It would be easier and faster if you post these in grapecity forum, or atleast look there.
Based on reply to this query:
Row header icon change in Edit mode of Wijmo5 Flex Grid | General Discussion | Wijmo 5 | GrapeCity Forums[
^], it seems you can define an ineer html for header which can contain an image.
Seems following should workout, example:
initialized(flex: wijmo.grid.FlexGrid, args) {
flex.itemFormatter = function (panel, r, c, cell) {
var editRange = panel.grid.editRange;
if (panel.cellType == wijmo.grid.CellType.RowHeader) {
cell.innerHTML = "<img src='resources/collapsed.png' alt='image'/>";
cell.innerText = "";
}
}
}
}
I have not worked or I know of it, you need to try for such specific third party related queries and issues.