Add a larger constraints demo

Currently, this mainly demonstrates the scalability
limits of the constraints solver. For comparison,
the same demo can be run with the grid layout.

demos/gtk-demo/constraints.c

@@ -1,4 +1,4 @@
-/* Constraints
+/* Constraints/Simple
  *
  * GtkConstraintLayout provides a layout manager that uses relations
  * between widgets (also known as "constraints") to compute the position

demos/gtk-demo/constraints2.c

@@ -0,0 +1,190 @@
+/* Constraints/Grid
+ *
+ * GtkConstraintLayout lets you define complex layouts
+ * like grids.
+ */
+
+#include <glib/gi18n.h>
+#include <gtk/gtk.h>
+
+G_DECLARE_FINAL_TYPE (ComplexGrid, complex_grid, COMPLEX, GRID, GtkWidget)
+
+struct _ComplexGrid
+{
+  GtkWidget parent_instance;
+
+  GtkWidget *button1, *button2, *button3;
+  GtkWidget *button4, *button5;
+};
+
+G_DEFINE_TYPE (ComplexGrid, complex_grid, GTK_TYPE_WIDGET)
+
+static void
+complex_grid_destroy (GtkWidget *widget)
+{
+  ComplexGrid *self = COMPLEX_GRID (widget);
+
+  g_clear_pointer (&self->button1, gtk_widget_destroy);
+  g_clear_pointer (&self->button2, gtk_widget_destroy);
+  g_clear_pointer (&self->button3, gtk_widget_destroy);
+  g_clear_pointer (&self->button4, gtk_widget_destroy);
+  g_clear_pointer (&self->button5, gtk_widget_destroy);
+
+  GTK_WIDGET_CLASS (complex_grid_parent_class)->destroy (widget);
+}
+
+static void
+complex_grid_class_init (ComplexGridClass *klass)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+
+  widget_class->destroy = complex_grid_destroy;
+
+  gtk_widget_class_set_layout_manager_type (widget_class, GTK_TYPE_CONSTRAINT_LAYOUT);
+}
+
+/* Layout:
+ *
+ *   +--------------------------------------+
+ *   |             +-----------+            |
+ *   |             |  Child 4  |            |
+ *   | +-----------+-----------+----------+ |
+ *   | |  Child 1  |  Child 2  |  Child 3 | |
+ *   | +-----------+-----------+----------+ |
+ *   |             |  Child 5  |            |
+ *   |             +-----------+            |
+ *   +--------------------------------------+
+ *
+ */
+static void
+build_constraints (ComplexGrid         *self,
+                   GtkConstraintLayout *manager)
+{
+  GtkGridConstraint *constraint;
+  GtkConstraint *s;
+
+  s = gtk_constraint_new (NULL, GTK_CONSTRAINT_ATTRIBUTE_LEFT,
+                          GTK_CONSTRAINT_RELATION_EQ,
+                          self->button1, GTK_CONSTRAINT_ATTRIBUTE_LEFT,
+                          1.0, 0.0,
+                          GTK_CONSTRAINT_STRENGTH_REQUIRED);
+  gtk_constraint_layout_add_constraint (manager, s);
+
+  s = gtk_constraint_new (self->button3, GTK_CONSTRAINT_ATTRIBUTE_RIGHT,
+                          GTK_CONSTRAINT_RELATION_EQ,
+                          NULL, GTK_CONSTRAINT_ATTRIBUTE_RIGHT,
+                          1.0, 0.0,
+                          GTK_CONSTRAINT_STRENGTH_REQUIRED);
+  gtk_constraint_layout_add_constraint (manager, s);
+
+  s = gtk_constraint_new (NULL, GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                          GTK_CONSTRAINT_RELATION_EQ,
+                          self->button4, GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                          1.0, 0.0,
+                          GTK_CONSTRAINT_STRENGTH_REQUIRED);
+  gtk_constraint_layout_add_constraint (manager, s);
+
+  s = gtk_constraint_new (NULL, GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                          GTK_CONSTRAINT_RELATION_EQ,
+                          self->button5, GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                          1.0, 0.0,
+                          GTK_CONSTRAINT_STRENGTH_REQUIRED);
