[retro-gtk/wip/aplazas/gl-display] draw the texture

[Adrien Plazas <aplazas src gnome org>]

commit 9c2c79dda1f80f2457d0e1d60de4a9f877faa895
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Tue Nov 14 09:24:34 2017 +0100

    draw the texture

 retro-gtk/retro-gl-display-vertex.glsl |   11 ++++++++++-
 retro-gtk/retro-gl-display.c           |    7 +++++++
 2 files changed, 17 insertions(+), 1 deletions(-)
---
diff --git a/retro-gtk/retro-gl-display-vertex.glsl b/retro-gtk/retro-gl-display-vertex.glsl
index c7b54e8..529d345 100644
--- a/retro-gtk/retro-gl-display-vertex.glsl
+++ b/retro-gtk/retro-gl-display-vertex.glsl
@@ -5,8 +5,17 @@ in vec2 texture_coordinates;
 
 out vec2 texture_coordinates_frag;
 
+uniform float relative_aspect_ratio;
+
 void main ()
 {
   texture_coordinates_frag = texture_coordinates;
-  gl_Position = vec4 (position, 0.0, 1.0);
+  if (relative_aspect_ratio > 1.0f)
+    gl_Position = vec4 (position.x / relative_aspect_ratio,
+                        position.y,
+                        0.0, 1.0);
+  else
+    gl_Position = vec4 (position.x,
+                        position.y * relative_aspect_ratio,
+                        0.0, 1.0);
 }
diff --git a/retro-gtk/retro-gl-display.c b/retro-gtk/retro-gl-display.c
index e307814..13b693c 100644
--- a/retro-gtk/retro-gl-display.c
+++ b/retro-gtk/retro-gl-display.c
@@ -173,6 +173,7 @@ retro_gl_display_render (RetroGLDisplay *self)
   gdouble x = 0.0;
   gdouble y = 0.0;
   GLenum filter;
+  GLint relative_aspect_ratio;
 
   g_return_val_if_fail (self != NULL, FALSE);
 
@@ -209,6 +210,12 @@ retro_gl_display_render (RetroGLDisplay *self)
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, filter);
 
+  relative_aspect_ratio = glGetUniformLocation (self->shader_program, "relative_aspect_ratio");
+  glUniform1f (relative_aspect_ratio,
+               (gfloat) gtk_widget_get_allocated_width (GTK_WIDGET (self)) /
+               (gfloat) gtk_widget_get_allocated_height (GTK_WIDGET (self)) /
+               self->aspect_ratio);
+
   glDrawElements (GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
 
   return FALSE;