ui: Calculate DPI and set the actual scale based on DPI

internal/ui/scaling.go

@@ -1,23 +0,0 @@
-// 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 !linux
-
-package ui
-
-func adjustScaleForGLFW(scale int) int {
-	// On Windows and OSX, GLFW already considers High-DPI scaling
-	// and scale doesn't have to be adjusted.
-	return scale
-}

internal/ui/scaling_linux.go

@@ -1,49 +0,0 @@
-// 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
-
-import (
-	"fmt"
-	"os/exec"
-	"regexp"
-	"strconv"
-)
-
-var scalingFactorSyntax = regexp.MustCompile(`\Auint32\s+(\d+)\s*\z`)
-var deviceScaleFactor = 0
-
-// adjustScaleForGLFW adjusts the given scale which is passed to the GLFW API.
-func adjustScaleForGLFW(scale int) int {
-	if 0 < deviceScaleFactor {
-		return scale * deviceScaleFactor
-	}
-	// Execute gsettings command instead of calling gtk functions so as not to depend on
-	// gobject-2.0 library.
-	c := exec.Command("gsettings", "get", "org.gnome.desktop.interface", "scaling-factor")
-	o, err := c.Output()
-	if err != nil {
-		panic(fmt.Sprintf("ui: executing gsettings error %v", err))
-	}
-	m := scalingFactorSyntax.FindStringSubmatch(string(o))
-	if m == nil {
-		panic("ui: gsettings result syntax is not expected")
-	}
-	s, err := strconv.Atoi(m[1])
-	if err != nil {
-		panic(fmt.Sprintf("ui: %v", err))
-	}
-	deviceScaleFactor = s
-	return scale * deviceScaleFactor
-}

internal/ui/ui_glfw.go

@@ -90,12 +90,12 @@ func SwapBuffers() {
 
 func SetScreenSize(width, height int) (bool, int) {
 	result := currentUI.setScreenSize(width, height, currentUI.scale)
-	return result, currentUI.actualScale
+	return result, currentUI.actualScale()
 }
 
 func SetScreenScale(scale int) (bool, int) {
 	result := currentUI.setScreenSize(currentUI.width, currentUI.height, scale)
-	return result, currentUI.actualScale
+	return result, currentUI.actualScale()
 }
 
 type userInterface struct {
@@ -103,21 +103,30 @@ type userInterface struct {
 	width             int
 	height            int
 	scale             int
-	actualScale int
+	deviceScaleFactor float64
 	context           *opengl.Context
 }
 
 func (u *userInterface) start(width, height, scale int, title string) (actualScale int, err error) {
+	m := glfw.GetPrimaryMonitor()
+	mw, _ := m.GetPhysicalSize()
+	v := m.GetVideoMode()
+	dpi := float64(v.Width) * 25.4 / float64(mw)
+	u.deviceScaleFactor = dpi / 96
+
 	u.setScreenSize(width, height, scale)
 	u.window.SetTitle(title)
 	u.window.Show()
 
-	videoMode := glfw.GetPrimaryMonitor().GetVideoMode()
-	x := (videoMode.Width - width*adjustScaleForGLFW(scale)) / 2
-	y := (videoMode.Height - height*adjustScaleForGLFW(scale)) / 3
+	x := (v.Width - width*u.actualScale()) / 2
+	y := (v.Height - height*u.actualScale()) / 3
 	u.window.SetPos(x, y)
 
-	return u.actualScale, nil
+	return u.actualScale(), nil
+}
+
+func (u *userInterface) actualScale() int {
+	return int(float64(u.scale) * u.deviceScaleFactor)
 }
 
 func (u *userInterface) pollEvents() error {
@@ -159,6 +168,7 @@ func (u *userInterface) setScreenSize(width, height, scale int) bool {
 	if u.width == width && u.height == height && u.scale == scale {
 		return false
 	}
+	u.scale = scale
 
 	// To make sure the current existing framebuffers are rendered,
 	// swap buffers here before SetSize is called.
@@ -171,7 +181,7 @@ func (u *userInterface) setScreenSize(width, height, scale int) bool {
 		window.SetFramebufferSizeCallback(nil)
 		close(ch)
 	})
-	window.SetSize(width*adjustScaleForGLFW(scale), height*adjustScaleForGLFW(scale))
+	window.SetSize(width*u.actualScale(), height*u.actualScale())
 
 event:
 	for {
@@ -184,10 +194,5 @@ event:
 	}
 	u.width = width
 	u.height = height
-	u.scale = scale
-
-	// For retina displays, recalculate the scale with the framebuffer size.
-	windowWidth, _ := window.GetFramebufferSize()
-	u.actualScale = windowWidth / width
 	return true
 }