[gimp] app: add gimpdisplayshell-utils.[ch]

[N/A <ell src gnome org>]

commit fff57f84a0765811b90b9fa28bf1a92e19042974
Author: Ell <ell_se yahoo com>
Date:   Fri Dec 22 06:58:54 2017 -0500

    app: add gimpdisplayshell-utils.[ch]
    
    ... should have been part of last commit.

 app/display/gimpdisplayshell-utils.c |   60 ++++++++++++++++++++++++++++++++++
 app/display/gimpdisplayshell-utils.h |   31 +++++++++++++++++
 2 files changed, 91 insertions(+), 0 deletions(-)
---
diff --git a/app/display/gimpdisplayshell-utils.c b/app/display/gimpdisplayshell-utils.c
new file mode 100644
index 0000000..ea0f3eb
--- /dev/null
+++ b/app/display/gimpdisplayshell-utils.c
@@ -0,0 +1,60 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl.h>
+#include <gtk/gtk.h>
+
+#include "libgimpmath/gimpmath.h"
+
+#include "display-types.h"
+
+#include "core/gimp-utils.h"
+
+#include "gimpdisplayshell.h"
+#include "gimpdisplayshell-utils.h"
+
+
+gdouble
+gimp_display_shell_get_constrained_line_offset_angle (GimpDisplayShell *shell)
+{
+  g_return_val_if_fail (GIMP_IS_DISPLAY_SHELL (shell), 0.0);
+
+  if (shell->flip_horizontally ^ shell->flip_vertically)
+    return +shell->rotate_angle;
+  else
+    return -shell->rotate_angle;
+}
+
+void
+gimp_display_shell_constrain_line (GimpDisplayShell *shell,
+                                   gdouble           start_x,
+                                   gdouble           start_y,
+                                   gdouble          *end_x,
+                                   gdouble          *end_y,
+                                   gint              n_snap_lines)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (end_x != NULL);
+  g_return_if_fail (end_y != NULL);
+
+  gimp_constrain_line (start_x, start_y,
+                       end_x,   end_y,
+                       n_snap_lines,
+                       gimp_display_shell_get_constrained_line_offset_angle (shell));
+}
diff --git a/app/display/gimpdisplayshell-utils.h b/app/display/gimpdisplayshell-utils.h
new file mode 100644
index 0000000..a9a2f83
--- /dev/null
+++ b/app/display/gimpdisplayshell-utils.h
@@ -0,0 +1,31 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GIMP_DISPLAY_SHELL_UTILS_H__
+#define __GIMP_DISPLAY_SHELL_UTILS_H__
+
+
+gdouble   gimp_display_shell_get_constrained_line_offset_angle (GimpDisplayShell *shell);
+void      gimp_display_shell_constrain_line                    (GimpDisplayShell *shell,
+                                                                gdouble          start_x,
+                                                                gdouble          start_y,
+                                                                gdouble         *end_x,
+                                                                gdouble         *end_y,
+                                                                gint             n_snap_lines);
+
+
+#endif  /*  __GIMP_DISPLAY_SHELL_UTILS_H__  */