+  gtk_constraint_layout_add_constraint (manager, s);
+
+  constraint = gtk_grid_constraint_new ();
+  g_object_set (constraint, "column-homogeneous", TRUE, NULL);
+  gtk_grid_constraint_add (constraint,
+                           self->button1,
+                           0, 1, 0, 1);
+  gtk_grid_constraint_add (constraint,
+                           self->button2,
+                           1, 2, 0, 1);
+  gtk_grid_constraint_add (constraint,
+                           self->button3,
+                           2, 3, 0, 1);
+  gtk_constraint_layout_add_grid_constraint (manager, constraint);
+
+  constraint = gtk_grid_constraint_new ();
+  g_object_set (constraint, "row-homogeneous", TRUE, NULL);
+  gtk_grid_constraint_add (constraint,
+                           self->button4,
+                           0, 1, 0, 1);
+  gtk_grid_constraint_add (constraint,
+                           self->button2,
+                           0, 1, 1, 2);
+  gtk_grid_constraint_add (constraint,
+                           self->button5,
+                           0, 1, 2, 3);
+  gtk_constraint_layout_add_grid_constraint (manager, constraint);
+}
+
+static void
+complex_grid_init (ComplexGrid *self)
+{
+  GtkWidget *widget = GTK_WIDGET (self);
+  GtkLayoutManager *manager = gtk_widget_get_layout_manager (GTK_WIDGET (self));
+
+  self->button1 = gtk_button_new_with_label ("Child 1");
+  gtk_widget_set_parent (self->button1, widget);
+  gtk_widget_set_name (self->button1, "button1");
+
+  self->button2 = gtk_button_new_with_label ("Child 2");
+  gtk_widget_set_parent (self->button2, widget);
+  gtk_widget_set_name (self->button2, "button2");
+
+  self->button3 = gtk_button_new_with_label ("Child 3");
+  gtk_widget_set_parent (self->button3, widget);
+  gtk_widget_set_name (self->button3, "button3");
+
+  self->button4 = gtk_button_new_with_label ("Child 4");
+  gtk_widget_set_parent (self->button4, widget);
+  gtk_widget_set_name (self->button4, "button4");
+
+  self->button5 = gtk_button_new_with_label ("Child 5");
+  gtk_widget_set_parent (self->button5, widget);
+  gtk_widget_set_name (self->button5, "button5");
+
+  build_constraints (self, GTK_CONSTRAINT_LAYOUT (manager));
+}
+
+GtkWidget *
+do_constraints2 (GtkWidget *do_widget)
+{
+ static GtkWidget *window;
+
+ if (!window)
+   {
+     GtkWidget *header, *box, *grid, *button;
+
+     window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+     gtk_window_set_display (GTK_WINDOW (window), gtk_widget_get_display (do_widget));
+
+     header = gtk_header_bar_new ();
+     gtk_header_bar_set_title (GTK_HEADER_BAR (header), "Constraints");
+     gtk_header_bar_set_show_title_buttons (GTK_HEADER_BAR (header), FALSE);
+     gtk_window_set_titlebar (GTK_WINDOW (window), header);
+     g_signal_connect (window, "destroy",
+                       G_CALLBACK (gtk_widget_destroyed), &window);
+
+     box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 12);
+     gtk_container_add (GTK_CONTAINER (window), box);
+
+     grid = g_object_new (complex_grid_get_type (), NULL);
+     gtk_widget_set_hexpand (grid, TRUE);
+     gtk_widget_set_vexpand (grid, TRUE);
+     gtk_container_add (GTK_CONTAINER (box), grid);
+
+     button = gtk_button_new_with_label ("Close");
+     gtk_container_add (GTK_CONTAINER (box), button);
+     gtk_widget_set_hexpand (grid, TRUE);
+     g_signal_connect_swapped (button, "clicked",
+                               G_CALLBACK (gtk_widget_destroy), window);
+   }
+
+ if (!gtk_widget_get_visible (window))
+   gtk_widget_show (window);
+ else
+   gtk_widget_destroy (window);
+
+ return window;
+}

