Support GLShaderNode in backends

For vulkan/broadway this just means to ignore it, but for the gl
backend we support (with up to 4 texture inputs, which is similar to
what shadertoy does, so should be widely supported).

1 files changed, 21 insertions, 0 deletions

diff --git a/gsk/resources/glsl/custom.glsl b/gsk/resources/glsl/custom.glsl
new file mode 100644
index 0000000000..d2aed97fc8
--- /dev/null
+++ b/gsk/resources/glsl/custom.glsl
@@ -0,0 +1,21 @@
+// VERTEX_SHADER:
+void main() {
+  gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
+  vUv = vec2(aUv.x, aUv.y);
+}
+
+// FRAGMENT_SHADER:
+// The shader supplies:
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv);
+
+uniform vec2 u_size;
+uniform sampler2D u_source2;
+uniform sampler2D u_source3;
+uniform sampler2D u_source4;
+
+void main() {
+  vec4 fragColor;
+  vec2 fragCoord = vec2(vUv.x * u_size.x, (1.0-vUv.y) * u_size.y);
+  mainImage(fragColor, fragCoord, u_size, vUv);
+  gskSetOutputColor(fragColor);
+}