diff --git a/app/internal/wm/gl_js.go b/app/internal/wm/gl_js.go
index 28a6bf01..1f5a998c 100644
--- a/app/internal/wm/gl_js.go
+++ b/app/internal/wm/gl_js.go
@@ -8,13 +8,11 @@ import (
 
 	"gioui.org/gpu"
 	"gioui.org/internal/gl"
-	"gioui.org/internal/srgb"
 )
 
 type context struct {
-	ctx     js.Value
-	cnv     js.Value
-	srgbFBO *srgb.FBO
+	ctx js.Value
+	cnv js.Value
 }
 
 func newContext(w *window) (*context, error) {
@@ -43,19 +41,9 @@ func (c *context) API() gpu.API {
 }
 
 func (c *context) Release() {
-	if c.srgbFBO != nil {
-		c.srgbFBO.Release()
-		c.srgbFBO = nil
-	}
 }
 
 func (c *context) Present() error {
-	if c.srgbFBO != nil {
-		c.srgbFBO.Blit()
-	}
-	if c.srgbFBO != nil {
-		c.srgbFBO.AfterPresent()
-	}
 	if c.ctx.Call("isContextLost").Bool() {
 		return errors.New("context lost")
 	}
@@ -67,20 +55,6 @@ func (c *context) Lock() {}
 func (c *context) Unlock() {}
 
 func (c *context) MakeCurrent() error {
-	if c.srgbFBO == nil {
-		var err error
-		c.srgbFBO, err = srgb.New(gl.Context(c.ctx))
-		if err != nil {
-			c.Release()
-			c.srgbFBO = nil
-			return err
-		}
-	}
-	w, h := c.cnv.Get("width").Int(), c.cnv.Get("height").Int()
-	if err := c.srgbFBO.Refresh(w, h); err != nil {
-		c.Release()
-		return err
-	}
 	return nil
 }
 
diff --git a/gpu/compute.go b/gpu/compute.go
index 17ca4455..7f3b744d 100644
--- a/gpu/compute.go
+++ b/gpu/compute.go
@@ -280,7 +280,7 @@ func (g *compute) Frame() error {
 		Y: (viewport.Y + tileHeightPx - 1) / tileHeightPx,
 	}
 
-	defFBO := g.ctx.BeginFrame()
+	defFBO := g.ctx.BeginFrame(viewport)
 	defer g.ctx.EndFrame()
 
 	if g.drawOps.profile && g.timers.t == nil && g.ctx.Caps().Features.Has(driver.FeatureTimers) {
diff --git a/gpu/gpu.go b/gpu/gpu.go
index d84ca3d8..9ca9fa02 100644
--- a/gpu/gpu.go
+++ b/gpu/gpu.go
@@ -425,9 +425,9 @@ func (g *gpu) Collect(viewport image.Point, frameOps *op.Ops) {
 }
 
 func (g *gpu) Frame() error {
-	defFBO := g.ctx.BeginFrame()
-	defer g.ctx.EndFrame()
 	viewport := g.renderer.blitter.viewport
+	defFBO := g.ctx.BeginFrame(viewport)
+	defer g.ctx.EndFrame()
 	for _, img := range g.drawOps.imageOps {
 		expandPathOp(img.path, img.clip)
 	}
diff --git a/gpu/headless/driver_test.go b/gpu/headless/driver_test.go
index 01323dee..98e209ce 100644
--- a/gpu/headless/driver_test.go
+++ b/gpu/headless/driver_test.go
@@ -174,7 +174,7 @@ func newDriver(t *testing.T) driver.Device {
 	if err != nil {
 		t.Fatal(err)
 	}
-	b.BeginFrame()
+	b.BeginFrame(image.Pt(1, 1))
 	t.Cleanup(func() {
 		b.EndFrame()
 		ctx.ReleaseCurrent()
diff --git a/gpu/internal/d3d11/d3d11_windows.go b/gpu/internal/d3d11/d3d11_windows.go
index 7ecd963f..50fb77de 100644
--- a/gpu/internal/d3d11/d3d11_windows.go
+++ b/gpu/internal/d3d11/d3d11_windows.go
@@ -164,7 +164,7 @@ func newDirect3D11Device(api driver.Direct3D11) (driver.Device, error) {
 	return b, nil
 }
 
