DVX BASIC IDE Guide

DVX BASIC is a Visual BASIC development environment for the DVX GUI System. It provides a VB3-style integrated development environment with a code editor, form designer, project system, and a full interactive debugger -- all running natively on DOS under the DVX windowing system.

This guide covers every feature of the IDE: menus, toolbar, editor, form designer, project management, debugger, and auxiliary windows.

1. Overview

The DVX BASIC IDE is modeled after Visual Basic 3.0. It consists of several floating windows arranged on the DVX desktop:

• Main Toolbar Window -- anchored at the top of the screen. Contains the menu bar, toolbar buttons, and status bar.
• Code Editor -- the primary editing surface for BASIC source code, with Object/Event dropdowns, syntax highlighting, and line numbers.
• Form Designer -- a visual design surface for .frm files, showing a WYSIWYG preview of the form with grab handles for resizing controls.
• Project Explorer -- a tree view listing all files in the project.
• Toolbox -- a palette of available controls for placing on forms.
• Properties Panel -- a tree of controls and a list of editable properties for the selected control.
• Output Window -- displays PRINT output and runtime errors.
• Immediate Window -- an interactive REPL for evaluating expressions and modifying variables at runtime.
• Debug Windows -- Locals, Call Stack, Watch, and Breakpoints windows that appear automatically when debugging.

The IDE compiles BASIC source into bytecode and runs it in an integrated virtual machine (VM). Programs execute in cooperative slices (10,000 VM steps per slice), yielding to the DVX event loop between slices so the GUI remains responsive.

2. Menu Reference

File Menu

Edit Menu

Run Menu

View Menu

Window Menu

Tools Menu

Help Menu

3. Toolbar

The toolbar is organized into four groups separated by vertical dividers. Each button has a tooltip showing its name and keyboard shortcut.

File Group

Run Group

Debug Group

View Group

4. Code Editor

The Code Editor is the primary editing window for BASIC source code. It occupies the center of the screen, below the toolbar and above the Output and Immediate windows.

Object and Function Dropdowns

At the top of the Code Editor are two dropdown lists:

• Object -- lists (General) plus all objects (form name, control names, menu item names). Selecting an object filters the Function dropdown.
• Function -- lists all event handlers (procedures) for the selected object. Implemented handlers are listed first (plain text); unimplemented handlers follow in brackets (e.g., [Click]). Selecting an unimplemented event creates a new event handler stub.

The editor shows one procedure at a time. Each procedure has its own buffer, and switching between them is instantaneous. The (General) section contains module-level declarations and code.

Syntax Highlighting

The editor applies real-time syntax coloring as you type. The following categories are highlighted in distinct colors:

Editor Features

• Line numbers -- displayed in the gutter on the left side.
• Auto-indent -- new lines are automatically indented to match the previous line.
• Tab handling -- the Tab key is captured by the editor. Tab width and whether to insert spaces or tab characters are configurable in Preferences (default: 3 spaces).
• Gutter click -- clicking in the line number gutter toggles a breakpoint on that line.
• Line decorations -- breakpoint lines show a red dot in the gutter. The current debug line (when paused) is highlighted with a yellow background.

5. Form Designer

The Form Designer provides a visual design surface for editing .frm files. Switch to it with Shift+F7 or the Design toolbar button. It opens in a separate window showing a WYSIWYG preview of the form.

Design Surface

• Grid snapping -- controls snap to an 8-pixel grid (DSGN_GRID_SIZE) when placed or resized.
• Selection -- click a control to select it. The selected control is highlighted with grab handles.
• Grab handles -- 6x6 pixel handles appear on the right edge (E), bottom edge (S), and bottom-right corner (SE) of the selected control. Drag a handle to resize the control.
• Reordering -- drag a control vertically to reorder it within the form's layout (VBox/HBox).
• Placing controls -- select a control type in the Toolbox, then click on the form to place a new instance. The control is auto-named (e.g., Command1, Command2). Clicking the same tool again deselects it (toggles back to pointer mode).
• Menu bar preview -- if the form has menu items (defined via the Menu Editor), a preview menu bar is rendered on the design window.
• Delete key -- removes the selected control from the form.

Form Properties

Forms have the following design-time properties: Name, Caption, Width, Height, Left, Top, Layout (VBox or HBox), Centered, AutoSize, and Resizable.

