[gtk/constraint-grid-3: 1/2] Add a grid constraint implementation

[Matthias Clasen <matthiasc src gnome org>]

commit 0468238871033f620bed6ce1b60597f97e8261c6
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Jul 2 12:51:44 2019 -0400

    Add a grid constraint implementation
    
    This is a convenience class that can create
    all the constraints to set up a grid.

 gtk/gtk.h               |   1 +
 gtk/gtkgridconstraint.c | 346 ++++++++++++++++++++++++++++++++++++++++++++++++
 gtk/gtkgridconstraint.h |  59 +++++++++
 gtk/meson.build         |   1 +
 4 files changed, 407 insertions(+)
---
diff --git a/gtk/gtk.h b/gtk/gtk.h
index ecf4829339..59f441bd70 100644
--- a/gtk/gtk.h
+++ b/gtk/gtk.h
@@ -132,6 +132,7 @@
 #include <gtk/gtkgesturezoom.h>
 #include <gtk/gtkglarea.h>
 #include <gtk/gtkgrid.h>
+#include <gtk/gtkgridconstraint.h>
 #include <gtk/gtkgridlayout.h>
 #include <gtk/gtkheaderbar.h>
 #include <gtk/gtkicontheme.h>
diff --git a/gtk/gtkgridconstraint.c b/gtk/gtkgridconstraint.c
new file mode 100644
index 0000000000..3b03a18368
--- /dev/null
+++ b/gtk/gtkgridconstraint.c
@@ -0,0 +1,346 @@
+/* gtkgridconstraint.c: Make a grid with constraints
+ * Copyright 2019  Red Hat, inc.
+ *
+ * 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: Matthias Clasen
+ */
+
+#include "config.h"
+
+#include "gtkgridconstraint.h"
+
+#include "gtkintl.h"
+#include "gtktypebuiltins.h"
+
+typedef struct {
+  GtkConstraintTarget *child;
+  int left;
+  int right;
+  int top;
+  int bottom;
+} GtkGridConstraintChild;
+
+struct _GtkGridConstraint {
+  GObject parent;
+
+  GtkConstraintLayout *layout;
+
+  gboolean row_homogeneous;
+  gboolean column_homogeneous;
+
+  GPtrArray *children;
+  GPtrArray *constraints;
+};
+
+enum {
+  PROP_ROW_HOMOGENEOUS = 1,
+  PROP_COLUMN_HOMOGENEOUS,
+  N_PROPERTIES
+};
+
+static GParamSpec *obj_props[N_PROPERTIES];
+
+G_DEFINE_TYPE (GtkGridConstraint, gtk_grid_constraint, G_TYPE_OBJECT)
+
+static void
+gtk_constraint_set_property (GObject      *gobject,
+                             guint         prop_id,
+                             const GValue *value,
+                             GParamSpec   *pspec)
+{
+  GtkGridConstraint *self = GTK_GRID_CONSTRAINT (gobject);
+
+  switch (prop_id)
+    {
+    case PROP_ROW_HOMOGENEOUS:
+      self->row_homogeneous = g_value_get_boolean (value);
+      break;
+
+    case PROP_COLUMN_HOMOGENEOUS:
+      self->column_homogeneous = g_value_get_boolean (value);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_constraint_get_property (GObject    *gobject,
+                             guint       prop_id,
+                             GValue     *value,
+                             GParamSpec *pspec)
+{
+  GtkGridConstraint *self = GTK_GRID_CONSTRAINT (gobject);
+
+  switch (prop_id)
+    {
+    case PROP_ROW_HOMOGENEOUS:
+      g_value_set_boolean (value, self->row_homogeneous);
+      break;
+
+    case PROP_COLUMN_HOMOGENEOUS:
+      g_value_set_boolean (value, self->column_homogeneous);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_constraint_finalize (GObject *gobject)
+{
+  GtkGridConstraint *self = GTK_GRID_CONSTRAINT (gobject);
+
+  gtk_grid_constraint_detach (self);
+
+  g_ptr_array_free (self->children, TRUE);
+  g_ptr_array_free (self->constraints, TRUE);
+
+  G_OBJECT_CLASS (gtk_grid_constraint_parent_class)->finalize (gobject);
+}
+
+static void
+gtk_grid_constraint_class_init (GtkGridConstraintClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->set_property = gtk_constraint_set_property;
+  gobject_class->get_property = gtk_constraint_get_property;
+  gobject_class->finalize = gtk_constraint_finalize;
+
+  /**
+   * GtkGridConstraint:row-homogeneous:
+   *
+   * Whether to make all rows the same height.
+   */
+  obj_props[PROP_ROW_HOMOGENEOUS] =
+    g_param_spec_boolean ("row-homogeneous",
+                          P_("Row homogeneous"),
+                          P_("Row homogeneous"),
+                          FALSE,
+                          G_PARAM_READWRITE |
+                          G_PARAM_STATIC_STRINGS);
+
+  /**
+   * GtkGridConstraint:column-homogeneous:
+   *
+   * Whether to make all columns the same width.
