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)