Added callbacks & events when visibility of an overlay changes.

Added proxy that proxies overlay callbacks as well (on top of control callbacks).

ui/overlay.go

@@ -0,0 +1,6 @@
+package ui
+
+type Overlay interface {
+	OverlayShown()
+	OverlayHidden()
+}

ui/overlayproxy.go

@@ -0,0 +1,19 @@
+package ui
+
+type OverlayProxy struct {
+	Proxy
+}
+
+func (p *OverlayProxy) OverlayShown() {
+	overlay, ok := p.Content.(Overlay)
+	if ok {
+		overlay.OverlayShown()
+	}
+}
+
+func (p *OverlayProxy) OverlayHidden() {
+	overlay, ok := p.Content.(Overlay)
+	if ok {
+		overlay.OverlayHidden()
+	}
+}

ui/overlays.go

@@ -1,15 +1,27 @@
 package ui
 
-import "opslag.de/schobers/geom"
+import (
+	"opslag.de/schobers/geom"
+	"opslag.de/schobers/zntg"
+)
 
 var _ Control = &Overlays{}
 
+type OverlayVisibilityChangedArgs struct {
+	Name    string
+	Visible bool
+}
+
 type Overlays struct {
 	Proxy
 
 	overlays map[string]Control
 	order    []string
 	visible  map[string]bool
+
+	overlayHidden     zntg.Events
+	overlayShown      zntg.Events
+	visibilityChanged zntg.Events
 }
 
 func NewOverlays(over Control) *Overlays {
@@ -21,6 +33,27 @@ func NewOverlays(over Control) *Overlays {
 	}
 }
 
+func (o *Overlays) setVisibility(name string, visible bool) {
+	if o.visible[name] == visible {
+		return
+	}
+	o.visible[name] = visible
+	overlay, ok := o.overlays[name].(Overlay)
+	if ok {
+		if visible {
+			overlay.OverlayShown()
+		} else {
+			overlay.OverlayHidden()
+		}
+	}
+	o.visibilityChanged.Notify(OverlayVisibilityChangedArgs{Name: name, Visible: visible})
+	if visible {
+		o.overlayShown.Notify(name)
+	} else {
+		o.overlayHidden.Notify(name)
+	}
+}
+
 func (o *Overlays) AddOnTop(name string, control Control, visible bool) {
 	o.order = append(o.order, name)
 	o.overlays[name] = control