+   */
+  obj_props[PROP_COLUMN_HOMOGENEOUS] =
+    g_param_spec_boolean ("column-homogeneous",
+                          P_("Column homogeneous"),
+                          P_("Column homogeneous"),
+                          FALSE,
+                          G_PARAM_READWRITE |
+                          G_PARAM_STATIC_STRINGS);
+
+  g_object_class_install_properties (gobject_class, N_PROPERTIES, obj_props);
+}
+
+static void
+gtk_grid_constraint_init (GtkGridConstraint *self)
+{
+   self->children = g_ptr_array_new_with_free_func (g_free);
+   self->constraints = g_ptr_array_new ();
+}
+
+GtkGridConstraint *
+gtk_grid_constraint_new (void)
+{
+  return g_object_new (GTK_TYPE_GRID_CONSTRAINT, NULL);
+}
+
+
+/* Ensure that
+ * child1.width / child1.colspan == child2.width / child2.colspan
+ * (or equivalent for height )
+ */
+static void
+add_homogeneous_constraint (GtkGridConstraintChild *child1,
+                            GtkGridConstraintChild *child2,
+                            GtkConstraintAttribute  attr,
+                            GPtrArray              *constraints)
+{
+  int span1, span2;
+  GtkConstraint *constraint;
+
+  if (attr == GTK_CONSTRAINT_ATTRIBUTE_WIDTH)
+    {
+      span1 = child1->right - child1->left;
+      span2 = child2->right - child2->left;
+    }
+  else
+    {
+      span1 = child1->bottom - child1->top;
+      span2 = child2->bottom - child2->top;
+    }
+
+  constraint = gtk_constraint_new (child1->child, attr,
+                                   GTK_CONSTRAINT_RELATION_EQ,
+                                   child2->child, attr,
+                                   (double) span1 / (double) span2,
+                                   0.0,
+                                   GTK_CONSTRAINT_STRENGTH_REQUIRED);
+  g_ptr_array_add (constraints, constraint);
+}
+
+typedef struct {
+  GtkConstraintTarget *target;
+  GtkConstraintAttribute attr;
+} Attach;
+
+/* Ensure that the child variable @var is placed
+ * at the grid edge @pos. If we already have a variable
+ * that needs to end up there, we use it to assert
+ * var = vars[top], otherwise we put @var in the
+ * the list of variables.
+ */ 
+static void
+add_child_constraint (GtkConstraintTarget    *target,
+                      GtkConstraintAttribute  attr,
+                      int                     pos,
+                      GArray                 *vars,
+                      GPtrArray              *constraints)
+{
+  Attach *attach;
+
+  if (vars->len <= pos)
+    g_array_set_size (vars, pos + 1);
+
+  attach = &g_array_index (vars, Attach, pos);
+  if (attach->target == NULL)
+    {
+      attach->target = target;
+      attach->attr = attr;
+    }
+  else
+    {
+      GtkConstraint *constraint;
+
+      constraint = gtk_constraint_new (target, attr,
+                                       GTK_CONSTRAINT_RELATION_EQ,
+                                       attach->target, attach->attr,
+                                       1.0, 0.0,
+                                       GTK_CONSTRAINT_STRENGTH_REQUIRED);
+      g_ptr_array_add (constraints, constraint);
+    }
+}
+
+void
+gtk_grid_constraint_add (GtkGridConstraint *self,
+                         GtkWidget         *child,
+                         int                left,
+                         int                right,
+                         int                top,
+                         int                bottom)
+{
+  GtkGridConstraintChild *data;
+
+  g_return_if_fail (GTK_IS_GRID_CONSTRAINT (self));
+  g_return_if_fail (GTK_IS_WIDGET (child));
+  g_return_if_fail (left < right);
+  g_return_if_fail (top < bottom);
+  g_return_if_fail (self->layout == NULL);
+
+  data = g_new0 (GtkGridConstraintChild, 1);
+
+  data->child = GTK_CONSTRAINT_TARGET (child);
+  data->left = left;
+  data->right = right;
+  data->top = top;
+  data->bottom = bottom;
+
+  g_ptr_array_add (self->children, data);
+}
+
+gboolean
+gtk_grid_constraint_is_attached (GtkGridConstraint *self)
+{
+  return self->layout != NULL;
+}
+
+static void
+create_constraints (GtkGridConstraint *self)
+{
+  GArray *rows;
+  GArray *cols;
+  int i;
+
+  rows = g_array_new (FALSE, TRUE, sizeof (Attach));
