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我注意到 GtkTextView 的首选大小在其内容更改后不会立即更改，但只会在事件处理的某个时间后更改。

在下面的示例中，当您单击按钮时，GtkTextView 中的文本通过 gtk_text_buffer_set_text() 更新。新文本的长度足以导致换行，因此控件的首选高度应该改变。但是 gtk_widget_get_preferred_size() 仍然报告旧的首选高度。稍后，在“大小分配”事件处理程序中，gtk_widget_get_preferred_size() 已经报告了新内容的正确大小。

我试图了解按钮的“单击”事件处理程序的返回和“大小分配”事件处理程序之间发生了什么，这导致 GtkTextView 的首选大小更新以反映其更改的内容。

#include <gtk/gtk.h>

static bool button_clicked(GtkWidget* obj, GtkWidget* view)
{
  // set text in GtkTextView to
  const char* long_text="aaaaa aaaaa aaaaa aaaaa aaaaa aaaaa aaaaa";
  printf("----------------------------\n");
  printf("in button_clicked(): setting text\n");
  GtkTextBuffer* buffer = gtk_text_view_get_buffer(GTK_TEXT_VIEW(view));
  gtk_text_buffer_set_text(buffer, long_text, -1);

  GtkRequisition req;
  gtk_widget_get_preferred_size(view, &req, NULL);
  printf("in button_clicked(): preferred height = %u\n", req.height);
  return false;
}

static bool on_size_allocate(GtkWidget* obj, GdkRectangle *allocation, GtkWidget* view)
{
  GtkRequisition req;
  gtk_widget_get_preferred_size(view, &req, NULL);
  printf("in on_size_allocate(): preferred height = %u\n", req.height);
  return false;
}

static void activate(GtkApplication* app, gpointer user_data)
{
  GtkWidget *window;
  window = gtk_application_window_new(app);
  gtk_window_set_title(GTK_WINDOW (window), "Wrapped text");
  gtk_window_set_default_size(GTK_WINDOW (window), 200, 200);
  gtk_widget_show_all(window);

  GtkTextBuffer* buffer = gtk_text_buffer_new(NULL);

  GtkWidget* view = GTK_WIDGET(gtk_text_view_new_with_buffer(buffer));
  g_object_unref(buffer);
  gtk_widget_set_size_request(view, 180, -1);
  gtk_text_view_set_wrap_mode(GTK_TEXT_VIEW(view), GTK_WRAP_WORD_CHAR);
  g_signal_connect(view, "size-allocate", G_CALLBACK(on_size_allocate), view);

  GtkWidget *button = gtk_button_new_with_label("Set Text");
  g_signal_connect(button, "clicked", G_CALLBACK(button_clicked), view);

  GtkWidget* grid = gtk_grid_new();
  gtk_container_add(GTK_CONTAINER(window), grid);
  gtk_grid_attach(GTK_GRID(grid), button, 0, 0, 1, 1);
  gtk_grid_attach(GTK_GRID(grid), view, 0, 1, 1, 1);

  gtk_widget_show_all(window);
}

int main (int argc, char **argv)
{
  GtkApplication *app;
  int status;

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

  return status;
}

这显示：

in on_size_allocate(): preferred height = 17
----------------------------
in button_clicked(): setting text
in button_clicked(): preferred height = 17
in on_size_allocate(): preferred height = 34
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