demos/gtk-demo/constraints3.c

@@ -0,0 +1,355 @@
+/* Constraints/Words
+ *
+ * GtkConstraintLayout lets you define big grids.
+ */
+
+#include <glib/gi18n.h>
+#include <gtk/gtk.h>
+
+#define WORDS_TYPE_BASE (words_base_get_type ())
+#define WORDS_TYPE_GRID (words_grid_get_type ())
+#define WORDS_TYPE_CONSTRAINT (words_constraint_get_type ())
+
+typedef struct
+{
+  GtkWidget parent_instance;
+} WordsBase;
+
+typedef WordsBase WordsGrid;
+typedef WordsBase WordsConstraint;
+
+typedef GtkWidgetClass WordsBaseClass;
+typedef GtkWidgetClass WordsGridClass;
+typedef GtkWidgetClass WordsConstraintClass;
+
+G_DEFINE_TYPE (WordsBase, words_base, GTK_TYPE_WIDGET)
+G_DEFINE_TYPE (WordsGrid, words_grid, WORDS_TYPE_BASE)
+G_DEFINE_TYPE (WordsConstraint, words_constraint, WORDS_TYPE_BASE)
+
+static void
+words_grid_init (WordsGrid *words)
+{
+}
+
+static void
+words_grid_class_init (WordsGridClass *class)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+
+  gtk_widget_class_set_layout_manager_type (widget_class, GTK_TYPE_GRID_LAYOUT);
+}
+
+static void
+words_constraint_init (WordsGrid *words)
+{
+}
+
+static void
+words_constraint_class_init (WordsConstraintClass *class)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+
+  gtk_widget_class_set_layout_manager_type (widget_class, GTK_TYPE_CONSTRAINT_LAYOUT);
+}
+
+static void
+word_base_dispose (GObject *object)
+{
+  GtkWidget *self = GTK_WIDGET (object);
+  GtkWidget *child;
+
+  while ((child = gtk_widget_get_first_child (self)) != NULL)
+    gtk_widget_unparent (child);
+
+  G_OBJECT_CLASS (words_base_parent_class)->dispose (object);
+}
+
+static void
+words_base_class_init (WordsBaseClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->dispose = word_base_dispose;
+}
+
+static int num_words = 100;
+static gboolean use_constraints = FALSE;
+
+static void
+read_words (WordsBase *self)
+{
+  GBytes *data;
+  const char *words;
+  int left, top;
+  GtkWidget *child = NULL;
+  GtkLayoutManager *layout = gtk_widget_get_layout_manager (GTK_WIDGET (self));
+  GtkGridConstraint *grid;
+  GtkConstraint *constraint;
+  int count;
+  int rightmost;
+  GtkWidget *right_child = NULL;
+  gboolean use_constraint = GTK_IS_CONSTRAINT_LAYOUT (layout);
+
+  if (use_constraint)
+    {
+      grid = gtk_grid_constraint_new ();
+      g_object_set (grid,
+                    "row-homogeneous", TRUE,
+                    "column-homogeneous", FALSE,
+                    NULL);
+    }
+  else
+    {
+      gtk_grid_layout_set_row_homogeneous (GTK_GRID_LAYOUT (layout), TRUE);
+      gtk_grid_layout_set_column_homogeneous (GTK_GRID_LAYOUT (layout), FALSE);
+    }
+
+  data = g_resources_lookup_data ("/constraints3/words", 0, NULL);
+  words = g_bytes_get_data (data, NULL);
+  count = 0;
+
+  rightmost = 0;
+  left = 0;
+  top = 0;
+  while (words && words[0])
+    {
+      char *p = strchr (words, '\n');
+      char *word;
+      int len;
+
+      if (p)
+        {
+          word = strndup (words, p - words);
+          words = p + 1;
+        }
+      else
+        {
+          word = strdup (words);
+          words = NULL;
+        }
+
+      len = strlen (word);
+      child = gtk_button_new_with_label (word);
+
+      if (left + len > 50)
+        {
+          top++;
+          left = 0;
+        }
+
+      gtk_widget_set_parent (child, GTK_WIDGET (self));
+
+      if (left + len > rightmost)
+        {
+          rightmost = left + len;
+          right_child = child;
+        }
+
+      if (use_constraint)
+        {
+          gtk_grid_constraint_add (grid, child,
+                                   left, left + len,
+                                   top, top + 1);
+          if (left == 0 && top == 0)
+            {
+              constraint = gtk_constraint_new (NULL,
+                                               GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                                               GTK_CONSTRAINT_RELATION_EQ,
+                                               child,
+                                               GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                                               1.0,
+                                               0.0,
+                                               GTK_CONSTRAINT_STRENGTH_REQUIRED);
+              gtk_constraint_layout_add_constraint (GTK_CONSTRAINT_LAYOUT (layout),
+                                                    constraint);
+              constraint = gtk_constraint_new (NULL,
+                                               GTK_CONSTRAINT_ATTRIBUTE_LEFT,
+                                               GTK_CONSTRAINT_RELATION_EQ,
+                                               child,
+                                               GTK_CONSTRAINT_ATTRIBUTE_LEFT,
+                                               1.0,
+                                               0.0,
+                                               GTK_CONSTRAINT_STRENGTH_REQUIRED);
+               gtk_constraint_layout_add_constraint (GTK_CONSTRAINT_LAYOUT (layout),
+                                                     constraint);
+            }
+        }
+      else
+        {
+          GtkGridLayoutChild *grid_child = GTK_GRID_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (layout, child));
+
+          g_object_set (grid_child,
+                        "left-attach", left,
+                        "top-attach", top,
+                        "column-span", len,
+                        "row-span", 1,
+                        NULL);
+        }
+
+      left = left + len;
+      count++;
+
+      if (count >= num_words)
+        break;
+    }
+
+  if (use_constraint)
+    {
+      constraint = gtk_constraint_new (NULL,
+                                       GTK_CONSTRAINT_ATTRIBUTE_RIGHT,
+                                       GTK_CONSTRAINT_RELATION_EQ,
+                                       right_child,
