Add gnome-based wayland universal screenshot adapter

By default, flameshot uses the program's default dbus protocol interface
to communicate with gnome's screenshot protocol, but this is now broken
on some gnome installations, so we'll use gnome-screenshot as gnome's
wayland screenshot adapter and then communicate directly with the gnome
screenshot component!

To enable the GNOME-based generic wayland screenshot adapter, enable it
using the following cmake parameter:

```
-DUSE_WAYLAND_GNOME=true
```

src/CMakeLists.txt

@@ -216,13 +216,20 @@ target_link_libraries(
 )
 
 if (USE_WAYLAND_CLIPBOARD)
+  if(!USE_WAYLAND_GNOME)
+    message(WARNING "You have activated the USE_WAYLAND_CLIPBOARD option, but not the USE_WAYLAND_GNOME option. flameshot will use the dbus protocol to support wayland. if you are using gnome-based wayland, it is recommended that you enable USE_WAYLAND_GNOME")
+  endif()
   if(!USE_WAYLAND_GRIM)
     message(WARNING "You activated the USE_WAYLAND_CLIPBOARD option, but did not activate the USE_WAYLAND_GRIM option. Flameshot will use the dbus protocol to support wayland. If you use wlroots-based wayland, it is recommended to enable USE_WAYLAND_GRIM")
   endif()
   target_compile_definitions(flameshot PRIVATE USE_WAYLAND_CLIPBOARD=1)
   target_link_libraries(flameshot KF5::GuiAddons)
 endif()
 
+if(USE_WAYLAND_GNOME)
+    target_compile_definitions(flameshot PRIVATE USE_WAYLAND_GNOME=1)
+endif()
+
 if (USE_WAYLAND_GRIM)
     target_compile_definitions(flameshot PRIVATE USE_WAYLAND_GRIM=1)
 endif()

src/utils/screengrabber.cpp

@@ -26,6 +26,30 @@ ScreenGrabber::ScreenGrabber(QObject* parent)
   : QObject(parent)
 {}
 
+void ScreenGrabber::generalGnomeScreenshot(bool& ok, QPixmap& res)
+{
+#ifdef USE_WAYLAND_GNOME
+#if defined(Q_OS_LINUX) || defined(Q_OS_UNIX)
+    QProcess Process;
+    QString program = "gnome-screenshot";
+    QStringList arguments;
+    QString tmpFileName = "/tmp/gnome_flameshot_png";
+    arguments << "-f" << tmpFileName;
+    Process.start(program, arguments);
+    if (Process.waitForFinished()) {
+        res.load(tmpFileName);
+        ok = true;
+    } else {
+        ok = false;
+        AbstractLogger::error() << tr(
+          "The GNOME-based Universal wayland Screen Capture Adapter requires "
+          "gnome-screenshot as the screen capture component of wayland. If the "
+          "screen capture component is missing, please install it!");
+    }
+#endif
+#endif
+}
+
 void ScreenGrabber::generalGrimScreenshot(bool& ok, QPixmap& res)
 {
 #ifdef USE_WAYLAND_GRIM
@@ -125,6 +149,17 @@ QPixmap ScreenGrabber::grabEntireDesktop(bool& ok)
         // handle screenshot based on DE
         switch (m_info.windowManager()) {
             case DesktopInfo::GNOME:
+#ifndef USE_WAYLAND_GNOME
+                AbstractLogger::warning() << tr(
+                  "If the USE_WAYLAND_GNOME option is not enabled, the default "
+                  "dbus protocol will be used directly. Note that it is not "
+                  "recommended to use the default dbus protocol under wayland "
+                  "in gnome environments. It is recommended to recompile with "
+                  "the USE_WAYLAND_GNOME flag to activate the gnome-screenshot "
+                  "based generic wayland screenshot adapter");
+#else
+                generalGnomeScreenshot(ok, res);
+#endif
             case DesktopInfo::KDE:
                 freeDesktopPortal(ok, res);
                 break;

src/utils/screengrabber.h

@@ -17,6 +17,7 @@ class ScreenGrabber : public QObject
     QPixmap grabScreen(QScreen* screenNumber, bool& ok);
     void freeDesktopPortal(bool& ok, QPixmap& res);
     void generalGrimScreenshot(bool& ok, QPixmap& res);
+    void generalGnomeScreenshot(bool& ok, QPixmap& res);
     QRect desktopGeometry();
 
 private: