app,app/internal/wm: [macOS] refresh context on display change

The NSViewGlobalFrameDidChangeNotification notification is documented to
be fired every time [NSOpenGLContext update] needs to be called.
However, the notification fails to fire on my setup when a window is
moved to a display with a different pixel scale, which leads to
incorrectly sized output.

This change gets rid of the notification and updates the context before
every frame.

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

app/internal/wm/window.go

@@ -6,9 +6,10 @@ package wm
 
 import (
 	"errors"
-	"gioui.org/io/key"
 	"image/color"
 
+	"gioui.org/io/key"
+
 	"gioui.org/gpu"
 	"gioui.org/io/event"
 	"gioui.org/io/pointer"
@@ -69,6 +70,7 @@ type Context interface {
 	API() gpu.API
 	Present() error
 	MakeCurrent() error
+	Refresh() error
 	Release()
 	Lock()
 	Unlock()