[gtk+] Add glarea demo to gtk3-demo

[Matthias Clasen <matthiasc src gnome org>]

commit 62a26eb3c8627c31d823e37141fa31b1280c5184
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Oct 9 11:25:50 2014 +0200

    Add glarea demo to gtk3-demo

 demos/gtk-demo/Makefile.am        |    1 +
 demos/gtk-demo/demo.gresource.xml |    1 +
 demos/gtk-demo/glarea.c           |  184 +++++++++++++++++++++++++++++++++++++
 3 files changed, 186 insertions(+), 0 deletions(-)
---
diff --git a/demos/gtk-demo/Makefile.am b/demos/gtk-demo/Makefile.am
index 6b0b8da..de150dc 100644
--- a/demos/gtk-demo/Makefile.am
+++ b/demos/gtk-demo/Makefile.am
@@ -25,6 +25,7 @@ demos =                                               \
        event_axes.c                            \
        expander.c                              \
        gestures.c                              \
+       glarea.c                                \
        headerbar.c                             \
        hypertext.c                             \
        iconview.c                              \
diff --git a/demos/gtk-demo/demo.gresource.xml b/demos/gtk-demo/demo.gresource.xml
index e9c628d..d861199 100644
--- a/demos/gtk-demo/demo.gresource.xml
+++ b/demos/gtk-demo/demo.gresource.xml
@@ -95,6 +95,7 @@
     <file>expander.c</file>
     <file>flowbox.c</file>
     <file>gestures.c</file>
+    <file>glarea.c</file>
     <file>headerbar.c</file>
     <file>hypertext.c</file>
     <file>iconview.c</file>
diff --git a/demos/gtk-demo/glarea.c b/demos/gtk-demo/glarea.c
new file mode 100644
index 0000000..8ac5b37
--- /dev/null
+++ b/demos/gtk-demo/glarea.c
@@ -0,0 +1,184 @@
+/* OpenGL Area
+ *
+ * GtkGLArea is a widget that allows custom drawing using OpenGL calls.
+ */
+
+#include <gtk/gtk.h>
+#include <epoxy/gl.h>
+
+static GtkWidget *demo_window = NULL;
+
+/* the GtkGLArea widget */
+static GtkWidget *gl_area = NULL;
+
+enum {
+  X_AXIS,
+  Y_AXIS,
+  Z_AXIS,
+
+  N_AXIS
+};
+
+/* Rotation angles on each axis */
+static float rotation_angles[N_AXIS] = { 0.0 };
+
+/* The object we are drawing */
+static void
+draw_triangle (void)
+{
+  glColor3f (1.0f, 0.85f, 0.35f);
+  glBegin (GL_TRIANGLES);
+  {
+    glVertex3f ( 0.0,  0.6,  0.0);
+    glVertex3f (-0.2, -0.3,  0.0);
+    glVertex3f ( 0.2, -0.3,  0.0);
+  }
+  glEnd ();
+}
+
+/* The main rendering callback */
+static gboolean
+render (GtkGLArea    *area,
+        GdkGLContext *context)
+{
+  glClearColor (0.5, 0.5, 0.5, 1.0);
+  glClear (GL_COLOR_BUFFER_BIT);
+
+  glMatrixMode (GL_MODELVIEW);
+  glLoadIdentity ();
+  glRotatef (rotation_angles[X_AXIS], 1, 0, 0);
+  glRotatef (rotation_angles[Y_AXIS], 0, 1, 0);
+  glRotatef (rotation_angles[Z_AXIS], 0, 0, 1);
+
+  draw_triangle ();
+
+  glFlush ();
+
+  return TRUE;
+}
+
+static void
+on_axis_value_change (GtkAdjustment *adjustment,
+                      gpointer       data)
+{
+  int axis = GPOINTER_TO_INT (data);
+
+  g_assert (axis >= 0 && axis < N_AXIS);
+
+  /* Update the rotation angle */
+  rotation_angles[axis] = gtk_adjustment_get_value (adjustment);
+
+  /* Update the contents of the GL drawing area */
