Detect relocatable Qt build

src/appimagetool/appdirtool.go

@@ -311,7 +311,6 @@ func AppDirDeploy(path string) {
 	handleNvidia()
 
 	for _, lib := range allELFs {
-
 		deployElf(lib, appdir, err)
 		patchRpathsInElf(appdir, libraryLocationsInAppDir, lib)
 
@@ -1257,22 +1256,16 @@ func handleQt(appdir helpers.AppDir, qtVersion int) {
 
 	if qtVersion >= 5 {
 
-		// Actually the libQt5Core.so.5/libQt6Core.so.6 contains (always?) qt_prfxpath=... which tells us the location in which 'plugins/' is located
+		// When libQt5Core.so.5/libQt6Core.so.6 is built non-relocatable, it contains qt_prfxpath=...
+		// This tells us the path in which 'plugins/' is located
 
 		library, err := findLibrary(fmt.Sprintf("libQt%dCore.so.%d", qtVersion, qtVersion))
 		if err != nil {
 			helpers.PrintError(fmt.Sprintf("Could not find libQt%dCore.so.%d", qtVersion, qtVersion), err)
 			os.Exit(1)
 		}
 
-		f, err := os.Open(library)
-		defer f.Close()
-		if err != nil {
-			helpers.PrintError(fmt.Sprintf("Could not open libQt%dCore.so.%d", qtVersion, qtVersion), err)
-			os.Exit(1)
-		}
-
-		qtPrfxpath := getQtPrfxpath(f, err, qtVersion)
+		qtPrfxpath := getQtPrfxpath(library, qtVersion)
 
 		if qtPrfxpath == "" {
 			log.Println("Got empty qtPrfxpath, exiting")
@@ -1320,8 +1313,8 @@ func handleQt(appdir helpers.AppDir, qtVersion int) {
 			}
 		}
 
-        // platform plugin context - required for special characters - included if libQt5Gui.so.5/libQt6.Gui.so.6 is included
-        // similar to https://github.com/probonopd/linuxdeployqt/blob/42e51ea7c7a572a0aa1a21fc47d0f80032809d9d/tools/linuxdeployqt/shared.cpp#L1229
+		// platform plugin context - required for special characters - included if libQt5Gui.so.5/libQt6.Gui.so.6 is included
+		// similar to https://github.com/probonopd/linuxdeployqt/blob/42e51ea7c7a572a0aa1a21fc47d0f80032809d9d/tools/linuxdeployqt/shared.cpp#L1229
 		for _, lib := range allELFs {
 			if strings.HasSuffix(lib, fmt.Sprintf("libQt%dGui.so.%d", qtVersion, qtVersion)) == true {
 				if helpers.Exists(qtPrfxpath + "/plugins/platforminputcontexts/") {
@@ -1495,7 +1488,27 @@ func handleQt(appdir helpers.AppDir, qtVersion int) {
 	}
 }
 
-func getQtPrfxpath(f *os.File, err error, qtVersion int) string {
+func getQtPrfxpath(library string, qtVersion int) string {
+	// Some notes on Qt behavior:
+	// https://doc.qt.io/qt-5/qt-conf.html
+	// https://doc.qt.io/qt-6/qt-conf.html
+	//     qt.conf can be used to override default hardcoded paths
+	//     qt6.conf can be used when Qt6 and Qt5 are deployed side-by-side
+
+	// https://doc.qt.io/qt-5/qlibraryinfo.html
+	// https://doc.qt.io/qt-6/qlibraryinfo.html
+	//     Query paths at runtime using QLibraryInfo::location ( Qt5 ) and QLibraryInfo::path ( Qt6 )
+
+	// Qt source files relevant to this:
+	// qtbase/cmake/QtBuildRepoHelpers.cmake -- Configures prerequisites for QT_BUILD_INTERNALS_RELOCATABLE_INSTALL_PREFIX
+	// qtbase/cmake/QtBuildInternalsExtra.cmake.in -- Configures QT_BUILD_INTERNALS_RELOCATABLE_INSTALL_PREFIX ( relative path to Qt%d directory for relocatable library )
+	// qtbase/cmake/QtQmakeHelpers.cmake -- has function qt_generate_qconfig_cpp
+	// qtbase/src/corelib/CMakeLists.txt -- Configures qconfig.cpp.in
+	// qtbase/src/corelib/global/qconfig.cpp.in -- string constant with qt_prfxpath=
+	// qtbase/src/corelib/global/qlibraryinfo.h -- Class that handles Qt paths
+	// qtbase/src/corelib/global/qlibraryinfo.cpp -- "
+
+	// TODO IDEA: Use AppRun to generate qt.conf at application start?
 
 	// If the user has set $QTDIR or $QT_ROOT_DIR, use that instead of the one from qt_prfxpath in the library
 	qtPrefixEnv := os.Getenv("QTDIR")
@@ -1507,6 +1520,13 @@ func getQtPrfxpath(f *os.File, err error, qtVersion int) string {
 	    return qtPrefixEnv
 	}
 
+	f, err := os.Open(library)
+	if err != nil {
+		helpers.PrintError(fmt.Sprintf("Could not open libQt%dCore.so.%d", qtVersion, qtVersion), err)
+		os.Exit(1)
+	}
+	defer f.Close()
+
 	f.Seek(0, 0)
 	// Search from the beginning of the file
 	search := []byte("qt_prfxpath=")
@@ -1516,21 +1536,33 @@ func getQtPrfxpath(f *os.File, err error, qtVersion int) string {
 	// From the current location in the file, search to the next 0x00 byte
 	f.Seek(offset, 0)
 	length := ScanFile(f, search)
-	log.Println("Length of value of qt_prfxpath:", length)
-	// Now that we know where in the file the information is, go get it
-	f.Seek(offset, 0)
-	buf := make([]byte, length)
-	// Make a buffer that is exactly as long as the range we want to read
-	_, err = io.ReadFull(f, buf)
-	if err != nil {
-		helpers.PrintError("Unable to read qt_prfxpath", err)
-		os.Exit(1)
-	}
-	qt_prfxpath := strings.TrimSpace(string(buf))
-	log.Println("qt_prfxpath:", qt_prfxpath)
-	if qt_prfxpath == "" {
-		log.Println("Could not get qt_prfxpath")
-		return ""
+
+	var qt_prfxpath = ""
+
+	// When length is 0, Qt has been built as relocatable
+	if length == 0 {
+		// Directory should be in ../Qt${qtVersion}
+		// TODO: Check if this is true for relocatable binaries in Qt5
+		qt_prfxpath = filepath.Dir(library) + fmt.Sprintf("/../Qt%d", qtVersion)
+		log.Println("Using Qt prefix path:", qt_prfxpath)
+	} else {
+		log.Println("Length of value of qt_prfxpath:", length)
+
+		// Now that we know where in the file the information is, go get it
+		f.Seek(offset, 0)
+		buf := make([]byte, length)
+		// Make a buffer that is exactly as long as the range we want to read
+		_, err = io.ReadFull(f, buf)
+		if err != nil {
+			helpers.PrintError("Unable to read qt_prfxpath", err)
+			os.Exit(1)
+		}
+		qt_prfxpath = strings.TrimSpace(string(buf))
+		log.Println("qt_prfxpath:", qt_prfxpath)
+		if qt_prfxpath == "" {
+			log.Println("Could not get qt_prfxpath")
+			return ""
+		}
 	}
 
 	// Special case: