Fixed setting of default app in Properties dialog

GLib has a weird problem. On the one hand, `g_app_info_set_as_default_for_type()` writes to `~/.config/mimeapps.list`. On the other hand, the DE-specific list — e.g., `~/.config/lxqt-mimeapps.list` in LXQt — has priority over it and GLib respects that. Therefore, if the latter exists and contains some default apps, `g_app_info_set_as_default_for_type()` could not change them.

This patch solves the problem by adding a utility function that sets the default app directly inside the DE-specific list.

Also, see lxqt/libqtxdg#219.

src/appchooserdialog.cpp

@@ -20,6 +20,7 @@
 
 #include "appchooserdialog.h"
 #include "ui_app-chooser-dialog.h"
+#include "utilities.h"
 #include <QPushButton>
 #include <gio/gdesktopappinfo.h>
 #include <glib/gstdio.h>
@@ -245,7 +246,7 @@ void AppChooserDialog::accept() {
 #endif
             /* if need to set default */
             if(ui->setDefault->isChecked()) {
-                g_app_info_set_as_default_for_type(selectedApp_.get(), mimeType_->name(), nullptr);
+                setDefaultAppForType(selectedApp_, mimeType_);
             }
         }
     }

src/filepropsdialog.cpp

@@ -439,7 +439,7 @@ void FilePropsDialog::accept() {
     // applications
     if(mimeType && ui->openWith->isChanged()) {
         auto currentApp = ui->openWith->selectedApp();
-        g_app_info_set_as_default_for_type(currentApp.get(), mimeType->name(), nullptr);
+        setDefaultAppForType(currentApp, mimeType);
     }
 
     // check if chown or chmod is needed

src/utilities.cpp

@@ -26,6 +26,7 @@
 #include <QList>
 #include <QStringBuilder>
 #include <QMessageBox>
+#include <QStandardPaths>
 #include "fileoperation.h"
 #include <QEventLoop>
 
@@ -193,6 +194,38 @@ bool renameFile(std::shared_ptr<const Fm::FileInfo> file, QWidget* parent) {
     return true;
 }
 
+void setDefaultAppForType(const Fm::GAppInfoPtr app, std::shared_ptr<const Fm::MimeType> mimeType)
+{
+    // NOTE: "g_app_info_set_as_default_for_type()" writes to "~/.config/mimeapps.list"
+    // but we want to set the default app only for the current DE (e.g., LXQt).
+    // More importantly, if the DE-specific list already exists and contains some
+    // default apps, it will have priority over "~/.config/mimeapps.list" and so,
+    // "g_app_info_set_as_default_for_type()" could not change those apps.
+
+    if(app == nullptr || mimeType == nullptr) {
+        return;
+    }
+
+    // first find the DE's mimeapps list file
+    QByteArray mimeappsList = "mimeapps.list";
+    QList<QByteArray> desktopsList = qgetenv("XDG_CURRENT_DESKTOP").toLower().split(':');
+    if(!desktopsList.isEmpty()) {
+        mimeappsList = desktopsList.at(0) + "-" + mimeappsList;
+    }
+    QString configDir = QStandardPaths::writableLocation(QStandardPaths::ConfigLocation);
+    auto mimeappsListPath = CStrPtr(g_build_filename(configDir.toUtf8().constData(),
+                                                     mimeappsList.constData(),
+                                                     nullptr));
+
+    // set the default app in the DE's mimeapps list
+    const char* desktop_id = g_app_info_get_id(app.get());
+    GKeyFile* kf = g_key_file_new();
+    g_key_file_load_from_file(kf, mimeappsListPath.get(), G_KEY_FILE_NONE, nullptr);
+    g_key_file_set_string(kf, "Default Applications", mimeType->name(), desktop_id);
+    g_key_file_save_to_file(kf, mimeappsListPath.get(), nullptr);
+    g_key_file_free(kf);
+}
+
 // templateFile is a file path used as a template of the new file.
 void createFileOrFolder(CreateFileType type, FilePath parentDir, const TemplateItem* templ, QWidget* parent) {
     QString defaultNewName;

src/utilities.h

@@ -55,6 +55,8 @@ LIBFM_QT_API bool changeFileName(const Fm::FilePath& path, const QString& newNam
 
 LIBFM_QT_API bool renameFile(std::shared_ptr<const Fm::FileInfo> file, QWidget* parent = nullptr);
 
+LIBFM_QT_API void setDefaultAppForType(const Fm::GAppInfoPtr app, std::shared_ptr<const Fm::MimeType> mimeType);
+
 enum CreateFileType {
     CreateNewFolder,
     CreateNewTextFile,