Update comments

doc.go

@@ -50,8 +50,9 @@
 //     }
 //
 // In the API document, 'the main thread' means the goroutine in init(), main() and their callees without 'go'
-// statement. It is assured that 'the main thread' runs on the OS main thread. There are some Ebiten functions that
-// must be called on the main thread under some conditions (typically, before ebiten.RunGame is called).
+// statement. It is assured that 'the main thread' runs on the OS main thread. There are some Ebiten functions (e.g.,
+// DeviceScaleFactor) that must be called on the main thread under some conditions (typically, before ebiten.RunGame
+// is called).
 //
 // Environment variables
 //
@@ -72,5 +73,6 @@
 // `ebitengl` forces to use OpenGL in any environments.
 //
 // `ebitensinglethread` disables Ebiten's thread safety to unlock maximum performance. If you use this you will have
-// to manage threads yourself. Functions like IsKeyPressed will no longer be concurrent-safe with this build tag.
+// to manage threads yourself. Functions like IsKeyPressed will no longer be concurrent-safe with this build tag and
+// must be called from the main thread.
 package ebiten

internal/thread/thread.go

@@ -18,7 +18,7 @@ import (
 	"errors"
 )
 
-// Thread defines threading behavior in ebiten.
+// Thread defines threading behavior in Ebiten.
 type Thread interface {
 	Call(func() error) error
 	Loop()

run.go

@@ -297,7 +297,8 @@ func SetRunnableOnUnfocused(runnableOnUnfocused bool) {
 // DeviceScaleFactor might panic on init function on some devices like Android.
 // Then, it is not recommended to call DeviceScaleFactor from init functions.
 //
-// DeviceScaleFactor must be called on the main thread before the main loop, and is concurrent-safe after the main loop.
+// DeviceScaleFactor must be called on the main thread before the main loop, and is concurrent-safe after the main
+// loop.
 func DeviceScaleFactor() float64 {
 	return uiDriver().DeviceScaleFactor()
 }