why does dnd_drop_zone overwrite frame colors?

[j-n-f]

I was attempting to create a grid of drag-and-drop zones, and I was setting it up like this:

let drop_frame = egui::Frame::default()
    .fill(egui::Color32::BLACK);
ui.dnd_drop_zone::<Location, ()>(drop_frame, |ui| { /* ... */ })

When I start dragging items around, I see that it overwrote my frame color.

Looking at the documentation it says:

The given frame is used for its margins, but it color is ignored.

I tried:

let drop_frame = egui::Frame::default()
    .fill(egui::Color32::BLACK);
ui.dnd_drop_zone::<Location, ()>(drop_frame, |ui| {
    ui.visuals_mut().widgets.inactive.bg_fill = egui::Color32::BLACK;
    /* ... */
})

But the issue persists because it looks like add_contents gets called before the style override happens (https://github.com/emilk/egui/blob/emilk/release-0.27.2/crates/egui/src/ui.rs#L2249-L2261). It seems like this leaves no way to change the color of the frame.

Is there a reason it was done like this?

I'm starting to think maybe I just need to create a context where inactive.bg_fill is temporarily set to egui::Color32::TRANSPARENT, and then place that inside a frame with the color I want, but this seems like a really tedious workaround.

[j-n-f]

The workaround looks like this:

// Layout used to create an isolated context for style changes. May be a better way to do this.
ui.with_layout(egui::Layout::default(), |ui| {
    // when `dnd_drop_zone` overrides color, it will use this
    ui.visuals_mut().widgets.inactive.bg_fill = egui::Color32::TRANSPARENT;

    // this will be the displayed color of the drop zone
    let color_frame = egui::Frame::default().fill(egui::Color32::BLACK)
        .show(ui, |ui| {
            let drop_frame = egui::Frame::default();
            // We have control over drop zone color
            ui.dnd_drop_zone::<Location, ()>(drop_frame, |ui| { /* ... */ })
        });
});