Fix: Prevent drawing elements from previous page

Signed-off-by: Knut Ahlers <knut@ahlers.me>

cmd/streamdeck/display_color.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"image/color"
 
 	"github.com/pkg/errors"
@@ -12,7 +13,7 @@ func init() {
 
 type displayElementColor struct{}
 
-func (d displayElementColor) Display(idx int, attributes map[string]interface{}) error {
+func (d displayElementColor) Display(ctx context.Context, idx int, attributes map[string]interface{}) error {
 	if name, ok := attributes["color"].(string); ok {
 		return d.displayPredefinedColor(idx, name)
 	}
@@ -22,6 +23,11 @@ func (d displayElementColor) Display(idx int, attributes map[string]interface{})
 			return errors.New("RGBA color definition needs 4 hex values")
 		}
 
+		if err := ctx.Err(); err != nil {
+			// Page context was cancelled, do not draw
+			return err
+		}
+
 		return sd.FillColor(idx, color.RGBA{uint8(rgba[0].(int)), uint8(rgba[1].(int)), uint8(rgba[2].(int)), uint8(rgba[3].(int))})
 	}
 

cmd/streamdeck/display_exec.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"image"
 	"image/color"
@@ -30,7 +31,7 @@ type displayElementExec struct {
 	running bool
 }
 
-func (d displayElementExec) Display(idx int, attributes map[string]interface{}) error {
+func (d displayElementExec) Display(ctx context.Context, idx int, attributes map[string]interface{}) error {
 	var (
 		err error
 		img draw.Image = image.NewRGBA(image.Rect(0, 0, sd.IconSize(), sd.IconSize()))
@@ -141,6 +142,11 @@ func (d displayElementExec) Display(idx int, attributes map[string]interface{})
 		return nil
 	}
 
+	if err := ctx.Err(); err != nil {
+		// Page context was cancelled, do not draw
+		return err
+	}
+
 	return errors.Wrap(sd.FillImage(idx, img), "Unable to set image")
 }
 
@@ -152,7 +158,7 @@ func (d displayElementExec) NeedsLoop(attributes map[string]interface{}) bool {
 	return false
 }
 
-func (d *displayElementExec) StartLoopDisplay(idx int, attributes map[string]interface{}) error {
+func (d *displayElementExec) StartLoopDisplay(ctx context.Context, idx int, attributes map[string]interface{}) error {
 	d.running = true
 
 	var interval = 5 * time.Second
@@ -166,7 +172,7 @@ func (d *displayElementExec) StartLoopDisplay(idx int, attributes map[string]int
 				return
 			}
 
-			if err := d.Display(idx, attributes); err != nil {
+			if err := d.Display(ctx, idx, attributes); err != nil {
 				log.WithError(err).Error("Unable to refresh element")
 			}
 		}

cmd/streamdeck/display_image.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"image"
 	_ "image/jpeg"
 	_ "image/png"
@@ -15,7 +16,7 @@ func init() {
 
 type displayElementImage struct{}
 
-func (d displayElementImage) Display(idx int, attributes map[string]interface{}) error {
+func (d displayElementImage) Display(ctx context.Context, idx int, attributes map[string]interface{}) error {
 	filename, ok := attributes["path"].(string)
 	if !ok {
 		return errors.New("No path attribute specified")
@@ -34,5 +35,10 @@ func (d displayElementImage) Display(idx int, attributes map[string]interface{})
 
 	img = autoSizeImage(img, sd.IconSize())
 
+	if err := ctx.Err(); err != nil {
+		// Page context was cancelled, do not draw
+		return err
+	}
+
 	return errors.Wrap(sd.FillImage(idx, img), "Unable to set image")
 }

cmd/streamdeck/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"os/signal"
@@ -30,6 +31,8 @@ var (
 
 	userConfig          config
 	activePage          page
+	activePageCtx       context.Context
+	activePageCtxCancel context.CancelFunc
 	activePageName      string
 	activeLoops         []refreshingDisplayElement
 
@@ -208,6 +211,11 @@ func main() {
 }
 
 func togglePage(page string) error {
+	if activePageCtxCancel != nil {
+		// Ensure old display events are no longer executed
+		activePageCtxCancel()
+	}
+
 	// Reset potentially running looped elements
 	for _, l := range activeLoops {
 		if err := l.StopLoopDisplay(); err != nil {
@@ -218,11 +226,12 @@ func togglePage(page string) error {
 
 	activePage = userConfig.Pages[page]
 	activePageName = page
+	activePageCtx, activePageCtxCancel = context.WithCancel(context.Background())
 	sd.ClearAllKeys()
 
 	for idx, kd := range activePage.Keys {
 		if kd.Display.Type != "" {
-			if err := callDisplayElement(idx, kd); err != nil {
+			if err := callDisplayElement(activePageCtx, idx, kd); err != nil {
 				return errors.Wrapf(err, "Unable to execute display element on key %d", idx)
 			}
 		}

cmd/streamdeck/registry.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"reflect"
 	"sync"
 
@@ -13,12 +14,12 @@ type action interface {
 }
 
 type displayElement interface {
-	Display(idx int, attributes map[string]interface{}) error
+	Display(ctx context.Context, idx int, attributes map[string]interface{}) error
 }
 
 type refreshingDisplayElement interface {
 	NeedsLoop(attributes map[string]interface{}) bool
-	StartLoopDisplay(idx int, attributes map[string]interface{}) error
+	StartLoopDisplay(ctx context.Context, idx int, attributes map[string]interface{}) error
 	StopLoopDisplay() error
 }
 
@@ -54,7 +55,7 @@ func callAction(a dynamicElement) error {
 	return inst.Execute(a.Attributes)
 }
 
-func callDisplayElement(idx int, kd keyDefinition) error {
+func callDisplayElement(ctx context.Context, idx int, kd keyDefinition) error {
 	t, ok := registeredDisplayElements[kd.Display.Type]
 	if !ok {
 		return errors.Errorf("Unknown display type %q", kd.Display.Type)
@@ -74,8 +75,8 @@ func callDisplayElement(idx int, kd keyDefinition) error {
 			"display_type": kd.Display.Type,
 		}).Debug("Starting loop")
 		activeLoops = append(activeLoops, inst.(refreshingDisplayElement))
-		return inst.(refreshingDisplayElement).StartLoopDisplay(idx, kd.Display.Attributes)
+		return inst.(refreshingDisplayElement).StartLoopDisplay(ctx, idx, kd.Display.Attributes)
 	}
 
-	return inst.(displayElement).Display(idx, kd.Display.Attributes)
+	return inst.(displayElement).Display(ctx, idx, kd.Display.Attributes)
 }