Merge #2072

2072: [WIP] A third gfx example r=kvark a=ZeGentzy

Depends on #2071 and #2052 
PR checklist:
- [ ] `make` succeeds (on *nix)
- [ ] `make reftests` succeeds
- [ ] tested examples with the following backends:


Co-authored-by: Hal Gentz <[email protected]>

examples/Cargo.toml

@@ -12,6 +12,10 @@ dx12 = ["gfx-backend-dx12"]
 vulkan = ["gfx-backend-vulkan"]
 unstable = []
 
+[[bin]]
+name = "colour-uniform"
+path = "colour-uniform/main.rs"
+
 [[bin]]
 name = "quad"
 path = "quad/main.rs"
@@ -27,6 +31,7 @@ log = "0.4"
 winit = "0.16"
 glsl-to-spirv = "0.1.4"
 gfx-hal = { path = "../src/hal", version = "0.1" }
+gfx-backend-empty = { path = "../src/backend/empty", version = "0.1" }
 
 [dependencies.gfx-backend-gl]
 path = "../src/backend/gl"

examples/colour-uniform/data/quad.frag

@@ -0,0 +1,16 @@
+#version 450
+#extension GL_ARB_separate_shader_objects : enable
+
+layout(location = 0) in vec2 v_uv;
+layout(location = 0) out vec4 target0;
+
+layout(set = 0, binding = 0) uniform texture2D u_texture;
+layout(set = 0, binding = 1) uniform sampler u_sampler;
+
+layout(set = 1, binding = 0) uniform UBOCol {
+    vec4 color;
+} color_dat;
+
+void main() {
+    target0 = texture(sampler2D(u_texture, u_sampler), v_uv) * color_dat.color;
+}

examples/colour-uniform/data/quad.vert

@@ -0,0 +1,17 @@
+#version 450
+#extension GL_ARB_separate_shader_objects : enable
+
+layout(constant_id = 0) const float scale = 1.2f;
+
+layout(location = 0) in vec2 a_pos;
+layout(location = 1) in vec2 a_uv;
+layout(location = 0) out vec2 v_uv;
+
+out gl_PerVertex {
+    vec4 gl_Position;
+};
+
+void main() {
+    v_uv = a_uv;
+    gl_Position = vec4(scale * a_pos, 0.0, 1.0);
+}