Merge #17826: qt: Log Qt related info

a004673c54d4c015775e0baced21f3fa961bf754 qt: Add LogQtInfo() function (Hennadii Stepanov)

Pull request description:

  This PR adds some info to `debug.log` I found useful for testing (e.g., on Wayland) and debugging issues like #17153:

  ```
  $ ./src/qt/bitcoin-qt -printtoconsole | head -n 6
  2020-01-04T14:57:40Z [main] Bitcoin Core version v0.19.99.0-0df287f4e (release build)
  2020-01-04T14:57:40Z [main] InitParameterInteraction: parameter interaction: -externalip set -> setting -discover=0
  2020-01-04T14:57:40Z [main] Qt 5.9.5 (dynamic), plugin=xcb (dynamic)
  2020-01-04T14:57:40Z [main] System: Linux Mint 19.3, x86_64-little_endian-lp64
  2020-01-04T14:57:40Z [main] Screen: HDMI-1 1600x1200, pixel ratio=1.0
  2020-01-04T14:57:40Z [main] Assuming ancestors of block 00000000000000b7ab6ce61eb6d571003fbe5fe892da4c9b740c49a07542462d have valid signatures.
  ```

ACKs for top commit:
  laanwj:
    ACK a004673c54d4c015775e0baced21f3fa961bf754

Tree-SHA512: 496bcfd4870a2730eab92b96b3e74989a7904b21369c372b6d4368f4ca2c141e2fdc1348a1fdd18cb68bb144dcea01d3023bb782f9d030e330c187f6a5a1a082

src/qt/dash.cpp

@@ -587,6 +587,7 @@ int GuiMain(int argc, char* argv[])
     qInstallMessageHandler(DebugMessageHandler);
     // Allow parameter interaction before we create the options model
     app.parameterSetup();
+    GUIUtil::LogQtInfo();
     // Load custom application fonts and setup font management
     if (!GUIUtil::loadFonts()) {
         QMessageBox::critical(0, PACKAGE_NAME,

src/qt/guiutil.cpp

@@ -53,17 +53,23 @@
 #include <QFont>
 #include <QFontDatabase>
 #include <QFontMetrics>
+#include <QGuiApplication>
 #include <QKeyEvent>
 #include <QLineEdit>
+#include <QList>
 #include <QMouseEvent>
 #include <QPointer>
 #include <QProgressDialog>
+#include <QScreen>
 #include <QSettings>
+#include <QSize>
+#include <QString>
 #include <QTextDocument> // for Qt::mightBeRichText
 #include <QThread>
 #include <QTimer>
 #include <QUrlQuery>
 #include <QVBoxLayout>
+#include <QtGlobal>
 
 #if defined(Q_OS_MAC)
 
@@ -1876,4 +1882,23 @@ int TextWidth(const QFontMetrics& fm, const QString& text)
 #endif
 }
 
+void LogQtInfo()
+{
+#ifdef QT_STATIC
+    const std::string qt_link{"static"};
+#else
+    const std::string qt_link{"dynamic"};
+#endif
+#ifdef QT_STATICPLUGIN
+    const std::string plugin_link{"static"};
+#else
+    const std::string plugin_link{"dynamic"};
+#endif
+    LogPrintf("Qt %s (%s), plugin=%s (%s)\n", qVersion(), qt_link, QGuiApplication::platformName().toStdString(), plugin_link);
+    LogPrintf("System: %s, %s\n", QSysInfo::prettyProductName().toStdString(), QSysInfo::buildAbi().toStdString());
+    for (const QScreen* s : QGuiApplication::screens()) {
+        LogPrintf("Screen: %s %dx%d, pixel ratio=%.1f\n", s->name().toStdString(), s->size().width(), s->size().height(), s->devicePixelRatio());
+    }
+}
+
 } // namespace GUIUtil

src/qt/guiutil.h

@@ -475,6 +475,11 @@ namespace GUIUtil
      * In Qt 5.11 the QFontMetrics::horizontalAdvance() was introduced.
      */
     int TextWidth(const QFontMetrics& fm, const QString& text);
+
+    /**
+     * Writes to debug.log short info about the used Qt and the host system.
+     */
+    void LogQtInfo();
 } // namespace GUIUtil
 
 #endif // BITCOIN_QT_GUIUTIL_H