Split GTK integration into a singleton

Telegram/SourceFiles/platform/linux/linux_gtk_integration.h

@@ -0,0 +1,59 @@
+/*
+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
+*/
+#pragma once
+
+#include "core/file_utilities.h"
+
+namespace Platform {
+namespace internal {
+
+inline constexpr auto kDisableGtkIntegration = "TDESKTOP_DISABLE_GTK_INTEGRATION"_cs;
+
+class GtkIntegration {
+public:
+	static GtkIntegration *Instance();
+
+	void load();
+	[[nodiscard]] bool loaded() const;
+	[[nodiscard]] bool checkVersion(
+		uint major,
+		uint minor,
+		uint micro) const;
+
+	[[nodiscard]] std::optional<bool> getBoolSetting(
+		const QString &propertyName) const;
+
+	[[nodiscard]] std::optional<int> getIntSetting(
+		const QString &propertyName) const;
+
+	[[nodiscard]] std::optional<QString> getStringSetting(
+		const QString &propertyName) const;
+
+	using FileDialogType = ::FileDialog::internal::Type;
+	[[nodiscard]] bool fileDialogSupported() const;
+	[[nodiscard]] bool useFileDialog(
+		FileDialogType type = FileDialogType::ReadFile) const;
+	[[nodiscard]] bool getFileDialog(
+		QPointer<QWidget> parent,
+		QStringList &files,
+		QByteArray &remoteContent,
+		const QString &caption,
+		const QString &filter,
+		FileDialogType type,
+		QString startFile) const;
+	
+	[[nodiscard]] bool showOpenWithDialog(const QString &filepath) const;
+
+	[[nodiscard]] QImage getImageFromClipboard() const;
+
+private:
+	GtkIntegration();
+};
+
+} // namespace internal
+} // namespace Platform