Reduced the number of unnecessary error returns based on MSDN. The TODOs that used to be there have been moved to a new file; similar files for Mac and Linux will also be made.

checkbox.go

@@ -42,11 +42,7 @@ func (c *Checkbox) Checked() bool {
 	c.lock.Lock()
 	defer c.lock.Unlock()
 
-	check, err := c.sysData.isChecked()
-	if err != nil {
-		panic(err)		// TODO
-	}
-	return check
+	return c.sysData.isChecked()
 }
 
 func (c *Checkbox) make(window *sysData) error {

combobox.go

@@ -29,14 +29,14 @@ func NewCombobox(editable bool, items ...string) (c *Combobox) {
 // TODO Append, InsertBefore, Delete
 
 // Selection returns the current selection.
-func (c *Combobox) Selection() (string, error) {
+func (c *Combobox) Selection() string {
 	c.lock.Lock()
 	defer c.lock.Unlock()
 
 	if c.created {
 		return c.sysData.text()
 	}
-	return "", nil
+	return ""
 }
 
 // TODO SelectedIndex

lineedit.go

@@ -27,14 +27,14 @@ func NewLineEdit(text string) *LineEdit {
 // TODO SetText
 
 // Text returns the LineEdit's text.
-func (l *LineEdit) Text() (string, error) {
+func (l *LineEdit) Text() string {
 	l.lock.Lock()
 	defer l.lock.Unlock()
 
 	if l.created {
 		return l.sysData.text()
 	}
-	return l.initText, nil
+	return l.initText
 }
 
 // TODO adorn errors with what failed

main.go

@@ -30,19 +30,11 @@ mainloop:
 		case <-w.Closing:
 			break mainloop
 		case <-b.Clicked:
-			cs1, err := cb1.Selection()
-			if err != nil {
-				panic(err)
-			}
-			cs2, err := cb2.Selection()
-			if err != nil {
-				panic(err)
-			}
-			et, err := e.Text()
-			if err != nil {
-				panic(err)
-			}
-			err = w.SetTitle(fmt.Sprintf("%v | %s | %s | %s", c.Checked(), cs1, cs2, et))
+			err = w.SetTitle(fmt.Sprintf("%v | %s | %s | %s",
+				c.Checked(),
+				cb1.Selection(),
+				cb2.Selection(),
+				e.Text()))
 			if err != nil {
 				panic(err)
 			}

sysdata.go

@@ -27,7 +27,7 @@ func (c *cSysData) setText(text string) error {
 func (c *cSysData) setRect(x int, y int, width int, height int) error {
 	panic(runtime.GOOS + " sysData does not define setRect()")
 }
-func (c *cSysData) isChecked() (bool, error) {
+func (c *cSysData) isChecked() bool {
 	panic(runtime.GOOS + " sysData does not define isChecked()")
 }
 func (c *cSysData) text() (string, error) {

sysdata_windows.go

@@ -244,8 +244,7 @@ func (s *sysData) setRect(x int, y int, width int, height int) error {
 	return nil
 }
 
-// TODO figure out how to handle error
-func (s *sysData) isChecked() (bool, error) {
+func (s *sysData) isChecked() bool {
 	ret := make(chan uiret)
 	defer close(ret)
 	uitask <- &uimsg{
@@ -259,16 +258,14 @@ func (s *sysData) isChecked() (bool, error) {
 		ret:		ret,
 	}
 	r := <-ret
-	return r.ret == _BST_CHECKED, nil
+	return r.ret == _BST_CHECKED
 }
 
-// TODO adorn error messages with which part failed
-func (s *sysData) text() (str string, err error) {
+func (s *sysData) text() (str string) {
 	var tc []uint16
 
 	ret := make(chan uiret)
 	defer close(ret)
-	// TODO figure out how to handle errors
 	uitask <- &uimsg{
 		call:		_sendMessage,
 		p:		[]uintptr{
@@ -282,7 +279,6 @@ func (s *sysData) text() (str string, err error) {
 	r := <-ret
 	length := r.ret + 1		// terminating null
 	tc = make([]uint16, length)
-	// TODO figure out how to handle errors
 	uitask <- &uimsg{
 		call:		_sendMessage,
 		p:		[]uintptr{
@@ -294,8 +290,7 @@ func (s *sysData) text() (str string, err error) {
 		ret:		ret,
 	}
 	<-ret
-	// TODO check character count
-	return syscall.UTF16ToString(tc), nil
+	return syscall.UTF16ToString(tc)
 }
 
 // TODO figure out how to handle errors

winerrors.md

@@ -0,0 +1,4 @@
+- all SendMessage() calls
+- BM_GETCHECK (sysData.isChecked())
+- WM_GETTEXTLENGTH (LRESULT is unsinged so) (sysData.text())
+- WM_GETTEXT (WM_GETTEXTLENGTH docs say its result may be larger than the actual length, so we can't use that) (sysData.text())