6. Project System

Project Files (.dbp)

A DVX BASIC project is stored as a .dbp file (DVX BASIC Project). The project file records:

• Name -- the project display name (up to 32 characters).
• Startup Form -- which form to show automatically when the program starts.
• Metadata -- Author, Company, Version, Copyright, Description, and Icon Path (for compiled binaries).
• File list -- relative paths (8.3 DOS names) of all .bas and .frm files in the project. Each entry tracks whether it is a form file.

Source Map

When the project is compiled, all files are concatenated into a single source stream. A source map tracks which lines belong to which file, enabling accurate error reporting and debugger navigation across multiple files. For .frm files, an injected BEGINFORM directive is prepended to the code section.

Project Operations

Project Explorer

The Project Explorer is a tree view window listing all project files. Double-click a file to open it: .bas files open in Code view, .frm files open in Design view. The selected file in the Project Explorer determines the target for View > Code and View > Designer commands.

7. Properties Panel

The Properties panel (Window > Properties) has two sections:

• Control tree -- a TreeView at the top listing the form and all its controls in layout order. Click a control name to select it in both the Properties panel and the Form Designer. Drag items in the tree to reorder controls in the form's layout.
• Property list -- a two-column ListView below the tree showing property names and values for the selected control. Double-click a property value to edit it via an InputBox dialog. Changes take effect immediately in the designer preview.

Each control type exposes different properties (e.g., Caption, Text, Width, Height, MaxWidth, MaxHeight, Weight, Alignment, Enabled, Visible, and type-specific properties like DataSource and DataField for data-bound controls).

8. Toolbox

The Toolbox (Window > Toolbox) is a floating palette of buttons, one for each available control type. Controls are loaded dynamically from the widget plugin registry -- any widget DXE that provides a basName appears in the toolbox.

Click a tool to select it (the active tool name is stored in the designer state), then click on the form to place a new instance. Click the same tool again to deselect it and return to pointer mode.

Available Controls

9. Debugger

The DVX BASIC IDE includes a full interactive debugger. The debugger operates as a state machine with three states:

Starting a Debug Session

• Shift+F5 (Debug) -- compiles the project and starts execution in debug mode. Breakpoints are active but execution does not pause at the first statement.
• F8 (Step Into) -- if idle, starts a debug session and breaks at the first statement.
• F5 (Run) -- compiles and runs without the debugger. No breakpoints are active. If already paused, resumes execution with debugging disabled.

Breakpoints

Setting Breakpoints

• Press F9 to toggle a breakpoint on the current editor line.
• Click in the line number gutter to toggle a breakpoint on that line.

Breakpoint Validation

Not every line can have a breakpoint. The IDE validates the line content and silently refuses to set breakpoints on:

• Blank lines
• Comment lines (' or REM)
• SUB and FUNCTION declaration lines
• END SUB and END FUNCTION lines

Breakpoint Storage

Each breakpoint records the project file index, the code line number within the file, the procedure index, and the procedure name (as Object.Event). When the project is compiled, breakpoints are converted to concatenated source line numbers that match the VM's OP_LINE opcodes.

Visual Indicators

• Breakpoint lines show a red dot in the gutter.
• The current debug line (when paused) has a yellow background.

Breakpoint Adjustment on Edit

When lines are added or removed in the editor, breakpoints below the edit point are automatically shifted to stay on the correct line.

Stepping

The Debug Run Loop

When a program is running in debug mode, the IDE enters a cooperative loop:

1. The VM executes up to 10,000 steps per slice.
2. If the VM hits a breakpoint (BAS_VM_BREAKPOINT), the state transitions to DBG_PAUSED. The IDE navigates the code editor to the breakpoint line, highlights it in yellow, auto-opens the Locals and Call Stack windows, and updates all debug windows.
3. While paused, the IDE pumps dvxUpdate() continuously, keeping the GUI responsive. The user can inspect variables, modify them in the Immediate window, step, continue, or stop.
4. When the user resumes (F5/Shift+F5/F8/etc.), the state transitions back to DBG_RUNNING and the loop continues.

Stopping

Press Esc or click the Stop toolbar button at any time to halt execution. The VM is destroyed, debug state resets to DBG_IDLE, and the IDE restores the designer windows that were hidden at run start.

