[cogl] Add a cogl-point-sprites example

[Neil Roberts <nroberts src gnome org>]

commit e7ede458fde7207896e507d64b52b77777b3c872
Author: Neil Roberts <neil linux intel com>
Date:   Wed Aug 21 09:25:12 2013 +0100

    Add a cogl-point-sprites example
    
    This updates the old point sprites interactive test from Clutter to be
    a standalone Cogl example using the 2.0 API.

 examples/Makefile.am          |    4 +-
 examples/cogl-point-sprites.c |  325 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 328 insertions(+), 1 deletions(-)
---
diff --git a/examples/Makefile.am b/examples/Makefile.am
index 63682af..d9198a9 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -32,7 +32,7 @@ cogl_info_SOURCES = cogl-info.c
 cogl_info_LDADD = $(common_ldadd)
 
 if USE_GLIB
-programs += cogl-hello cogl-msaa cogl-gles2-context
+programs += cogl-hello cogl-msaa cogl-gles2-context cogl-point-sprites
 examples_datadir = $(pkgdatadir)/examples-data
 examples_data_DATA =
 
@@ -40,6 +40,8 @@ cogl_hello_SOURCES = cogl-hello.c
 cogl_hello_LDADD = $(common_ldadd)
 cogl_msaa_SOURCES = cogl-msaa.c
 cogl_msaa_LDADD = $(common_ldadd)
+cogl_point_sprites_SOURCES = cogl-point-sprites.c
+cogl_point_sprites_LDADD = $(common_ldadd)
 
