all: clean up code, upgrade to modern Go

Signed-off-by: ddkwork

app/gl_macos.go

@@ -8,7 +8,6 @@ package app
 import (
 	"errors"
 	"runtime"
-
 	"unsafe"
 
 	"gioui.org/gpu"

app/os_darwin.go

@@ -40,6 +40,7 @@ static CFTypeRef newNSString(unichar *chars, NSUInteger length) {
 }
 */
 import "C"
+
 import (
 	"errors"
 	"sync"

app/os_x11.go

@@ -26,6 +26,7 @@ package app
 
 */
 import "C"
+
 import (
 	"errors"
 	"fmt"
@@ -751,9 +752,7 @@ func (h *x11EventHandler) handleEvents() bool {
 	return redraw
 }
 
-var (
-	x11Threads sync.Once
-)
+var x11Threads sync.Once
 
 func init() {
 	x11Driver = newX11Window

app/window.go

@@ -444,10 +444,7 @@ func (c *callbacks) SetComposingRegion(r key.Range) {
 func (c *callbacks) EditorInsert(text string) {
 	sel := c.w.imeState.Selection.Range
 	c.EditorReplace(sel, text)
-	start := sel.Start
-	if sel.End < start {
-		start = sel.End
-	}
+	start := min(sel.End, sel.Start)
 	sel.Start = start + utf8.RuneCountInString(text)
 	sel.End = sel.Start
 	c.SetEditorSelection(sel)