McBasic™ 0.7.881 · Build 881 · 7 min read

Hands-on tutorial · Media & graphics

Control video playback

Build a video surface with honest loading and error feedback.

1 Form / control designs1 complete BASIC filesGuided sample project

Download complete project Complete event code

Video playback has asynchronous state transitions even when the file is local. Keep the source declaration with the project, preserve aspect behavior and react to Failed explicitly. Test the built application as well as the IDE run path.

Step 1Prepare a safe practice project#

Extract the archive into a new writable folder, separate from your own application. Open VideoPlayer.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": "6cb06642-8475-42ed-9154-e80282784d2f",
  "name": "VideoPlayerSample",
  "kind": "DesktopApp",
  "ai": {
    "storeChatsInProject": false
  },
  "language": {
    "dialect": "McBasic1",
    "requireExplicit": true,
    "compare": "Binary",
    "defaultArrayBase": 0
  },
  "application": {
    "bundleIdentifier": "com.mcbasic.samples.videoplayer",
    "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": [
    {
      "name": "DemoVideo",
      "path": "Resources/demo.mp4"
    }
  ],
  "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`	`"VideoPlayer — McBasic"`
`Width`	`700`
`Height`	`510`
`MinWidth`	`560`
`MinHeight`	`400`

Type	Name	Parent
VideoPlayer	`vidDemo`	Form
CommandButton	`cmdPlay`	Form
CommandButton	`cmdPause`	Form
CommandButton	`cmdStop`	Form
CommandButton	`cmdReload`	Form
Label	`lblStatus`	Form

vidDemo · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`24`
`Width`	`652`
`Height`	`320`
`Source`	`"DemoVideo"`
`AutoPlay`	`False`
`Loop`	`False`
`Volume`	`0.4`
`ControlsVisible`	`True`
`Stretch`	`"Uniform"`
Anchor edges	Left, Top, Right, Bottom

cmdPlay · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`362`
`Width`	`110`
`Height`	`36`
`Caption`	`"Play"`
Anchor edges	Left, Bottom

cmdPause · exact Inspector values

Property	Value
`Left`	`146`
`Top`	`362`
`Width`	`110`
`Height`	`36`
`Caption`	`"Pause"`
Anchor edges	Left, Bottom

cmdStop · exact Inspector values

Property	Value
`Left`	`268`
`Top`	`362`
`Width`	`110`
`Height`	`36`
`Caption`	`"Stop"`
Anchor edges	Left, Bottom

cmdReload · exact Inspector values

Property	Value
`Left`	`390`
`Top`	`362`
`Width`	`110`
`Height`	`36`
`Caption`	`"Reload"`
Anchor edges	Left, Bottom

lblStatus · exact Inspector values

Property	Value
`Left`	`24`
`Top`	`414`
`Width`	`652`
`Height`	`36`
`Caption`	`"Loading"`
Anchor edges	Left, Right, Bottom

Step 3Connect the events explicitly#

frmMain

Object	Event	Procedure	Parameters
`vidDemo`	`Loaded`	`vidDemo_Loaded`	`Loaded()`
`vidDemo`	`Completed`	`vidDemo_Completed`	`Completed()`
`vidDemo`	`Failed`	`vidDemo_Failed`	`Failed()`
`vidDemo`	`StateChanged`	`vidDemo_StateChanged`	`StateChanged()`
`cmdPlay`	`Click`	`cmdPlay_Click`	`Click()`
`cmdPause`	`Click`	`cmdPause_Click`	`Click()`
`cmdStop`	`Click`	`cmdStop_Click`	`Click()`
`cmdReload`	`Click`	`cmdReload_Click`	`Click()`
Form	`Load`	`Form_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()
    lblStatus.Caption = "Video state: " + vidDemo.State
End Sub

Private Sub cmdPlay_Click()

Enter the complete action, including its input checks and calls to helper procedures.

Forms/frmMain.bas · cmdPlay_Click

Private Sub cmdPlay_Click()
    If vidDemo.Duration > 0 Then
        vidDemo.Position = 0
    End If
    vidDemo.Play
End Sub

Private Sub cmdPause_Click()

Enter the complete action, including its input checks and calls to helper procedures.

