Respond to text as it changes
Update an output label immediately while respecting the current option state.
A Change handler is invoked after a value changes. Keep this handler short: normalize or display the input, but do not start an expensive operation for every keystroke. When a checkbox changes how text is displayed, update the output from both the checkbox and text events.
Step 1Prepare a safe practice project#
Extract the archive into a new writable folder, separate from your own application. Open LiveText.mcproj in McBasic™. Keep every declared source, layout, resource and migration file together.
To reconstruct it yourself, create a DesktopApp project and add the files declared below. In the complete project, follow these steps as a guided rebuild: replace each named source file once and Check after all its procedures are present.
Exact project configuration
{
"schemaVersion": 1,
"projectId": "d60b0640-478b-4800-9521-5810e93f3190",
"name": "LiveText",
"kind": "DesktopApp",
"language": {
"dialect": "McBasic1",
"requireExplicit": true,
"compare": "Binary",
"defaultArrayBase": 0
},
"application": {
"bundleIdentifier": "com.mcbasic.livetext",
"version": "0.1.0",
"buildNumber": "1",
"startupFormId": "form-main",
"shutdownMode": "OnStartupFormClosed"
},
"forms": [
{
"id": "form-main",
"typeName": "frmMain",
"layout": "Forms/frmMain.form.json",
"code": "Forms/frmMain.bas"
}
],
"modules": [],
"classes": [],
"tests": [],
"references": [],
"resources": [],
"targets": [
"osx-arm64"
],
"capabilities": []
}Step 2Build the Form and set its properties#
frmMain
Select the Form first and set its properties. Add containers before their children. These are initial Designer values, not statements to paste into a procedure.
| Form property | Value |
|---|---|
Caption | "Live Text — BASIC events" |
Height | 400 |
Width | 640 |
| Type | Name | Parent |
|---|---|---|
| TextBox | txtMessage | Form |
| Label | lblLabel1 | Form |
| CommandButton | cmdButton1 | Form |
| CheckBox | chkCheckBox1 | Form |
txtMessage · exact Inspector values
| Property | Value |
|---|---|
AccessibleName | "Message text" |
Enabled | True |
Height | 104 |
Left | 24 |
MultiLine | True |
ReadOnly | False |
TabIndex | 0 |
Text | "Hello, McBasic!\nType on a second line." |
Top | 24 |
Visible | True |
Width | 520 |
WordWrap | True |
| Anchor edges | Left, Top |
lblLabel1 · exact Inspector values
| Property | Value |
|---|---|
Caption | "Edit the text above to update this preview." |
Enabled | True |
Height | 96 |
Left | 24 |
TabIndex | 1 |
Top | 152 |
Visible | True |
Width | 520 |
| Anchor edges | Left, Top |
cmdButton1 · exact Inspector values
| Property | Value |
|---|---|
Caption | "Assign text with BASIC" |
Enabled | True |
Height | 32 |
Left | 24 |
TabIndex | 2 |
Top | 280 |
Visible | True |
Width | 220 |
| Anchor edges | Left, Top |
chkCheckBox1 · exact Inspector values
| Property | Value |
|---|---|
Caption | "Read-only input" |
Checked | False |
Enabled | True |
Height | 32 |
Left | 24 |
TabIndex | 3 |
Top | 328 |
Visible | True |
Width | 220 |
| Anchor edges | Left, Top |
Step 3Connect the events explicitly#
frmMain
| Object | Event | Procedure | Parameters |
|---|---|---|---|
txtMessage | Change | txtMessage_Change | Change() |
cmdButton1 | Click | cmdButton1_Click | Click() |
chkCheckBox1 | Change | chkCheckBox1_Change | Change() |
Step 4Enter the complete behavior#
Open the named source file. Enter declarations first, then every procedure. Expand a procedure for its full body, or copy the complete file. Helpers are required: do not stop after entering the first Click handler.
Forms/frmMain.bas
Enter these declarations at file scope, before the procedures.
Option ExplicitPrivate Sub chkCheckBox1_Change()
Read the current value or selection and update its dependent interface. The binding above determines which object calls this handler.
Private Sub chkCheckBox1_Change()
txtMessage.ReadOnly = chkCheckBox1.Checked
End SubPrivate Sub cmdButton1_Click()
Enter the complete action, including its input checks and calls to helper procedures.
Private Sub cmdButton1_Click()
txtMessage.Text = "Updated by BASIC"
txtMessage.AccessibleName = "Message updated by BASIC"
End SubPrivate Sub txtMessage_Change()
Read the current value or selection and update its dependent interface. The binding above determines which object calls this handler.
Private Sub txtMessage_Change()
lblLabel1.Caption = txtMessage.Text
End SubCopy the complete Forms/frmMain.bas file
Replace the file once; do not append duplicate procedures.
Option Explicit
Private Sub chkCheckBox1_Change()
txtMessage.ReadOnly = chkCheckBox1.Checked
End Sub
Private Sub cmdButton1_Click()
txtMessage.Text = "Updated by BASIC"
txtMessage.AccessibleName = "Message updated by BASIC"
End Sub
Private Sub txtMessage_Change()
lblLabel1.Caption = txtMessage.Text
End SubStep 5Keep resources and storage reproducible#
No external resource or migration files are declared. Any inline migration, seed data or local JSON is present in the code above. Runtime application data and private preferences are not included in the archive.
Step 6Check, run and test the result#
Save all files and run Check. Resolve diagnostics before Run. Developer CLI users can work from the extracted folder:
mcbasic check LiveText.mcproj
mcbasic run LiveText.mcprojAcceptance checklist
- Type a short message and verify the output updates.
- Toggle the checkbox after typing; the output should reflect the new option.
- Clear the text and test the command button.
Step 7Make one change and repeat the tests#
Move the shared display calculation into a private procedure and call it from both Change handlers.
Save a working Git checkpoint first. Change one behavior, Check again and repeat the acceptance checklist. Compare with the downloaded solution if a regression appears.
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