Re: CSS provider memory problem

[Eric Cashon via gtk-list]

 
When you first start your program and setup the CSS to style with, keep the 
pointer to the provider around so that you can reuse it. That way the program 
won't leak memory by getting a new provider each time that a CSS change is made 
in the program. 

I tried to put some CSS differences in the following test code that I have run 
into. Hopefully it is of some help.

Eric

/*
   gcc -Wall css_button1.c -o css_button1 `pkg-config --cflags --libs gtk+-3.0`
   Tested with GTK3.18 and GTK3.22 on Ubuntu16.04
*/
#include<gtk/gtk.h>

static gboolean blink(gpointer *data)
  {
    static gint flag=0;
    GError *error=NULL;
  
    if(flag)
      {
        gtk_css_provider_load_from_data((GtkCssProvider*)data[0], 
(gchar*)data[1], -1, &error);
        flag=0;
      }
    else
      {
        gtk_css_provider_load_from_data((GtkCssProvider*)data[0], 
(gchar*)data[2], -1, &error);
        flag=1;
      }

    if(error!=NULL)
      {
        g_print("%s\n", error->message);
        g_error_free(error);
      }

    return TRUE;
  }
int main(int argc, char *argv[])
  {
    gtk_init (&argc, &argv);

    GtkWidget *window=gtk_window_new (GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title(GTK_WINDOW(window), "CSS Button");
    gtk_window_set_default_size(GTK_WINDOW(window), 200, 100);
    gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    GtkWidget *button1=gtk_button_new_with_label("button1");
    gtk_widget_set_hexpand(button1, TRUE); 
    gtk_widget_set_vexpand(button1, TRUE);  
 
    GtkWidget *grid=gtk_grid_new();
    gtk_grid_attach(GTK_GRID(grid), button1, 0, 0, 1, 1);

    gtk_container_add(GTK_CONTAINER(window), grid);

    gtk_widget_show_all(window);

    //Setup CSS for the program.
    GError *css_error=NULL;
    gint minor_version=gtk_get_minor_version();
    gchar *css_string1=NULL;
    gchar *css_string2=NULL;
    //GTK CSS changed in 3.20.
    if(minor_version>20)
      {
        css_string1=g_strdup("button{background: red;}");
        css_string2=g_strdup("button{background: white;}");
      }
    else
      {
        css_string1=g_strdup("GtkButton{background: red;}");
        css_string2=g_strdup("GtkButton{background: white;}");
      }
    GtkCssProvider *provider=gtk_css_provider_new();
    GdkDisplay *display=gdk_display_get_default();
    GdkScreen *screen=gdk_display_get_default_screen(display);
    gtk_style_context_add_provider_for_screen(screen, 
GTK_STYLE_PROVIDER(provider), GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
    gtk_css_provider_load_from_data(provider, css_string1, -1, &css_error);
    //Print out the provider to see what is there.
    if(css_error==NULL)
      {
        gchar *string=gtk_css_provider_to_string(provider);
        g_print("%s\n", string);
        g_free(string);
      }
    else
      {
        g_print("CSS loader error %s\n", css_error->message);
        g_error_free(css_error);
      }
    g_object_unref(provider);

    gpointer data[]={provider, css_string1, css_string2};
    g_timeout_add(500, (GSourceFunc)blink, data);

    gtk_main();

    if(css_string1!=NULL) g_free(css_string1);
    if(css_string2!=NULL) g_free(css_string2);

    return 0;
  }  

 



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