EnvelopeGenerator/EnvelopeGenerator.ReceiverUI/Pages/ReportViewer.razor

@page "/reportviewer/"
@using System.Drawing
@using DevExpress.Drawing
@using DevExpress.Utils
@using DevExpress.XtraPrinting
@using DevExpress.XtraPrinting.Drawing
@using DevExpress.XtraReports.UI;
@using EnvelopeGenerator.ReceiverUI.Services;
@inject IJSRuntime JSRuntime
@inject InMemoryReportStorageWebExtension ReportStorage

<link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.min.css" rel="stylesheet" />
<link href="_content/DevExpress.Blazor.Reporting.Viewer/css/dx-blazor-reporting-components.bs5.css" rel="stylesheet" />

<div class="card m-3">
    <div class="card-body">
        <h5 class="card-title">Unterschrift</h5>
        <p class="card-text text-muted mb-2">Bitte fuegen Sie vor dem PDF-Export Ihre Unterschrift in das Feld unten ein.</p>
        <canvas id="receiver-signature-pad" width="420" height="150" class="border rounded bg-white w-100" style="max-width: 420px; touch-action: none;"></canvas>
        @if(!string.IsNullOrWhiteSpace(SignatureValidationMessage)) {
            <div class="text-danger mt-2">@SignatureValidationMessage</div>
        }
        <div class="mt-3 d-flex gap-2 flex-wrap">
            <button class="btn btn-outline-secondary" @onclick="ClearSignatureAsync">Unterschrift loeschen</button>
            <button class="btn btn-primary" @onclick="ApplySignatureAsync">Unterschrift zum Bericht hinzufuegen</button>
            <button class="btn btn-success" disabled="@(!SignatureApplied)" @onclick="ExportSignedPdfAsync">Signiertes PDF exportieren</button>
        </div>
    </div>
</div>

@if(Report is not null) {
    <DxReportViewer @key="ViewerKey" @ref="reportViewer" Report="Report" RootCssClasses="w-100 h-100" />
}

@code {
    DxReportViewer reportViewer;
    XtraReport? Report;
    bool SignatureApplied;
    string? SignatureValidationMessage;
    int ViewerKey;

    protected override async Task OnInitializedAsync() {
        Report = CreateReportInstance();

        await Task.CompletedTask;
    }

    protected override async Task OnAfterRenderAsync(bool firstRender) {
        if(firstRender)
            await JSRuntime.InvokeVoidAsync("receiverSignature.initialize", "receiver-signature-pad");
    }

    async Task ClearSignatureAsync() {
        await JSRuntime.InvokeVoidAsync("receiverSignature.clear", "receiver-signature-pad");
        SignatureApplied = false;
        SignatureValidationMessage = null;
        Report = CreateReportInstance();
        ViewerKey++;
    }

    async Task ApplySignatureAsync() {
        var signatureDataUrl = await JSRuntime.InvokeAsync<string?>("receiverSignature.getDataUrl", "receiver-signature-pad");

        if(string.IsNullOrWhiteSpace(signatureDataUrl)) {
            SignatureApplied = false;
            SignatureValidationMessage = "Die Unterschrift ist fuer den PDF-Export erforderlich.";
            return;
        }

        SignatureValidationMessage = null;
        Report = CreateSignedReportInstance(signatureDataUrl);
        SignatureApplied = true;
        ViewerKey++;
    }

    async Task ExportSignedPdfAsync() {
        if(!SignatureApplied || Report is null) {
            SignatureValidationMessage = "Bitte fuegen Sie die Unterschrift zuerst zum Bericht hinzu.";
            return;
        }

        await reportViewer.ExportToAsync(ExportFormat.Pdf);
    }

    XtraReport CreateReportInstance() {
        return ReportStorage.TryGetReport("LargeDatasetReport", out var savedReport)
            ? savedReport
            : PredefinedReports.ReportsFactory.GetReport("LargeDatasetReport");
    }

    XtraReport CreateSignedReportInstance(string signatureDataUrl) {
        var report = CreateReportInstance();
        AddSignature(report, signatureDataUrl);
        return report;
    }

    void ApplySignatureToReport(string signatureDataUrl) {
        Report ??= ReportStorage.TryGetReport("LargeDatasetReport", out var savedReport)
            ? savedReport
            : PredefinedReports.ReportsFactory.GetReport("LargeDatasetReport");

        AddSignature(Report, signatureDataUrl);
    }

    static void AddSignature(XtraReport report, string signatureDataUrl) {
        var imageBytes = Convert.FromBase64String(signatureDataUrl[(signatureDataUrl.IndexOf(',') + 1)..]);
        using var imageStream = new MemoryStream(imageBytes);
        var imageSource = new ImageSource(DXImage.FromStream(imageStream));
        var bottomMargin = report.Bands.OfType<BottomMarginBand>().FirstOrDefault();

        if(bottomMargin is null) {
            bottomMargin = new BottomMarginBand();
            report.Bands.Add(bottomMargin);
        }

        bottomMargin.HeightF = Math.Max(bottomMargin.HeightF, 120F);
        RemoveExistingSignature(bottomMargin);

        var signatureLabel = new XRLabel {
            Name = "receiverSignatureLabel",
            Text = $"Empfaengerunterschrift - {DateTime.Now:g}",
            BoundsF = new RectangleF(390F, 6F, 230F, 18F),
            Font = new DXFont("Open Sans", 8F, DXFontStyle.Bold),
            ForeColor = System.Drawing.Color.FromArgb(73, 80, 87),
            TextAlignment = TextAlignment.MiddleLeft
        };

        var signature = new XRPictureBox {
            Name = "receiverSignatureImage",
            ImageSource = imageSource,
            BoundsF = new RectangleF(390F, 28F, 230F, 70F),
            Sizing = ImageSizeMode.ZoomImage,
            Borders = BorderSide.Bottom,
            BorderColor = System.Drawing.Color.FromArgb(73, 80, 87)
        };

        bottomMargin.Controls.AddRange(new XRControl[] { signatureLabel, signature });
    }

    static void RemoveExistingSignature(BottomMarginBand bottomMargin) {
        var controls = bottomMargin.Controls
            .Cast<XRControl>()
            .Where(control => control.Name is "receiverSignatureLabel" or "receiverSignatureImage")
            .ToArray();

        foreach(var control in controls)
            bottomMargin.Controls.Remove(control);
    }
}