+                                       GTK_CONSTRAINT_ATTRIBUTE_RIGHT,
+                                       1.0,
+                                       0.0,
+                                       GTK_CONSTRAINT_STRENGTH_REQUIRED);
+      gtk_constraint_layout_add_constraint (GTK_CONSTRAINT_LAYOUT (layout),
+                                            constraint);
+      constraint = gtk_constraint_new (NULL,
+                                       GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                                       GTK_CONSTRAINT_RELATION_EQ,
+                                       child,
+                                       GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                                       1.0,
+                                       0.0,
+                                       GTK_CONSTRAINT_STRENGTH_REQUIRED);
+      gtk_constraint_layout_add_constraint (GTK_CONSTRAINT_LAYOUT (layout),
+                                            constraint);
+
+      gtk_constraint_layout_add_grid_constraint (GTK_CONSTRAINT_LAYOUT (layout),
+                                                 grid);
+    }
+
+  g_bytes_unref (data);
+}
+
+static void
+words_base_init (WordsBase *self)
+{
+  read_words (self);
+}
+
+static void
+show_words (GtkWidget *parent)
+{
+  GtkWidget *window;
+  GtkWidget *header, *box, *grid, *button;
+  GtkWidget *swin;
+
+  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_transient_for (GTK_WINDOW (window),
+                                GTK_WINDOW (gtk_widget_get_root (parent)));
+  gtk_window_set_modal (GTK_WINDOW (window), TRUE);
+
+  header = gtk_header_bar_new ();
+  gtk_header_bar_set_title (GTK_HEADER_BAR (header), use_constraints ? "Constraints" : "Grid");
+  gtk_header_bar_set_show_title_buttons (GTK_HEADER_BAR (header), FALSE);
+  gtk_window_set_titlebar (GTK_WINDOW (window), header);
+  gtk_window_set_resizable (GTK_WINDOW (window), TRUE);
+  gtk_window_set_default_size (GTK_WINDOW (window), 600, 400);
+
+  box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 0);
+  gtk_container_add (GTK_CONTAINER (window), box);
+
+  swin = gtk_scrolled_window_new (NULL, NULL);
+  gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (swin),
+                                  GTK_POLICY_AUTOMATIC,
+                                  GTK_POLICY_AUTOMATIC);
+  gtk_scrolled_window_set_propagate_natural_width (GTK_SCROLLED_WINDOW (swin), TRUE);
+  gtk_scrolled_window_set_propagate_natural_height (GTK_SCROLLED_WINDOW (swin), TRUE);
+  gtk_widget_set_hexpand (swin, TRUE);
+  gtk_widget_set_vexpand (swin, TRUE);
+  gtk_widget_set_halign (swin, GTK_ALIGN_FILL);
+  gtk_widget_set_valign (swin, GTK_ALIGN_FILL);
+  gtk_container_add (GTK_CONTAINER (box), swin);
+
+  if (use_constraints)
+    grid = g_object_new (WORDS_TYPE_CONSTRAINT, NULL);
+  else
+    grid = g_object_new (WORDS_TYPE_GRID, NULL);
+
+  gtk_widget_set_halign (swin, GTK_ALIGN_START);
+  gtk_widget_set_valign (swin, GTK_ALIGN_START);
+
+  gtk_container_add (GTK_CONTAINER (swin), grid);
+
+  button = gtk_button_new_with_label ("Close");
+  gtk_container_add (GTK_CONTAINER (box), button);
+  g_signal_connect_swapped (button, "clicked",
+                            G_CALLBACK (gtk_widget_destroy), window);
+
+  gtk_widget_show (window);
+}
+
+static void
+use_constraints_cb (GtkButton *button)
+{
+  use_constraints = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (button));
+}
+
+static void
+word_count_cb (GtkSpinButton *button)
+{
+  num_words = gtk_spin_button_get_value_as_int (button);
+}
+
+GtkWidget *
+do_constraints3 (GtkWidget *do_widget)
+{
+ static GtkWidget *window;
+
+ if (!window)
+   {
+     GtkWidget *header, *grid, *button, *label;
+
+     window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+
+     header = gtk_header_bar_new ();
+     gtk_header_bar_set_title (GTK_HEADER_BAR (header), "Words");
+     gtk_header_bar_set_show_title_buttons (GTK_HEADER_BAR (header), TRUE);
+     gtk_window_set_titlebar (GTK_WINDOW (window), header);
+     gtk_window_set_resizable (GTK_WINDOW (window), FALSE);
+     g_signal_connect (window, "destroy",
+                       G_CALLBACK (gtk_widget_destroyed), &window);
+
+     grid = gtk_grid_new ();
+     g_object_set (grid,
+                   "margin", 12,
+                   "row-spacing", 12,
+                   "column-spacing", 6,
+                   "halign", GTK_ALIGN_FILL,
+                   "valign", GTK_ALIGN_FILL,
+                   "hexpand", TRUE,
+                   "vexpand", TRUE,
+                   NULL);
+     gtk_container_add (GTK_CONTAINER (window), grid);
+
+     label = gtk_label_new ("Constraints:");
+     gtk_label_set_xalign (GTK_LABEL (label), 1.0);
+     gtk_grid_attach (GTK_GRID (grid), label, 0, 0, 1, 1);
+     button = gtk_check_button_new ();
+     g_signal_connect (button, "clicked", G_CALLBACK (use_constraints_cb), NULL);
+     gtk_grid_attach (GTK_GRID (grid), button, 1, 0, 1, 1);
+     label = gtk_label_new ("Words:");
+     gtk_label_set_xalign (GTK_LABEL (label), 1.0);
+     gtk_grid_attach (GTK_GRID (grid), label, 0, 1, 1, 1);
+     button = gtk_spin_button_new_with_range (0, 1300, 1);
+     g_signal_connect (button, "value-changed", G_CALLBACK (word_count_cb), NULL);
+     gtk_spin_button_set_value (GTK_SPIN_BUTTON (button), 10);
+     gtk_grid_attach (GTK_GRID (grid), button, 1, 1, 1, 1);
+
+     button = gtk_button_new_with_label ("Show");
+     gtk_widget_set_halign (button, GTK_ALIGN_END);
+     gtk_widget_set_valign (button, GTK_ALIGN_END);
+     g_signal_connect_swapped (button, "clicked",
+                               G_CALLBACK (show_words), window);
+     gtk_grid_attach (GTK_GRID (grid), button, 0, 2, 2, 1);
+   }
+
+ if (!gtk_widget_get_visible (window))
+   gtk_widget_show (window);
+ else
+   gtk_widget_destroy (window);
+
+ return window;
+}

