Introduction to Graphics

This section covers the basics of opening a window and drawing to the screen with RCBasic.

Opening a Window

Use OpenWindow() to create a graphics window before doing any drawing:

  fullscreen = false
vsync      = true

OpenWindow("My Graphics Window", 640, 480, fullscreen, vsync)

The window opens at 640 × 480 pixels. If the window could not be created OpenWindow returns false.

The Render Loop

A window opened without a render loop will close immediately. The following skeleton keeps the window alive until the user presses Escape:

  While NOT Key(K_ESCAPE)
    Update()   ' MUST be called every frame
Wend

Update() is the most important call in any graphical program. Every frame it:

Renders all visible canvases to the window.
Polls keyboard, mouse, joystick, and window events.
Steps the physics simulation (2D and 3D).

Canvas System

RCBasic renders everything through virtual render targets called canvases. There are three types:

Type	Description
2D Paint Canvas	For drawing commands: `DrawImage`, `Rect`, `FloodFill`, etc.
Sprite Layer	Renders sprites. Has infinite 2D space; only the viewport area is shown.
3D Canvas	A 3D viewport with its own camera. Multiple 3D canvases re-render the scene each frame, so use sparingly.

Drawing with a Paint Canvas

Open a canvas with OpenCanvas(), set it as active with Canvas(), then issue drawing commands inside the render loop:

  fullscreen = false
vsync      = true

OpenWindow("My Graphics Window", 640, 480, fullscreen, vsync)

paint_canvas = OpenCanvas(640, 480, 0, 0, 640, 480, 1)

Canvas(paint_canvas)   ' make this canvas active

While NOT Key(K_ESCAPE)
    ClearCanvas()                          ' clear each frame

    SetColor( RGB(200, 0, 0) )            ' draw color → red
    RectFill(20, 20, 50, 50)              ' filled rectangle

    Update()
Wend

OpenCanvas(w, h, vp_x, vp_y, vp_w, vp_h, mode) — the last parameter: 0 = solid background, 1 = transparent background.
ClearCanvas() resets the drawing surface each frame. Omit it only when you want the previous frame to persist (e.g. a paint application).

Key Drawing Functions

Function	Description
`SetColor()`	Set the current draw colour using `RGB()` or `RGBA()`.
`RectFill()`	Draw a filled rectangle.
`Rect()`	Draw a rectangle outline.
`CircleFill()`	Draw a filled circle.
`Line()`	Draw a line between two points.
`DrawImage()`	Blit a loaded image onto the canvas.
`DrawText()`	Render text using a loaded font.