--- xpdf-qt/XpdfViewer.cc.orig	2024-02-08 04:32:41.000000000 +0800
+++ xpdf-qt/XpdfViewer.cc	2024-07-28 11:58:15.000000000 +0800
@@ -49,6 +49,9 @@
 #include <QToolBar>
 #include <QTreeView>
 #include <QVBoxLayout>
+#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
+#include <QDesktopWidget>
+#endif
 #include "GString.h"
 #include "GList.h"
 #include "GlobalParams.h"
@@ -883,7 +886,11 @@
   }
 
   QSize hint = sizeHint();
+#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
   QRect screen = QGuiApplication::primaryScreen()->availableGeometry();
+#else
+  QRect screen = QApplication::desktop()->availableGeometry();
+#endif
   int w = hint.width();
   int h = hint.height();
   if (w > screen.width() - 60) {
@@ -2794,6 +2801,7 @@
 
   // for historical reasons xpdf uses X11 button numbering for mouse
   // wheel events
+#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
   QPoint delta = e->angleDelta();
   if (delta.y() > 0) {
     keyCode = xpdfKeyCodeMousePress4;
@@ -2804,8 +2812,12 @@
   } else if (delta.x() < 0) {
     keyCode = xpdfKeyCodeMousePress7;
   } else {
+#endif
     return;
+#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
   }
+#endif
+
   if ((cmds = globalParams->getKeyBinding(keyCode,
 					  getModifiers(e->modifiers()),
 					  getContext(e->modifiers())))) {

--- xpdf-qt/XpdfWidget.cc.orig	2024-02-08 04:32:41.000000000 +0800
+++ xpdf-qt/XpdfWidget.cc	2024-07-28 11:56:14.000000000 +0800
@@ -1282,7 +1282,7 @@
     } else if (color == pdfImageColorGray) {
       mode = splashModeMono8;
       paperColor[0] = 0xff;
-      format = QImage::Format_Grayscale8;
+      format = QImage::Format_Indexed8;
     } else {
       mode = splashModeRGB8;
       paperColor[0] = paperColor[1] = paperColor[2] = 0xff;
@@ -1388,7 +1388,7 @@
     } else if (color == pdfImageColorGray) {
       mode = splashModeMono8;
       paperColor[0] = 0xff;
-      format = QImage::Format_Grayscale8;
+      format = QImage::Format_Indexed8;
     } else {
       mode = splashModeRGB8;
       paperColor[0] = paperColor[1] = paperColor[2] = 0xff;
@@ -2163,7 +2163,9 @@
   lastMousePressTime[1] = lastMousePressTime[2];
   lastMousePressX[2] = e->pos().x();
   lastMousePressY[2] = e->pos().y();
+#if QT_VERSION >= 0x050000
   lastMousePressTime[2] = e->timestamp();
+#endif
   lastMouseEventWasPress = true;
   if (!mousePassthrough) {
     x = (int)(e->pos().x() * scaleFactor);
@@ -2202,6 +2204,7 @@
   // single clicks just have to be "nearby"
   ulong maxTime = (ulong)QApplication::doubleClickInterval();
   int maxDistance = QApplication::startDragDistance();
+#if QT_VERSION >= 0x050000
   if (e->timestamp() - lastMousePressTime[0] < 2 * maxTime &&
       abs(e->pos().x() - lastMousePressX[0])
         + abs(e->pos().y() - lastMousePressY[0]) <= maxDistance) {
@@ -2220,6 +2223,12 @@
 	       + abs(e->pos().y() - lastMousePressY[2]) <= maxDistance) {
     emit mouseClick(e);
   }
+#else
+    if (abs(e->pos().x() - lastMousePressX[2])
+	       + abs(e->pos().y() - lastMousePressY[2]) <= maxDistance) {
+    emit mouseClick(e);
+  }
+#endif
 }
 
 void XpdfWidget::mouseMoveEvent(QMouseEvent *e) {

--- xpdf-qt/QtPDFCore.cc.orig	2024-02-08 04:32:41.000000000 +0800
+++ xpdf-qt/QtPDFCore.cc	2024-07-28 11:59:05.000000000 +0800
@@ -24,6 +24,9 @@
 #include <QStyle>
 #include <QUrl>
 #include <QWidget>
+#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
+#include <QDesktopWidget>
+#endif
 #include "gmem.h"
 #include "gmempp.h"
 #include "gfile.h"
@@ -98,10 +101,10 @@
 }
 
 double QtPDFCore::computeScaleFactor() {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
   // get Qt's HiDPI scale factor
   QGuiApplication *app = (QGuiApplication *)QGuiApplication::instance();
   QScreen *screen = app->primaryScreen();
-#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
   return screen->devicePixelRatio();
 #else
   return 1;
@@ -109,9 +112,13 @@
 }
 
 int QtPDFCore::computeDisplayDpi() {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
   QGuiApplication *app = (QGuiApplication *)QGuiApplication::instance();
   QScreen *screen = app->primaryScreen();
   return (int)(screen->logicalDotsPerInch() * computeScaleFactor());
+#else
+  return (int)(qApp->desktop()->logicalDpiX() * computeScaleFactor());
+#endif
 }
 
 //------------------------------------------------------------------------

--- xpdf-qt/XpdfWidgetPrint.cc.orig	2024-02-08 04:32:41.000000000 +0800
+++ xpdf-qt/XpdfWidgetPrint.cc	2024-07-28 11:54:37.000000000 +0800
@@ -62,7 +62,11 @@
   QPrinter::ColorMode colorMode;
   QSize paperSize;
   QPrinter::PaperSource paperSource;
+#if QT_VERSION >= 0x050000
   QPageLayout::Orientation pageOrientation;
+#else
+  QPrinter::Orientation pageOrientation;
+#endif
   FILE *f;
   GBool deletePDFFile;
   int startPage, endPage, pg, i;
@@ -117,9 +121,14 @@
   //--- get other parameters
 
   colorMode = prt->colorMode();
+#if QT_VERSION >= 0x050000
   paperSize = prt->pageLayout().pageSize().sizePoints();
   paperSource = prt->paperSource();
   pageOrientation = prt->pageLayout().orientation();
+#else
+  paperSource = prt->paperSource();
+  pageOrientation = prt->orientation();
+#endif
 
   //--- create the Session and PrintSettings
 
@@ -232,7 +241,7 @@
   //--- set page orientation
 
   PMGetAdjustedPaperRect(pageFormat, &paperRect);
-  if (pageOrientation == QPageLayout::Landscape) {
+  if (pageOrientation == QPrinter::Landscape) {
     PMSetOrientation(pageFormat, kPMLandscape, kPMUnlocked);
     paperRect2 = CGRectMake(paperRect.top,
 			    paperRect.left,