app: add error result to context.RenderTarget

Vulkan may report VK_ERROR_OUT_OF_DATE_KHR which is not a fatal error.

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

app/d3d11_windows.go

@@ -53,10 +53,10 @@ func (c *d3d11Context) API() gpu.API {
 	return gpu.Direct3D11{Device: unsafe.Pointer(c.dev)}
 }
 
-func (c *d3d11Context) RenderTarget() gpu.RenderTarget {
+func (c *d3d11Context) RenderTarget() (gpu.RenderTarget, error) {
 	return gpu.Direct3D11RenderTarget{
 		RenderTarget: unsafe.Pointer(c.renderTarget),
-	}
+	}, nil
 }
 
 func (c *d3d11Context) Present() error {

app/gl_js.go

@@ -36,8 +36,8 @@ func newContext(w *window) (*glContext, error) {
 	return c, nil
 }
 
-func (c *glContext) RenderTarget() gpu.RenderTarget {
-	return gpu.OpenGLRenderTarget{}
+func (c *glContext) RenderTarget() (gpu.RenderTarget, error) {
+	return gpu.OpenGLRenderTarget{}, nil
 }
 
 func (c *glContext) API() gpu.API {

app/gl_macos.go

@@ -72,8 +72,8 @@ func newContext(w *window) (*glContext, error) {
 	return c, nil
 }
 
-func (c *glContext) RenderTarget() gpu.RenderTarget {
-	return gpu.OpenGLRenderTarget{}
+func (c *glContext) RenderTarget() (gpu.RenderTarget, error) {
+	return gpu.OpenGLRenderTarget{}, nil
 }
 
 func (c *glContext) API() gpu.API {

app/metal_darwin.go

@@ -111,21 +111,21 @@ func newMtlContext(w *window) (*mtlContext, error) {
 	return c, nil
 }
 
-func (c *mtlContext) RenderTarget() gpu.RenderTarget {
+func (c *mtlContext) RenderTarget() (gpu.RenderTarget, error) {
 	if c.drawable != 0 || c.texture != 0 {
-		panic("a previous RenderTarget wasn't Presented")
+		return nil, errors.New("metal:a previous RenderTarget wasn't Presented")
 	}
 	c.drawable = C.nextDrawable(c.layer)
 	if c.drawable == 0 {
-		panic("metal: [CAMetalLayer nextDrawable] failed")
+		return nil, errors.New("metal: [CAMetalLayer nextDrawable] failed")
 	}
 	c.texture = C.drawableTexture(c.drawable)
 	if c.texture == 0 {
-		panic("metal: CADrawable.texture is nil")
+		return nil, errors.New("metal: CADrawable.texture is nil")
 	}
 	return gpu.MetalRenderTarget{
 		Texture: unsafe.Pointer(c.texture),
-	}
+	}, nil
 }
 
 func (c *mtlContext) API() gpu.API {

app/os.go

@@ -105,7 +105,7 @@ type frameEvent struct {
 
 type context interface {
 	API() gpu.API
-	RenderTarget() gpu.RenderTarget
+	RenderTarget() (gpu.RenderTarget, error)
 	Present() error
 	Refresh() error
 	Release()

app/window.go

@@ -198,7 +198,11 @@ func (w *Window) render(frame *op.Ops, viewport image.Point) error {
 	} else {
 		w.gpu.Clear(color.NRGBA{A: 0xff, R: 0xff, G: 0xff, B: 0xff})
 	}
-	if err := w.gpu.Frame(frame, w.ctx.RenderTarget(), viewport); err != nil {
+	target, err := w.ctx.RenderTarget()
+	if err != nil {
+		return err
+	}
+	if err := w.gpu.Frame(frame, target, viewport); err != nil {
 		return err
 	}
 	return w.ctx.Present()

internal/egl/egl.go

@@ -97,8 +97,8 @@ func NewContext(disp NativeDisplayType) (*Context, error) {
 	return c, nil
 }
 
-func (c *Context) RenderTarget() gpu.RenderTarget {
-	return gpu.OpenGLRenderTarget{}
+func (c *Context) RenderTarget() (gpu.RenderTarget, error) {
+	return gpu.OpenGLRenderTarget{}, nil
 }
 
 func (c *Context) API() gpu.API {