Re: Scrolling to a line in GtkTextView

[Reuben Rissler <silrep emypeople net>]

On 02/12/2019 12:47 PM, Mitko Haralanov via gtk-app-devel-list wrote:
> Hi,
>
> In my application, I would like to have a GtkTextView be scrolled to a
> particular line after the GtkTextBuffer is loaded.
This was already discussed 
https://stackoverflow.com/questions/48934458/gtk-sourceview-scroll-to-mark-not-working.

Basically, the GUI calculations are not done and the lines aren't 
calculated, therefore you need to scroll after the GUI rendering is 
finished. Use idle_add or timeout_add.
> According to the documentation, I can use gtk_text_view_scroll_to_mark() in
> order to reliably scroll to the desired line after the line height
> computation has been completed. In practice that doesn't work reliably.
> Below is the code snippet that I am using:
>
>
> while (delay++ < 100)
> g_main_context_iteration(NULL, FALSE);
> debug("Scrolling to line: %lu", lineno);
> gtk_text_buffer_get_iter_at_line(GTK_TEXT_BUFFER(priv->sourceBuf),
> &iter, (gint)(lineno - 1));
> debug("Line: %d, offset: %d", gtk_text_iter_get_line(&iter),
>        gtk_text_iter_get_offset(&iter));
> gtk_text_buffer_place_cursor(GTK_TEXT_BUFFER(priv->sourceBuf), &iter);
> mark = gtk_text_buffer_get_mark(GTK_TEXT_BUFFER(priv->sourceBuf),
> "result-view-search");
> gtk_text_buffer_move_mark(GTK_TEXT_BUFFER(priv->sourceBuf), mark,
>    &iter);
> gtk_text_view_scroll_to_mark(GTK_TEXT_VIEW(priv->sourceView), mark, 0.0,
>       TRUE, 0.0, 0.5);
>
> What I am noticing is that the reliability of this highly depends on the
> line number to which I want to scroll and the length of the busy loop in
> the beginning - the higher the line number, the longer the busy loop needs
> to be in order to reliably scroll to that line.
>
> If the busy loop is not long enough, the text view does scroll but not the
> correct line.
>
> What is the proper way to correctly and reliably scroll a GtkTextView to a
> certain line?
>
> Thank you,
> Mitko
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