This closes qax-os#2113, AddFormControl function support set cell link for check box

Author: xuri

Diff for: vml.go

@@ -372,7 +372,11 @@ func (f *File) commentsWriter() {
 // by given worksheet name and form control options. Supported form control
 // type: button, check box, group box, label, option button, scroll bar and
 // spinner. If set macro for the form control, the workbook extension should be
-// XLSM or XLTM. Scroll value must be between 0 and 30000.
+// XLSM or XLTM. Scroll value must be between 0 and 30000. Please note that if a
+// cell link is set for a checkbox form control, Excelize will not assign a
+// value to the linked cell when the checkbox is checked. To reflect the
+// checkbox state, please use the 'SetCellValue' function to manually set the
+// linked cell's value to true.
 //
 // Example 1, add button form control with macro, rich-text, custom button size,
 // print property on Sheet1!A2, and let the button do not move or size with
@@ -826,6 +830,9 @@ func (f *File) addFormCtrlShape(preset formCtrlPreset, col, row int, anchor stri
 	if (opts.Type == FormControlCheckBox || opts.Type == FormControlOptionButton) && opts.Checked {
 		sp.ClientData.Checked = 1
 	}
+	if opts.FormControl.Type == FormControlCheckBox {
+		sp.ClientData.FmlaLink = opts.CellLink
+	}
 	return &sp, sp.addFormCtrl(opts)
 }
 

Diff for: vml_test.go

@@ -192,7 +192,7 @@ func TestFormControl(t *testing.T) {
 		},
 		{
 			Cell: "A6", Type: FormControlCheckBox, Text: "Check Box 2",
-			Format: GraphicOptions{Positioning: "twoCell"},
+			CellLink: "C5", Format: GraphicOptions{Positioning: "twoCell"},
 		},
 		{
 			Cell: "A7", Type: FormControlOptionButton, Text: "Option Button 1", Checked: true,