gpu,gpu/gl: implement shader uniform buffers

Emulate them for the OpenGL ES backend because 2.0 doesn't support uniform
buffers. The future d3d backend only supports uniform (constant) buffers.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/build.go

@@ -85,16 +85,17 @@ func generate() error {
 	for _, shader := range shaders {
 		const nvariants = 2
 		var variants [nvariants]struct {
-			gles2    string
-			hlslSrc  string
-			hlsl     []byte
-			inputs   []InputLocation
-			uniforms []UniformLocation
+			gles2       string
+			hlslSrc     string
+			hlsl        []byte
+			inputs      []InputLocation
+			uniforms    []UniformLocation
+			uniformSize int
 		}
 		args := [nvariants]shaderArgs{
 			{
-				FetchColorExpr: `color.color`,
-				Header:         `layout(binding=0) uniform Color { vec4 color; } color;`,
+				FetchColorExpr: `_color`,
+				Header:         `layout(binding=0) uniform Color { vec4 _color; };`,
 			},
 			{
 				FetchColorExpr: `texture(tex, vUV)`,
@@ -108,7 +109,7 @@ func generate() error {
 			}
 			// Make the GL ES 2 source compatible with desktop GL 3.
 			gles2 = "#version 100\n" + gles2
-			inputs, uniforms, err := parseReflection(reflect)
+			inputs, uniforms, uniformSize, err := parseReflection(reflect)
 			if err != nil {
 				return err
 			}
@@ -137,6 +138,7 @@ func generate() error {
 			variants[i].hlsl = hlslc
 			variants[i].inputs = inputs
 			variants[i].uniforms = uniforms
+			variants[i].uniformSize = uniformSize
 		}
 		name := filepath.Base(shader)
 		name = strings.ReplaceAll(name, ".", "_")
@@ -163,6 +165,7 @@ func generate() error {
 					fmt.Fprintf(&out, "{Name: %q, Type: %d, Size: %d, Offset: %d},\n", u.Name, u.Type, u.Size, u.Offset)
 				}
 				fmt.Fprintf(&out, "},\n")
+				fmt.Fprintf(&out, "UniformSize: %d,\n", src.uniformSize)
 			}
 			fmt.Fprintf(&out, "GLES2: %#v,\n", src.gles2)
 			fmt.Fprintf(&out, "/*\n%s\n*/\n", src.hlslSrc)
@@ -188,7 +191,7 @@ func generate() error {
 	return ioutil.WriteFile("shaders.go", gosrc, 0644)
 }
 
-func parseReflection(jsonData []byte) ([]InputLocation, []UniformLocation, error) {
+func parseReflection(jsonData []byte) ([]InputLocation, []UniformLocation, int, error) {
 	type InputReflection struct {
 		ID            int    `json:"id"`
 		Name          string `json:"name"`
@@ -221,14 +224,14 @@ func parseReflection(jsonData []byte) ([]InputLocation, []UniformLocation, error
 	}
 	var reflect shaderMetadata
 	if err := json.Unmarshal(jsonData, &reflect); err != nil {
-		return nil, nil, fmt.Errorf("parseReflection: %v", err)
+		return nil, nil, 0, fmt.Errorf("parseReflection: %v", err)
 	}
 	var inputs []InputLocation
 	inputRef := reflect.VS.Inputs
 	for _, input := range inputRef {
 		dataType, dataSize, err := parseDataType(input.Type)
 		if err != nil {
-			return nil, nil, err
+			return nil, nil, 0, fmt.Errorf("parseReflection: %v", err)
 		}
 		inputs = append(inputs, InputLocation{
 			Name:          input.Name,
@@ -247,22 +250,24 @@ func parseReflection(jsonData []byte) ([]InputLocation, []UniformLocation, error
 	if len(shaderBlocks) == 0 {
 		shaderBlocks = reflect.FS.UniformBuffers
 	}
+	blockOffset := 0
 	for _, block := range shaderBlocks {
 		for _, member := range block.Members {
 			dataType, size, err := parseDataType(member.Type)
 			if err != nil {
-				return nil, nil, err
+				return nil, nil, 0, fmt.Errorf("parseReflection: %v", err)
 			}
 			ublocks = append(ublocks, UniformLocation{
 				// Synthetic name generated by glslcc.
 				Name:   fmt.Sprintf("_%d.%s", block.ID, member.Name),
 				Type:   dataType,
 				Size:   size,
-				Offset: member.Offset,
+				Offset: blockOffset + member.Offset,
 			})
 		}
+		blockOffset += block.Size
 	}
-	return inputs, ublocks, nil
+	return inputs, ublocks, blockOffset, nil
 }
 
 func parseDataType(t string) (DataType, int, error) {