Gtk4. Migration Label and tooltip from gtk3

Platform
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1

Original issue is gtk4: missbehavior of the Gtk::Label tooltip (#6674) · Issues · GNOME / gtk · GitLab
The problem here is: When application have a lot of labels there are separate threads which can change tooltips for any label. In UI for those unchanged Labels - tooltips are flickering or even disappeared
Code in gtk3

#include <thread>
#include <iomanip>

void setTlpMarkup(GtkWidget *wg, char* markUp) {
  if (wg) {
    while(true) {
      auto t = std::time(nullptr);
      auto tm = *std::localtime(&t);
      std::ostringstream oss;
      oss << std::put_time(&tm, "%d-%m-%Y %H-%M-%S");
      auto str = std::string(markUp) + ' ' + oss.str();

      gtk_widget_set_tooltip_markup(wg, str.c_str());
      std::this_thread::sleep_for(std::chrono::seconds(2));
    }
  }
}

static GtkWidget *lLabel, *rLabel;
std::thread lT, rT;

static void
activate (GtkApplication *app,
          gpointer        user_data)
{
  GtkWidget *window;
  GtkWidget *mainBox, *lBox, *rBox;

  mainBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
  lBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
  rBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);

  gtk_box_pack_start(GTK_BOX(mainBox), lBox, true, true, 0);
  gtk_box_pack_end(GTK_BOX(mainBox), rBox, true, true, 0);

  // Labels
  lLabel = gtk_label_new("Left Label");
  rLabel = gtk_label_new("Right Label");
  gtk_box_pack_start(GTK_BOX(lBox), lLabel, true, true, 0);
  gtk_box_pack_start(GTK_BOX(rBox), rLabel, true, true, 0);

  window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Hello");
  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  gtk_container_add (GTK_CONTAINER (window), mainBox);
  gtk_window_present (GTK_WINDOW (window));

  gtk_widget_set_tooltip_markup(lLabel, (char*)"Left tooltip");

//  lT = std::thread(setTlpMarkup, lLabel, (char*)"Left tooltip");
  rT = std::thread(setTlpMarkup, rLabel, (char*)"Right tooltip");
  gtk_widget_show_all (window);
}

int main(int argc, char* argv[]) {
  GtkApplication *app;
  int status{0};

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}

Code in gtk4

#include <gtk/gtk.h>
#include <thread>
#include <iomanip>

void setTlpMarkup(GtkWidget *wg, char* markUp) {
  if (wg) {
    while(true) {
      auto t = std::time(nullptr);
      auto tm = *std::localtime(&t);
      std::ostringstream oss;
      oss << std::put_time(&tm, "%d-%m-%Y %H-%M-%S");
      auto str = std::string(markUp) + ' ' + oss.str();

      gtk_widget_set_tooltip_markup(wg, str.c_str());
      std::this_thread::sleep_for(std::chrono::seconds(2));
    }
  }
}

static GtkWidget *lLabel, *rLabel;
std::thread lT, rT;

static void
activate (GtkApplication *app,
          gpointer        user_data)
{
  GtkWidget *window;
  GtkWidget *mainBox, *lBox, *rBox;

  mainBox = gtk_center_box_new();
  lBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
  rBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);

  gtk_center_box_set_start_widget(GTK_CENTER_BOX(mainBox), lBox);
  gtk_center_box_set_end_widget(GTK_CENTER_BOX(mainBox), rBox);

  // Labels
  lLabel = gtk_label_new("Left Label");
  rLabel = gtk_label_new("Right Label");
  gtk_box_append(GTK_BOX(lBox), lLabel);
  gtk_box_append(GTK_BOX(rBox), rLabel);

  window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Hello");
  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  gtk_window_set_child (GTK_WINDOW (window), mainBox);
  gtk_window_present (GTK_WINDOW (window));

  gtk_widget_set_tooltip_markup(lLabel, (char*)"Left tooltip");

//  lT = std::thread(setTlpMarkup, lLabel, (char*)"Left tooltip");
  rT = std::thread(setTlpMarkup, rLabel, (char*)"Right tooltip");
}

int main(int argc, char* argv[]) {
  GtkApplication *app;
  int status{0};

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}
2

As I said on GitLab:

You cannot call GTK API in a thread. If you are doing busy work in a thread, and you wish to update the UI, you have to schedule a call into the main loop, by using API like g_idle_add_once() or g_main_context_invoke().

