Added monitor cache and scale cache (#731)

internal/devicescale/impl_unix.go

@@ -19,11 +19,14 @@
 package devicescale
 
 import (
+	"math"
 	"os"
 	"os/exec"
 	"regexp"
 	"strconv"
 	"strings"
+	"sync/atomic"
+	"time"
 )
 
 type desktop int
@@ -37,6 +40,29 @@ const (
 	desktopXfce
 )
 
+var (
+	cachedScale     uint64 // use atomic to read/write as multiple goroutines touch it.
+	cacheUpdateWait = time.Millisecond * 100
+)
+
+func init() {
+	go scaleUpdater()
+}
+
+func impl(x, y int) float64 {
+	return math.Float64frombits(atomic.LoadUint64(&cachedScale))
+}
+
+// run as goroutine. Will keep the desktop scale up to date.
+// This can be removed once the scale change event is implemented in GLFW 3.3
+func scaleUpdater() {
+	for {
+		s := getscale(0, 0)
+		atomic.StoreUint64(&cachedScale, math.Float64bits(s))
+		time.Sleep(cacheUpdateWait)
+	}
+}
+
 func currentDesktop() desktop {
 	tokens := strings.Split(os.Getenv("XDG_CURRENT_DESKTOP"), ":")
 	switch tokens[len(tokens)-1] {
@@ -95,30 +121,24 @@ func cinnamonScale() float64 {
 	return float64(s)
 }
 
-func impl(x, y int) float64 {
-	// TODO: Can Linux has different scales for multiple monitors?
+func getscale(x, y int) float64 {
+	s := -1.0
 	switch currentDesktop() {
 	case desktopGnome:
-		s := gnomeScale()
-		if s <= 0 {
-			return 1
-		}
-		return s
+		// TODO: Support wayland and per-monitor scaling https://wiki.gnome.org/HowDoI/HiDpi
+		s = gnomeScale()
 	case desktopCinnamon:
-		s := cinnamonScale()
-		if s <= 0 {
-			return 1
-		}
-		return s
+		s = cinnamonScale()
 	case desktopUnity:
-		// TODO: Implement
-		return 1
+		// TODO: Implement, supports per-monitor scaling
 	case desktopKDE:
-		// TODO: Implement
-		return 1
+		// TODO: Implement, appears to support per-monitor scaling
 	case desktopXfce:
 		// TODO: Implement
-		return 1
 	}
-	return 1
+	if s <= 0 {
+		s = 1
+	}
+
+	return s
 }

internal/ui/ui_glfw.go

@@ -76,6 +76,10 @@ func init() {
 	if err := initialize(); err != nil {
 		panic(err)
 	}
+	glfw.SetMonitorCallback(func(monitor *glfw.Monitor, event glfw.MonitorEvent) {
+		cacheMonitors()
+	})
+	cacheMonitors()
 }
 
 func initialize() error {
@@ -117,6 +121,44 @@ func initialize() error {
 	return nil
 }
 
+type cachedMonitor struct {
+	m  *glfw.Monitor
+	vm *glfw.VidMode
+	// Pos of monitor in virtual coords
+	x int
+	y int
+}
+
+// monitors is the monitor list cache for desktop glfw compile targets.
+// populated by 'cacheMonitors' which is called on init and every
+// monitor config change event.
+var monitors []*cachedMonitor
+
+func cacheMonitors() {
+	monitors = make([]*cachedMonitor, 0, 3)
+	ms := glfw.GetMonitors()
+	for _, m := range ms {
+		x, y := m.GetPos()
+		monitors = append(monitors, &cachedMonitor{
+			m:  m,
+			vm: m.GetVideoMode(),
+			x:  x,
+			y:  y,
+		})
+	}
+}
+
+// getCachedMonitor returns a monitor for the given window x/y
+// returns false if monitor is not found.
+func getCachedMonitor(wx, wy int) (*cachedMonitor, bool) {
+	for _, m := range monitors {
+		if m.x <= wx && wx < m.x+m.vm.Width && m.y <= wy && wy < m.y+m.vm.Height {
+			return m, true
+		}
+	}
+	return nil, false
+}
+
 func Loop(ch <-chan error) error {
 	currentUI.setRunning(true)
 	if err := mainthread.Loop(ch); err != nil {
@@ -552,6 +594,10 @@ func (u *userInterface) getScale() float64 {
 
 // actualScreenScale must be called from the main thread.
 func (u *userInterface) actualScreenScale() float64 {
+	// Avoid calling monitor.GetPos if we have the monitor position cached already.
+	if cm, ok := getCachedMonitor(u.window.GetPos()); ok {
+		return u.getScale() * devicescale.GetAt(cm.x, cm.y)
+	}
 	return u.getScale() * devicescale.GetAt(u.currentMonitor().GetPos())
 }
 

internal/ui/ui_unix.go

@@ -26,7 +26,11 @@ import (
 
 func glfwScale() float64 {
 	// This function must be called on the main thread.
-	return devicescale.GetAt(currentUI.currentMonitor().GetPos())
+	cm, ok := getCachedMonitor(currentUI.window.GetPos())
+	if !ok {
+		return devicescale.GetAt(currentUI.currentMonitor().GetPos())
+	}
+	return devicescale.GetAt(cm.x, cm.y)
 }
 
 func adjustWindowPosition(x, y int) (int, int) {
@@ -35,14 +39,8 @@ func adjustWindowPosition(x, y int) (int, int) {
 
 func (u *userInterface) currentMonitorImpl() *glfw.Monitor {
 	// TODO: Return more appropriate display.
-	w := u.window
-	wx, wy := w.GetPos()
-	for _, m := range glfw.GetMonitors() {
-		mx, my := m.GetPos()
-		v := m.GetVideoMode()
-		if mx <= wx && wx < mx+v.Width && my <= wy && wy < my+v.Height {
-			return m
-		}
+	if cm, ok := getCachedMonitor(u.window.GetPos()); ok {
+		return cm.m
 	}
 	return glfw.GetPrimaryMonitor()
 }