demos/gtk-demo/demo.gresource.xml

@@ -12,6 +12,9 @@
   <gresource prefix="/builder">
     <file>demo.ui</file>
   </gresource>
+  <gresource prefix="/constraints3">
+    <file>words</file>
+  </gresource>
   <gresource prefix="/css_accordion">
     <file>css_accordion.css</file>
     <file>reset.css</file>
@@ -151,6 +154,8 @@
     <file>colorsel.c</file>
     <file>combobox.c</file>
     <file>constraints.c</file>
+    <file>constraints2.c</file>
+    <file>constraints3.c</file>
     <file>css_accordion.c</file>
     <file>css_basics.c</file>
     <file>css_blendmodes.c</file>

demos/gtk-demo/meson.build

@@ -9,6 +9,8 @@ demos = files([
   'colorsel.c',
   'combobox.c',
   'constraints.c',
+  'constraints2.c',
+  'constraints3.c',
   'css_accordion.c',
   'css_basics.c',
   'css_blendmodes.c',

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>

gtk/gtkconstraintlayout.c

@@ -62,6 +62,7 @@
 #include "gtkconstraintlayout.h"
 
 #include "gtkconstraintprivate.h"
+#include "gtkgridconstraintprivate.h"
 #include "gtkconstraintexpressionprivate.h"
 #include "gtkconstraintsolverprivate.h"
 #include "gtklayoutchild.h"
@@ -105,6 +106,8 @@ struct _GtkConstraintLayout
    * parent widget, using the public API objects.
    */
   GHashTable *constraints;
+
+  GHashTable *grid_constraints;
 };
 
 G_DEFINE_TYPE (GtkConstraintLayoutChild, gtk_constraint_layout_child, GTK_TYPE_LAYOUT_CHILD)
@@ -361,6 +364,7 @@ gtk_constraint_layout_finalize (GObject *gobject)
 
   g_clear_pointer (&self->bound_attributes, g_hash_table_unref);
   g_clear_pointer (&self->constraints, g_hash_table_unref);
+  g_clear_pointer (&self->grid_constraints, g_hash_table_unref);
 
   G_OBJECT_CLASS (gtk_constraint_layout_parent_class)->finalize (gobject);
 }
@@ -693,7 +697,7 @@ gtk_constraint_layout_measure (GtkLayoutManager *manager,
 
       child_info = GTK_CONSTRAINT_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (manager, child));
 
-      gtk_widget_measure (child, orientation, for_size,
+      gtk_widget_measure (child, orientation, -1,
                           &min_size, &nat_size,
                           NULL, NULL);
 
@@ -769,15 +773,15 @@ gtk_constraint_layout_measure (GtkLayoutManager *manager,
    * natural state of the system. Once we get the value out, we can
    * remove these constraints
    */
-  gtk_constraint_solver_add_edit_variable (solver, size, GTK_CONSTRAINT_WEIGHT_WEAK + 1);
-  gtk_constraint_solver_add_edit_variable (solver, opposite_size, GTK_CONSTRAINT_WEIGHT_WEAK + 2);
-
-  gtk_constraint_solver_begin_edit (solver);
-
-  gtk_constraint_solver_suggest_value (solver, size, 0.0);
-  gtk_constraint_solver_suggest_value (solver, opposite_size, for_size >= 0 ? for_size : 0.0);
-
-  gtk_constraint_solver_resolve (solver);
+  if (for_size > 0)
+    {
+      gtk_constraint_solver_add_edit_variable (solver, opposite_size, GTK_CONSTRAINT_WEIGHT_MEDIUM * 2.0);
+      gtk_constraint_solver_begin_edit (solver);
+      gtk_constraint_solver_suggest_value (solver, opposite_size, for_size);
+      gtk_constraint_solver_resolve (solver);
+      gtk_constraint_solver_remove_edit_variable (solver, opposite_size);
+      gtk_constraint_solver_end_edit (solver);
+    }
 