 if BUILD_COGL_PANGO
 programs += cogl-crate
diff --git a/examples/cogl-point-sprites.c b/examples/cogl-point-sprites.c
new file mode 100644
index 0000000..8f90805
--- /dev/null
+++ b/examples/cogl-point-sprites.c
@@ -0,0 +1,325 @@
+#include <cogl/cogl.h>
+#include <glib.h>
+#include <stdlib.h>
+#include <math.h>
+#include <string.h>
+
+#define N_FIREWORKS 32
+/* Units per second per second */
+#define GRAVITY -1.5f
+
+#define N_SPARKS (N_FIREWORKS * 32) /* Must be a power of two */
+#define TIME_PER_SPARK 0.01f /* in seconds */
+
+#define TEXTURE_SIZE 32
+
+typedef struct
+{
+  uint8_t red, green, blue, alpha;
+} Color;
+
+typedef struct
+{
+  float size;
+  float x, y;
+  float start_x, start_y;
+  Color color;
+
+  /* Velocities are in units per second */
+  float initial_x_velocity;
+  float initial_y_velocity;
+
+  GTimer *timer;
+} Firework;
+
+typedef struct
+{
+  float x, y;
+  Color color;
+  Color base_color;
+} Spark;
+
+typedef struct
+{
+  Firework fireworks[N_FIREWORKS];
+
+  int next_spark_num;
+  Spark sparks[N_SPARKS];
+  GTimer *last_spark_time;
+
+  CoglContext *context;
+  CoglFramebuffer *fb;
+  CoglPipeline *pipeline;
+  CoglPrimitive *primitive;
+  CoglAttributeBuffer *attribute_buffer;
+} Data;
+
+static CoglTexture *
+generate_round_texture (CoglContext *context)
+{
+  uint8_t *p, *data;
+  int x, y;
+  CoglTexture2D *tex;
+
+  p = data = g_malloc (TEXTURE_SIZE * TEXTURE_SIZE * 4);
+
+  /* Generate a white circle which gets transparent towards the edges */
+  for (y = 0; y < TEXTURE_SIZE; y++)
+    for (x = 0; x < TEXTURE_SIZE; x++)
+      {
+        int dx = x - TEXTURE_SIZE / 2;
+        int dy = y - TEXTURE_SIZE / 2;
+        float value = sqrtf (dx * dx + dy * dy) * 255.0 / (TEXTURE_SIZE / 2);
+        if (value > 255.0f)
+          value = 255.0f;
+        value = 255.0f - value;
+        *(p++) = value;
+        *(p++) = value;
+        *(p++) = value;
+        *(p++) = value;
+      }
+
+  tex = cogl_texture_2d_new_from_data (context,
+                                       TEXTURE_SIZE, TEXTURE_SIZE,
+                                       COGL_PIXEL_FORMAT_RGBA_8888_PRE,
+                                       COGL_PIXEL_FORMAT_ANY,
+                                       TEXTURE_SIZE * 4,
+                                       data,
+                                       NULL /* error */);
+
+  g_free (data);
+
+  return COGL_TEXTURE (tex);
+}
+
+static void
+paint (Data *data)
+{
+  int i;
+  float diff_time;
+
+  /* Update all of the firework's positions */
+  for (i = 0; i < N_FIREWORKS; i++)
+    {
+      Firework *firework = data->fireworks + i;
+
+      if ((fabsf (firework->x - firework->start_x) > 2.0f) ||
+          firework->y < -1.0f)
+        {
+          firework->size = g_random_double_range (0.001f, 0.1f);
+          firework->start_x = 1.0f + firework->size;
+          firework->start_y = -1.0f;
+          firework->initial_x_velocity = g_random_double_range (-0.1f, -2.0f);
+          firework->initial_y_velocity = g_random_double_range (0.1f, 4.0f);
+          g_timer_reset (firework->timer);
+
+          /* Pick a random color out of six */
+          if (g_random_boolean ())
+            {
+              memset (&firework->color, 0, sizeof (Color));
+              ((uint8_t *) &firework->color)[g_random_int_range (0, 3)] = 255;
+            }
+          else
+            {
+              memset (&firework->color, 255, sizeof (Color));
+              ((uint8_t *) &firework->color)[g_random_int_range (0, 3)] = 0;
+            }
+          firework->color.alpha = 255;
+
+          /* Fire some of the fireworks from the other side */
+          if (g_random_boolean ())
+            {
+              firework->start_x = -firework->start_x;
+              firework->initial_x_velocity = -firework->initial_x_velocity;
+            }
+        }
+
+      diff_time = g_timer_elapsed (firework->timer, NULL);
+
+      firework->x = (firework->start_x +
+                     firework->initial_x_velocity * diff_time);
+
+      firework->y = ((firework->initial_y_velocity * diff_time +
+                      0.5f * GRAVITY * diff_time * diff_time) +
+                     firework->start_y);
+    }
+
+  diff_time = g_timer_elapsed (data->last_spark_time, NULL);
+  if (diff_time < 0.0f || diff_time >= TIME_PER_SPARK)
+    {
+      /* Add a new spark for each firework, overwriting the oldest ones */
+      for (i = 0; i < N_FIREWORKS; i++)
+        {
+          Spark *spark = data->sparks + data->next_spark_num;
+          Firework *firework = data->fireworks + i;
+
+          spark->x = (firework->x +
+                      g_random_double_range (-firework->size / 2.0f,
+                                             firework->size / 2.0f));
+          spark->y = (firework->y +
+                      g_random_double_range (-firework->size / 2.0f,
+                                             firework->size / 2.0f));
+          spark->base_color = firework->color;
+
+          data->next_spark_num = (data->next_spark_num + 1) & (N_SPARKS - 1);
+        }
