[glsl-out] Explicitly set location bindings

src/back/glsl/mod.rs

@@ -811,8 +811,22 @@ impl<'a, W: Write> Writer<'a, W> {
                 }
 
                 // Write the storage class
-                write!(self.out, "{} ", if output { "out" } else { "in" })?;
-
+                if self.options.version >= Version::Embedded(310)
+                    || self.options.version >= Version::Desktop(410)
+                {
+                    if let Binding::Location(index, ..) = *binding {
+                        write!(
+                            self.out,
+                            "layout(location = {}) {} ",
+                            index,
+                            if output { "out" } else { "in" }
+                        )?;
+                    } else {
+                        write!(self.out, "{} ", if output { "out" } else { "in" })?;
+                    }
+                } else {
+                    write!(self.out, "{} ", if output { "out" } else { "in" })?;
+                }
                 // Write the type
                 // `write_type` adds no leading or trailing spaces
                 self.write_type(ty)?;

tests/out/quad-Fragment.glsl.snap

@@ -13,8 +13,8 @@ struct VertexOutput {
 
 uniform highp sampler2D _group_0_binding_0;
 
-in vec2 _in_location_0;
-out vec4 _out_location_0;
+layout(location = 0) in vec2 _in_location_0;
+layout(location = 0) out vec4 _out_location_0;
 
 void main() {
     vec2 uv2 = _in_location_0;

tests/out/quad-Vertex.glsl.snap

@@ -11,9 +11,9 @@ struct VertexOutput {
     vec4 position;
 };
 
-in vec2 _in_location_0;
-in vec2 _in_location_1;
-out vec2 _out_location_0;
+layout(location = 0) in vec2 _in_location_0;
+layout(location = 1) in vec2 _in_location_1;
+layout(location = 0) out vec2 _out_location_0;
 
 void main() {
     vec2 pos = _in_location_0;

tests/out/shadow-Fragment.glsl.snap

@@ -22,9 +22,9 @@ readonly buffer Lights_block_1 {
 
 uniform highp sampler2DArrayShadow _group_0_binding_2;
 
-in vec3 _in_location_0;
-in vec4 _in_location_1;
-out vec4 _out_location_0;
+layout(location = 0) in vec3 _in_location_0;
+layout(location = 1) in vec4 _in_location_1;
+layout(location = 0) out vec4 _out_location_0;
 
 float fetch_shadow(uint light_id, vec4 homogeneous_coords) {
     if((homogeneous_coords[3] <= 0.0)) {

tests/out/skybox-Fragment.glsl.snap

@@ -13,8 +13,8 @@ struct VertexOutput {
 
 uniform highp samplerCube _group_0_binding_1;
 
-in vec3 _in_location_0;
-out vec4 _out_location_0;
+layout(location = 0) in vec3 _in_location_0;
+layout(location = 0) out vec4 _out_location_0;
 
 void main() {
     vec3 uv1 = _in_location_0;

tests/out/skybox-Vertex.glsl.snap

@@ -16,7 +16,7 @@ uniform Data_block_0 {
     mat4x4 view;
 } _group_0_binding_0;
 
-out vec3 _out_location_0;
+layout(location = 0) out vec3 _out_location_0;
 
 void main() {
     uint vertex_index = uint(gl_VertexID);