Add support for Cocoa TextView OnChange callback

ui/internal/cocoa/textview.go

@@ -9,7 +9,7 @@ import "unsafe"
 // TextView - represents a textView control that can trigger actions.
 type TextView struct {
 	ptr      C.TextViewPtr
-	callback func()
+	callback func(string)
 }
 
 var textviews []*TextView
@@ -26,6 +26,11 @@ func NewTextView(x int, y int, width int, height int) *TextView {
 	return tv
 }
 
+// GetText gets the text of the text view
+func (textview *TextView) GetText() string {
+	return C.GoString(C.TextView_Text(textview.ptr))
+}
+
 // SetText sets the text of the text view
 func (textview *TextView) SetText(text string) {
 	cText := C.CString(text)
@@ -50,3 +55,16 @@ func (c *TextView) SetEditable(editable bool) {
 		C.TextView_SetEditable(c.ptr, 0)
 	}
 }
+
+func (c *TextView) OnChange(fn func(value string)) {
+	c.callback = fn
+}
+
+//export onTextViewDidChange
+func onTextViewDidChange(id C.int) {
+	textViewId := int(id)
+	if textViewId < len(textviews) && textviews[textViewId].callback != nil {
+		tf := textviews[textViewId]
+		tf.callback(tf.GetText())
+	}
+}

ui/internal/cocoa/textview.h

@@ -11,6 +11,7 @@
 typedef void *TextViewPtr;
 
 TextViewPtr TextView_New(int goTextViewId, int x, int y, int w, int h);
+const char *TextView_Text(TextViewPtr textViewPtr);
 void TextView_SetText(TextViewPtr textViewPtr, const char *text);
 void TextView_Remove(TextViewPtr textViewPtr);
 void TextView_SetFontSize(TextViewPtr textViewPtr, int size);

ui/internal/cocoa/textview.m

@@ -1,5 +1,6 @@
 #import "textview.h"
 #include "_cgo_export.h"
+#import "textviewdelegate.h"
 
 @implementation TextViewHandler
 @end
@@ -9,6 +10,10 @@ TextViewPtr TextView_New(int goTextViewId, int x, int y, int w, int h) {
   NSTextView *textView =
       [[[NSTextView alloc] initWithFrame:NSMakeRect(x, y, w, h)] autorelease];
 
+  id d = [[TextViewDelegate alloc] init];
+  [d setGoTextViewId:goTextViewId];
+  [textView setDelegate:d];
+
   NSScrollView *scrollView =
       [[[NSScrollView alloc] initWithFrame:NSMakeRect(x, y, w, h)] autorelease];
   [scrollView setDocumentView:textView];
@@ -20,6 +25,12 @@ TextViewPtr TextView_New(int goTextViewId, int x, int y, int w, int h) {
   return (TextViewPtr)scrollView;
 }
 
+const char *TextView_Text(TextViewPtr ptr) {
+  NSTextView *c = ((NSScrollView *)ptr).documentView;
+  return
+      [[[c textStorage] string] cStringUsingEncoding:NSISOLatin1StringEncoding];
+}
+
 void TextView_SetText(TextViewPtr ptr, const char *text) {
   NSTextView *c = ((NSScrollView *)ptr).documentView;
   [c setString:[NSString stringWithUTF8String:text]];

ui/internal/cocoa/textviewdelegate.h

@@ -0,0 +1,7 @@
+#import <Cocoa/Cocoa.h>
+
+@interface TextViewDelegate : NSObject <NSTextViewDelegate>
+
+@property(assign) int goTextViewId;
+
+@end

ui/internal/cocoa/textviewdelegate.m

@@ -0,0 +1,17 @@
+#import "textviewdelegate.h"
+#include "_cgo_export.h"
+
+@implementation TextViewDelegate
+
+- (void)dealloc {
+  [super dealloc];
+}
+
+- (void)textDidChange:(NSNotification *)aNotification {
+  //   NSTextField *textField = [aNotification object];
+  //   const char *text = [[textField stringValue]
+  //   cStringUsingEncoding:NSUTF8StringEncoding];
+  onTextViewDidChange([self goTextViewId]);
+}
+
+@end

ui/texteditor_cocoa.go

@@ -25,6 +25,8 @@ func (w *TextEditor) Update(nextComponent spot.Control) bool {
 		w.ref.SetFontSize(w.FontSize)
 	}
 
+	w.ref.OnChange(next.OnChange)
+
 	return true
 }
 
@@ -41,6 +43,7 @@ func (w *TextEditor) Mount(parent spot.Control) any {
 	if w.FontSize > 0 {
 		w.ref.SetFontSize(w.FontSize)
 	}
+	w.ref.OnChange(w.OnChange)
 
 	if window, ok := parent.(*Window); ok && window != nil && window.ref != nil {
 		window.ref.AddTextView(w.ref)