-func (b *Backend) BeginFrame() driver.Framebuffer {
+func (b *Backend) BeginFrame(viewport image.Point) driver.Framebuffer {
 	renderTarget, depthView := b.ctx.OMGetRenderTargets()
 	// Assume someone else is holding on to the render targets.
 	if renderTarget != nil {
diff --git a/gpu/internal/driver/driver.go b/gpu/internal/driver/driver.go
index 14d3d85d..97dbcf78 100644
--- a/gpu/internal/driver/driver.go
+++ b/gpu/internal/driver/driver.go
@@ -12,7 +12,7 @@ import (
 // APIs such as OpenGL, Direct3D useful for rendering Gio
 // operations.
 type Device interface {
-	BeginFrame() Framebuffer
+	BeginFrame(viewport image.Point) Framebuffer
 	EndFrame()
 	Caps() Caps
 	NewTimer() Timer
diff --git a/gpu/internal/opengl/opengl.go b/gpu/internal/opengl/opengl.go
index 13c6d0ee..b6497536 100644
--- a/gpu/internal/opengl/opengl.go
+++ b/gpu/internal/opengl/opengl.go
@@ -12,6 +12,7 @@ import (
 
 	"gioui.org/gpu/internal/driver"
 	"gioui.org/internal/gl"
+	"gioui.org/internal/srgb"
 )
 
 // Backend implements driver.Device.
@@ -30,6 +31,9 @@ type Backend struct {
 	// Single channel alpha textures.
 	alphaTriple textureTriple
 	srgbaTriple textureTriple
+
+	sRGBFBO *srgb.FBO
+	defFBO  gl.Framebuffer
 }
 
 // State tracking.
@@ -169,15 +173,43 @@ func newOpenGLDevice(api driver.OpenGL) (driver.Device, error) {
 	return b, nil
 }
 
-func (b *Backend) BeginFrame() driver.Framebuffer {
+func (b *Backend) BeginFrame(viewport image.Point) driver.Framebuffer {
 	// Assume GL state is reset between frames.
 	b.state = glstate{}
-	fboID := gl.Framebuffer(b.funcs.GetBinding(gl.FRAMEBUFFER_BINDING))
-	return &gpuFramebuffer{backend: b, obj: fboID, foreign: true}
+	b.defFBO = gl.Framebuffer(b.funcs.GetBinding(gl.FRAMEBUFFER_BINDING))
+	// Determine color encoding of the output framebuffer.
+	var fbEncoding int
+	if !b.defFBO.Valid() {
+		fbEncoding = b.funcs.GetFramebufferAttachmentParameteri(gl.FRAMEBUFFER, gl.BACK, gl.FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING)
+	} else {
+		fbEncoding = b.funcs.GetFramebufferAttachmentParameteri(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING)
+	}
+	renderFBO := b.defFBO
+	if fbEncoding == gl.LINEAR {
+		if b.sRGBFBO == nil {
+			// Framebuffer is not in sRGB format. Emulate it.
+			sfbo, err := srgb.New(b.funcs)
+			if err != nil {
+				panic(err)
+			}
+			b.sRGBFBO = sfbo
+		}
+		if err := b.sRGBFBO.Refresh(viewport); err != nil {
+			panic(err)
+		}
+		renderFBO = b.sRGBFBO.Framebuffer()
+	}
+	b.funcs.BindFramebuffer(gl.FRAMEBUFFER, renderFBO)
+	return &gpuFramebuffer{backend: b, obj: renderFBO, foreign: true}
 }
 
 func (b *Backend) EndFrame() {
 	b.funcs.ActiveTexture(gl.TEXTURE0)
+	if b.sRGBFBO != nil {
+		b.funcs.BindFramebuffer(gl.FRAMEBUFFER, b.defFBO)
+		b.sRGBFBO.Blit()
+	}
+	b.funcs.BindFramebuffer(gl.FRAMEBUFFER, b.defFBO)
 }
 
 func (b *Backend) Caps() driver.Caps {
@@ -313,6 +345,10 @@ func glErr(f *gl.Functions) error {
 }
 
 func (b *Backend) Release() {
+	if b.sRGBFBO != nil {
+		b.sRGBFBO.Release()
+	}
+	*b = Backend{}
 }
 
 func (b *Backend) MemoryBarrier() {
diff --git a/internal/egl/egl.go b/internal/egl/egl.go
index 61ecbfe6..8c0554fd 100644
--- a/internal/egl/egl.go
+++ b/internal/egl/egl.go
@@ -11,7 +11,6 @@ import (
 	"strings"
 
