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/app.go

@@ -12,7 +12,7 @@ import (
 // ViewEvent carries the platform specific window handles for
 // a Window.
 //
-// ViewEvent is implemented on Android and macOS.
+// ViewEvent is implemented for Android, macOS, Windows.
 type ViewEvent = wm.ViewEvent
 
 // extraArgs contains extra arguments to append to

app/internal/wm/d3d11_windows.go

@@ -71,6 +71,10 @@ func (c *d3d11Context) Present() error {
 	return err
 }
 
+func (c *d3d11Context) Refresh() error {
+	return nil
+}
+
 func (c *d3d11Context) MakeCurrent() error {
 	var width, height int
 	c.win.w.Run(func() {

app/internal/wm/egl_android.go

@@ -34,6 +34,10 @@ func (c *context) Release() {
 	}
 }
 
+func (c *context) Refresh() error {
+	return nil
+}
+
 func (c *context) MakeCurrent() error {
 	c.Context.ReleaseSurface()
 	var (

app/internal/wm/egl_wayland.go

@@ -48,6 +48,10 @@ func (c *context) Release() {
 	}
 }
 
+func (c *context) Refresh() error {
+	return nil
+}
+
 func (c *context) MakeCurrent() error {
 	c.Context.ReleaseSurface()
 	if c.eglWin != nil {

app/internal/wm/egl_windows.go

@@ -34,6 +34,10 @@ func (c *glContext) Release() {
 	}
 }
 
+func (c *glContext) Refresh() error {
+	return nil
+}
+
 func (c *glContext) MakeCurrent() error {
 	c.Context.ReleaseSurface()
 	var (

app/internal/wm/egl_x11.go

@@ -31,6 +31,10 @@ func (c *x11Context) Release() {
 	}
 }
 
+func (c *x11Context) Refresh() error {
+	return nil
+}
+
 func (c *x11Context) MakeCurrent() error {
 	c.Context.ReleaseSurface()
 	win, width, height := c.win.window()

app/internal/wm/gl_ios.go

@@ -100,6 +100,10 @@ func (c *context) Lock() {}
 
 func (c *context) Unlock() {}
 
+func (c *context) Refresh() error {
+	return nil
+}
+
 func (c *context) MakeCurrent() error {
 	if C.gio_makeCurrent(c.ctx) == 0 {
 		return errors.New("[EAGLContext setCurrentContext] failed")

app/internal/wm/gl_js.go

@@ -54,6 +54,10 @@ func (c *context) Lock() {}
 
 func (c *context) Unlock() {}
 
+func (c *context) Refresh() error {
+	return nil
+}
+
 func (c *context) MakeCurrent() error {
 	return nil
 }

app/internal/wm/gl_macos.go

@@ -19,6 +19,7 @@ import (
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createGLContext(void);
 __attribute__ ((visibility ("hidden"))) void gio_setContextView(CFTypeRef ctx, CFTypeRef view);
 __attribute__ ((visibility ("hidden"))) void gio_makeCurrentContext(CFTypeRef ctx);
+__attribute__ ((visibility ("hidden"))) void gio_updateContext(CFTypeRef ctx);
 __attribute__ ((visibility ("hidden"))) void gio_flushContextBuffer(CFTypeRef ctx);
 __attribute__ ((visibility ("hidden"))) void gio_clearCurrentContext(void);
 __attribute__ ((visibility ("hidden"))) void gio_lockContext(CFTypeRef ctxRef);
@@ -74,6 +75,13 @@ func (c *context) Unlock() {
 	C.gio_unlockContext(c.ctx)
 }
 
+func (c *context) Refresh() error {
+	c.Lock()
+	defer c.Unlock()
+	C.gio_updateContext(c.ctx)
+	return nil
+}
+
 func (c *context) MakeCurrent() error {
 	c.Lock()
 	defer c.Unlock()

app/internal/wm/gl_macos.m

@@ -8,20 +8,6 @@
 #include <OpenGL/OpenGL.h>
 #include "_cgo_export.h"
 
