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_wayland.go

@@ -19,7 +19,6 @@ import (
 	"unicode/utf8"
 	"unsafe"
 
-	"gioui.org/ui"
 	"gioui.org/ui/f32"
 	"gioui.org/ui/key"
 	"gioui.org/ui/pointer"
@@ -237,8 +236,8 @@ func createNativeWindow(opts *WindowOptions) (*window, error) {
 	C.free(unsafe.Pointer(title))
 
 	_, _, cfg := w.config()
-	w.width = cfg.Pixels(opts.Width)
-	w.height = cfg.Pixels(opts.Height)
+	w.width = cfg.Px(opts.Width)
+	w.height = cfg.Px(opts.Height)
 	if conn.decor != nil {
 		// Request server side decorations.
 		w.decor = C.zxdg_decoration_manager_v1_get_toplevel_decoration(conn.decor, w.topLvl)
@@ -1020,11 +1019,11 @@ func (w *window) updateOutputs() {
 	}
 }
 
-func (w *window) config() (int, int, ui.Config) {
+func (w *window) config() (int, int, Config) {
 	width, height := w.width*w.scale, w.height*w.scale
-	return width, height, ui.Config{
-		PxPerDp: w.ppdp * float32(w.scale),
-		PxPerSp: w.ppsp * float32(w.scale),
+	return width, height, Config{
+		pxPerDp: w.ppdp * float32(w.scale),
+		pxPerSp: w.ppsp * float32(w.scale),
 	}
 }
 
@@ -1036,7 +1035,7 @@ func (w *window) draw(sync bool) {
 		return
 	}
 	width, height, cfg := w.config()
-	if cfg == (ui.Config{}) {
+	if cfg == (Config{}) {
 		return
 	}
 	if animating && w.lastFrameCallback == nil {
@@ -1044,7 +1043,7 @@ func (w *window) draw(sync bool) {
 		// Use the surface as listener data for gio_onFrameDone.
 		C.gio_wl_callback_add_listener(w.lastFrameCallback, unsafe.Pointer(w.surf))
 	}
-	cfg.Now = time.Now()
+	cfg.now = time.Now()
 	w.w.event(DrawEvent{
 		Size: image.Point{
 			X: width,