+  gtk_widget_queue_draw (gl_area);
+}
+
+static GtkWidget *
+create_axis_slider (int axis)
+{
+  GtkWidget *box, *label, *slider;
+  GtkAdjustment *adj;
+  const char *text;
+
+  box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, FALSE);
+
+  switch (axis)
+    {
+    case X_AXIS:
+      text = "X axis";
+      break;
+
+    case Y_AXIS:
+      text = "Y axis";
+      break;
+
+    case Z_AXIS:
+      text = "Z axis";
+      break;
+
+    default:
+      g_assert_not_reached ();
+    }
+
+  label = gtk_label_new (text);
+  gtk_container_add (GTK_CONTAINER (box), label);
+  gtk_widget_show (label);
+
+  adj = gtk_adjustment_new (0.0, 0.0, 360.0, 1.0, 12.0, 0.0);
+  g_signal_connect (adj, "value-changed",
+                    G_CALLBACK (on_axis_value_change),
+                    GINT_TO_POINTER (axis));
+  slider = gtk_scale_new (GTK_ORIENTATION_HORIZONTAL, adj);
+  gtk_container_add (GTK_CONTAINER (box), slider);
+  gtk_widget_set_hexpand (slider, TRUE);
+  gtk_widget_show (slider);
+
+  gtk_widget_show (box);
+
+  return box;
+}
+
+static void
+close_window (GtkWidget *widget)
+{
+  /* Reset the state */
+  demo_window = NULL;
+  gl_area = NULL;
+
+  rotation_angles[X_AXIS] = 0.0;
+  rotation_angles[Y_AXIS] = 0.0;
+  rotation_angles[Z_AXIS] = 0.0;
+}
+
+GtkWidget *
+create_glarea_window (GtkWidget *do_widget)
+{
+  GtkWidget *window, *box, *button, *controls;
+  int i;
+
+  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+  gtk_window_set_screen (GTK_WINDOW (window), gtk_widget_get_screen (do_widget));
+  gtk_window_set_title (GTK_WINDOW (window), "GtkGLArea - Golden Triangle");
+  gtk_window_set_default_size (GTK_WINDOW (window), 400, 400);
+  gtk_container_set_border_width (GTK_CONTAINER (window), 12);
+  g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
+
+  box = gtk_box_new (GTK_ORIENTATION_VERTICAL, FALSE);
+  gtk_box_set_spacing (GTK_BOX (box), 6);
+  gtk_container_add (GTK_CONTAINER (window), box);
+
+  gl_area = gtk_gl_area_new ();
+  gtk_widget_set_hexpand (gl_area, TRUE);
+  gtk_widget_set_vexpand (gl_area, TRUE);
+  gtk_container_add (GTK_CONTAINER (box), gl_area);
+
+  /* the main "draw" call for GtkGLArea */
+  g_signal_connect (gl_area, "render", G_CALLBACK (render), NULL);
+
+  controls = gtk_box_new (GTK_ORIENTATION_VERTICAL, FALSE);
+  gtk_container_add (GTK_CONTAINER (box), controls);
+  gtk_widget_set_hexpand (controls, TRUE);
+
+  for (i = 0; i < N_AXIS; i++)
+    gtk_container_add (GTK_CONTAINER (controls), create_axis_slider (i));
+
+  button = gtk_button_new_with_label ("Quit");
+  gtk_widget_set_hexpand (button, TRUE);
+  gtk_container_add (GTK_CONTAINER (box), button);
+  g_signal_connect_swapped (button, "clicked", G_CALLBACK (gtk_widget_destroy), window);
+
+  return window;
+}
+
+GtkWidget*
+do_glarea (GtkWidget *do_widget)
+{
+  if (demo_window == NULL)
+    demo_window = create_glarea_window (do_widget);
+
+  if (!gtk_widget_get_visible (demo_window))
+    gtk_widget_show_all (demo_window);
+  else
+    gtk_widget_destroy (demo_window);
+
+  return demo_window;
+}