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Drawing with the VSN1 Screen

You can draw shapes and text on the VSN1 screen using the Screen Draw element. Screen size is 320px*240px and drawing happens at a fast refresh rate (up to 20fps), so it's great for updating values or displaying information in real time.

How Drawing Works​

To draw anything on the screen, you use functions like draw_rectangle_filled() or draw_text_fast().

However, drawing commands only prepare the content in a background buffer. To show the result on the actual screen, you must call:

self:draw_swap()

Why you need draw_swap()​

After using any draw_ function, you need to tell the system when to actually update the screen. That’s what self:draw_swap() does — it swaps the buffer and pushes the visuals to the display.

Why is it useful to call draw_swap() separately?

Because you can decide exactly when to update. For example, if you’re using an if-else branch, you can draw only the part you want and skip unnecessary updates. This makes your drawing logic more flexible and efficient.

Always use self: before drawing​

Before any drawing function, always use self: so it knows which screen you're targeting. This is important if you have multiple screens in your setup — or later when we support two screens in one module. If you forget self:, nothing will be drawn because the system doesn't know where to draw.

Coordinates and Colors​

When you draw a shape or text, you usually need to provide:

  • X and Y coordinates — where to draw it on the screen
  • Size or dimensions — for example: width and height in pixels
  • Color — in RGB format

Coordinates​

Most drawing functions use:

  • x and y for the top-left corner or starting point
  • width and height or an end point (x2, y2) depending on the shape

For example:

self:draw_rectangle_filled(10, 5, 40, 20, {0, 0, 0})

Draws a filled rectangle at position (10, 5), with a width of 40 pixels and height of 20 pixels.

Colors (RGB Format)​

All drawing functions use RGB color values in the format:

{red, green, blue} Each value is from 0 to 255 (8-bit color per channel). Examples:

Red: {255, 0, 0}

Green: {0, 255, 0}

Blue: {0, 0, 255}

White: {255, 255, 255}

Black: {0, 0, 0}

You can customize colors for text, shapes, or backgrounds however you like.

A Basic Example — Draw the Endless Potmeter Value​

This is a simple example that clears the screen, writes the value of an Endless encoder, and updates the screen:

self:draw_rectangle_filled(0, 0, 23 * 5, 22, {0, 0, 0})
self:draw_text_fast(element[8]:endless_value(), 0, 0, 22, {255, 22, 22})
self:draw_swap()

What it does:​

draw_rectangle_filled() is used to always clear the background, so old numbers don’t stay on the screen. Try deleting this line and see what happens — the numbers won’t be fully cleared when changing from a 5-digit to a 1-digit number.

draw_text_fast() draws the current value of the Endless encoder.

draw_swap() updates the screen with everything you just drew.