[gnome-system-monitor] Preserve tree scroll position at top/bottom when new processes are added. https://bugzilla.gnome.org

[Robert Roth <robertroth src gnome org>]

commit 561378bd53e02e73f0d43850e47d536dd6699d38
Author: Robert Roth <robert roth off gmail com>
Date:   Mon May 6 02:10:11 2013 +0300

    Preserve tree scroll position at top/bottom when new processes are added.
    https://bugzilla.gnome.org/show_bug.cgi?id=92724

 src/procman-app.h |    4 ++++
 src/proctable.cpp |   30 +++++++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletions(-)
---
diff --git a/src/procman-app.h b/src/procman-app.h
index d698649..ad9ecc0 100644
--- a/src/procman-app.h
+++ b/src/procman-app.h
@@ -201,6 +201,10 @@ public:
     guint             timeout;
     guint             disk_timeout;
 
+    GtkTreePath      *top_of_tree;
+    gdouble          last_vscroll_max;
+    gdouble          last_vscroll_value;
+
     PrettyTable      *pretty_table;
 
     GSettings        *settings;
diff --git a/src/proctable.cpp b/src/proctable.cpp
index 975dcc7..e4da3bb 100644
--- a/src/proctable.cpp
+++ b/src/proctable.cpp
@@ -973,8 +973,36 @@ proctable_update_list (ProcmanApp *app)
     glibtop_get_cpu (&cpu);
     app->cpu_total_time = MAX(cpu.total - app->cpu_total_time_last, 1);
     app->cpu_total_time_last = cpu.total;
-
+    
+    GtkAdjustment* vadjustment = GTK_ADJUSTMENT(gtk_scrollable_get_vadjustment(GTK_SCROLLABLE(app->tree)));
     refresh_list (app, pid_list, proclist.number);
+    
+    // juggling with tree scroll position to fix https://bugzilla.gnome.org/show_bug.cgi?id=92724
+    GtkTreePath* current_top;
+    gtk_tree_view_get_path_at_pos(GTK_TREE_VIEW(app->tree), 0,0, &current_top, NULL, NULL, NULL);
+    gdouble current_max = gtk_adjustment_get_upper(vadjustment);
+    gdouble current_value = gtk_adjustment_get_value(vadjustment);
+    if (app->top_of_tree) {
+        // if the visible cell from the top of the tree is still the same, as last time 
+        if (gtk_tree_path_compare(app->top_of_tree, current_top) == 0) 
+        {   
+            //but something from the scroll parameters has changed compared to the last values
+            if (app->last_vscroll_value==0 && current_value!=app->last_vscroll_value) 
+            {
+                // the tree was scrolled to top, and something has been added above the current top row
+                gtk_tree_view_scroll_to_point(GTK_TREE_VIEW(app->tree), -1, 0);
+            } 
+            else if (current_max > app->last_vscroll_max && current_value == app->last_vscroll_value)
+            {
+                // the tree was scrolled to bottom, something has been added below the current bottom row
+                gtk_tree_view_scroll_to_point(GTK_TREE_VIEW(app->tree), -1, current_max);
+            }
+        }
+        gtk_tree_path_free(app->top_of_tree);
+    }
+    app->top_of_tree = current_top;
+    app->last_vscroll_value = current_value;
+    app->last_vscroll_max = current_max;
 
     g_free (pid_list);