[retro-gtk/wip/aplazas/gl-display] Display the video output

[Adrien Plazas <aplazas src gnome org>]

commit 8879edcfc2beea9965aa0786131f48934d3f2e76
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Fri Nov 10 14:11:37 2017 +0100

    Display the video output
    
    Colors are broken and the video is flipped vertically.

 retro-gtk/retro-gl-display.c |   72 ++++++++++++++++++++++++++++++++++++-----
 1 files changed, 63 insertions(+), 9 deletions(-)
---
diff --git a/retro-gtk/retro-gl-display.c b/retro-gtk/retro-gl-display.c
index db48b4b..22cbfa3 100644
--- a/retro-gtk/retro-gl-display.c
+++ b/retro-gtk/retro-gl-display.c
@@ -17,6 +17,7 @@ struct _RetroGLDisplay
 
   GLuint vertex_array_object;
   GLuint shader_program;
+  GLuint readFboId;
 };
 
 G_DEFINE_TYPE (RetroGLDisplay, retro_gl_display, GTK_TYPE_GL_AREA)
@@ -83,10 +84,8 @@ retro_gl_display_get_video_box (RetroGLDisplay *self,
 float points[] = {
   -0.5f,  0.5f,  0.0f,
    0.5f,  0.5f,  0.0f,
-  -0.5f, -0.5f,  0.0f,
-   0.5f,  0.5f,  0.0f,
-  -0.5f, -0.5f,  0.0f,
    0.5f, -0.5f,  0.0f,
+  -0.5f, -0.5f,  0.0f,
 };
 
 static void
@@ -105,7 +104,7 @@ retro_gl_display_realize (RetroGLDisplay *self)
   // Prepare the vertex buffer
   glGenBuffers (1, &vertex_buffer_object);
   glBindBuffer (GL_ARRAY_BUFFER, vertex_buffer_object);
-  glBufferData (GL_ARRAY_BUFFER, 18 * sizeof (float), points, GL_STATIC_DRAW);
+  glBufferData (GL_ARRAY_BUFFER, 12 * sizeof (float), points, GL_STATIC_DRAW);
 
   // Prepare the vertex array
   glGenVertexArrays (1, &vertex_array_object);
@@ -136,6 +135,23 @@ retro_gl_display_realize (RetroGLDisplay *self)
   glAttachShader (shader_program, fragment_shader);
   glLinkProgram (shader_program);
 
+  /* GLuint tex = 0; */
+  /* glGenTextures (1, &tex); */
+  /* glBindTexture (GL_TEXTURE_2D, tex); */
+
+  /* // Black/white checkerboard */
+  /* float pixels[] = { */
+  /*   0.0f, 0.0f, 0.0f,   1.0f, 1.0f, 1.0f, */
+  /*   1.0f, 1.0f, 1.0f,   0.0f, 0.0f, 0.0f */
+  /* }; */
+  /* glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_FLOAT, pixels); */
+
+  /* glGenFramebuffers(1, &self->readFboId); */
+  /* glBindFramebuffer(GL_READ_FRAMEBUFFER, self->readFboId); */
+  /* glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, */
+  /*                        GL_TEXTURE_2D, tex, 0); */
+  /* glBindFramebuffer(GL_READ_FRAMEBUFFER, 0); */
+
   self->vertex_array_object = vertex_array_object;
   self->shader_program = shader_program;
 }
@@ -152,10 +168,28 @@ retro_gl_display_unrealize (RetroGLDisplay *self)
 static gboolean
 retro_gl_display_render (RetroGLDisplay *self)
 {
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-  glUseProgram(self->shader_program);
-  glBindVertexArray(self->vertex_array_object);
-  glDrawArrays(GL_TRIANGLES, 0, 6);
+  gdouble w = 0.0;
+  gdouble h = 0.0;
+  gdouble x = 0.0;
+  gdouble y = 0.0;
+
+  g_return_val_if_fail (self != NULL, FALSE);
+
+  retro_gl_display_get_video_box (self, &w, &h, &x, &y);
+
+  glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  glUseProgram (self->shader_program);
+  glBindVertexArray (self->vertex_array_object);
+  glDrawArrays (GL_TRIANGLE_FAN, 0, 4);
+
+  glBindFramebuffer (GL_READ_FRAMEBUFFER, self->readFboId);
+  glBlitFramebuffer (0, 0,
+                     gdk_pixbuf_get_width (self->pixbuf),
+                     gdk_pixbuf_get_height (self->pixbuf),
+                     (GLint) x, (GLint) y, (GLint) (x + w), (GLint) (y + h),
+                     GL_COLOR_BUFFER_BIT,
+                     GL_LINEAR);
+  glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
 
   return FALSE;
 }
@@ -360,9 +394,29 @@ retro_gl_display_set_pixbuf (RetroGLDisplay *self,
 
   g_clear_object (&self->pixbuf);
 
-  if (pixbuf != NULL)
+  if (pixbuf != NULL) {
     self->pixbuf = g_object_ref (pixbuf);
 
+    GLuint tex = 0;
+    glGenTextures (1, &tex);
+    glBindTexture (GL_TEXTURE_2D, tex);
+
+    glTexImage2D (GL_TEXTURE_2D,
+                  0,
+                  GL_RGB,
+                  gdk_pixbuf_get_width (self->pixbuf),
+                  gdk_pixbuf_get_height (self->pixbuf),
+                  0,
+                  GL_RGBA, GL_UNSIGNED_INT_8_8_8_8,
+                  gdk_pixbuf_get_pixels (self->pixbuf));
+
+    glGenFramebuffers(1, &self->readFboId);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, self->readFboId);
+    glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                           GL_TEXTURE_2D, tex, 0);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
+  }
+
   g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_PIXBUF]);
 }