Forms/frmMain.bas · cmdPause_Click

Private Sub cmdPause_Click()
    vidDemo.Pause
End Sub

Private Sub cmdStop_Click()

Enter the complete action, including its input checks and calls to helper procedures.

Forms/frmMain.bas · cmdStop_Click

Private Sub cmdStop_Click()
    vidDemo.Stop
End Sub

Private Sub cmdReload_Click()

Enter the complete action, including its input checks and calls to helper procedures.

Forms/frmMain.bas · cmdReload_Click

Private Sub cmdReload_Click()
    vidDemo.Load
End Sub

Private Sub vidDemo_Loaded()

Enter this helper in the named source file, outside every other procedure. Its callers are included in the same project.

Forms/frmMain.bas · vidDemo_Loaded

Private Sub vidDemo_Loaded()
    lblStatus.Caption = "Loaded " + vidDemo.Source + " (" + CStr(vidDemo.Duration) + " s)"
End Sub

Private Sub vidDemo_Completed()

Enter this helper in the named source file, outside every other procedure. Its callers are included in the same project.

Forms/frmMain.bas · vidDemo_Completed

Private Sub vidDemo_Completed()
    lblStatus.Caption = "Playback completed"
End Sub

Private Sub vidDemo_Failed()

Enter this helper in the named source file, outside every other procedure. Its callers are included in the same project.

Forms/frmMain.bas · vidDemo_Failed

Private Sub vidDemo_Failed()
    lblStatus.Caption = vidDemo.Error
End Sub

Private Sub vidDemo_StateChanged()

Enter this helper in the named source file, outside every other procedure. Its callers are included in the same project.

Forms/frmMain.bas · vidDemo_StateChanged

Private Sub vidDemo_StateChanged()
    lblStatus.Caption = "Video state: " + vidDemo.State
    If vidDemo.Playing Then
        lblStatus.Caption = lblStatus.Caption + " at " + CStr(vidDemo.Position) + " s"
    ElseIf vidDemo.Paused Then
        lblStatus.Caption = "Paused at " + CStr(vidDemo.Position) + " s"
    End If
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()
    lblStatus.Caption = "Video state: " + vidDemo.State
End Sub

Private Sub cmdPlay_Click()
    If vidDemo.Duration > 0 Then
        vidDemo.Position = 0
    End If
    vidDemo.Play
End Sub

Private Sub cmdPause_Click()
    vidDemo.Pause
End Sub

Private Sub cmdStop_Click()
    vidDemo.Stop
End Sub

Private Sub cmdReload_Click()
    vidDemo.Load
End Sub

Private Sub vidDemo_Loaded()
    lblStatus.Caption = "Loaded " + vidDemo.Source + " (" + CStr(vidDemo.Duration) + " s)"
End Sub

Private Sub vidDemo_Completed()
    lblStatus.Caption = "Playback completed"
End Sub

Private Sub vidDemo_Failed()
    lblStatus.Caption = vidDemo.Error
End Sub

Private Sub vidDemo_StateChanged()
    lblStatus.Caption = "Video state: " + vidDemo.State
    If vidDemo.Playing Then
        lblStatus.Caption = lblStatus.Caption + " at " + CStr(vidDemo.Position) + " s"
    ElseIf vidDemo.Paused Then
        lblStatus.Caption = "Paused at " + CStr(vidDemo.Position) + " s"
    End If
End Sub

Step 5Keep resources and storage reproducible#

Keep the following files at their declared relative paths. Apply migrations before the first query. Media and report resources must travel with the build.

File	Purpose
`Resources/demo.mp4`	Bundled asset / license

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 VideoPlayer.mcbproj
mcbasic run VideoPlayer.mcbproj

Acceptance checklist

Load and play the sample video.
Pause and resume, then stop.
Reload the asset.
Run the built app and verify the video resource is present.

Step 7Make one change and repeat the tests#

Add a loading label that is cleared by Loaded and replaced by an error on Failed.

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

Control video playback

Step 1Prepare a safe practice project#

Step 2Build the Form and set its properties#

frmMain

Step 3Connect the events explicitly#

frmMain

Step 4Enter the complete behavior#

Forms/frmMain.bas

Step 5Keep resources and storage reproducible#

Step 6Check, run and test the result#

Acceptance checklist

Step 7Make one change and repeat the tests#

Continue learning#

`Forms/frmMain.bas`