Split GTK integration into a singleton

Telegram/SourceFiles/platform/linux/linux_gtk_integration_dummy.cpp

@@ -0,0 +1,74 @@
+/*
+This file is part of Telegram Desktop,
+the official desktop application for the Telegram messaging service.
+
+For license and copyright information please follow this link:
+https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
+*/
+#include "platform/linux/linux_gtk_integration.h"
+
+namespace Platform {
+namespace internal {
+
+GtkIntegration::GtkIntegration() {
+}
+
+GtkIntegration *GtkIntegration::Instance() {
+	return nullptr;
+}
+
+void GtkIntegration::load() {
+}
+
+bool GtkIntegration::loaded() const {
+	return false;
+}
+
+bool GtkIntegration::checkVersion(uint major, uint minor, uint micro) const {
+	return false;
+}
+
+std::optional<bool> GtkIntegration::getBoolSetting(
+		const QString &propertyName) const {
+	return std::nullopt;
+}
+
+std::optional<int> GtkIntegration::getIntSetting(
+		const QString &propertyName) const {
+	return std::nullopt;
+}
+
+std::optional<QString> GtkIntegration::getStringSetting(
+		const QString &propertyName) const {
+	return std::nullopt;
+}
+
+bool GtkIntegration::fileDialogSupported() const {
+	return false;
+}
+
+bool GtkIntegration::useFileDialog(FileDialogType type) const {
+	return false;
+}
+
+bool GtkIntegration::getFileDialog(
+		QPointer<QWidget> parent,
+		QStringList &files,
+		QByteArray &remoteContent,
+		const QString &caption,
+		const QString &filter,
+		FileDialogType type,
+		QString startFile) const {
+	return false;
+}
+
+bool GtkIntegration::showOpenWithDialog(const QString &filepath) const {
+	return false;
+}
+
+QImage GtkIntegration::getImageFromClipboard() const {
+	return {};
+}
+
+} // namespace internal
+} // namespace Platform