[retro-gtk/wip/aplazas/gl-display: 8/10] colorful blinking triangle

[Adrien Plazas <aplazas src gnome org>]

commit 71eecc85da0d727c85186f1740ad435db4e9849c
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Mon Nov 13 11:49:22 2017 +0100

    colorful blinking triangle

 .editorconfig                            |    6 ++++++
 retro-gtk/retro-gl-display-fragment.glsl |   14 ++++++++++----
 retro-gtk/retro-gl-display-vertex.glsl   |   14 ++++++++++----
 retro-gtk/retro-gl-display.c             |   30 ++++++++++++++++++++++++++++++
 4 files changed, 56 insertions(+), 8 deletions(-)
---
diff --git a/.editorconfig b/.editorconfig
index 14415a2..58edaa8 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -11,6 +11,12 @@ tab_size = 2
 indent_style = space
 max_line_length = 80
 
+[*.glsl]
+indent_size = 2
+tab_size = 2
+indent_style = space
+max_line_length = 80
+
 [*.{ui,xml,modules}]
 indent_size = 2
 tab_size = 2
diff --git a/retro-gtk/retro-gl-display-fragment.glsl b/retro-gtk/retro-gl-display-fragment.glsl
index f70065a..8747d24 100644
--- a/retro-gtk/retro-gl-display-fragment.glsl
+++ b/retro-gtk/retro-gl-display-fragment.glsl
@@ -1,6 +1,12 @@
-#version 400
+#version 150 core
 
-out vec4 frag_colour;
-void main() {
-  frag_colour = vec4(0.5, 0.0, 0.5, 1.0);
+in vec3 Color;
+
+out vec4 outColor;
+
+uniform float triangleColor;
+
+void main ()
+{
+  outColor = vec4 (Color * triangleColor, 1.0);
 }
diff --git a/retro-gtk/retro-gl-display-vertex.glsl b/retro-gtk/retro-gl-display-vertex.glsl
index d2107ad..aa8c092 100644
--- a/retro-gtk/retro-gl-display-vertex.glsl
+++ b/retro-gtk/retro-gl-display-vertex.glsl
@@ -1,6 +1,12 @@
-#version 400
+#version 150 core
 
-in vec3 vp;
-void main() {
-  gl_Position = vec4(vp, 1.0);
+in vec2 position;
+in vec3 color;
+
+out vec3 Color;
+
+void main ()
+{
+  Color = color;
+  gl_Position = vec4 (position, 0.0, 1.0);
 }
diff --git a/retro-gtk/retro-gl-display.c b/retro-gtk/retro-gl-display.c
index ebbcf0b..9b1e448 100644
--- a/retro-gtk/retro-gl-display.c
+++ b/retro-gtk/retro-gl-display.c
@@ -69,9 +69,17 @@ retro_gl_display_get_video_box (RetroGLDisplay *self,
   *y = (h - *height) / 2;
 }
 
+float vertices[] = {
+     0.0f,  0.5f, 1.0f, 0.0f, 0.0f, // Vertex 1: Red
+     0.5f, -0.5f, 0.0f, 1.0f, 0.0f, // Vertex 2: Green
+    -0.5f, -0.5f, 0.0f, 0.0f, 1.0f  // Vertex 3: Blue
+};
+
 static void
 retro_gl_display_realize (RetroGLDisplay *self)
 {
+  GLuint vertex_buffer_object;
+  GLuint vertex_array_object;
   GLuint vertex_shader;
   GLuint fragment_shader;
   GLuint shader_program;
@@ -80,6 +88,13 @@ retro_gl_display_realize (RetroGLDisplay *self)
 
   gtk_gl_area_make_current (GTK_GL_AREA (self));
 
+  glGenBuffers (1, &vertex_buffer_object);
+  glBindBuffer (GL_ARRAY_BUFFER, vertex_buffer_object);
+  glBufferData (GL_ARRAY_BUFFER, sizeof (vertices), vertices, GL_STATIC_DRAW);
+
+  glGenVertexArrays (1, &vertex_array_object);
+  glBindVertexArray (vertex_array_object);
+
   // Prepare the vertex shader
   shader_source_bytes = g_resources_lookup_data ("/org/gnome/Retro/retro-gl-display-vertex.glsl", 0, NULL);
   shader_source = g_bytes_get_data (shader_source_bytes, NULL);
@@ -102,6 +117,17 @@ retro_gl_display_realize (RetroGLDisplay *self)
   glAttachShader (shader_program, fragment_shader);
   glLinkProgram (shader_program);
 
+  glUseProgram (shader_program);
+  GLint position_attrib = glGetAttribLocation (shader_program, "position");
+  glVertexAttribPointer (position_attrib, 2, GL_FLOAT, GL_FALSE,
+                         5 * sizeof (float), 0);
+  glEnableVertexAttribArray (position_attrib);
+
+  GLint colAttrib = glGetAttribLocation (shader_program, "color");
+  glEnableVertexAttribArray (colAttrib);
+  glVertexAttribPointer (colAttrib, 3, GL_FLOAT, GL_FALSE,
+                         5 * sizeof (float), (void *) (2 * sizeof(float)));
+
   self->shader_program = shader_program;
 }
 
@@ -141,6 +167,8 @@ retro_gl_display_render (RetroGLDisplay *self)
 
   glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glUseProgram (self->shader_program);
+  GLint uniColor = glGetUniformLocation (self->shader_program, "triangleColor");
+  glUniform1f (uniColor, (g_get_monotonic_time () % 1000000) / 1000000.0f);
 
   glBindFramebuffer (GL_READ_FRAMEBUFFER, self->framebuffer);
   glBlitFramebuffer (0, 0,
@@ -151,6 +179,8 @@ retro_gl_display_render (RetroGLDisplay *self)
                      filter);
   glBindFramebuffer (GL_READ_FRAMEBUFFER, 0);
 
+  glDrawArrays (GL_TRIANGLES, 0, 3);
+
   return FALSE;
 }