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I've got a layer with nodes features on which I may want to display two images, a main one and a background one. This page : shows what I want: the shadow is under the golden item (it's more obvious when we move the png with a dev tool). For this, they use:

// Set the external graphic and background graphic images.
externalGraphic: "../img/marker-gold.png",
backgroundGraphic: "./img/marker_shadow.png",

// Makes sure the background graphic is placed correctly relative
// to the external graphic.
backgroundXOffset: 0,
backgroundYOffset: -7,

// Set the z-indexes of both graphics to make sure the background
// graphics stay in the background (shadows on top of markers looks
// odd; let's not do that).
graphicZIndex: MARKER_Z_INDEX, //11
backgroundGraphicZIndex: SHADOW_Z_INDEX, //10

Obviously it's not about real CSS z-index since the DOM element both have a z-index: auto in the end. But whatever, I wanna try this myself (not at the layer construction but afterwards):

style["backgroundGraphic"] = './img/marker-shadow.png';
style["externalGraphic"] ='./img/marker-gold.png';
style['graphicZIndex'] = 1;
style['backgroundGraphicZIndex'] = style['graphicZIndex']-1;

The images are displayed. But while one could think the backgroundGraphic would automatically go under the externalGraphic, the contrary actually happens. Fine, I'll just add the z-index thing:

style['graphicZIndex'] = 1;
style['backgroundGraphicZIndex'] = style['graphicZIndex']-1;

But it changes absolutely nothing. How do I get my background underneath?

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