The reason why you’re seeing odd behaviour is that you’re using GTK API from multiple threads, and you’re blocking in the middle on a thread.

GTK is thread aware, but not thread safe: only the thread that initialised GTK and is spinning the main loop can use GTK API; every other thread must schedule UI updates into the main loop.

For more information:

3

Thank you , let me try another approach

4

Hi @ebassi
I’ve rewritten incoming example for gtk4. Now I’m using Glib::Dispatcher but unfortunately no any luck. Even separate thread now is just doing emits … and tooltip is refreshed by the callback function the problem with tooltip flickering still persists

#include <gtk/gtk.h>
#include <thread>
#include <iomanip>
#include <glibmm/dispatcher.h>
#include <spdlog/spdlog.h>

static GtkWidget *lLabel, *rLabel;
std::thread lT, rT;
/// Emitting on this dispatcher triggers a update() call
Glib::Dispatcher dp;

void setTlpMarkup(GtkWidget *wg, char* markUp) {
  if (wg) {
      auto t = std::time(nullptr);
      auto tm = *std::localtime(&t);
      std::ostringstream oss;
      oss << std::put_time(&tm, "%d-%m-%Y %H-%M-%S");
      auto str = std::string(markUp) + ' ' + oss.str();
      gtk_widget_set_tooltip_markup(wg, str.c_str());
    }
}

static void
activate (GtkApplication *app,
          gpointer        user_data)
{
  GtkWidget *window;
  GtkWidget *mainBox, *lBox, *rBox;

  mainBox = gtk_center_box_new();
  lBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
  rBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);

  gtk_center_box_set_start_widget(GTK_CENTER_BOX(mainBox), lBox);
  gtk_center_box_set_end_widget(GTK_CENTER_BOX(mainBox), rBox);

  // Labels
  lLabel = gtk_label_new("Left Label");
  rLabel = gtk_label_new("Right Label");
  gtk_box_append(GTK_BOX(lBox), lLabel);
  gtk_box_append(GTK_BOX(rBox), rLabel);

  window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Hello");
  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  gtk_window_set_child (GTK_WINDOW (window), mainBox);
  gtk_window_present (GTK_WINDOW (window));

  gtk_widget_set_tooltip_markup(lLabel, (char*)"Left tooltip");

//  lT = std::thread(setTlpMarkup, lLabel, (char*)"Left tooltip");
//  rT = std::thread(setTlpMarkup, rLabel, (char*)"Right tooltip");
  rT = std::thread([](){
    while(true) {
      std::this_thread::sleep_for(std::chrono::seconds(2));
      dp.emit();
    }
  });
}

int main(int argc, char* argv[]) {
  GtkApplication *app;
  int status{0};

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  dp.connect([] {
          try {
            setTlpMarkup(rLabel, (char*)"Right tooltip");
          } catch (const std::exception& e) {
            spdlog::error("{}: {}", "setTlpMarkup", e.what());
          }
        });
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}
5

I have no idea what Glib::Dispatcher is, so I’ll leave somebody else fluent in the C++ bindings take over from here.

6

Hi,

Can you try replacing

dp.emit();

by

g_idle_add_once([] {
          try {
            setTlpMarkup(rLabel, (char*)"Right tooltip");
          } catch (const std::exception& e) {
            spdlog::error("{}: {}", "setTlpMarkup", e.what());
          }
        }, NULL);

?

I never used Glib::Dispatcher, seems to be some C++ specific API, but the examples I found by googling use a lot of mutextes… I suspect it’s not thread-safe.

7

Hi @gwillems and @ebassi , unfortunately no luck with provided replacing.
To me it seems like gtk recreates tooltip instance which leads to tooltip flickering … but it just my guesses …
UPD: If I use set_markup method - Labels work OK without any flickering. The problem persist only for tooltip due to I believe it belongs to Widget class … not to Label.
UPD2: I tried the same example with mutex

void setTlpMarkup(GtkWidget *wg, char* markUp) {
  if (wg) {
      auto t = std::time(nullptr);
      auto tm = *std::localtime(&t);
      std::ostringstream oss;
      oss << std::put_time(&tm, "%d-%m-%Y %H-%M-%S");
      auto str = std::string(markUp) + ' ' + oss.str();
      std::lock_guard<std::mutex> lock(m_Mutex);
      gtk_widget_set_tooltip_markup(wg, str.c_str());
    }
}

