textinput: add clear methods

Add clear methods to reset the underlying GapBuffer and reset cursor
positions

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>

src/widgets/TextInput.zig

@@ -97,6 +97,18 @@ pub fn draw(self: *TextInput, win: Window) void {
     win.showCursor(cursor_idx, 0);
 }
 
+pub fn clearAndFree(self: *TextInput) void {
+    self.buf.clearAndFree();
+    self.cursor_idx = 0;
+    self.grapheme_count = 0;
+}
+
+pub fn clearRetainingCapacity(self: *TextInput) void {
+    self.buf.clearRetainingCapacity();
+    self.cursor_idx = 0;
+    self.grapheme_count = 0;
+}
+
 // returns the number of bytes before the cursor
 // (since GapBuffers are strictly speaking not contiguous, this is a number in 0..realLength()
 // which would need to be fed to realIndex() to get an actual offset into self.buf.items.ptr)