diff --git a/app/loop.go b/app/loop.go
index 6007df05..1d388b62 100644
--- a/app/loop.go
+++ b/app/loop.go
@@ -97,10 +97,9 @@ func (l *renderLoop) renderLoop(ctx wm.Context) error {
 				} else {
 					g.Clear(color.NRGBA{A: 0xff, R: 0xff, G: 0xff, B: 0xff})
 				}
-				g.Collect(frame.viewport, frame.ops)
+				res.err = g.Frame(frame.ops, ctx.RenderTarget(), frame.viewport)
 				// Signal that we're done with the frame ops.
 				l.ack <- struct{}{}
-				res.err = g.Frame(ctx.RenderTarget())
 				if res.err == nil {
 					res.err = ctx.Present()
 				}
diff --git a/gpu/compute.go b/gpu/compute.go
index 8fe104ef..d630818f 100644
--- a/gpu/compute.go
+++ b/gpu/compute.go
@@ -559,7 +559,12 @@ func newShaders(ctx driver.Device, vsrc, fsrc shader.Sources) (vert driver.Verte
 	return
 }
 
-func (g *compute) Collect(viewport image.Point, ops *op.Ops) {
+func (g *compute) Frame(frameOps *op.Ops, target RenderTarget, viewport image.Point) error {
+	g.collect(viewport, frameOps)
+	return g.frame(target)
+}
+
+func (g *compute) collect(viewport image.Point, ops *op.Ops) {
 	g.viewport = viewport
 	g.collector.reset()
 	for i := range g.output.layerAtlases {
@@ -575,7 +580,7 @@ func (g *compute) Clear(col color.NRGBA) {
 	g.collector.clearColor = f32color.LinearFromSRGB(col)
 }
 
-func (g *compute) Frame(target RenderTarget) error {
+func (g *compute) frame(target RenderTarget) error {
 	viewport := g.viewport
 	defFBO := g.ctx.BeginFrame(target, g.collector.clear, viewport)
 	defer g.ctx.EndFrame()
diff --git a/gpu/gpu.go b/gpu/gpu.go
index 826aebd9..f3bc42fb 100644
--- a/gpu/gpu.go
+++ b/gpu/gpu.go
@@ -43,12 +43,10 @@ type GPU interface {
 	Release()
 	// Clear sets the clear color for the next Frame.
 	Clear(color color.NRGBA)
-	// Collect the graphics operations from frame, given the viewport.
-	Collect(viewport image.Point, frame *op.Ops)
-	// Frame draws the collected operations to target.
-	Frame(target RenderTarget) error
+	// Frame draws the graphics operations from op into a viewport of target.
+	Frame(frame *op.Ops, target RenderTarget, viewport image.Point) error
 	// Profile returns the last available profiling information. Profiling
-	// information is requested when Collect sees an io/profile.Op, and the result
+	// information is requested when Frame sees an io/profile.Op, and the result
 	// is available through Profile at some later time.
 	Profile() string
 }
@@ -399,7 +397,12 @@ func (g *gpu) Release() {
 	g.ctx.Release()
 }
 
-func (g *gpu) Collect(viewport image.Point, frameOps *op.Ops) {
+func (g *gpu) Frame(frameOps *op.Ops, target RenderTarget, viewport image.Point) error {
+	g.collect(viewport, frameOps)
+	return g.frame(target)
+}
+
+func (g *gpu) collect(viewport image.Point, frameOps *op.Ops) {
 	g.renderer.blitter.viewport = viewport
 	g.renderer.pather.viewport = viewport
 	g.drawOps.reset(g.cache, viewport)
@@ -413,7 +416,7 @@ func (g *gpu) Collect(viewport image.Point, frameOps *op.Ops) {
 	}
 }
 
-func (g *gpu) Frame(target RenderTarget) error {
+func (g *gpu) frame(target RenderTarget) error {
 	viewport := g.renderer.blitter.viewport
 	defFBO := g.ctx.BeginFrame(target, g.drawOps.clear, viewport)
 	defer g.ctx.EndFrame()
diff --git a/gpu/headless/headless.go b/gpu/headless/headless.go
index 14c8df7e..5870bf06 100644
--- a/gpu/headless/headless.go
+++ b/gpu/headless/headless.go
@@ -109,8 +109,7 @@ func (w *Window) Release() {
 func (w *Window) Frame(frame *op.Ops) error {
 	return contextDo(w.ctx, func() error {
 		w.gpu.Clear(color.NRGBA{})
-		w.gpu.Collect(w.size, frame)
-		return w.gpu.Frame(driver.RenderTarget(w.fbo))
+		return w.gpu.Frame(frame, driver.RenderTarget(w.fbo), w.size)
 	})
 }
 
diff --git a/io/system/system.go b/io/system/system.go
index f1279f9a..e1458252 100644
--- a/io/system/system.go
+++ b/io/system/system.go
@@ -26,27 +26,8 @@ type FrameEvent struct {
 	Size image.Point
 	// Insets is the insets to apply.
 	Insets Insets
-	// Frame is the callback to supply the list of
-	// operations to complete the FrameEvent.
-	//
-	// Note that the operation list and the operations themselves
-	// may not be mutated until another FrameEvent is received from
-	// the same event source.
-	// That means that calls to frame.Reset and changes to referenced
-	// data such as ImageOp backing images should happen between
-	// receiving a FrameEvent and calling Frame.
-	//
-	// Example:
-	//
-	//  var w *app.Window
-	//  var frame *op.Ops
-	//  for e := range w.Events() {
-	//      if e, ok := e.(system.FrameEvent); ok {
-	//          // Call frame.Reset and manipulate images for ImageOps
-	//          // here.
-	//          e.Frame(frame)
-	//      }
-	//  }
+	// Frame completes the FrameEvent by drawing the graphical operations
+	// from ops into the window.
 	Frame func(frame *op.Ops)
 	// Queue supplies the events for event handlers.
 	Queue event.Queue
diff --git a/op/paint/paint.go b/op/paint/paint.go
index 7eed07cb..be090cf5 100644
--- a/op/paint/paint.go
+++ b/op/paint/paint.go
@@ -16,9 +16,6 @@ import (
 )
 
 // ImageOp sets the brush to an image.
-//
-// Note: the ImageOp may keep a reference to the backing image.
-// See NewImageOp for details.
 type ImageOp struct {
 	uniform bool
 	color   color.NRGBA
@@ -47,9 +44,7 @@ type LinearGradientOp struct {
 type PaintOp struct {
 }
 
-// NewImageOp creates an ImageOp backed by src. See
-// gioui.org/io/system.FrameEvent for a description of when data
-// referenced by operations is safe to re-use.
+// NewImageOp creates an ImageOp backed by src.
 //
 // NewImageOp assumes the backing image is immutable, and may cache a
 // copy of its contents in a GPU-friendly way. Create new ImageOps to