10. Debug Windows

When the debugger pauses, the Locals and Call Stack windows are auto-opened (if not already visible). The Watch and Breakpoints windows can be opened manually from the Window menu.

Locals Window

Shows variables for the current execution scope. Displayed as a three-column ListView:

The Locals window displays:

• Local variables for the current procedure (matched by proc index).
• Global (module-level) variables.
• Form-scoped variables for the current form (if the program is executing within a form context).

Up to 64 variables are displayed. The window is resizable.

Call Stack Window

Shows the current call chain as a two-column ListView:

The current location is shown first, followed by each caller in the call stack (walking from the deepest frame back to the module entry point). Up to 32 frames are displayed.

Watch Window

Allows monitoring arbitrary expressions while debugging. The window has a text input at the top and a two-column ListView below:

Adding Watch Expressions

Type an expression in the text input and press Enter. Up to 16 watch expressions can be active at once.

Watch Expression Syntax

Watch expressions support:

• Simple variable names: x, count
• Array subscripts: arr(5), matrix(2, 3)
• UDT field access: player.name
• Combined: items(i).price
• Arbitrary BASIC expressions (compiled and evaluated against the paused VM's state): x + y * 2, Len(name$)

Editing and Deleting

• Double-click or press Enter on a watch entry to move it back into the input box for editing.
• Press Delete to remove the selected watch expression.

Breakpoints Window

Lists all set breakpoints as a three-column ListView:

• Double-click a breakpoint to navigate the code editor to that location.
• Press Delete to remove selected breakpoints (multi-select is supported).

11. Immediate Window

The Immediate window is an interactive REPL at the bottom-right of the screen. Type a line of BASIC and press Enter to evaluate it. Results appear inline below your input.

Expression Evaluation

If the input is not a recognized statement keyword, it is automatically wrapped in a PRINT statement. For example, typing 2 + 2 evaluates as PRINT 2 + 2 and displays 4.

You can also type full statements:

• PRINT x * 2 -- evaluate and print an expression.
• DIM tmp As Integer -- declare a temporary variable.
• LET x = 42 -- explicit assignment (see below).

Parse or runtime errors are displayed inline with an Error: prefix.

Inspecting Variables While Paused

When the debugger is paused at a breakpoint, the Immediate window has access to the running VM's state. Global variable values are copied into the evaluation VM, so expressions like count or name$ & " test" display live values.

Assigning Variables While Paused

When paused, you can modify variables in the running program directly from the Immediate window using assignment syntax:

variableName = newValue

The optional LET keyword is also accepted:

LET variableName = newValue

Assignment works for:

• Scalar variables -- x = 42, name$ = "test"
• Array elements -- arr(5) = 100, matrix(2, 3) = 7.5
• UDT fields -- player.score = 1000
• Combined -- items(0).price = 9.99

The new value is written directly into the VM's live variable slot (local, global, or form scope). A confirmation message is displayed, and the Locals and Watch windows update automatically to reflect the change.

If the assignment target cannot be resolved (unknown variable, out-of-bounds index, wrong type), an error message is displayed.

12. Output Window

The Output window is a read-only TextArea at the bottom-left of the screen. It displays:

• PRINT output -- all PRINT statement output from the running program is appended here.
• Runtime errors -- if the VM encounters a runtime error (division by zero, out-of-bounds, etc.), the error message and line number are displayed in the output with an Error on line N: prefix.
• Compile errors -- if compilation fails, the error message and location are shown.

The output buffer holds up to 32,768 characters. Use Run > Clear Output to clear it.

INPUT statements prompt the user via a modal InputBox dialog; the prompt text is also echoed to the Output window.

13. Find / Replace

Open with Ctrl+F (Find) or Ctrl+H (Replace). The Find/Replace dialog is modeless -- it stays open while you continue editing.

Dialog Controls

Buttons

Keyboard Shortcut

F3 repeats the last search (Find Next) without opening the dialog.

14. Preferences

Open via Tools > Preferences. Settings are saved to dvxbasic.ini in the app's config directory.

Editor Section

New Project Defaults Section

These fields set the default values for new project metadata:

Keyboard Shortcut Summary

DVX BASIC 1.0 -- Copyright 2026 Scott Duensing