 	"gioui.org/gpu"
-	"gioui.org/internal/srgb"
 )
 
 type Context struct {
@@ -20,8 +19,6 @@ type Context struct {
 	eglSurf       _EGLSurface
 	width, height int
 	refreshFBO    bool
-	// For sRGB emulation.
-	srgbFBO *srgb.FBO
 }
 
 type eglContext struct {
@@ -60,10 +57,6 @@ const (
 )
 
 func (c *Context) Release() {
-	if c.srgbFBO != nil {
-		c.srgbFBO.Release()
-		c.srgbFBO = nil
-	}
 	c.ReleaseSurface()
 	if c.eglCtx != nil {
 		eglDestroyContext(c.disp, c.eglCtx.ctx)
@@ -73,15 +66,9 @@ func (c *Context) Release() {
 }
 
 func (c *Context) Present() error {
-	if c.srgbFBO != nil {
-		c.srgbFBO.Blit()
-	}
 	if !eglSwapBuffers(c.disp, c.eglSurf) {
 		return fmt.Errorf("eglSwapBuffers failed (%x)", eglGetError())
 	}
-	if c.srgbFBO != nil {
-		c.srgbFBO.AfterPresent()
-	}
 	return nil
 }
 
@@ -151,24 +138,6 @@ func (c *Context) MakeCurrent() error {
 	if !eglMakeCurrent(c.disp, c.eglSurf, c.eglSurf, c.eglCtx.ctx) {
 		return fmt.Errorf("eglMakeCurrent error 0x%x", eglGetError())
 	}
-	if c.eglCtx.srgb || c.eglSurf == nilEGLSurface {
-		return nil
-	}
-	if c.srgbFBO == nil {
-		var err error
-		c.srgbFBO, err = srgb.New(nil)
-		if err != nil {
-			c.ReleaseCurrent()
-			return err
-		}
-	}
-	if c.refreshFBO {
-		c.refreshFBO = false
-		if err := c.srgbFBO.Refresh(c.width, c.height); err != nil {
-			c.ReleaseCurrent()
-			return err
-		}
-	}
 	return nil
 }
 
@@ -268,7 +237,7 @@ func createSurface(disp _EGLDisplay, eglCtx *eglContext, win NativeWindowType) (
 	surfAttribs = append(surfAttribs, _EGL_NONE)
 	eglSurf := eglCreateWindowSurface(disp, eglCtx.config, win, surfAttribs)
 	if eglSurf == nilEGLSurface && eglCtx.srgb {
-		// Try again without sRGB
+		// Try again without sRGB.
 		eglCtx.srgb = false
 		surfAttribs = []_EGLint{_EGL_NONE}
 		eglSurf = eglCreateWindowSurface(disp, eglCtx.config, win, surfAttribs)
diff --git a/internal/gl/gl.go b/internal/gl/gl.go
index 9696c716..be9de35f 100644
--- a/internal/gl/gl.go
+++ b/internal/gl/gl.go
@@ -10,6 +10,7 @@ type (
 const (
 	ALL_BARRIER_BITS                      = 0xffffffff
 	ARRAY_BUFFER                          = 0x8892
+	BACK                                  = 0x0405
 	BLEND                                 = 0xbe2
 	CLAMP_TO_EDGE                         = 0x812f
 	COLOR_ATTACHMENT0                     = 0x8ce0
diff --git a/internal/gl/gl_unix.go b/internal/gl/gl_unix.go
index 50fbc684..f7e7a66c 100644
--- a/internal/gl/gl_unix.go
+++ b/internal/gl/gl_unix.go
@@ -436,6 +436,15 @@ func (f *Functions) GetFramebufferAttachmentParameteri(target, attachment, pname
 	return int(f.ints[0])
 }
 
+func (f *Functions) GetInteger4(pname Enum) [4]int {
+	C.glGetIntegerv(C.GLenum(pname), &f.ints[0])
+	var r [4]int
+	for i := range r {
+		r[i] = int(f.ints[i])
+	}
+	return r
+}
+
 func (f *Functions) GetInteger(pname Enum) int {
 	C.glGetIntegerv(C.GLenum(pname), &f.ints[0])
 	return int(f.ints[0])
diff --git a/internal/gl/gl_windows.go b/internal/gl/gl_windows.go
index 099c82b7..68004696 100644
--- a/internal/gl/gl_windows.go
+++ b/internal/gl/gl_windows.go
@@ -292,6 +292,14 @@ func (c *Functions) GetFramebufferAttachmentParameteri(target, attachment, pname
 	p, _, _ := syscall.Syscall(_glGetFramebufferAttachmentParameteri.Addr(), 3, uintptr(target), uintptr(attachment), uintptr(pname))
 	return int(p)
 }
+func (c *Functions) GetInteger4(pname Enum) [4]int {
+	syscall.Syscall(_glGetIntegerv.Addr(), 2, uintptr(pname), uintptr(unsafe.Pointer(&c.int32s[0])), 0)
+	var r [4]int
+	for i := range r {
+		r[i] = int(c.int32s[i])
+	}
+	return r
+}
 func (c *Functions) GetInteger(pname Enum) int {
 	syscall.Syscall(_glGetIntegerv.Addr(), 2, uintptr(pname), uintptr(unsafe.Pointer(&c.int32s[0])), 0)
 	return int(c.int32s[0])
diff --git a/internal/gl/types.go b/internal/gl/types.go
index 45db3bed..bbd28951 100644
--- a/internal/gl/types.go
+++ b/internal/gl/types.go
@@ -14,6 +14,10 @@ type (
 	Object       struct{ V uint }
 )
 
