[sysprof] libsysprof-ui: improve marks drawing a bit

[Christian Hergert <chergert src gnome org>]

commit 4af22435db01cecac4fc8d82c59bb06280a3e2be
Author: Christian Hergert <chergert redhat com>
Date:   Mon May 13 00:38:15 2019 -0700

    libsysprof-ui: improve marks drawing a bit

 src/libsysprof-ui/sysprof-cell-renderer-duration.c | 16 ++++++++--------
 src/libsysprof-ui/sysprof-marks-model.c            | 12 ++++++++----
 2 files changed, 16 insertions(+), 12 deletions(-)
---
diff --git a/src/libsysprof-ui/sysprof-cell-renderer-duration.c 
b/src/libsysprof-ui/sysprof-cell-renderer-duration.c
index fc26ffa..94bd7b7 100644
--- a/src/libsysprof-ui/sysprof-cell-renderer-duration.c
+++ b/src/libsysprof-ui/sysprof-cell-renderer-duration.c
@@ -65,14 +65,11 @@ sysprof_cell_renderer_duration_render (GtkCellRenderer      *renderer,
   g_assert (cr != NULL);
   g_assert (GTK_IS_WIDGET (widget));
 
-  if (priv->begin_time == priv->end_time)
-    return;
-
-  if (priv->end_time < priv->begin_time)
-    return;
-
-  if (priv->begin_time > priv->zoom_end || priv->end_time < priv->zoom_begin)
-    return;
+  if (priv->end_time >= priv->begin_time)
+    {
+      if (priv->begin_time > priv->zoom_end || priv->end_time < priv->zoom_begin)
+        return;
+    }
 
   style_context = gtk_widget_get_style_context (widget);
   gtk_style_context_get_color (style_context,
@@ -84,6 +81,9 @@ sysprof_cell_renderer_duration_render (GtkCellRenderer      *renderer,
   x1 = (priv->begin_time - priv->zoom_begin) / zoom_range * cell_area->width;
   x2 = (priv->end_time - priv->zoom_begin) / zoom_range * cell_area->width;
 
+  if (x2 < x1)
+    x2 = x1;
+
   r.x = cell_area->x + x1;
   r.y = cell_area->y;
   r.width = MAX (1.0, x2 - x1);
diff --git a/src/libsysprof-ui/sysprof-marks-model.c b/src/libsysprof-ui/sysprof-marks-model.c
index 139c8ea..17ee2cf 100644
--- a/src/libsysprof-ui/sysprof-marks-model.c
+++ b/src/libsysprof-ui/sysprof-marks-model.c
@@ -294,10 +294,14 @@ item_compare (gconstpointer a,
   const Item *ia = a;
   const Item *ib = b;
 
-  if (ia->begin_time == ib->begin_time)
-    return ia->end_time - ib->end_time;
-
-  return ia->begin_time - ib->begin_time;
+  if (ia->begin_time < ib->begin_time)
+    return -1;
+  else if (ia->begin_time > ib->begin_time)
+    return 1;
+  else if (ia->end_time > ib->end_time)
+    return 1;
+  else
+    return 0;
 }
 
 static void