Somewhat better NvFlinger (I guess) (fixes #30)

Ryujinx.Graphics/Gal/OpenGL/FbVtxShader.glsl

@@ -0,0 +1,26 @@
+#version 330 core
+
+precision highp float;
+
+uniform vec2 window_size;
+uniform mat2 transform;
+
+layout(location = 0) in vec2 in_position;
+layout(location = 1) in vec2 in_tex_coord;
+
+out vec2 tex_coord;
+
+// Have a fixed aspect ratio, fit the image within the available space.
+vec2 get_scale_ratio(void) {
+    vec2 native_size = vec2(1280, 720);
+    vec2 ratio = vec2(
+        (window_size.y * native_size.x) / (native_size.y * window_size.x),
+        (window_size.x * native_size.y) / (native_size.x * window_size.y)
+    );
+    return min(ratio, 1);
+}
+
+void main(void) {
+    tex_coord = in_tex_coord;
+    gl_Position = vec4((transform * in_position) * get_scale_ratio(), 0, 1);
+}