But again no luck

8

Hi @ebassi and @gwillems
Finally I’ve rewritten this code on pure C using pure GTK API using signals. And the problem still persists. So separate thread now just sends “thread_signal” signals. In the main loop I’m using subscription on this signals with the callback function * notify_cb*

See the code now

#include <gtk/gtk.h>
#include <thread>
#include <iomanip>
#include <spdlog/spdlog.h>

static GtkWidget *lLabel, *rLabel;
std::thread lT, rT;
guint mySig{g_signal_new("thread_finished",
             G_TYPE_OBJECT, G_SIGNAL_RUN_FIRST,
             0, NULL, NULL,
             g_cclosure_marshal_VOID__BOXED,
             G_TYPE_NONE, 1, GDK_TYPE_EVENT)};

void setTlpMarkup(GtkWidget *wg, char* markUp) {
  if (wg) {
      auto t = std::time(nullptr);
      auto tm = *std::localtime(&t);
      std::ostringstream oss;
      oss << std::put_time(&tm, "%d-%m-%Y %H-%M-%S");
      auto str = std::string(markUp) + ' ' + oss.str();
      gtk_widget_set_tooltip_markup(wg, str.c_str());
    }
}

void notify_cb() {
  try {
    setTlpMarkup(rLabel, (char*)"Right tooltip");
  } catch (const std::exception& e) {
    spdlog::error("{}: {}", "setTlpMarkup", e.what());
  }
}


static void
activate (GtkApplication *app,
          gpointer        user_data)
{
  GtkWidget *window;
  GtkWidget *mainBox, *lBox, *rBox;

  mainBox = gtk_center_box_new();
  lBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);
  rBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5);

  gtk_center_box_set_start_widget(GTK_CENTER_BOX(mainBox), lBox);
  gtk_center_box_set_end_widget(GTK_CENTER_BOX(mainBox), rBox);

  // Labels
  lLabel = gtk_label_new("Left Label");
  rLabel = gtk_label_new("Right Label");
  gtk_box_append(GTK_BOX(lBox), lLabel);
  gtk_box_append(GTK_BOX(rBox), rLabel);

  window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Hello");
  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  gtk_window_set_child (GTK_WINDOW (window), mainBox);
  gtk_window_present (GTK_WINDOW (window));

  gtk_widget_set_tooltip_markup(lLabel, (char*)"Left tooltip");

  rT = std::thread([app](){
    while(true) {
      std::this_thread::sleep_for(std::chrono::seconds(2));
      g_signal_emit_by_name(app, "thread_finished");
    }
  });
}

int main(int argc, char* argv[]) {
  GtkApplication *app;
  int status{0};

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  g_signal_connect(G_OBJECT(app), "thread_finished", G_CALLBACK(notify_cb), NULL);
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}
9

I made some tests with gdb and the version of your program with Glib::Dispatcher.
The pure C version would probably lead to the same conclusion.

The call to gtk_widget_set_tooltip_markup() results, among many other things, in a
call to gtk_tooltip_handle_event_internal() with the following code:

	    /* Is the pointer above another widget now? */
	    if (GTK_TOOLTIP_VISIBLE (tooltip))
	      hide_tooltip |= target_widget != tooltip->tooltip_widget;

If the pointer (i.e. the mouse cursor) is above the widget whose tooltip is being
set, the tooltip is not hidden.

If the cursor is, for instance, over the left label when the right label’s tooltip
is being changed, the tooltip is hidden. In this case the code snippet above is
executed only every second time the tooltip changes. The remaining changes execute
code in gtk_tooltip_handle_event_internal() that shows the tooltip.

I haven’t tried to understand exactly how this works, but I doubt that you can
avoid the flickering tooltip by fixes outside gtk itself.

1 Like
10

Hi @kjellahl , @gwillems , @ebassi
Even thought the application can handle this issue itself what is I see this is pure Gdk issue. In order to do migration of the application from gtk3 to gtk4 I have to do some additional trick, hacks and revise the whole application architecture. Where in original gtk3 it was not even an issue.
In the same time If application uses Gtk::Label which derives from Gtk:Widget it looks awkward when it’s possible to change Label text using set_text/set_markup but in the same time experiences the problem with set_tooltip_text/set_tooltip_markup

Is it possible to fix the issue in GTK framework ?

11

I agree the behavior is weird and annoying.

I’ll have a look and try to fix this.

1 Like
12

Thank you @gwillems .

1 Like