gpu: update gioui.org/shader for portable materials.vert shader

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

gpu/compute.go

@@ -893,9 +893,10 @@ restart:
 			m.cpuTex = cpu.NewImageRGBA(texSize, texSize)
 		}
 	}
-	// Transform to clip space: [-1, -1] - [1, 1].
-	g.materials.vert.uniforms.scale = [2]float32{2 / float32(texSize), 2 / float32(texSize)}
-	g.materials.vert.uniforms.pos = [2]float32{-1, -1}
+	// Transform to clip space: [-1, -1] - [1, 1] and flip Y-axis to cancel the implied transformation
+	// between framebuffer and texture space.
+	g.materials.vert.uniforms.scale = [2]float32{2 / float32(texSize), -2 / float32(texSize)}
+	g.materials.vert.uniforms.pos = [2]float32{-1, +1}
 	g.materials.vert.buf.Upload(byteslice.Struct(g.materials.vert.uniforms))
 	vertexData := byteslice.Slice(m.quads)
 	n := pow2Ceil(len(vertexData))

gpu/gpu.go

@@ -135,7 +135,7 @@ type imageOp struct {
 
 // shaderModuleVersion is the exact version of gioui.org/shader expected by
 // this package. Shader programs are not backwards or forwards compatible.
-const shaderModuleVersion = "v0.0.0-20210816161847-c12352edbd45"
+const shaderModuleVersion = "v0.0.0-20210820085839-484f7c0305de"
 
 func decodeStrokeOp(data []byte) clip.StrokeStyle {
 	_ = data[4]