[desktop_drop] temporary workaround to ignore the redundant signal on KDE (#325)

* temporary workaround to fix the redundant signal on KDE

* native workaround

* use `g_ascii_strdown`

* use `gboolean`

Author: sun-jiao

packages/desktop_drop/linux/desktop_drop_plugin.cc

@@ -4,8 +4,6 @@
 #include <gtk/gtk.h>
 #include <sys/utsname.h>
 
-#include <cstring>
-
 #define DESKTOP_DROP_PLUGIN(obj) \
   (G_TYPE_CHECK_INSTANCE_CAST((obj), desktop_drop_plugin_get_type(), \
                               DesktopDropPlugin))
@@ -14,6 +12,9 @@ struct _DesktopDropPlugin {
   GObject parent_instance;
 };
 
+static gboolean isKDE = FALSE;
+static gboolean ignoreNext = FALSE;
+
 G_DEFINE_TYPE(DesktopDropPlugin, desktop_drop_plugin, g_object_get_type())
 
 void on_drag_data_received(GtkWidget *widget, GdkDragContext *drag_context,
@@ -31,6 +32,11 @@ void on_drag_data_received(GtkWidget *widget, GdkDragContext *drag_context,
 
 void on_drag_motion(GtkWidget *widget, GdkDragContext *drag_context,
                     gint x, gint y, guint time, gpointer user_data) {
+  if (ignoreNext) {
+    ignoreNext = FALSE;
+    return;
+  }
+
   auto *channel = static_cast<FlMethodChannel *>(user_data);
   double point[] = {double(x), double(y)};
   g_autoptr(FlValue) args = fl_value_new_float_list(point, 2);
@@ -59,7 +65,23 @@ static void desktop_drop_plugin_class_init(DesktopDropPluginClass *klass) {
   G_OBJECT_CLASS(klass)->dispose = desktop_drop_plugin_dispose;
 }
 
-static void desktop_drop_plugin_init(DesktopDropPlugin *self) {}
+static void desktop_drop_plugin_init(DesktopDropPlugin *self) {
+  const char * desktopEnv = std::getenv("XDG_CURRENT_DESKTOP");
+  if (desktopEnv) {
+    const char * lowercaseDesktopEnv = g_ascii_strdown(desktopEnv, -1);
+
+    if (strcmp(lowercaseDesktopEnv, "kde") == 0 || strcmp(lowercaseDesktopEnv, "plasma") == 0) {
+        isKDE = TRUE;
+    }
+  }
+}
+
+static void on_focus_in_event(GtkWidget *widget, GdkEventFocus *event, gpointer user_data) {
+  if (isKDE) {
+    ignoreNext = TRUE;
+  }
+  return;
+}
 
 static void method_call_cb(FlMethodChannel *channel, FlMethodCall *method_call,
                            gpointer user_data) {
@@ -93,6 +115,8 @@ void desktop_drop_plugin_register_with_registrar(FlPluginRegistrar *registrar) {
                    G_CALLBACK(on_drag_data_received), channel);
   g_signal_connect(GTK_WIDGET(fl_view), "drag-leave",
                    G_CALLBACK(on_drag_leave), channel);
+  g_signal_connect(fl_view, "focus-in-event",
+                   G_CALLBACK(on_focus_in_event), nullptr);
 
   g_object_unref(plugin);
 }