+func (u Framebuffer) Valid() bool {
+	return u.V != 0
+}
+
 func (u Uniform) Valid() bool {
 	return u.V != -1
 }
diff --git a/internal/gl/types_js.go b/internal/gl/types_js.go
index 584c2af1..a1d27f2e 100644
--- a/internal/gl/types_js.go
+++ b/internal/gl/types_js.go
@@ -16,6 +16,10 @@ type (
 	Object       js.Value
 )
 
+func (f Framebuffer) Valid() bool {
+	return !js.Value(f).IsUndefined() && !js.Value(f).IsNull()
+}
+
 func (p Program) Valid() bool {
 	return !js.Value(p).IsUndefined() && !js.Value(p).IsNull()
 }
diff --git a/internal/srgb/srgb.go b/internal/srgb/srgb.go
index 2109ef7e..d72e4859 100644
--- a/internal/srgb/srgb.go
+++ b/internal/srgb/srgb.go
@@ -3,7 +3,9 @@
 package srgb
 
 import (
+	"errors"
 	"fmt"
+	"image"
 	"runtime"
 	"strings"
 
@@ -15,22 +17,18 @@ import (
 // for gamma-correct rendering on platforms without
 // sRGB enabled native framebuffers.
 type FBO struct {
-	c             *gl.Functions
-	width, height int
-	frameBuffer   gl.Framebuffer
-	depthBuffer   gl.Renderbuffer
-	colorTex      gl.Texture
-	blitted       bool
-	quad          gl.Buffer
-	prog          gl.Program
-	gl3           bool
+	c           *gl.Functions
+	viewport    image.Point
+	srgbBuffer  gl.Framebuffer
+	depthBuffer gl.Renderbuffer
+	colorTex    gl.Texture
+	blitted     bool
+	quad        gl.Buffer
+	prog        gl.Program
+	gl3         bool
 }
 
-func New(ctx gl.Context) (*FBO, error) {
-	f, err := gl.NewFunctions(ctx)
-	if err != nil {
-		return nil, err
-	}
+func New(f *gl.Functions) (*FBO, error) {
 	var gl3 bool
 	glVer := f.GetString(gl.VERSION)
 	ver, _, err := gl.ParseGLVersion(glVer)
@@ -48,7 +46,7 @@ func New(ctx gl.Context) (*FBO, error) {
 	s := &FBO{
 		c:           f,
 		gl3:         gl3,
-		frameBuffer: f.CreateFramebuffer(),
+		srgbBuffer:  f.CreateFramebuffer(),
 		colorTex:    f.CreateTexture(),
 		depthBuffer: f.CreateRenderbuffer(),
 	}
@@ -81,7 +79,6 @@ func (s *FBO) Blit() {
 		s.c.BufferSubData(gl.ARRAY_BUFFER, 0, coords)
 		s.blitted = true
 	}
-	s.c.BindFramebuffer(gl.FRAMEBUFFER, gl.Framebuffer{})
 	s.c.UseProgram(s.prog)
 	s.c.BindTexture(gl.TEXTURE_2D, s.colorTex)
 	s.c.BindBuffer(gl.ARRAY_BUFFER, s.quad)
@@ -93,38 +90,38 @@ func (s *FBO) Blit() {
 	s.c.BindTexture(gl.TEXTURE_2D, gl.Texture{})
 	s.c.DisableVertexAttribArray(0)
 	s.c.DisableVertexAttribArray(1)
-	s.c.BindFramebuffer(gl.FRAMEBUFFER, s.frameBuffer)
+	s.c.BindFramebuffer(gl.FRAMEBUFFER, s.srgbBuffer)
 	s.c.InvalidateFramebuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0)
 	s.c.InvalidateFramebuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT)
-	// The Android emulator requires framebuffer 0 bound at eglSwapBuffer time.
-	// Bind the sRGB framebuffer again in afterPresent.
-	s.c.BindFramebuffer(gl.FRAMEBUFFER, gl.Framebuffer{})
 }
 
