gpu/internal/driver: introduce and use FeatureSRGB

No functional changes; a follow-up will implement graceful fallback in
the compute renderer.

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

gpu/gpu.go

@@ -9,6 +9,7 @@ package gpu
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"image"
 	"image/color"
@@ -360,6 +361,9 @@ func New(api API) (GPU, error) {
 	defer d.EndFrame()
 	forceCompute := os.Getenv("GIORENDERER") == "forcecompute"
 	feats := d.Caps().Features
+	if !feats.Has(driver.FeatureSRGB) {
+		return nil, errors.New("gpu: no sRGB texture formats found")
+	}
 	switch {
 	case !forceCompute && feats.Has(driver.FeatureFloatRenderTargets):
 		return newGPU(d)

gpu/internal/d3d11/d3d11_windows.go

@@ -128,6 +128,7 @@ func newDirect3D11Device(api driver.Direct3D11) (driver.Device, error) {
 		ctx: dev.GetImmediateContext(),
 		caps: driver.Caps{
 			MaxTextureSize: 2048, // 9.1 maximum
+			Features:       driver.FeatureSRGB,
 		},
 		depthStates: make(map[depthState]*d3d11.DepthStencilState),
 		blendStates: make(map[blendState]*d3d11.BlendState),

gpu/internal/driver/driver.go

@@ -212,6 +212,7 @@ const (
 	FeatureTimers Features = 1 << iota
 	FeatureFloatRenderTargets
 	FeatureCompute
+	FeatureSRGB
 )
 
 const (

gpu/internal/opengl/opengl.go

@@ -182,10 +182,7 @@ func newOpenGLDevice(api driver.OpenGL) (driver.Device, error) {
 		return nil, err
 	}
 	floatTriple, ffboErr := floatTripleFor(f, ver, exts)
-	srgbaTriple, err := srgbaTripleFor(ver, exts)
-	if err != nil {
-		return nil, err
-	}
+	srgbaTriple, srgbErr := srgbaTripleFor(ver, exts)
 	gles30 := gles && ver[0] >= 3
 	gles31 := gles && (ver[0] > 3 || (ver[0] == 3 && ver[1] >= 1))
 	gl40 := !gles && ver[0] >= 4
@@ -199,6 +196,9 @@ func newOpenGLDevice(api driver.OpenGL) (driver.Device, error) {
 		srgbaTriple: srgbaTriple,
 	}
 	b.feats.BottomLeftOrigin = true
+	if srgbErr == nil {
+		b.feats.Features |= driver.FeatureSRGB
+	}
 	if ffboErr == nil {
 		b.feats.Features |= driver.FeatureFloatRenderTargets
 	}