Get scale factor from GTK on Linux

Telegram/SourceFiles/platform/linux/linux_gtk_integration.cpp

@@ -9,6 +9,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 
 #include "platform/linux/linux_gtk_integration_p.h"
 #include "base/platform/base_platform_info.h"
+#include "platform/linux/linux_desktop_environment.h"
 #include "platform/linux/linux_xlib_helper.h"
 #include "platform/linux/linux_gdk_helper.h"
 #include "platform/linux/linux_gtk_file_dialog.h"
@@ -207,6 +208,28 @@ bool CursorSizeShouldBeSet() {
 	return Result;
 }
 
+void SetScaleFactor() {
+	Core::Sandbox::Instance().customEnterFromEventLoop([] {
+		const auto integration = GtkIntegration::Instance();
+		if (!integration || !DesktopEnvironment::IsGtkBased()) {
+			return;
+		}
+
+		const auto scaleFactor = integration->scaleFactor();
+		if (!scaleFactor.has_value()) {
+			return;
+		}
+
+		LOG(("GTK scale factor: %1").arg(*scaleFactor));
+
+		const int scale = *scaleFactor
+			* 100
+			/ Core::Sandbox::Instance().devicePixelRatio();
+
+		cSetScreenScale(std::clamp(scale, 100, 300));
+	});
+}
+
 void SetIconTheme() {
 	Core::Sandbox::Instance().customEnterFromEventLoop([] {
 		const auto integration = GtkIntegration::Instance();
@@ -312,6 +335,10 @@ void GtkIntegration::load() {
 	}
 
 	if (GtkLoaded) {
+		LOAD_GTK_SYMBOL(lib_gtk, "gdk_display_get_default", gdk_display_get_default);
+		LOAD_GTK_SYMBOL(lib_gtk, "gdk_display_get_primary_monitor", gdk_display_get_primary_monitor);
+		LOAD_GTK_SYMBOL(lib_gtk, "gdk_monitor_get_scale_factor", gdk_monitor_get_scale_factor);
+
 		LOAD_GTK_SYMBOL(lib_gtk, "gdk_pixbuf_new_from_file_at_size", gdk_pixbuf_new_from_file_at_size);
 		LOAD_GTK_SYMBOL(lib_gtk, "gdk_pixbuf_get_has_alpha", gdk_pixbuf_get_has_alpha);
 		LOAD_GTK_SYMBOL(lib_gtk, "gdk_pixbuf_get_pixels", gdk_pixbuf_get_pixels);
@@ -329,6 +356,7 @@ void GtkIntegration::load() {
 		LOAD_GTK_SYMBOL(lib_gtk, "gtk_app_chooser_get_app_info", gtk_app_chooser_get_app_info);
 		LOAD_GTK_SYMBOL(lib_gtk, "gtk_app_chooser_get_type", gtk_app_chooser_get_type);
 
+		SetScaleFactor();
 		SetIconTheme();
 		SetCursorSize();
 
@@ -417,6 +445,18 @@ std::optional<QString> GtkIntegration::getStringSetting(
 	return str;
 }
 
+std::optional<int> GtkIntegration::scaleFactor() const {
+	if (!loaded()
+		|| (gdk_display_get_default == nullptr)
+		|| (gdk_display_get_primary_monitor == nullptr)
+		|| (gdk_monitor_get_scale_factor == nullptr)) {
+		return std::nullopt;
+	}
+
+	return gdk_monitor_get_scale_factor(
+		gdk_display_get_primary_monitor(gdk_display_get_default()));
+}
+
 bool GtkIntegration::fileDialogSupported() const {
 	return FileDialog::Gtk::Supported();
 }

Telegram/SourceFiles/platform/linux/linux_gtk_integration.h

@@ -34,6 +34,8 @@ public:
 	[[nodiscard]] std::optional<QString> getStringSetting(
 		const QString &propertyName) const;
 
+	[[nodiscard]] std::optional<int> scaleFactor() const;
+
 	using FileDialogType = ::FileDialog::internal::Type;
 	[[nodiscard]] bool fileDialogSupported() const;
 	[[nodiscard]] bool useFileDialog(

Telegram/SourceFiles/platform/linux/linux_gtk_integration_dummy.cpp

@@ -43,6 +43,10 @@ std::optional<QString> GtkIntegration::getStringSetting(
 	return std::nullopt;
 }
 
+std::optional<int> GtkIntegration::scaleFactor() const {
+	return std::nullopt;
+}
+
 bool GtkIntegration::fileDialogSupported() const {
 	return false;
 }

Telegram/SourceFiles/platform/linux/linux_gtk_integration_p.h

@@ -27,6 +27,7 @@ extern "C" {
 #endif // !LINK_TO_GTK
 
 // To be able to compile with gtk-2.0 headers as well
+#define GdkMonitor GdkScreen
 typedef struct _GtkAppChooser GtkAppChooser;
 
 namespace Platform {
@@ -147,6 +148,9 @@ inline bool g_type_cit_helper(Object *instance, GType iface_type) {
 
 inline gint (*gtk_dialog_run)(GtkDialog *dialog) = nullptr;
 inline GdkAtom (*gdk_atom_intern)(const gchar *atom_name, gboolean only_if_exists) = nullptr;
+inline GdkDisplay* (*gdk_display_get_default)(void) = nullptr;
+inline GdkMonitor* (*gdk_display_get_primary_monitor)(GdkDisplay *display) = nullptr;
+inline int (*gdk_monitor_get_scale_factor)(GdkMonitor *monitor) = nullptr;
 inline GdkPixbuf* (*gdk_pixbuf_new_from_file_at_size)(const gchar *filename, int width, int height, GError **error) = nullptr;
 inline gboolean (*gdk_pixbuf_get_has_alpha)(const GdkPixbuf *pixbuf) = nullptr;
 inline guchar* (*gdk_pixbuf_get_pixels)(const GdkPixbuf *pixbuf) = nullptr;