[sysprof] libsysprof-ui: add fit-width zoom helper

[Christian Hergert <chergert src gnome org>]

commit ce3e7c5f4e21ac28dbff6164fca4f51bf2bb0103
Author: Christian Hergert <chergert redhat com>
Date:   Tue May 14 21:09:24 2019 -0700

    libsysprof-ui: add fit-width zoom helper

 src/libsysprof-ui/sysprof-zoom-manager.c | 12 ++++++++++++
 src/libsysprof-ui/sysprof-zoom-manager.h |  4 ++++
 2 files changed, 16 insertions(+)
---
diff --git a/src/libsysprof-ui/sysprof-zoom-manager.c b/src/libsysprof-ui/sysprof-zoom-manager.c
index cdb0665..41a74fe 100644
--- a/src/libsysprof-ui/sysprof-zoom-manager.c
+++ b/src/libsysprof-ui/sysprof-zoom-manager.c
@@ -515,3 +515,15 @@ sysprof_zoom_manager_get_width_for_duration (SysprofZoomManager *self,
 
   return (gdouble)duration / (gdouble)NSEC_PER_SEC * DEFAULT_PIXELS_PER_SEC * self->zoom;
 }
+
+gdouble
+sysprof_zoom_manager_fit_zoom_for_duration (SysprofZoomManager *self,
+                                            gint64              duration,
+                                            gint                width)
+{
+  g_return_val_if_fail (SYSPROF_IS_ZOOM_MANAGER (self), 1.0);
+  g_return_val_if_fail (duration >= 0, 1.0);
+
+  return ((gdouble)width / DEFAULT_PIXELS_PER_SEC) /
+         ((gdouble)duration / (gdouble)NSEC_PER_SEC);
+}
diff --git a/src/libsysprof-ui/sysprof-zoom-manager.h b/src/libsysprof-ui/sysprof-zoom-manager.h
index 78e4b57..5b777b2 100644
--- a/src/libsysprof-ui/sysprof-zoom-manager.h
+++ b/src/libsysprof-ui/sysprof-zoom-manager.h
@@ -70,5 +70,9 @@ gint                sysprof_zoom_manager_get_width_for_duration (SysprofZoomMana
 SYSPROF_AVAILABLE_IN_ALL
 gint64              sysprof_zoom_manager_get_duration_for_width (SysprofZoomManager *self,
                                                                  gint                width);
+SYSPROF_AVAILABLE_IN_ALL
+gdouble             sysprof_zoom_manager_fit_zoom_for_duration  (SysprofZoomManager *self,
+                                                                 gint64              duration,
+                                                                 gint                width);
 
 G_END_DECLS