Gracefully handle missing Libpcap on Windows

Issue a message to the user if WinPcap/Npcap is not found.
Delay load Libpcap on Windows, so that if WinPcap/Npcap is not installed,
the main application will still open.

CMakeLists.txt

@@ -234,14 +234,9 @@ target_link_libraries(sACNView PRIVATE ${SACNVIEW_QT_LIBRARIES})
 
 # Link PCap/WinPCap libraries
 target_link_libraries(sACNView PRIVATE ${PCAP_LIBS})
-
-if(WIN32)
-  # Copy WinPCap DLLs
-  foreach(DLLFILE IN LISTS PCAP_LIBS)
-    add_custom_command (TARGET sACNView POST_BUILD
-      COMMAND ${CMAKE_COMMAND} -E copy_if_different
-      $<TARGET_FILE:${DLLFILE}> $<TARGET_FILE_DIR:sACNView>)
-  endforeach()
+if(MSVC)
+    target_link_libraries(sACNView PRIVATE delayimp)
+    target_link_options(sACNView PRIVATE "/DELAYLOAD:wpcap.dll")
 endif()
 
 # Blake2

src/pcap/pcapplayback.cpp

@@ -8,6 +8,11 @@
 #include <QThread>
 #include <QDebug>
 
+#ifdef Q_OS_WIN
+#include <windows.h>
+#include <delayimp.h>
+#endif
+
 PcapPlayback::PcapPlayback(QWidget *parent) :
     QWidget(parent),
     ui(new Ui::PcapPlayback),
@@ -22,6 +27,41 @@ PcapPlayback::~PcapPlayback()
     delete ui;
 }
 
+bool PcapPlayback::foundLibPcap()
+{
+#ifdef Q_OS_WIN
+    const auto checkDelayException = [](int exception_value) {
+        if (exception_value == VcppException(ERROR_SEVERITY_ERROR, ERROR_MOD_NOT_FOUND)
+            || exception_value == VcppException(ERROR_SEVERITY_ERROR, ERROR_PROC_NOT_FOUND)) {
+            return EXCEPTION_EXECUTE_HANDLER;
+        }
+        return EXCEPTION_CONTINUE_SEARCH;
+    };
+
+    __try {
+        HRESULT hr = __HrLoadAllImportsForDll("wpcap.dll");
+        if (FAILED(hr)) {
+            return false;
+        }
+    } __except (checkDelayException(GetExceptionCode())) {
+        return false;
+    }
+#endif
+    return true;
+}
+
+std::string PcapPlayback::getLibPcapVersion()
+{
+    if (foundLibPcap()) {
+        const char *version = pcap_lib_version();
+        return std::string(version);
+    }
+    else
+    {
+        return {};
+    }
+}
+
 void PcapPlayback::openThread()
 {
     if (sender) {
@@ -59,6 +99,18 @@ void PcapPlayback::playbackThreadClosed()
 
 void PcapPlayback::on_btnOpen_clicked()
 {
+    if (!foundLibPcap()) {
+        QMessageBox::critical(
+            this,
+            tr("Pcap not found"),
+#ifdef Q_OS_WIN
+            tr("Pcap not found, please install Wireshark"));
+#else
+            tr("Libpcap not found, please install"));
+#endif
+        return;
+    }
+
     /* Select file to open */
     QString fileName = QFileDialog::getOpenFileName(this,
             tr("Open Capture"),

src/pcap/pcapplayback.h

@@ -16,6 +16,9 @@ class PcapPlayback : public QWidget
     explicit PcapPlayback(QWidget *parent = 0);
     ~PcapPlayback();
 
+    static bool foundLibPcap();
+    static std::string getLibPcapVersion();
+
 private slots:
     void on_btnOpen_clicked();
     void on_btnStartPause_clicked();

src/ui/aboutdialog.cpp

@@ -16,7 +16,7 @@
 #include "aboutdialog.h"
 #include "ui_aboutdialog.h"
 #include "consts.h"
-#include <pcap.h>
+#include "pcap/pcapplayback.h"
 #include "translations/translations.h"
 
 #include <QTimer>
@@ -73,12 +73,15 @@ aboutDialog::aboutDialog(QWidget* parent) :
   }
 
   {
-    const char* libpcap = pcap_lib_version();
-    ui->lblLibs->setText(
-      tr("<p>This application uses <a href=\"https://www.tcpdump.org/\">libpcap</a><br>"
-        "%1<br>"
-        "Licensed under the <a href=\"https://opensource.org/licenses/BSD-3-Clause\">The 3-Clause BSD License</a></p>")
-      .arg(QString::fromUtf8(libpcap)));
+    ui->lblLibs->clear();
+    if (PcapPlayback::foundLibPcap())
+    {
+        ui->lblLibs->setText(
+          tr("<p>This application uses <a href=\"https://www.tcpdump.org/\">libpcap</a><br>"
+            "%1<br>"
+            "Licensed under the <a href=\"https://opensource.org/licenses/BSD-3-Clause\">The 3-Clause BSD License</a></p>")
+              .arg(QString::fromStdString(PcapPlayback::getLibPcapVersion())));
+    }
     ui->lblLibs->setText(ui->lblLibs->text() +
       tr("<p>This application uses <a href=\"https://www.blake2.net/\">BLAKE2</a><br>"
         "Licensed under the <a href=\"https://creativecommons.org/publicdomain/zero/1.0/\">Creative Commons Zero v1.0 Universal</a></p>"));