Started adding TextField.ReadOnly() and implemented it (mostly) on Windows.

basicctrls.go

@@ -57,6 +57,11 @@ type TextField interface {
 	// The string passed to Invalid will be displayed to the user to inform them of what specifically is wrong with the input.
 	// Pass an empty string to remove the warning.
 	Invalid(reason string)
+
+	// ReadOnly and SetReadOnly get and set whether the TextField is read-only.
+	// A read-only TextField cannot be changed by the user, but its text can still be manipulated in other ways (selecting, copying, etc.).
+	ReadOnly() bool
+	SetReadOnly(readonly bool)
 }
 
 // NewTextField creates a new TextField.
@@ -127,6 +132,7 @@ func NewGroup(text string, control Control) Group {
 // TODO rename to TextBox? merge with TextField (but cannot use Invalid())? enable/disable line wrapping?
 // TODO events
 // TODO Tab key - insert horizontal tab or tab stop?
+// TODO ReadOnly
 type Textbox interface {
 	Control
 

basicctrls_windows.c

@@ -128,6 +128,19 @@ void textfieldHideInvalidBalloonTip(HWND hwnd)
 		xpanic("error hiding TextField.Invalid() balloon tip", GetLastError());
 }
 
+// also good for Textbox
+int textfieldReadOnly(HWND hwnd)
+{
+	return (GetWindowLongPtrW(hwnd, GWL_STYLE) & ES_READONLY) != 0;
+}
+
+// also good for Textbox
+void textfieldSetReadOnly(HWND hwnd, BOOL readonly)
+{
+	if (SendMessageW(hwnd, EM_SETREADONLY, (WPARAM) readonly, 0) == 0)
+		xpanic("error setting TextField/Textbox as read-only/not read-only", GetLastError());
+}
+
 static LRESULT CALLBACK groupSubProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR id, DWORD_PTR data)
 {
 	LRESULT lResult;

common_windows.c

@@ -85,6 +85,7 @@ BOOL sharedWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT *
 		return TRUE;
 	case WM_CTLCOLORSTATIC:
 	case WM_CTLCOLORBTN:
+		// TODO exempt read-only textboxes
 		if (SetBkMode((HDC) wParam, TRANSPARENT) == 0)
 			xpanic("error setting transparent background mode to Labels", GetLastError());
 		paintControlBackground((HWND) lParam, (HDC) wParam);

textfield_windows.go

@@ -58,6 +58,18 @@ func (t *textfield) Invalid(reason string) {
 	C.textfieldSetAndShowInvalidBalloonTip(t.hwnd, toUTF16(reason))
 }
 
+func (t *textfield) ReadOnly() bool {
+	return C.textfieldReadOnly(t.hwnd) != 0
+}
+
+func (t *textfield) SetReadOnly(readonly bool) {
+	if readonly {
+		C.textfieldSetReadOnly(t.hwnd, C.TRUE)
+		return
+	}
+	C.textfieldSetReadOnly(t.hwnd, C.FALSE)
+}
+
 //export textfieldChanged
 func textfieldChanged(data unsafe.Pointer) {
 	t := (*textfield)(data)

winapi_windows.h

@@ -74,6 +74,8 @@ extern void checkboxSetChecked(HWND, BOOL);
 extern void setTextFieldSubclass(HWND, void *);
 extern void textfieldSetAndShowInvalidBalloonTip(HWND, WCHAR *);
 extern void textfieldHideInvalidBalloonTip(HWND);
+extern int textfieldReadOnly(HWND);
+extern void textfieldSetReadOnly(HWND, BOOL);
 extern void setGroupSubclass(HWND, void *);
 extern HWND newUpDown(HWND, void *);
 extern void setSpinboxEditSubclass(HWND, void *);

zz_test.go

@@ -54,6 +54,8 @@ var ddata = []dtype{
 type testwin struct {
 	t          Tab
 	w          Window
+	roenter	TextField
+	roro		TextField
 	repainter  *repainter
 	fe         *ForeignEvent
 	festack    Stack
@@ -176,6 +178,13 @@ func (tw *testwin) make(done chan struct{}) {
 		done <- struct{}{}
 		return true
 	})
+	tw.roenter = NewTextField()
+	tw.roro = NewTextField()
+	tw.roro.SetReadOnly(true)
+	tw.roenter.OnChanged(func() {
+		tw.roro.SetText(tw.roenter.Text())
+	})
+	tw.t.Append("Read-Only", newVerticalStack(tw.roenter, tw.roro))
 	tw.icons, tw.il = readIcons() // repainter uses these
 	tw.repainter = newRepainter(15)
 	tw.t.Append("Repaint", tw.repainter.grid)