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Build 881
Hands-on tutorial · Media & graphics

Display a scalar measurement

Present a bounded measurement with a Gauge.

1 Form / control designs1 complete BASIC filesGuided sample project

A gauge summarizes a value; it does not explain its source. Keep the range and units explicit in the surrounding interface. If the underlying operation fails, do not retain a stale measurement without identifying it as stale.

Step 1Prepare a safe practice project#

Extract the archive into a new writable folder, separate from your own application. Open Gauge.mcbproj 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
project.mcproj
{
  "schemaVersion": 1,
  "projectId": "5b253ff1-d8ea-4b21-9d0b-49f7b0db4d6f",
  "name": "GaugeSample",
  "kind": "DesktopApp",
  "ai": {
    "storeChatsInProject": false
  },
  "language": {
    "dialect": "McBasic1",
    "requireExplicit": true,
    "compare": "Binary",
    "defaultArrayBase": 0
  },
  "application": {
    "bundleIdentifier": "com.mcbasic.samples.gauge",
    "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 propertyValue
Caption"Gauge — McBasic"
Width560
Height300
MinWidth440
MinHeight240
TypeNameParent
GaugegaugeProgressForm
LabellblHelpForm
gaugeProgress · exact Inspector values
PropertyValue
Left48
Top66
Width420
Height64
Minimum0
Maximum100
Value64
Caption"Import progress"
ShowValueTrue
TabIndex0
VisibleTrue
EnabledTrue
Anchor edgesLeft, Top, Right
lblHelp · exact Inspector values
PropertyValue
Left48
Top154
Width420
Height48
Caption"Gauge is a McBasic-owned control composed from Avalonia primitives."
TabIndex1
VisibleTrue
EnabledTrue
Anchor edgesLeft, Top, Right

Step 3Connect the events explicitly#

frmMain

ObjectEventProcedureParameters
gaugeProgressChangegaugeProgress_ChangeChange()
FormLoadForm_Load()

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.

Forms/frmMain.bas · declarations
Option Explicit
Private Sub Form_Load()

Initialize state before enabling dependent actions. Keep the shared declarations and startup dependencies with this procedure.

Forms/frmMain.bas · Form_Load
Private Sub Form_Load()
    gaugeProgress.Minimum = 0
    gaugeProgress.Maximum = 100
    gaugeProgress.Caption = "Import progress"
    gaugeProgress.Value = 64
    gaugeProgress.ShowValue = True
    lblHelp.Caption = "Gauge is a McBasic-owned control composed from Avalonia primitives."
End Sub
Private Sub gaugeProgress_Change()

Read the current value or selection and update its dependent interface. The binding above determines which object calls this handler.

Forms/frmMain.bas · gaugeProgress_Change
Private Sub gaugeProgress_Change()
    lblHelp.Caption = "Import progress: " & gaugeProgress.Value
End Sub
Copy the complete Forms/frmMain.bas file

Replace the file once; do not append duplicate procedures.

Forms/frmMain.bas
Option Explicit

Private Sub Form_Load()
    gaugeProgress.Minimum = 0
    gaugeProgress.Maximum = 100
    gaugeProgress.Caption = "Import progress"
    gaugeProgress.Value = 64
    gaugeProgress.ShowValue = True
    lblHelp.Caption = "Gauge is a McBasic-owned control composed from Avalonia primitives."
End Sub

Private Sub gaugeProgress_Change()
    lblHelp.Caption = "Import progress: " & gaugeProgress.Value
End Sub

Step 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:

Developer CLI
mcbasic check Gauge.mcbproj
mcbasic run Gauge.mcbproj

Acceptance checklist

  • Run and inspect the initial measurement.
  • Change the authored value and run again.
  • Test both range endpoints.

Step 7Make one change and repeat the tests#

Add a label for units and update it from the same source as the gauge.

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.

Source baseline 20f4bfed6b · Build manifest