Revert "internal/restorable: remove unnecessary functions and variables around shaders"

This reverts commit 4f3e00ec3a.

Updates #3083

internal/atlas/image.go

@@ -408,7 +408,7 @@ func (i *Image) drawTriangles(srcs [graphics.ShaderSrcImageCount]*Image, vertice
 			vertices[i+2] += oxf
 			vertices[i+3] += oyf
 		}
-		if shader.ir.Unit == shaderir.Texels {
+		if shader.ensureShader().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

@@ -75,12 +75,6 @@ func (s *Shader) deallocate() {
 }
 
 var (
-	NearestFilterShader = &Shader{
-		shader: restorable.NearestFilterShader,
-		ir:     restorable.LinearFilterShaderIR,
-	}
-	LinearFilterShader = &Shader{
-		shader: restorable.LinearFilterShader,
-		ir:     restorable.LinearFilterShaderIR,
-	}
+	NearestFilterShader = &Shader{shader: restorable.NearestFilterShader}
+	LinearFilterShader  = &Shader{shader: restorable.LinearFilterShader}
 )

internal/restorable/images.go

@@ -23,11 +23,13 @@ import (
 // images is a set of Image objects.
 type images struct {
 	images  map[*Image]struct{}
+	shaders map[*Shader]struct{}
 }
 
 // theImages represents the images for the current process.
 var theImages = &images{
 	images:  map[*Image]struct{}{},
+	shaders: map[*Shader]struct{}{},
 }
 
 func SwapBuffers(graphicsDriver graphicsdriver.Graphics) error {
@@ -62,11 +64,19 @@ func (i *images) add(img *Image) {
 	i.images[img] = struct{}{}
 }
 
+func (i *images) addShader(shader *Shader) {
+	i.shaders[shader] = struct{}{}
+}
+
 // remove removes img from the images.
 func (i *images) remove(img *Image) {
 	delete(i.images, img)
 }
 
+func (i *images) removeShader(shader *Shader) {
+	delete(i.shaders, shader)
+}
+
 var graphicsDriverInitialized bool
 
 // InitializeGraphicsDriverState initializes the graphics driver state.

internal/restorable/shader.go

@@ -27,25 +27,36 @@ import (
 
 type Shader struct {
 	shader *graphicscommand.Shader
+	ir     *shaderir.Program
 }
 
 func NewShader(ir *shaderir.Program) *Shader {
 	s := &Shader{
 		shader: graphicscommand.NewShader(ir),
+		ir:     ir,
 	}
+	theImages.addShader(s)
 	return s
 }
 
 func (s *Shader) Dispose() {
+	theImages.removeShader(s)
 	s.shader.Dispose()
 	s.shader = nil
+	s.ir = nil
+}
+
+func (s *Shader) restore() {
+	s.shader = graphicscommand.NewShader(s.ir)
+}
+
+func (s *Shader) Unit() shaderir.Unit {
+	return s.ir.Unit
 }
 
 var (
 	NearestFilterShader *Shader
-	NearestFilterShaderIR *shaderir.Program
 	LinearFilterShader  *Shader
-	LinearFilterShaderIR  *shaderir.Program
 	clearShader         *Shader
 )
 
@@ -79,9 +90,7 @@ func init() {
 	if err := wg.Wait(); err != nil {
 		panic(err)
 	}
-	NearestFilterShaderIR = nearestIR
 	NearestFilterShader = NewShader(nearestIR)
-	LinearFilterShaderIR = linearIR
 	LinearFilterShader = NewShader(linearIR)
 	clearShader = NewShader(clearIR)
 }