-@interface GioGLContext : NSOpenGLContext
-@end
-
-@implementation GioGLContext
-- (void) notifyUpdate:(NSNotification*)notification {
-	CGLLockContext([self CGLContextObj]);
-	[self update];
-	CGLUnlockContext([self CGLContextObj]);
-}
-- (void)dealloc {
-	[[NSNotificationCenter defaultCenter] removeObserver:self];
-}
-@end
-
 CFTypeRef gio_createGLContext(void) {
 	@autoreleasepool {
 		NSOpenGLPixelFormatAttribute attr[] = {
@@ -36,20 +22,16 @@ CFTypeRef gio_createGLContext(void) {
 		};
 		NSOpenGLPixelFormat *pixFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attr];
 
-		GioGLContext *ctx = [[GioGLContext alloc] initWithFormat:pixFormat shareContext: nil];
+		NSOpenGLContext *ctx = [[NSOpenGLContext alloc] initWithFormat:pixFormat shareContext: nil];
 		return CFBridgingRetain(ctx);
 	}
 }
 
 void gio_setContextView(CFTypeRef ctxRef, CFTypeRef viewRef) {
-	GioGLContext *ctx = (__bridge GioGLContext *)ctxRef;
+	NSOpenGLContext *ctx = (__bridge NSOpenGLContext *)ctxRef;
 	NSView *view = (__bridge NSView *)viewRef;
 	[view setWantsBestResolutionOpenGLSurface:YES];
 	[ctx setView:view];
-	[[NSNotificationCenter defaultCenter] addObserver:ctx
-											 selector:@selector(notifyUpdate:)
-												 name:NSViewGlobalFrameDidChangeNotification
-											   object:view];
 }
 
 void gio_clearCurrentContext(void) {
@@ -58,6 +40,13 @@ void gio_clearCurrentContext(void) {
 	}
 }
 
+void gio_updateContext(CFTypeRef ctxRef) {
+	@autoreleasepool {
+		NSOpenGLContext *ctx = (__bridge NSOpenGLContext *)ctxRef;
+		[ctx update];
+	}
+}
+
 void gio_makeCurrentContext(CFTypeRef ctxRef) {
 	@autoreleasepool {
 		NSOpenGLContext *ctx = (__bridge NSOpenGLContext *)ctxRef;

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()

app/loop.go

@@ -17,6 +17,7 @@ type renderLoop struct {
 	drawing bool
 	err     error
 
+	ctx        wm.Context
 	frames     chan frame
 	results    chan frameResult
 	refresh    chan struct{}
@@ -38,6 +39,7 @@ type frameResult struct {
 
 func newLoop(ctx wm.Context) (*renderLoop, error) {
 	l := &renderLoop{
+		ctx:        ctx,
 		frames:     make(chan frame),
 		results:    make(chan frameResult),
 		refresh:    make(chan struct{}),
@@ -132,6 +134,7 @@ func (l *renderLoop) Summary() string {
 }
 
 func (l *renderLoop) Refresh() {
+	l.ctx.Refresh()
 	if l.err != nil {
 		return
 	}

app/window.go

@@ -414,6 +414,12 @@ func (w *Window) destroy(err error) {
 	}
 }
 
+func (w *Window) refresh() {
+	w.driverRun(func(_ wm.Driver) {
+		w.loop.Refresh()
+	})
+}
+
 func (w *Window) destroyGPU() {
 	if w.loop != nil {
 		w.loop.Release()
@@ -473,7 +479,7 @@ func (w *Window) run(opts *wm.Options) {
 					if e2.Stage < system.StageRunning {
 						w.destroyGPU()
 					} else {
-						w.loop.Refresh()
+						w.refresh()
 					}
 				}
 				w.stage = e2.Stage
@@ -495,7 +501,7 @@ func (w *Window) run(opts *wm.Options) {
 				w.out <- e2.FrameEvent
 				if w.loop != nil {
 					if e2.Sync {
-						w.loop.Refresh()
+						w.refresh()
 					}
 				}
 				frame, gotFrame := w.waitFrame()