Auto scrolling GtkScrolledWindow with GtkTextView wrapped in GtkBox - c

Question

When I have GtkTextView in GtkScrolledWindow, it scrolls automatically when user appends new line at the bottom of the widget. When I put GtkTextView in GtkBox and then in GtkScrolledWindow I doesn't work. I need to put box between GtkTextView and scrollbar and I can't do that without placing whole thing in another box. Is there any way to preserve autoscrolling behaviour when using GtkBox inside GtkScrolledWindow?
There is code that ilustrates my problem:
#include <gtk/gtk.h>
int main(int argc, char *argv[]) {
GtkWidget *window;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_default_size(GTK_WINDOW(window),
gdk_screen_width()*0.5, gdk_screen_height()*0.5);
GtkWidget *main = gtk_box_new(0, 0);
gtk_container_add(GTK_CONTAINER(window), main);
/*/////////////////////////////////////////////////*/
/* IMPORTANT PART */
/* FIRST CASE (this one works correctly) */
GtkWidget *scrolled_window_first = gtk_scrolled_window_new(NULL, NULL);
GtkWidget *text_view_first = gtk_text_view_new();
gtk_container_add(GTK_CONTAINER(scrolled_window_first), text_view_first);
gtk_box_pack_start(GTK_BOX(main), scrolled_window_first, 1, 1, 0);
/* SECOND CASE (there is no auto scroll which I need) */
GtkWidget *scrolled_window_second = gtk_scrolled_window_new(NULL, NULL);
GtkWidget *text_view_second = gtk_text_view_new();
GtkWidget *box_from_second_example = gtk_box_new(0, 0);
GtkWidget *example_box_before_scroller = gtk_box_new(0,0);
GtkWidget *example_label = gtk_label_new("I need this box badly!");
gtk_box_pack_start(GTK_BOX(box_from_second_example), text_view_second, 1, 1, 0);
gtk_container_add(GTK_CONTAINER(scrolled_window_second), box_from_second_example);
gtk_container_add(GTK_CONTAINER(box_from_second_example), example_box_before_scroller);
gtk_box_pack_start(GTK_BOX(main), scrolled_window_second, 1, 1, 0);
/* END IMPORTANT PART */
/*/////////////////////////////////////////////////*/
gtk_container_add(GTK_CONTAINER(example_box_before_scroller), example_label);
g_signal_connect(GTK_WINDOW(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);
gtk_widget_show_all(window);
gtk_main ();
return 0;
}

Answer 1

The problem is GtkTextView implements GtkScrollable but GtkBox does not. This is not a minor issue: if you want to go the GtkBox way you should put it inside a GtkViewport and add the scrollability stuff... quite some code that involves deep understanding of how the whole thing scrolls.
Anyway if you are lazy enough you could also note GtkTextview is a GtkContainer. In other words you could add widgets around the GtkTextview without the need to incomodate GtkBox. Not exactly what you were looking for but maybe good enough for your purposes:
#include <gtk/gtk.h>
gint main(gint argc, gchar **argv)
{
GtkWidget *window, *scrolled_window, *text_view, *label;
gtk_init(&argc, &argv);
text_view = gtk_text_view_new();
gtk_text_buffer_set_text(gtk_text_view_get_buffer(GTK_TEXT_VIEW(text_view)),
"1\n\n\n2\n\n\n3\n\n\n4\n\n\n5\n\n\n6\n\n\n7\n\n\n8", -1);
/* Use this to set the size you want to reserve on the right */
gtk_text_view_set_border_window_size(GTK_TEXT_VIEW(text_view),
GTK_TEXT_WINDOW_RIGHT,
130);
/* Add whatever you want instead of a GtkLabel */
gtk_text_view_add_child_in_window(GTK_TEXT_VIEW(text_view),
gtk_label_new("You badly need this"),
GTK_TEXT_WINDOW_RIGHT,
0, 0);
scrolled_window = gtk_scrolled_window_new(NULL, NULL);
gtk_container_add(GTK_CONTAINER(scrolled_window), text_view);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_default_size(GTK_WINDOW(window), 320, 240);
gtk_container_add(GTK_CONTAINER(window), scrolled_window);
gtk_widget_show_all(window);
gtk_main ();
return 0;
}

Answer 2

Did you try to modify the GtkAdjustments the textview creates by default (GtkScrolledWindow implements the GtkScrollable afaik).
GtkAdjustment * gtk_scrollable_get_hadjustment (GtkScrollable *scrollable);
I think the best approach would be to detect insertions to the GtkTextBuffer (get the views buffer via
GtkTextBuffer * gtk_text_view_get_buffer (GtkTextView *text_view);
and hook a callback (which tests for \n) to its insert-text g_signal and use
void gtk_adjustment_set_value (GtkAdjustment *adjustment,
gdouble value);
to modify the scrolling height.
Note that this is untested and a simpler method might be around the corner.