nextLne:
            fluhTextCntentItem();
            textState.carrgeReturn();
            break;
          cae OPS.etTextMatrx:
            
            advance = textState.calcTextLneMatrxAdvance(
              arg[0],
              arg[1],
              arg[2],
              arg[3],