-func (s *FBO) AfterPresent() {
-	s.c.BindFramebuffer(gl.FRAMEBUFFER, s.frameBuffer)
+func (s *FBO) Framebuffer() gl.Framebuffer {
+	return s.srgbBuffer
 }
 
-func (s *FBO) Refresh(w, h int) error {
-	s.width, s.height = w, h
-	if w == 0 || h == 0 {
+func (s *FBO) Refresh(viewport image.Point) error {
+	if viewport.X == 0 || viewport.Y == 0 {
+		return errors.New("srgb: zero-sized framebuffer")
+	}
+	if s.viewport == viewport {
 		return nil
 	}
+	s.viewport = viewport
 	s.c.BindTexture(gl.TEXTURE_2D, s.colorTex)
 	if s.gl3 {
-		s.c.TexImage2D(gl.TEXTURE_2D, 0, gl.SRGB8_ALPHA8, w, h, gl.RGBA, gl.UNSIGNED_BYTE)
+		s.c.TexImage2D(gl.TEXTURE_2D, 0, gl.SRGB8_ALPHA8, viewport.X, viewport.Y, gl.RGBA, gl.UNSIGNED_BYTE)
 	} else /* EXT_sRGB */ {
-		s.c.TexImage2D(gl.TEXTURE_2D, 0, gl.SRGB_ALPHA_EXT, w, h, gl.SRGB_ALPHA_EXT, gl.UNSIGNED_BYTE)
+		s.c.TexImage2D(gl.TEXTURE_2D, 0, gl.SRGB_ALPHA_EXT, viewport.X, viewport.Y, gl.SRGB_ALPHA_EXT, gl.UNSIGNED_BYTE)
 	}
 	currentRB := gl.Renderbuffer(s.c.GetBinding(gl.RENDERBUFFER_BINDING))
 	s.c.BindRenderbuffer(gl.RENDERBUFFER, s.depthBuffer)
-	s.c.RenderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, w, h)
+	s.c.RenderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, viewport.X, viewport.Y)
 	s.c.BindRenderbuffer(gl.RENDERBUFFER, currentRB)
-	s.c.BindFramebuffer(gl.FRAMEBUFFER, s.frameBuffer)
+	s.c.BindFramebuffer(gl.FRAMEBUFFER, s.srgbBuffer)
 	s.c.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, s.colorTex, 0)
 	s.c.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, s.depthBuffer)
 	if st := s.c.CheckFramebufferStatus(gl.FRAMEBUFFER); st != gl.FRAMEBUFFER_COMPLETE {
-		return fmt.Errorf("sRGB framebuffer incomplete (%dx%d), status: %#x error: %x", s.width, s.height, st, s.c.GetError())
+		return fmt.Errorf("sRGB framebuffer incomplete (%dx%d), status: %#x error: %x", viewport.X, viewport.Y, st, s.c.GetError())
 	}
 
 	if runtime.GOOS == "js" {
@@ -136,9 +133,9 @@ func (s *FBO) Refresh(w, h int) error {
 		var pixel [4]byte
 		s.c.ReadPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixel[:])
 		if pixel[0] == 128 { // Correct sRGB color value is ~188
-			s.c.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, w, h, gl.RGBA, gl.UNSIGNED_BYTE)
+			s.c.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, viewport.X, viewport.Y, gl.RGBA, gl.UNSIGNED_BYTE)
 			if st := s.c.CheckFramebufferStatus(gl.FRAMEBUFFER); st != gl.FRAMEBUFFER_COMPLETE {
-				return fmt.Errorf("fallback RGBA framebuffer incomplete (%dx%d), status: %#x error: %x", s.width, s.height, st, s.c.GetError())
+				return fmt.Errorf("fallback RGBA framebuffer incomplete (%dx%d), status: %#x error: %x", viewport.X, viewport.Y, st, s.c.GetError())
 			}
 		}
 	}
@@ -147,7 +144,7 @@ func (s *FBO) Refresh(w, h int) error {
 }
 
 func (s *FBO) Release() {
-	s.c.DeleteFramebuffer(s.frameBuffer)
+	s.c.DeleteFramebuffer(s.srgbBuffer)
 	s.c.DeleteTexture(s.colorTex)
 	s.c.DeleteRenderbuffer(s.depthBuffer)
 	if s.blitted {