[gtk/constraint-flexible-space: 9/9] Add an interactive constraints demo

[Matthias Clasen <matthiasc src gnome org>]

commit 1ae24aa025c60d7c535b0a8ae43701d124b51413
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jun 26 03:35:10 2019 +0000

    Add an interactive constraints demo

 demos/gtk-demo/constraints.c      |   2 +-
 demos/gtk-demo/constraints2.c     | 245 ++++++++++++++++++++++++++++++++++++++
 demos/gtk-demo/demo.gresource.xml |   1 +
 demos/gtk-demo/meson.build        |   1 +
 4 files changed, 248 insertions(+), 1 deletion(-)
---
diff --git a/demos/gtk-demo/constraints.c b/demos/gtk-demo/constraints.c
index 0383dc403e..87f05c7ba5 100644
--- a/demos/gtk-demo/constraints.c
+++ b/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
diff --git a/demos/gtk-demo/constraints2.c b/demos/gtk-demo/constraints2.c
new file mode 100644
index 0000000000..1d3e788c9f
--- /dev/null
+++ b/demos/gtk-demo/constraints2.c
@@ -0,0 +1,245 @@
+/* Constraints/Interactive
+ *
+ * Demonstrate how constraints can be updates during
+ * user interaction.
+ */
+
+#include <glib/gi18n.h>
+#include <gtk/gtk.h>
+
+G_DECLARE_FINAL_TYPE (InteractiveGrid, interactive_grid, INTERACTIVE, GRID, GtkWidget)
+
+struct _InteractiveGrid
+{
+  GtkWidget parent_instance;
+
+  GtkWidget *button1, *button2;
+  GtkWidget *button3;
+  GtkConstraintGuide *guide;
+  GtkConstraint *constraint;
+};
+
+G_DEFINE_TYPE (InteractiveGrid, interactive_grid, GTK_TYPE_WIDGET)
+
+static void
+interactive_grid_destroy (GtkWidget *widget)
+{
+  InteractiveGrid *self = INTERACTIVE_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);
+
+  GTK_WIDGET_CLASS (interactive_grid_parent_class)->destroy (widget);
+}
+
+static void
+interactive_grid_class_init (InteractiveGridClass *klass)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+
+  widget_class->destroy = interactive_grid_destroy;
+
+  gtk_widget_class_set_layout_manager_type (widget_class, GTK_TYPE_CONSTRAINT_LAYOUT);
+}
+
+static void
+build_constraints (InteractiveGrid          *self,
+                   GtkConstraintLayout *manager)
+{
+  self->guide = g_object_new (GTK_TYPE_CONSTRAINT_GUIDE, NULL);
+  gtk_constraint_layout_add_guide (manager, self->guide);
+
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new_constant (GTK_CONSTRAINT_TARGET (self->guide),
+                        GTK_CONSTRAINT_ATTRIBUTE_WIDTH,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        0.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (NULL,
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->button1),
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        1.0,
+                        -8.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button1),
+                        GTK_CONSTRAINT_ATTRIBUTE_END,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->guide),
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        1.0,
+                        0.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button2),
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->guide),
+                        GTK_CONSTRAINT_ATTRIBUTE_END,
+                        1.0,
+                        0.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button2),
+                        GTK_CONSTRAINT_ATTRIBUTE_END,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        NULL,
+                        GTK_CONSTRAINT_ATTRIBUTE_END,
+                        1.0,
+                        -8.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (NULL,
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->button3),
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        1.0,
+                        -8.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button3),
+                        GTK_CONSTRAINT_ATTRIBUTE_END,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->guide),
+                        GTK_CONSTRAINT_ATTRIBUTE_START,
+                        1.0,
+                        0.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (NULL,
+                        GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->button1),
+                        GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                        1.0,
+                        -8.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button2),
+                        GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->button1),
+                        GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                        1.0,
+                        0.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button3),
+                        GTK_CONSTRAINT_ATTRIBUTE_TOP,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        GTK_CONSTRAINT_TARGET (self->button2),
+                        GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                        1.0,
+                        0.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+  gtk_constraint_layout_add_constraint (manager,
+    gtk_constraint_new (GTK_CONSTRAINT_TARGET (self->button3),
+                        GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                        GTK_CONSTRAINT_RELATION_EQ,
+                        NULL,
+                        GTK_CONSTRAINT_ATTRIBUTE_BOTTOM,
+                        1.0,
+                        -8.0,
+                        GTK_CONSTRAINT_STRENGTH_REQUIRED));
+}
+
+static void
+drag_cb (GtkGestureDrag  *drag,
+         double           offset_x,
+         double           offset_y,
+         InteractiveGrid      *self)
+{
+  GtkConstraintLayout *layout = gtk_widget_get_layout_manager (self);
+  double x, y;
+
+  if (self->constraint)
+    {
+      gtk_constraint_layout_remove_constraint (layout, self->constraint);
+      g_clear_object (&self->constraint);
+    }
+
+  gtk_gesture_drag_get_start_point (drag, &x, &y);
+  self->constraint = gtk_constraint_new_constant (GTK_CONSTRAINT_TARGET (self->guide),
+                                                  GTK_CONSTRAINT_ATTRIBUTE_LEFT,
+                                                  GTK_CONSTRAINT_RELATION_EQ,
+                                                  x + offset_x,
+                                                  GTK_CONSTRAINT_STRENGTH_REQUIRED);
+  gtk_constraint_layout_add_constraint (layout, g_object_ref (self->constraint));
+  gtk_widget_queue_allocate (self);
+}
+
+static void
+interactive_grid_init (InteractiveGrid *self)
+{
+  GtkWidget *widget = GTK_WIDGET (self);
+  GtkGesture *drag;
+
+  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");
+
+  GtkLayoutManager *manager = gtk_widget_get_layout_manager (GTK_WIDGET (self));
+  build_constraints (self, GTK_CONSTRAINT_LAYOUT (manager));
+
+  drag = gtk_gesture_drag_new ();
+  g_signal_connect (drag, "drag-update", G_CALLBACK (drag_cb), self);
+  gtk_widget_add_controller (self, drag);
+}
+
+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 (interactive_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;
+}
diff --git a/demos/gtk-demo/demo.gresource.xml b/demos/gtk-demo/demo.gresource.xml
index 124eeeaee4..f3d400bba3 100644
--- a/demos/gtk-demo/demo.gresource.xml
+++ b/demos/gtk-demo/demo.gresource.xml
@@ -151,6 +151,7 @@
     <file>colorsel.c</file>
     <file>combobox.c</file>
     <file>constraints.c</file>
+    <file>constraints2.c</file>
     <file>css_accordion.c</file>
     <file>css_basics.c</file>
     <file>css_blendmodes.c</file>
diff --git a/demos/gtk-demo/meson.build b/demos/gtk-demo/meson.build
index e60d7e32a8..6d4bd03fad 100644
--- a/demos/gtk-demo/meson.build
+++ b/demos/gtk-demo/meson.build
@@ -9,6 +9,7 @@ demos = files([
   'colorsel.c',
   'combobox.c',
   'constraints.c',
+  'constraints2.c',
   'css_accordion.c',
   'css_basics.c',
   'css_blendmodes.c',