ui/app: (macOS) use a consistent and constant backing store constant

Compute and keep constant the pixel density, to avoid window content
changes when moving to another monitor with a different density.

Use backing store scale, not content scale for input events.

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

ui/app/gl_macos.m

@@ -13,7 +13,7 @@
 
 static void handleMouse(NSView *view, NSEvent *event, int typ, CGFloat dx, CGFloat dy) {
 	NSPoint p = [view convertPoint:[event locationInWindow] fromView:nil];
-	CGFloat scale = view.layer.contentsScale;
+	CGFloat scale = view.window.backingScaleFactor;
 	if (!event.hasPreciseScrollingDeltas) {
 		// dx and dy are in rows and columns.
 		dx *= 10;

ui/app/os_macos.go

@@ -33,6 +33,7 @@ type window struct {
 	view  C.CFTypeRef
 	w     *Window
 	stage Stage
+	ppdp  float32
 }
 
 type viewCmd struct {
@@ -183,11 +184,14 @@ func gio_onFocus(view C.CFTypeRef, focus C.BOOL) {
 }
 
 func (w *window) draw(sync bool) {
-	width, height := int(C.gio_viewWidth(w.view)+.5), int(C.gio_viewHeight(w.view)+.5)
-	if width == 0 || height == 0 {
+	wf, hf := float32(C.gio_viewWidth(w.view)), float32(C.gio_viewHeight(w.view))
+	if wf == 0 || hf == 0 {
 		return
 	}
-	cfg := getConfig()
+	scale := float32(C.gio_getViewBackingScale(w.view))
+	width := int(wf*scale + .5)
+	height := int(hf*scale + .5)
+	cfg := configFor(w.ppdp, scale)
 	cfg.now = time.Now()
 	w.setStage(StageRunning)
 	w.w.event(DrawEvent{
@@ -200,12 +204,17 @@ func (w *window) draw(sync bool) {
 	})
 }
 
-func getConfig() Config {
+func getPixelsPerDp(scale float32) float32 {
 	ppdp := float32(C.gio_getPixelsPerDP())
-	ppdp *= monitorScale
+	ppdp = ppdp * scale * monitorScale
 	if ppdp < minDensity {
 		ppdp = minDensity
 	}
+	return ppdp / scale
+}
+
+func configFor(ppdp, scale float32) Config {
+	ppdp = ppdp * scale
 	return Config{
 		pxPerDp: ppdp,
 		pxPerSp: ppdp,
@@ -240,8 +249,10 @@ func gio_onShow(view C.CFTypeRef) {
 //export gio_onCreate
 func gio_onCreate(view C.CFTypeRef) {
 	viewDo(view, func(views viewMap, view C.CFTypeRef) {
+		scale := float32(C.gio_getBackingScale())
 		w := &window{
 			view: view,
+			ppdp: getPixelsPerDp(scale),
 		}
 		wopts := <-mainWindow.out
 		w.w = wopts.window
@@ -262,10 +273,15 @@ func Main() {
 		// TODO: return this error from CreateWindow.
 		panic(errors.New("CreateWindow: failed to create view"))
 	}
-	cfg := getConfig()
+	scale := float32(C.gio_getBackingScale())
+	ppdp := getPixelsPerDp(scale)
+	cfg := configFor(ppdp, scale)
 	opts := wopts.opts
 	w := cfg.Px(opts.Width)
 	h := cfg.Px(opts.Height)
+	// Window sizes is on screen coordinates, not device pixels.
+	w = int(float32(w) / scale)
+	h = int(float32(h) / scale)
 	title := C.CString(opts.Title)
 	defer C.free(unsafe.Pointer(title))
 	C.gio_main(view, title, C.CGFloat(w), C.CGFloat(h))

ui/app/os_macos.h

@@ -13,5 +13,7 @@ __attribute__ ((visibility ("hidden"))) CGFloat gio_viewHeight(CFTypeRef viewRef
 __attribute__ ((visibility ("hidden"))) void gio_setAnimating(CFTypeRef viewRef, BOOL anim);
 __attribute__ ((visibility ("hidden"))) void gio_updateDisplayLink(CFTypeRef viewRef, CGDirectDisplayID dispID);
 __attribute__ ((visibility ("hidden"))) CGFloat gio_getPixelsPerDP(void);
+__attribute__ ((visibility ("hidden"))) CGFloat gio_getBackingScale(void);
+__attribute__ ((visibility ("hidden"))) CGFloat gio_getViewBackingScale(CFTypeRef viewRef);
 
