GMF:如何让网格显示在background，而不是foreground

前言

很久没写文章了，准备写一系列关于Eclipse RCP /Plugin的文章。这些文章都是trouble shooting性质的，不准备写的很细，当你碰到这样的问题，google到时，能帮你把问题解决了，这就ok了。另外有些问题我也是不求甚解的，哈。

正文

GMF中，Grid，也就是用来对齐的网格，默认是显示在foreground的，这样网格就会覆盖在你的图形上面，看上去很糟糕。解决办法是在Editor中configureGraphicalViewer()方法添加如下代码

protected void configureGraphicalViewer() {
    super.configureGraphicalViewer();
    DiagramEditorContextMenuProvider provider = new DiagramEditorContextMenuProvider(this, getDiagramGraphicalViewer());
    getDiagramGraphicalViewer().setContextMenu(provider);
    getSite().registerContextMenu(ActionIds.DIAGRAM_EDITOR_CONTEXT_MENU, provider, getDiagramGraphicalViewer());
     
    //ADDED START
    DiagramRootEditPart root = (DiagramRootEditPart) getDiagramGraphicalViewer().getRootEditPart();
    Layer printableLayers = (Layer)root.getLayer(LayerConstants.PRINTABLE_LAYERS);
    Layer gridLayer = (Layer)root.getLayer(LayerConstants.GRID_LAYER);
    if (printableLayers != null && gridLayer != null){
        LayeredPane paneForPrintable = (LayeredPane)printableLayers.getParent();
        LayeredPane paneForGrid = (LayeredPane)gridLayer.getParent();
        if (paneForGrid == paneForPrintable) {
            paneForGrid.removeLayer(LayerConstants.GRID_LAYER);
            paneForGrid.addLayerBefore(gridLayer, LayerConstants.GRID_LAYER, LayerConstants.PRINTABLE_LAYERS);
        }
    }
    //ADDED END
}