ui,ui/app: convert Config to an interface

To keep the interface slim, remove the helper methods and shorten
the essential method, Pixels, to Px.

Add and use unexported Config implementation in the app package.

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

ui/app/os_macos.go

@@ -19,7 +19,6 @@ import (
 	"time"
 	"unsafe"
 
-	"gioui.org/ui"
 	"gioui.org/ui/f32"
 	"gioui.org/ui/key"
 	"gioui.org/ui/pointer"
@@ -142,7 +141,7 @@ func (w *window) draw(sync bool) {
 		return
 	}
 	cfg := getConfig()
-	cfg.Now = time.Now()
+	cfg.now = time.Now()
 	w.setStage(StageRunning)
 	w.w.event(DrawEvent{
 		Size: image.Point{
@@ -154,15 +153,15 @@ func (w *window) draw(sync bool) {
 	})
 }
 
-func getConfig() ui.Config {
+func getConfig() Config {
 	ppdp := float32(C.gio_getPixelsPerDP())
 	ppdp *= monitorScale
 	if ppdp < minDensity {
 		ppdp = minDensity
 	}
-	return ui.Config{
-		PxPerDp: ppdp,
-		PxPerSp: ppdp,
+	return Config{
+		pxPerDp: ppdp,
+		pxPerSp: ppdp,
 	}
 }
 
@@ -216,8 +215,8 @@ func Main() {
 	}
 	cfg := getConfig()
 	opts := singleWindow.opts
-	w := cfg.Pixels(opts.Width)
-	h := cfg.Pixels(opts.Height)
+	w := cfg.Px(opts.Width)
+	h := cfg.Px(opts.Height)
 	title := C.CString(opts.Title)
 	defer C.free(unsafe.Pointer(title))
 	C.gio_main(view, title, C.CGFloat(w), C.CGFloat(h))