Share graphics API layer between tests/examples (#603)

The `render-test` project has an in-progress graphics API abstraction layer, and it makes sense to share this code with our examples rather than write a bunch of redundant code between examples and tests.

Most of this change is just moving files from `tools/render-test/*` to a new library project at `tools/slang-graphics/`. The most complicated code change there is renaming from `render_test` to `slang_graphics`.

The existing `hello` example was ported to use the graphics API layer instead of raw D3D11 API calls. It is still hard-coded to use the D3D11 back-end and the `SLANG_DXBC` target, so more work is needed if we want to actually support multiple APIs in the examples.

I also went ahead and implemented an extremely rudimentary set of APIs to abstract over the Windows platform calls that were being made in the example, so that we could potentially run that same example on other platforms. I did *not* port `render-test` to use those APIs, and I also did not implement them for anything but Windows (my assumption is that for most other platforms we would just use SDL2, and require people to ensure it is installed to their machine before building Slang examples).

1 files changed, 24 insertions, 21 deletions

diff --git a/examples/hello/hello.slang b/examples/hello/hello.slang
index f495d12b4..5a68979ce 100644
--- a/examples/hello/hello.slang
+++ b/examples/hello/hello.slang
@@ -1,24 +1,28 @@
 // hello.slang
 
+// This file provides a simple vertex and fragment shader that can be compiled
+// using Slang. This code should also be valid as HLSL, and thus it does not
+// use any of the new language features supported by Slang.
+
 cbuffer Uniforms
 {
-	float4x4 modelViewProjection;
+    float4x4 modelViewProjection;
 }
 
 struct AssembledVertex
 {
-	float3	position;
-	float3	color;
+    float3	position : POSITION;
+    float3	color    : COLOR;
 };
 
 struct CoarseVertex
 {
-	float3	color;
+    float3 color;
 };
 
 struct Fragment
 {
-	float4 color;
+    float4 color;
 };
 
 
@@ -26,48 +30,47 @@ struct Fragment
 
 struct VertexStageInput
 {
-	AssembledVertex assembledVertex	: A;
+    AssembledVertex assembledVertex;
 };
 
 struct VertexStageOutput
 {
-	CoarseVertex	coarseVertex	: CoarseVertex;
-	float4			sv_position		: SV_Position;
+    CoarseVertex    coarseVertex    : CoarseVertex;
+    float4          sv_position     : SV_Position;
 };
 
 VertexStageOutput vertexMain(VertexStageInput input)
 {
-	VertexStageOutput output;
+    VertexStageOutput output;
 
-	float3 position = input.assembledVertex.position;
-	float3 color	= input.assembledVertex.color;
+    float3 position = input.assembledVertex.position;
+    float3 color    = input.assembledVertex.color;
 
-	output.coarseVertex.color = color;
-	output.sv_position = mul(modelViewProjection, float4(position, 1.0));
+    output.coarseVertex.color = color;
+    output.sv_position = mul(modelViewProjection, float4(position, 1.0));
 
-	return output;
+    return output;
 }
 
 // Fragment Shader
 
 struct FragmentStageInput
 {
-	CoarseVertex	coarseVertex	: CoarseVertex;
+    CoarseVertex    coarseVertex    : CoarseVertex;
 };
 
 struct FragmentStageOutput
 {
-	Fragment fragment	: SV_Target;
+    Fragment fragment   : SV_Target;
 };
 
 FragmentStageOutput fragmentMain(FragmentStageInput input)
 {
-	FragmentStageOutput output;
+    FragmentStageOutput output;
 
-	float3 color = input.coarseVertex.color;
+    float3 color = input.coarseVertex.color;
 
-	output.fragment.color = float4(color, 1.0);
+    output.fragment.color = float4(color, 1.0);
 
-	return output;
+    return output;
 }
-