btcpayserver/BTCPayServer/Views/Server/Theme.cshtml

@model BTCPayServer.Services.ThemeSettings
@{
    ViewData.SetActivePageAndTitle(ServerNavPages.Theme, "Theme");
}

@section PageFootContent {
    <partial name="_ValidationScriptsPartial" />
}

<h2 class="mb-4">@ViewData["PageTitle"]</h2>

<div class="row">
    <div class="col-lg-6">
        <form method="post">
            <h4 class="mb-3">Custom theme</h4>
            <p>Use the default Light or Dark Themes, or provide a CSS theme file below.</p>
            @if (!ViewContext.ModelState.IsValid)
            {
                <div asp-validation-summary="All" class="text-danger"></div>
            }
            <div class="form-group d-flex align-items-center">
                <input asp-for="CustomTheme" type="checkbox" class="btcpay-toggle me-2" data-bs-toggle="collapse" data-bs-target="#CustomThemeSettings" aria-expanded="@Model.CustomTheme" aria-controls="CustomThemeSettings" />
                <label asp-for="CustomTheme" class="form-label mb-0"></label>
                <span asp-validation-for="CustomTheme" class="text-danger"></span>
            </div>
            <div class="collapse @(Model.CustomTheme ? "show" : "")" id="CustomThemeSettings">
                <div class="form-group">
                    <label asp-for="CustomThemeCssUri" class="form-label"></label>
                    <a href="https://docs.btcpayserver.org/Development/Theme/#1-custom-themes" target="_blank" rel="noreferrer noopener">
                        <span class="fa fa-question-circle-o text-secondary" title="More information..."></span>
                    </a>
                    <input asp-for="CustomThemeCssUri" class="form-control" />
                    <span asp-validation-for="CustomThemeCssUri" class="text-danger"></span>
                </div>
            </div>
            
            <button type="submit" class="btn btn-primary" name="command" value="Save">Save</button>
        </form>
    </div>
</div>