[retro-gtk/pointer: 1/4] video: Add get_coordinates_on_display()

[Adrien Plazas <aplazas src gnome org>]

commit 406427bab612ac9995077ddf1f581ce823257874
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Tue Jul 25 12:10:30 2017 +0200

    video: Add get_coordinates_on_display()
    
    This will be used to support the Libretro pointer controllers.

 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 5302b78..19c271a 100644
--- a/retro-gtk/video/cairo-display.vala
+++ b/retro-gtk/video/cairo-display.vala
@@ -39,6 +39,17 @@ public class Retro.CairoDisplay : Gtk.DrawingArea {
                queue_draw ();
        }
 
+       public bool get_coordinates_on_display (double widget_x, double widget_y, out double display_x, out 
double display_y) {
+               double w, h, x, y;
+               get_video_box (out w, out h, out x, out y);
+
+               // Return coordinates as a [-1.0,1.0] scale, (0.0,0.0) is the center.
+               display_x = ((widget_x-x) * 2.0 - w) / w;
+               display_y = ((widget_y-y) * 2.0 - h) / h;
+
+               return (-1.0 <= display_x <= 1.0) && (-1.0 <= display_y <= 1.0);
+       }
+
        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);