internal/glfw: do not panic for an error at Monitor.GetContentScale

Updates #2488

internal/devicescale/impl_desktop.go

@@ -37,10 +37,15 @@ func impl(x, y int) float64 {
 	// Keep calling GetContentScale until the returned scale is 0 (#2051).
 	// Retry this at most 5 times to avoid an inifinite loop.
 	for i := 0; i < 5; i++ {
-		sx, _ := monitorAt(x, y).GetContentScale()
+		// An error can happen e.g. when entering a screensaver on Windows (#2488).
-		if sx != 0 {
+		sx, _, err := monitorAt(x, y).GetContentScale()
-			return float64(sx)
+		if err != nil {
+			continue
 		}
+		if sx == 0 {
+			continue
+		}
+		return float64(sx)
 	}
 	return 1
 }

internal/glfw/glfw_notwindows.go

@@ -70,8 +70,9 @@ type Monitor struct {
 	m *glfw.Monitor
 }
 
-func (m *Monitor) GetContentScale() (float32, float32) {
+func (m *Monitor) GetContentScale() (float32, float32, error) {
-	return m.m.GetContentScale()
+	x, y := m.m.GetContentScale()
+	return x, y, nil
 }
 
 func (m *Monitor) GetPos() (x, y int) {

internal/glfw/glfw_windows.go

@@ -34,12 +34,8 @@ func CreateStandardCursor(shape StandardCursor) *Cursor {
 
 type Monitor glfwwin.Monitor
 
-func (m *Monitor) GetContentScale() (float32, float32) {
+func (m *Monitor) GetContentScale() (float32, float32, error) {
-	sx, sy, err := (*glfwwin.Monitor)(m).GetContentScale()
+	return (*glfwwin.Monitor)(m).GetContentScale()
-	if err != nil {
-		panic(err)
-	}
-	return sx, sy
 }
 
 func (m *Monitor) GetPos() (int, int) {