Gtk, контекст OpenGL и GdkCursor случайным образом сбрасывают курсор ⇐ C++

[Гость]

Context:
We've recently upgraded from gtk2 to gtk3 and for this had to get rid of GtkGLExt as our OpenGL context as it does not support gtk3. Doing so we've decided to use wglContext and setting the render context ourself. We develop a heavily multi-threaded software where there's roughly a dozen of these contexts running simultaneously so we cannot go for a GdkGLContext as this is not thread-safe.

The rendering itself works and we have multiple GtkDrawingAreas where we render various images into from their corresponding thread and these are successfully displayed.
Problem
All of these DrawingAreas use GdkCursors to change the windows cursor so that the user can have a better usability. This worked like a charm in gtk2 and in gtk3 we're observing this weird behavior where the cursor is seemingly randomly resetting to the default cursor. When listening to the cursor changes we do not get any notification to this back-to-default-reset.

I have already tried GdkGLContext and with the minimal working example, and it works as wished. However, I did not find a way to have multiple render contexts be active for multiple threads at the same time using GdkGLContext. If I understand the documentation correctly, then GDK isn't supporting multi threading in Windows at all.

I would greatly appreciate any pointers as I'm getting to a point where I am loosing my mind about this issue.

Interesting note: We've also observed that if you drag the mouse while the left mouse button is pressed down the mouse cursor does NOT randomly reset. Maybe this is useful information, maybe not...
Minimal working example
This example gives a overview how we're setting up a single of these drawing areas. The window will be empty (as nothing is rendered) but the cursor flickering can still be observed.
// just a simple window that contains a drawing area // that we want to use as the openGL context // and have a cursor stay auto pDialog = gtk_window_new(GtkWindowType::GTK_WINDOW_TOPLEVEL); auto pDrawingArea = gtk_drawing_area_new(); gtk_container_add(GTK_CONTAINER(pDialog), pDrawingArea); gtk_widget_show_all(pDialog); auto pGDKwindow = gtk_widget_get_window(pDrawingArea); //// Add events to the event box gint iEvents = (GDK_POINTER_MOTION_MASK); gtk_widget_add_events(pDrawingArea, iEvents); g_object_ref_sink(pDrawingArea); // just a dumb bombardment of mouse changes on move g_signal_connect(pDrawingArea, "motion-notify-event", G_CALLBACK(+[](GtkWidget * pWidget, gpointer data) { auto pCursor = gdk_cursor_new(GdkCursorType::GDK_DOUBLE_ARROW); gdk_window_set_cursor(gtk_widget_get_window(pWidget), pCursor); gdk_cursor_unref(pCursor); return FALSE; }), NULL); //opengl context creation (see https://www.khronos.org/opengl/wiki/Cre ... text_(WGL) ) PIXELFORMATDESCRIPTOR pfd = { .nSize = sizeof(pfd), .nVersion = 1, .dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER, .iPixelType = PFD_TYPE_RGBA, .cColorBits = 32, .cAlphaBits = 8, .cDepthBits = 24, .cStencilBits = 8, .iLayerType = PFD_MAIN_PLANE, }; HDC window_dc = GetDC(static_cast(gdk_win32_window_get_handle(pGDKwindow))); int pixel_format = ChoosePixelFormat(window_dc, &pfd); SetPixelFormat(window_dc, pixel_format, &pfd); HGLRC context = wglCreateContext(window_dc); wglMakeCurrent(window_dc, context); // just iterate to show the window and display the bug do { gtk_main_iteration_do(true); } while (true);

Источник: https://stackoverflow.com/questions/781 ... the-cursor