ui: Get correct device scale for iOS

internal/graphics/opengl/context_mobile.go

@@ -44,8 +44,6 @@ type context struct {
 	gl          mgl.Context
 	worker      mgl.Worker
 	initialized chan struct{}
-	screenFramebufferWidth  int
-	screenFramebufferHeight int
 }
 
 func NewContext() (*Context, error) {
@@ -81,22 +79,11 @@ func NewContext() (*Context, error) {
 		c.BlendFunc(CompositeModeSourceOver)
 		f := c.gl.GetInteger(mgl.FRAMEBUFFER_BINDING)
 		c.screenFramebuffer = Framebuffer(mgl.Framebuffer{uint32(f)})
-		// It is invalid to get the size of the deafult framebuffer.
-		if c.screenFramebuffer.Value != 0 {
-			width := c.gl.GetRenderbufferParameteri(mgl.RENDERBUFFER, mgl.RENDERBUFFER_WIDTH)
-			height := c.gl.GetRenderbufferParameteri(mgl.RENDERBUFFER, mgl.RENDERBUFFER_HEIGHT)
-			c.screenFramebufferWidth = width
-			c.screenFramebufferHeight = height
-		}
 		close(c.initialized)
 	}()
 	return c, nil
 }
 
-func (c *Context) ScreenFramebufferSize() (int, int) {
-	return c.screenFramebufferWidth, c.screenFramebufferHeight
-}
-
 func (c *Context) Resume() error {
 	c.locationCache = newLocationCache()
 	c.lastFramebuffer = invalidFramebuffer

internal/ui/ui_android.go

@@ -0,0 +1,19 @@
+// Copyright 2016 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ui
+
+func deviceScale() int {
+	return 1
+}

internal/ui/ui_ios.go

@@ -0,0 +1,31 @@
+// Copyright 2016 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build ios darwin,arm darwin,arm64
+
+package ui
+
+// #cgo CFLAGS: -x objective-c
+// #cgo LDFLAGS: -framework Foundation -framework UIKit
+//
+// #import <UIKit/UIKit.h>
+//
+// static int devicePixelRatio() {
+//   return [[UIScreen mainScreen] scale];
+// }
+import "C"
+
+func deviceScale() int {
+	return int(C.devicePixelRatio())
+}

internal/ui/ui_mobile.go

@@ -77,7 +77,6 @@ type userInterface struct {
 	width       int
 	height      int
 	scale       int
-	framebufferScale int
 	sizeChanged bool
 }
 
@@ -147,17 +146,7 @@ func (u *userInterface) ScreenScale() int {
 }
 
 func (u *userInterface) actualScreenScale() int {
-	if u.framebufferScale == 0 {
-		width, _ := glContext.ScreenFramebufferSize()
-		if width == 0 {
-			// Android
-			u.framebufferScale = 1
-		} else {
-			// iOS
-			u.framebufferScale = width / u.width
-		}
-	}
-	return u.scale * u.framebufferScale
+	return u.scale * deviceScale()
 }
 
 func UpdateTouches(touches []Touch) {