   GTK_NOTE (LAYOUT,
             g_print ("layout %p preferred %s size: %.3f (for opposite size: %d)\n",
@@ -788,11 +792,6 @@ gtk_constraint_layout_measure (GtkLayoutManager *manager,
 
   value = gtk_constraint_variable_get_value (size);
 
-  gtk_constraint_solver_remove_edit_variable (solver, size);
-  gtk_constraint_solver_remove_edit_variable (solver, opposite_size);
-
-  gtk_constraint_solver_end_edit (solver);
-
   for (guint i = 0; i < size_constraints->len; i++)
     {
       GtkConstraintRef *ref = g_ptr_array_index (size_constraints, i);
@@ -982,6 +981,9 @@ gtk_constraint_layout_allocate (GtkLayoutManager *manager,
   gtk_constraint_solver_remove_constraint (solver, stay_l);
 }
 
+static void layout_add_grid_constraint (GtkConstraintLayout *manager,
+                                        GtkGridConstraint   *constraint);
+
 static void
 gtk_constraint_layout_root (GtkLayoutManager *manager)
 {
@@ -1001,9 +1003,15 @@ gtk_constraint_layout_root (GtkLayoutManager *manager)
   while (g_hash_table_iter_next (&iter, &key, NULL))
     {
       GtkConstraint *constraint = key;
-
       layout_add_constraint (self, constraint);
     }
+
+  g_hash_table_iter_init (&iter, self->grid_constraints);
+  while (g_hash_table_iter_next (&iter, &key, NULL))
+    {
+      GtkGridConstraint *constraint = key;
+      layout_add_grid_constraint (self, constraint);
+    }
 }
 
 static void
@@ -1025,6 +1033,14 @@ gtk_constraint_layout_unroot (GtkLayoutManager *manager)
       gtk_constraint_detach (constraint);
     }
 
+  g_hash_table_iter_init (&iter, self->grid_constraints);
+  while (g_hash_table_iter_next (&iter, &key, NULL))
+    {
+      GtkGridConstraint *constraint = key;
+
+      gtk_grid_constraint_detach (constraint);
+    }
+
   self->solver = NULL;
 }
 
@@ -1057,6 +1073,10 @@ gtk_constraint_layout_init (GtkConstraintLayout *self)
     g_hash_table_new_full (NULL, NULL,
                            (GDestroyNotify) g_object_unref,
                            NULL);
+  self->grid_constraints =
+    g_hash_table_new_full (NULL, NULL,
+                           (GDestroyNotify) g_object_unref,
+                           NULL);
 }
 
 /**
@@ -1101,6 +1121,8 @@ gtk_constraint_layout_add_constraint (GtkConstraintLayout *manager,
   layout_add_constraint (manager, constraint);
 
   g_hash_table_add (manager->constraints, constraint);
+
+  gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (manager));
 }
 
 /**
@@ -1121,4 +1143,212 @@ gtk_constraint_layout_remove_constraint (GtkConstraintLayout *manager,
 