+  cols = g_array_new (FALSE, TRUE, sizeof (Attach));
+
+  for (i = 0; i < self->children->len; i++)
+    {
+      GtkGridConstraintChild *child = g_ptr_array_index (self->children, i);
+
+      add_child_constraint (child->child, GTK_CONSTRAINT_ATTRIBUTE_TOP, child->top, rows, self->constraints);
+      add_child_constraint (child->child, GTK_CONSTRAINT_ATTRIBUTE_BOTTOM, child->bottom, rows, 
self->constraints);
+      add_child_constraint (child->child, GTK_CONSTRAINT_ATTRIBUTE_LEFT, child->left, cols, 
self->constraints);
+      add_child_constraint (child->child, GTK_CONSTRAINT_ATTRIBUTE_RIGHT, child->right, cols, 
self->constraints);
+    }
+
+  for (i = 1; i < self->children->len; i++)
+    {
+      GtkGridConstraintChild *child1 = g_ptr_array_index (self->children, i);
+      GtkGridConstraintChild *child2 = g_ptr_array_index (self->children, i - 1);
+      if (self->row_homogeneous)
+        add_homogeneous_constraint (child1, child2, GTK_CONSTRAINT_ATTRIBUTE_HEIGHT, self->constraints);
+      if (self->column_homogeneous)
+       add_homogeneous_constraint (child1, child2, GTK_CONSTRAINT_ATTRIBUTE_WIDTH, self->constraints);
+    }
+
+  g_array_free (rows, TRUE);
+  g_array_free (cols, TRUE);
+}
+
+void
+gtk_grid_constraint_attach (GtkGridConstraint   *self,
+                            GtkConstraintLayout *layout)
+{
+  int i;
+
+  g_return_if_fail (self->layout == NULL);
+
+  self->layout = layout;
+
+  create_constraints (self);
+
+  for (i = 0; i < self->constraints->len; i++)
+    {
+      GtkConstraint *constraint = g_ptr_array_index (self->constraints, i);
+      gtk_constraint_layout_add_constraint (layout, g_object_ref (constraint));
+    }
+}
+
+void
+gtk_grid_constraint_detach (GtkGridConstraint *self)
+{
+  int i;
+
+  if (self->layout == NULL)
+    return;
+
+  for (i = 0; i < self->constraints->len; i++)
+    {
+      GtkConstraint *constraint = g_ptr_array_index (self->constraints, i);
+      gtk_constraint_layout_remove_constraint (self->layout, constraint);
+    }
+
+  self->layout = NULL;
+}
diff --git a/gtk/gtkgridconstraint.h b/gtk/gtkgridconstraint.h
new file mode 100644
index 0000000000..fb885d33f7
--- /dev/null
+++ b/gtk/gtkgridconstraint.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2019 Red Hat, Inc.
+ *
+ * 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/>.
+ */
+
+#ifndef __GTK_GRID_CONSTRAINT_H__
+#define __GTK_GRID_CONSTRAINT_H__
+
+#include <gtk/gtkwidget.h>
+#include <gtk/gtkconstraintlayout.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_GRID_CONSTRAINT (gtk_grid_constraint_get_type ())
+
+/**
+ * GtkGridConstraint:
+ *
+ * An object used for managing constraints for children in
+ * a constraints layout that are to be arranged in a grid.
+ */
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_FINAL_TYPE (GtkGridConstraint, gtk_grid_constraint, GTK, GRID_CONSTRAINT, GObject)
+
+GDK_AVAILABLE_IN_ALL
+GtkGridConstraint * gtk_grid_constraint_new     (void);
+
+GDK_AVAILABLE_IN_ALL
+void                gtk_grid_constraint_add     (GtkGridConstraint   *self,
+                                                 GtkWidget           *child,
+                                                 int                  left,
+                                                 int                  right,
+                                                 int                  top,
+                                                 int                  bottom);
+
+GDK_AVAILABLE_IN_ALL
+void     gtk_grid_constraint_attach      (GtkGridConstraint   *self,
+                                          GtkConstraintLayout *layout);
+GDK_AVAILABLE_IN_ALL
+void     gtk_grid_constraint_detach      (GtkGridConstraint   *self);
+GDK_AVAILABLE_IN_ALL
+gboolean gtk_grid_constraint_is_attached (GtkGridConstraint   *self);
+
+
+G_END_DECLS
+
+#endif  /* __GTK_GRID_CONSTRAINT_H__ */
diff --git a/gtk/meson.build b/gtk/meson.build
index 428e1e49ab..310cf6704d 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -254,6 +254,7 @@ gtk_public_sources = files([
   'gtkgesturezoom.c',
   'gtkglarea.c',
   'gtkgrid.c',
+  'gtkgridconstraint.c',
   'gtkgridlayout.c',
   'gtkheaderbar.c',
   'gtkicontheme.c',