我试图解决这个问题,当我点击“button1”时,“on_draw_event”函数被调用(有效),并且在我的“darea”绘图区域中显示一条线(不起作用)。
这是我的代码:
#include <gtk/gtk.h>
static gboolean on_draw_event(GtkWidget *button, cairo_t *darea)
{
printf ("function: on_draw_event\n");
cairo_set_source_rgb(darea, 0, 255, 0);
cairo_set_line_width(darea, 0.5);
cairo_move_to(darea, 0, 100);
cairo_line_to(darea, 400, 100);
cairo_stroke(darea);
return FALSE;
}
int main (int argc, char *argv[])
{
GtkWidget *window;
GtkWidget *darea;
GtkWidget *myGrid;
GtkWidget *button1;
GtkWidget *button2;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_POPUP);
myGrid = gtk_grid_new ();
darea = gtk_drawing_area_new();
gtk_widget_set_size_request(darea, 400, 400);
button1 = gtk_button_new_with_label ("BUTTON 1");
button2 = gtk_button_new_with_label ("QUIT");
gtk_grid_attach(GTK_GRID(myGrid), button1, 0, 0, 1, 1);
gtk_grid_attach(GTK_GRID(myGrid), darea, 0, 1, 1, 1);
gtk_grid_attach(GTK_GRID(myGrid), button2, 0, 2, 1, 1);
gtk_container_add(GTK_CONTAINER(window), myGrid);
g_signal_connect(G_OBJECT(button2), "clicked", G_CALLBACK(gtk_main_quit), NULL);
g_signal_connect(button1, "clicked", G_CALLBACK(on_draw_event), darea);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_widget_show_all(window);
gtk_main();
return 0;
}
如果我能改变 “g_signal_connect(按钮1,“单击”,G_CALLBACK(on_draw_event),darea);“ 到 “g_signal_connect(G_OBJECT(darea),”绘制“,G_CALLBACK(on_draw_event),NULL);” 该线将被绘制,但我希望它等待我的按钮单击。希望有人能阻止我,问题不大。
谢谢。
最佳答案
正如发布的那样,您的示例崩溃了,因为您将绘图回调连接到 clicked
信号。调用时,回调会获取无意义的参数并终止。
要“等待按钮单击”,请引入一个标志来告诉您按钮是否已被单击。在 on_draw_event
中查询该标志,并将其设置在按钮的 clicked
回调中。
为实现上述内容而修改的示例如下所示:
#include <gtk/gtk.h>
static gboolean on_draw_event(GtkWidget *darea, cairo_t *cr,
gboolean *draw_line)
{
if (!*draw_line)
return FALSE;
printf ("function: on_draw_event\n");
cairo_set_source_rgb(cr, 0, 255, 0);
cairo_set_line_width(cr, 0.5);
cairo_move_to(cr, 0, 100);
cairo_line_to(cr, 400, 100);
cairo_stroke(cr);
return FALSE;
}
static void on_button1_clicked(GtkWidget *button, gboolean *draw_line)
{
*draw_line = TRUE;
/* Make sure the widget is repainted after the click.
gtk_widget_queue_draw() should better be invoked with just the
drawing area, but this code accesses the common parent for
simplicity. Passing darea in a struct whose address is provided as
user_data (along with gboolean *draw_line) is left as exercise. */
gtk_widget_queue_draw(gtk_widget_get_parent(button));
}
int main (int argc, char *argv[])
{
GtkWidget *window;
GtkWidget *darea;
GtkWidget *myGrid;
GtkWidget *button1;
GtkWidget *button2;
gboolean draw_line = FALSE;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_POPUP);
myGrid = gtk_grid_new ();
darea = gtk_drawing_area_new();
gtk_widget_set_size_request(darea, 400, 400);
button1 = gtk_button_new_with_label ("BUTTON 1");
button2 = gtk_button_new_with_label ("QUIT");
gtk_grid_attach(GTK_GRID(myGrid), button1, 0, 0, 1, 1);
gtk_grid_attach(GTK_GRID(myGrid), darea, 0, 1, 1, 1);
gtk_grid_attach(GTK_GRID(myGrid), button2, 0, 2, 1, 1);
gtk_container_add(GTK_CONTAINER(window), myGrid);
g_signal_connect(G_OBJECT(button2), "clicked", G_CALLBACK(gtk_main_quit), NULL);
g_signal_connect(button1, "clicked", G_CALLBACK(on_button1_clicked), &draw_line);
g_signal_connect(G_OBJECT(darea), "draw", G_CALLBACK(on_draw_event), &draw_line);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
gtk_widget_show_all(window);
gtk_main();
return 0;
}
关于c - GTK3 开罗 g_signal_connect : Dont get the point,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34656461/