 #endif

ui/app/os_macos.m

@@ -13,8 +13,8 @@
 
 @implementation GioDelegate
 - (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
-    [[NSRunningApplication currentApplication] activateWithOptions:(NSApplicationActivateAllWindows | NSApplicationActivateIgnoringOtherApps)];
-    [self.window makeKeyAndOrderFront:self];
+	[[NSRunningApplication currentApplication] activateWithOptions:(NSApplicationActivateAllWindows | NSApplicationActivateIgnoringOtherApps)];
+	[self.window makeKeyAndOrderFront:self];
 	gio_onShow((__bridge CFTypeRef)self.window.contentView);
 }
 - (void)applicationDidHide:(NSNotification *)aNotification {
@@ -31,7 +31,8 @@
 }
 - (void)windowDidChangeScreen:(NSNotification *)notification {
 	CGDirectDisplayID dispID = [[[self.window screen] deviceDescription][@"NSScreenNumber"] unsignedIntValue];
-	gio_updateDisplayLink((__bridge CFTypeRef)self.window.contentView, dispID);
+	CFTypeRef view = (__bridge CFTypeRef)self.window.contentView;
+	gio_updateDisplayLink(view, dispID);
 }
 - (void)windowDidBecomeKey:(NSNotification *)notification {
 	gio_onFocus((__bridge CFTypeRef)self.window.contentView, YES);
@@ -48,14 +49,12 @@
 
 CGFloat gio_viewHeight(CFTypeRef viewRef) {
 	NSView *view = (__bridge NSView *)viewRef;
-    NSRect bounds = [view convertRectToBacking:[view bounds]];
-	return bounds.size.height;
+	return [view bounds].size.height;
 }
 
 CGFloat gio_viewWidth(CFTypeRef viewRef) {
 	NSView *view = (__bridge NSView *)viewRef;
-    NSRect bounds = [view convertRectToBacking:[view bounds]];
-	return bounds.size.width;
+	return [view bounds].size.width;
 }
 
 // Points pr. dp.
@@ -68,8 +67,18 @@ static CGFloat getPointsPerDP(NSScreen *screen) {
 
 // Pixels pr dp.
 CGFloat gio_getPixelsPerDP(void) {
-    NSScreen *screen = [NSScreen mainScreen];
-    return [screen backingScaleFactor] * getPointsPerDP(screen);
+	NSScreen *screen = [NSScreen mainScreen];
+	return getPointsPerDP(screen);
+}
+
+CGFloat gio_getBackingScale() {
+	NSScreen *screen = [NSScreen mainScreen];
+	return [screen backingScaleFactor];
+}
+
+CGFloat gio_getViewBackingScale(CFTypeRef viewRef) {
+	NSView *view = (__bridge NSView *)viewRef;
+	return [view.window backingScaleFactor];
 }
 
 void gio_main(CFTypeRef viewRef, const char *title, CGFloat width, CGFloat height) {
@@ -94,11 +103,6 @@ void gio_main(CFTypeRef viewRef, const char *title, CGFloat width, CGFloat heigh
 		[menuBar addItem:mainMenu];
 		[NSApp setMainMenu:menuBar];
 
-		// Width and height are in pixels; convert to points
-		CGFloat scale = [[NSScreen mainScreen] backingScaleFactor];
-		width /= scale;
-		height /= scale;
-
 		NSRect rect = NSMakeRect(0, 0, width, height);
 		NSWindowStyleMask styleMask = NSWindowStyleMaskTitled |
 			NSWindowStyleMaskResizable |