[retro-gtk] cairo-display: Set pixbuf dpi

[Adrien Plazas <aplazas src gnome org>]

commit 80214aa27884da01911fdc270313f5fa7584769f
Author: Mateusz Sieczko <arvamer gmail com>
Date:   Thu Mar 16 19:51:59 2017 +0100

    cairo-display: Set pixbuf dpi
    
    This will allow GNOME Games to save aspect ratio with screenshot.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=769833

 retro-gtk/video/cairo-display.vala |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)
---
diff --git a/retro-gtk/video/cairo-display.vala b/retro-gtk/video/cairo-display.vala
index 5227815..ba1fb6b 100644
--- a/retro-gtk/video/cairo-display.vala
+++ b/retro-gtk/video/cairo-display.vala
@@ -1,6 +1,10 @@
 // This file is part of retro-gtk. License: GPLv3
 
 public class Retro.CairoDisplay : Gtk.DrawingArea {
+       // Because gdk-pixbuf saves dpi as integer we have to multiply it by big
+       // enough number to represent aspect ratio precisely.
+       private const float Y_DPI = 1000000.0f;
+
        public Gdk.Pixbuf pixbuf { set; get; }
 
        private Core core;
@@ -36,6 +40,13 @@ public class Retro.CairoDisplay : Gtk.DrawingArea {
        private void on_video_output (uint8[] data, uint width, uint height, size_t pitch, PixelFormat 
pixel_format, float aspect_ratio) {
                this.aspect_ratio = aspect_ratio;
                pixbuf = gdk_pixbuf_new_from_video (data, width, height, pitch, pixel_format);
+
+               var x_dpi = aspect_ratio * Y_DPI;
+               var x_dpi_string = x_dpi.to_string ();
+               var y_dpi_string = Y_DPI.to_string ();
+
+               pixbuf.set_option ("x-dpi", x_dpi_string);
+               pixbuf.set_option ("y-dpi", y_dpi_string);
        }
 
        public void show_video () {