Add constraint solver

GtkConstraintSolver is an implementation of the Cassowary constraint
solving algorithm:

  http://constraints.cs.washington.edu/cassowary/

The Cassowary method allows to incrementally solve a tableau of linear
equations, in the form of:

  x = y × coefficient + constant

with different weights, or strengths, applied to each one.

These equations can be used to describe constraints applied to a layout
of UI elements, which allows layout managers using the Cassowary method
to quickly, and efficiently, lay out widgets in complex relations
between themselves and their parent container.

1 files changed, 114 insertions, 0 deletions

diff --git a/gtk/gtkconstraintsolverprivate.h b/gtk/gtkconstraintsolverprivate.h
new file mode 100644
index 0000000000..807b0b08d6
--- /dev/null
+++ b/gtk/gtkconstraintsolverprivate.h
@@ -0,0 +1,114 @@
+/* gtkconstraintsolverprivate.h: Constraint solver based on the Cassowary method
+ * Copyright 2019  GNOME Foundation
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Emmanuele Bassi
+ */
+
+#pragma once
+
+#include "gtkconstrainttypesprivate.h"
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_CONSTRAINT_SOLVER (gtk_constraint_solver_get_type())
+
+G_DECLARE_FINAL_TYPE (GtkConstraintSolver, gtk_constraint_solver, GTK, CONSTRAINT_SOLVER, GObject)
+
+GtkConstraintSolver *
+gtk_constraint_solver_new (void);
+
+void
+gtk_constraint_solver_freeze (GtkConstraintSolver *solver);
+
+void
+gtk_constraint_solver_thaw (GtkConstraintSolver *solver);
+
+void
+gtk_constraint_solver_resolve (GtkConstraintSolver *solver);
+
+GtkConstraintVariable *
+gtk_constraint_solver_create_variable (GtkConstraintSolver *solver,
+                                       const char          *prefix,
+                                       const char          *name,
+                                       double               value);
+
+GtkConstraintRef *
+gtk_constraint_solver_add_constraint (GtkConstraintSolver     *solver,
+                                      GtkConstraintVariable   *variable,
+                                      GtkConstraintRelation    relation,
+                                      GtkConstraintExpression *expression,
+                                      double                   strength);
+
+void
+gtk_constraint_solver_remove_constraint (GtkConstraintSolver *solver,
+                                         GtkConstraintRef    *reference);
+
+GtkConstraintRef *
+gtk_constraint_solver_add_stay_variable (GtkConstraintSolver   *solver,
+                                         GtkConstraintVariable *variable,
+                                         double                 strength);
+
+void
+gtk_constraint_solver_remove_stay_variable (GtkConstraintSolver   *solver,
+                                            GtkConstraintVariable *variable);
+
+gboolean
+gtk_constraint_solver_has_stay_variable (GtkConstraintSolver   *solver,
+                                         GtkConstraintVariable *variable);
+
+GtkConstraintRef *
+gtk_constraint_solver_add_edit_variable (GtkConstraintSolver   *solver,
+                                         GtkConstraintVariable *variable,
+                                         double                 strength);
+
+void
+gtk_constraint_solver_remove_edit_variable (GtkConstraintSolver   *solver,
+                                            GtkConstraintVariable *variable);
+
+gboolean
+gtk_constraint_solver_has_edit_variable (GtkConstraintSolver   *solver,
+                                         GtkConstraintVariable *variable);
+
+void
+gtk_constraint_solver_suggest_value (GtkConstraintSolver   *solver,
+                                     GtkConstraintVariable *variable,
+                                     double                 value);
+
+void
+gtk_constraint_solver_begin_edit (GtkConstraintSolver *solver);
+
+void
+gtk_constraint_solver_end_edit (GtkConstraintSolver *solver);
+
+void
+gtk_constraint_solver_note_added_variable (GtkConstraintSolver *self,
+                                           GtkConstraintVariable *variable,
+                                           GtkConstraintVariable *subject);
+
+void
+gtk_constraint_solver_note_removed_variable (GtkConstraintSolver *self,
+                                             GtkConstraintVariable *variable,
+                                             GtkConstraintVariable *subject);
+
+void
+gtk_constraint_solver_clear (GtkConstraintSolver *solver);
+
+char *
+gtk_constraint_solver_to_string (GtkConstraintSolver *solver);
+
+G_END_DECLS