   gtk_constraint_detach (constraint);
   g_hash_table_remove (manager->constraints, constraint);
+
+  gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (manager));
+}
+
+void
+gtk_constraint_layout_add_grid_constraint (GtkConstraintLayout *manager,
+                                           GtkGridConstraint   *constraint)
+{
+  g_return_if_fail (GTK_IS_CONSTRAINT_LAYOUT (manager));
+  g_return_if_fail (GTK_IS_GRID_CONSTRAINT (constraint));
+  g_return_if_fail (!gtk_grid_constraint_is_attached (constraint));
+
+  layout_add_grid_constraint (manager, constraint);
+
+  g_hash_table_add (manager->grid_constraints, constraint);
+}
+
+static GtkConstraintVariable **
+allocate_variables (GtkConstraintSolver *solver,
+                    const char          *name,
+                    int                  n)
+{
+  GtkConstraintVariable **vars;
+  int i;
+
+  vars = g_new (GtkConstraintVariable *, n);
+  for (i = 0; i < n; i++)
+    {
+      char *vname = g_strdup_printf ("%s%d", name, i);
+      vars[i] = gtk_constraint_solver_create_variable (solver, NULL, vname, 0.0);
+    }
+
+  return vars;
+}
+
+#if 0
+static void
+add_ordering_constraints (GtkConstraintSolver    *solver,
+                          GtkConstraintVariable **vars,
+                          int                     n_vars,
+                          GPtrArray              *refs)
+{
+  int i;
+
+  for (i = 1; i < n_vars; i++)
+    {
+      GtkConstraintRef *ref;
+
+      ref = gtk_constraint_solver_add_constraint (solver,
+                                                  vars[i],
+                                                  GTK_CONSTRAINT_RELATION_GE,
+                                                  gtk_constraint_expression_new_from_variable (vars[i - 1]),
+                                                  GTK_CONSTRAINT_WEIGHT_MEDIUM);
+      g_ptr_array_add (refs, ref);
+    }
+}
+#endif
+
+static void
+add_homogeneous_constraints (GtkConstraintSolver    *solver,
+                             GtkConstraintVariable **vars,
+                             int                     n_vars,
+                             GPtrArray              *refs)
+{
+  int i;
+
+  for (i = 2; i < n_vars; i++)
+    {
+      GtkConstraintExpressionBuilder builder;
+      GtkConstraintRef *ref;
+
+      gtk_constraint_expression_builder_init (&builder, solver);
+      gtk_constraint_expression_builder_term (&builder, vars[i]);
+      gtk_constraint_expression_builder_plus (&builder);
+      gtk_constraint_expression_builder_term (&builder, vars[i - 2]);
+      gtk_constraint_expression_builder_divide_by (&builder);
+      gtk_constraint_expression_builder_constant (&builder, 2.0);
+
+      ref = gtk_constraint_solver_add_constraint (solver,
+                                                  vars[i - 1],
+                                                  GTK_CONSTRAINT_RELATION_EQ,
+                                                  gtk_constraint_expression_builder_finish (&builder),
+                                                  GTK_CONSTRAINT_WEIGHT_REQUIRED);
+      g_ptr_array_add (refs, ref);
+    }
+}
+
+static void
+add_child_constraints (GtkConstraintLayout     *manager,
+                       GtkConstraintSolver     *solver,
+                       GtkGridConstraintChild  *child,
+                       GtkConstraintVariable  **rows,
+                       GtkConstraintVariable  **cols,
+                       GPtrArray               *refs)
+{
+  GtkConstraintLayoutChild *info;
+  GtkConstraintVariable *var;
+  GtkConstraintVariable *var1;
+  GtkConstraintRef *ref;
+
+  info = GTK_CONSTRAINT_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (GTK_LAYOUT_MANAGER (manager), child->child));
+
+  var = get_child_attribute (info, solver, child->child, GTK_CONSTRAINT_ATTRIBUTE_LEFT);
+  var1 = cols[child->left];
+
+  ref = gtk_constraint_solver_add_constraint (solver,
+                                              var,
+                                              GTK_CONSTRAINT_RELATION_EQ,
+                                              gtk_constraint_expression_new_from_variable (var1),
+                                              GTK_CONSTRAINT_WEIGHT_REQUIRED);
+  g_ptr_array_add (refs, ref);
+
+  var = get_child_attribute (info, solver, child->child, GTK_CONSTRAINT_ATTRIBUTE_RIGHT);
+  var1 = cols[child->right];
+
+  ref = gtk_constraint_solver_add_constraint (solver,
+                                              var,
+                                              GTK_CONSTRAINT_RELATION_EQ,
+                                              gtk_constraint_expression_new_from_variable (var1),
+                                              GTK_CONSTRAINT_WEIGHT_REQUIRED);
+  g_ptr_array_add (refs, ref);
+
+  var = get_child_attribute (info, solver, child->child, GTK_CONSTRAINT_ATTRIBUTE_TOP);
+  var1 = rows[child->top];
+
+  ref = gtk_constraint_solver_add_constraint (solver,
+                                              var,
+                                              GTK_CONSTRAINT_RELATION_EQ,
+                                              gtk_constraint_expression_new_from_variable (var1),
+                                              GTK_CONSTRAINT_WEIGHT_REQUIRED);
+  g_ptr_array_add (refs, ref);
+
+  var = get_child_attribute (info, solver, child->child, GTK_CONSTRAINT_ATTRIBUTE_BOTTOM);
+  var1 = rows[child->bottom];
+
+  ref = gtk_constraint_solver_add_constraint (solver,
+                                              var,
+                                              GTK_CONSTRAINT_RELATION_EQ,
+                                              gtk_constraint_expression_new_from_variable (var1),
+                                              GTK_CONSTRAINT_WEIGHT_REQUIRED);
+  g_ptr_array_add (refs, ref);
+}
+
+static void
+layout_add_grid_constraint (GtkConstraintLayout *manager,
+                            GtkGridConstraint   *constraint)
+{
+  GtkWidget *layout_widget;
+  GtkConstraintSolver *solver;
+  GtkConstraintVariable **rows;
+  GtkConstraintVariable **cols;
+  int n_rows, n_cols;
+  GPtrArray *refs;
+  int i;
+
+  if (gtk_grid_constraint_is_attached (constraint))
+    return;
+
+  layout_widget = gtk_layout_manager_get_widget (GTK_LAYOUT_MANAGER (manager));
+  if (layout_widget == NULL)
+    return;
+
+  solver = gtk_constraint_layout_get_solver (manager);
+  if (solver == NULL)
+    return;
+
+  gtk_constraint_solver_freeze (solver);
+
+  refs = g_ptr_array_new ();
+
+  n_rows = n_cols = 0;
+  for (i = 0; i < constraint->children->len; i++)
+    {
+      GtkGridConstraintChild *child = g_ptr_array_index (constraint->children, i);
+      n_rows = MAX (n_rows, child->bottom);
+      n_cols = MAX (n_cols, child->right);
+    }
+  n_rows++;
+  n_cols++;
+
+  rows = allocate_variables (solver, "row", n_rows);
+  cols = allocate_variables (solver, "col", n_cols);
+
+#if 0
+  //FIXME for some reason, these 'obvious' constraints
+  // make things unstable (and they are not really needed)
+  add_ordering_constraints (solver, rows, n_rows, refs);
+  add_ordering_constraints (solver, cols, n_cols, refs);
+#endif
+
+  if (constraint->row_homogeneous)
+    add_homogeneous_constraints (solver, rows, n_rows, refs);
+  if (constraint->column_homogeneous)
+    add_homogeneous_constraints (solver, cols, n_cols, refs);
+
+  for (i = 0; i < constraint->children->len; i++)
+    {
+      GtkGridConstraintChild *child = g_ptr_array_index (constraint->children, i);
+      add_child_constraints (manager, solver, child, rows, cols, refs);
+    }
+
+  gtk_grid_constraint_attach (constraint, solver, refs);
+
+  g_free (rows);
+  g_free (cols);
+  g_ptr_array_unref (refs);
+
+  gtk_constraint_solver_thaw (solver);
 }