+
+      /* Update the colour of each spark */
+      for (i = 0; i < N_SPARKS; i++)
+        {
+          float color_value;
+
+          /* First spark is the oldest */
+          Spark *spark = data->sparks + ((data->next_spark_num + i)
+                                         & (N_SPARKS - 1));
+
+          color_value = i / (N_SPARKS - 1.0f);
+          spark->color.red = spark->base_color.red * color_value;
+          spark->color.green = spark->base_color.green * color_value;
+          spark->color.blue = spark->base_color.blue * color_value;
+          spark->color.alpha = 255.0f * color_value;
+        }
+
+      g_timer_reset (data->last_spark_time);
+    }
+
+  cogl_buffer_set_data (COGL_BUFFER (data->attribute_buffer),
+                        0, /* offset */
+                        data->sparks,
+                        sizeof (data->sparks),
+                        NULL /* error */);
+
+  cogl_framebuffer_clear4f (data->fb, COGL_BUFFER_BIT_COLOR, 0, 0, 0, 1);
+
+  cogl_primitive_draw (data->primitive,
+                       data->fb,
+                       data->pipeline);
+
+  cogl_onscreen_swap_buffers (COGL_ONSCREEN (data->fb));
+}
+
+static void
+create_primitive (Data *data)
+{
+  CoglAttribute *attributes[2];
+  int i;
+
+  data->attribute_buffer =
+    cogl_attribute_buffer_new_with_size (data->context,
+                                         sizeof (data->sparks));
+  cogl_buffer_set_update_hint (COGL_BUFFER (data->attribute_buffer),
+                               COGL_BUFFER_UPDATE_HINT_DYNAMIC);
+
+  attributes[0] = cogl_attribute_new (data->attribute_buffer,
+                                      "cogl_position_in",
+                                      sizeof (Spark),
+                                      G_STRUCT_OFFSET (Spark, x),
+                                      2, /* n_components */
+                                      COGL_ATTRIBUTE_TYPE_FLOAT);
+  attributes[1] = cogl_attribute_new (data->attribute_buffer,
+                                      "cogl_color_in",
+                                      sizeof (Spark),
+                                      G_STRUCT_OFFSET (Spark, color),
+                                      4, /* n_components */
+                                      COGL_ATTRIBUTE_TYPE_UNSIGNED_BYTE);
+
+  data->primitive =
+    cogl_primitive_new_with_attributes (COGL_VERTICES_MODE_POINTS,
+                                        N_SPARKS,
+                                        attributes,
+                                        G_N_ELEMENTS (attributes));
+
+  for (i = 0; i < G_N_ELEMENTS (attributes); i++)
+    cogl_object_unref (attributes[i]);
+}
+
+static void
+frame_event_cb (CoglOnscreen *onscreen,
+                CoglFrameEvent event,
+                CoglFrameInfo *info,
+                void *user_data)
+{
+  Data *data = user_data;
+
+  if (event == COGL_FRAME_EVENT_SYNC)
+    paint (data);
+}
+
+int
+main (int argc, char *argv[])
+{
+  CoglTexture *tex;
+  CoglOnscreen *onscreen;
+  GSource *cogl_source;
+  GMainLoop *loop;
+  Data data;
+  int i;
+
+  data.context = cogl_context_new (NULL, NULL);
+
+  create_primitive (&data);
+
+  data.pipeline = cogl_pipeline_new (data.context);
+  data.last_spark_time = g_timer_new ();
+  data.next_spark_num = 0;
+  cogl_pipeline_set_point_size (data.pipeline, TEXTURE_SIZE);
+
+  tex = generate_round_texture (data.context);
+  cogl_pipeline_set_layer_texture (data.pipeline, 0, tex);
+  cogl_object_unref (tex);
+
+  cogl_pipeline_set_layer_point_sprite_coords_enabled (data.pipeline,
+                                                       0, /* layer */
+                                                       TRUE,
+                                                       NULL /* error */);
+
+  for (i = 0; i < N_FIREWORKS; i++)
+    {
+      data.fireworks[i].x = -FLT_MAX;
+      data.fireworks[i].y = FLT_MAX;
+      data.fireworks[i].size = 0.0f;
+      data.fireworks[i].timer = g_timer_new ();
+    }
+
+  for (i = 0; i < N_SPARKS; i++)
+    {
+      data.sparks[i].x = 2.0f;
+      data.sparks[i].y = 2.0f;
+    }
+
+  onscreen = cogl_onscreen_new (data.context, 800, 600);
+  cogl_onscreen_show (onscreen);
+  data.fb = COGL_FRAMEBUFFER (onscreen);
+
+  cogl_source = cogl_glib_source_new (data.context, G_PRIORITY_DEFAULT);
+
+  g_source_attach (cogl_source, NULL);
+
+  cogl_onscreen_add_frame_callback (onscreen,
+                                    frame_event_cb,
+                                    &data,
+                                    NULL /* destroy notify */);
+
+  loop = g_main_loop_new (NULL, TRUE);
+
+  paint (&data);
+
+  g_main_loop_run (loop);
+
+  g_main_loop_unref (loop);
+
+  g_source_destroy (cogl_source);
+
+  cogl_object_unref (data.pipeline);
+  cogl_object_unref (data.attribute_buffer);
+  cogl_object_unref (data.primitive);
+  cogl_object_unref (onscreen);
+  cogl_object_unref (data.context);
+
+  g_timer_destroy (data.last_spark_time);
+
+  for (i = 0; i < N_FIREWORKS; i++)
+    g_timer_destroy (data.fireworks[i].timer);
+
+  return 0;
+}