如何在 gtk2 中刷新 cairo 绘图？

Question

我在刷新 cairo 绘图时遇到问题。它不起作用，我不知道为什么。你可以帮帮我吗？我想在执行分析功能时创建一个新的 "drawing"。

我创建了这样的东西：

d_area = gtk_drawing_area_new();

然后我把它打包成滚动的window:

gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(formula_scrolled_window), d_area);

然后：

g_signal_connect(G_OBJECT(d_area), "expose_event", G_CALLBACK(expose_event_callback), NULL);

但在它之前我有：

g_signal_connect(G_OBJECT(search_entry), "activate", G_CALLBACK(analyse), &window_and_search_entry);

功能分析：

ELEMENT *analyse(GtkWidget *widget, WINDOW_AND_SEARCH_ENTRY *data)
{
    const gchar *text = gtk_entry_get_text(GTK_ENTRY(data->search_entry));
    main_window = data->window;
    d_area = GTK_DRAWING_AREA(data->d_area); //do I nedd it?


    foo = operate(text, GTK_WIDGET(data->window));

    print_on_console_with_new_line(foo);

    g_signal_connect(G_OBJECT(d_area), "expose_event", G_CALLBACK(expose_event_callback), NULL); //do I need it??
    do_drawing(cr, foo); //is it good 
    g_signal_connect(G_OBJECT(d_area), "expose_event", G_CALLBACK(expose_event_callback), NULL); //do I need it??


}

并且：

gboolean expose_event_callback (GtkWidget *widget, GdkEventExpose *event, gpointer data)
{


  cr = gdk_cairo_create (gtk_widget_get_window (widget)); 
  do_drawing(cr, foo);
  return FALSE;
}

最后：

void do_drawing(cairo_t *cr, ELEMENT *p) 
{
gdouble font_size = 20.0;

cairo_set_source_rgb(cr, 0, 0, 0);
cairo_select_font_face(cr, "Sans", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
cairo_set_font_size(cr, font_size);


cairo_move_to(cr, lala, 30.0);
cairo_show_text(cr, "6");  
lala += 30;

}

Answer 1

尝试在 do_drawing() 函数的开头添加这个

cairo_set_source_rgb(cr, 1., 1., 1.); 
cairo_paint(cr);

同时对您的 gtk 小部件执行此操作以更新它

gtk_widget_queue_draw(formula_scrolled_window);

如何在 gtk2 中刷新 cairo 绘图？

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