gtk/gtkconstraintlayout.h

@@ -20,6 +20,7 @@
 
 #include <gtk/gtklayoutmanager.h>
 #include <gtk/gtkconstraint.h>
+#include <gtk/gtkgridconstraint.h>
 
 G_BEGIN_DECLS
 
@@ -45,6 +46,10 @@ GDK_AVAILABLE_IN_ALL
 void                    gtk_constraint_layout_remove_constraint (GtkConstraintLayout *manager,
                                                                  GtkConstraint       *constraint);
 
+GDK_AVAILABLE_IN_ALL
+void                    gtk_constraint_layout_add_grid_constraint (GtkConstraintLayout *manager,
+                                                                   GtkGridConstraint   *constraint);
+
 /**
  * GtkConstraintLayoutChild:
  *

gtk/gtkgridconstraint.c

@@ -0,0 +1,206 @@
+/* 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 "gtkgridconstraintprivate.h"
+
+#include "gtkintl.h"
+#include "gtktypebuiltins.h"
+
+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_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);
+}
+
+GtkGridConstraint *
+gtk_grid_constraint_new (void)
+{
+  return g_object_new (GTK_TYPE_GRID_CONSTRAINT, NULL);
+}
+
+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->refs == NULL);
+
+  data = g_new0 (GtkGridConstraintChild, 1);
+
+  data->child = 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->refs != NULL;
+}
+
+void
+gtk_grid_constraint_attach (GtkGridConstraint   *self,
+                            GtkConstraintSolver *solver,
+                            GPtrArray           *refs)
+{
+  g_return_if_fail (self->refs == NULL);
+
+  self->solver = solver;
+  self->refs = g_ptr_array_ref (refs);
+}
+
+void gtk_grid_constraint_detach (GtkGridConstraint *self)
+{
+  int i;
+
+  if (self->refs == NULL)
+    return;
+
+  for (i = 0; i < self->refs->len; i++)
+    {
+      GtkConstraintRef *ref = g_ptr_array_index (self->refs, i);
+      gtk_constraint_solver_remove_constraint (self->solver, ref);
+    }
+
+  g_clear_pointer (&self->refs, g_ptr_array_unref);
+}

gtk/gtkgridconstraint.h

@@ -0,0 +1,49 @@
+/*
+ * 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>
+
+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);
+
+G_END_DECLS
+
+#endif  /* __GTK_GRID_CONSTRAINT_H__ */

gtk/gtkgridconstraintprivate.h

@@ -0,0 +1,47 @@
+/* 
+ * 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 "gtkgridconstraint.h"
+#include "gtkconstraintsolverprivate.h"
+
+typedef struct {
+  GtkWidget *child;
+  int left;
+  int right;
+  int top;
+  int bottom;
+} GtkGridConstraintChild;
+
+struct _GtkGridConstraint {
+  GObject parent;
+
+  gboolean row_homogeneous;
+  gboolean column_homogeneous;
+
+  GPtrArray *children;
+
+  GtkConstraintSolver *solver;
+  GPtrArray           *refs;
+};
+
+gboolean gtk_grid_constraint_is_attached (GtkGridConstraint *constraint);
+void gtk_grid_constraint_attach (GtkGridConstraint   *constraint,
+                                 GtkConstraintSolver *solver,
+                                 GPtrArray           *refs);
+void gtk_grid_constraint_detach (GtkGridConstraint *constraint);

gtk/meson.build

@@ -252,6 +252,7 @@ gtk_public_sources = files([
   'gtkgesturezoom.c',
   'gtkglarea.c',
   'gtkgrid.c',
+  'gtkgridconstraint.c',
   'gtkgridlayout.c',
   'gtkheaderbar.c',
   'gtkicontheme.c',