internal/atlas: reduce the access to (*restorable.Shader).Unit

internal/atlas/image.go

@@ -405,7 +405,7 @@ func (i *Image) drawTriangles(srcs [graphics.ShaderSrcImageCount]*Image, vertice
 			vertices[i+2] += oxf
 			vertices[i+3] += oyf
 		}
-		if shader.ensureShader().Unit() == shaderir.Texels {
+		if shader.unit == shaderir.Texels {
 			sw, sh := srcs[0].backend.restorable.InternalSize()
 			swf, shf := float32(sw), float32(sh)
 			for i := 0; i < n; i += graphics.VertexFloatCount {

internal/atlas/shader.go

@@ -24,6 +24,7 @@ import (
 type Shader struct {
 	ir     *shaderir.Program
 	shader *restorable.Shader
+	unit   shaderir.Unit
 	name   string
 }
 
@@ -32,6 +33,7 @@ func NewShader(ir *shaderir.Program, name string) *Shader {
 	return &Shader{
 		ir:   ir,
 		name: name,
+		unit: ir.Unit,
 	}
 }
 
@@ -77,6 +79,12 @@ func (s *Shader) deallocate() {
 }
 
 var (
-	NearestFilterShader = &Shader{shader: restorable.NearestFilterShader}
+	NearestFilterShader = &Shader{
-	LinearFilterShader  = &Shader{shader: restorable.LinearFilterShader}
+		shader: restorable.NearestFilterShader,
+		unit:   restorable.NearestFilterShader.Unit(),
+	}
+	LinearFilterShader = &Shader{
+		shader: restorable.LinearFilterShader,
+		unit:   restorable.LinearFilterShader.Unit(),
+	}
 )