[noob] light with svg

I’m looking for an example on how to create custom widget : I want to be able to create something similar to a light, but using a custom svn image.
I.E : to be able to draw or not an image on top of the module.
what is the most simple way?

(I found answer for custom switch, but I don’t need the user interaction part)



Take a look at the SvgButton source code for reference: https://github.com/VCVRack/Rack/blob/v1/include/app/SvgButton.hpp

Maybe there is an easier way, but what I would do is make a new custom widget inheriting from TransparentWidget which basically copies SvgButton without the click functionality. I think this is what the widget should look like, but WARNING: I didn’t actually run this code so there are probably errors.

struct ChCustomWidget : TransparentWidget {
	ChModule *module;
	widget::FramebufferWidget *fb;
	widget::SvgWidget *sw;

	ChCustomWidget() {

	void addFrame(std::shared_ptr<Svg> svg) {
		// If this is our first frame, automatically set SVG and size
		if (!sw->svg) {
			box.size = sw->box.size;
			fb->box.size = sw->box.size;

	void draw(const DrawArgs &args) override {
		if (module) {
			fb->dirty = true;
		else {



Your Module (of type ChModule in my example) must have a member svgIndex which tells the widget which svg to show. Instantiate the ChCustomWidget in your ModuleWidget constructor like this:

ChCustomWidget *chWidget = new ChCustomWidget();
			chWidget->module = module;
			chWidget->box.pos = Vec(20, 20);

I adapted @computerscare 's code and got it working. One big difference is that I pass in a pointer to a boolean instead of a pointer to the entire module. I’m hoping that this will make the code more reusable between different modules.

Here’s what I came up with:

struct StepLightWidget : SvgWidget

  bool *state_bool_ptr = NULL;
  std::vector<std::shared_ptr<window::Svg>> frames;

  StepLightWidget(bool *state)
    addFrame(APP->window->loadSvg(asset::plugin(pluginInstance, "res/groovebox/groove_box_led.svg")));
    addFrame(APP->window->loadSvg(asset::plugin(pluginInstance, "res/groovebox/groove_box_led_lit.svg")));

    this->state_bool_ptr = state;

  void addFrame(std::shared_ptr<Svg> svg)

    // If this is our first frame, automatically set SVG and size
    if (!this->svg)
      box.size = svg->getSize();

  void step() override

    if (state_bool_ptr != NULL)
      this->setSvg(frames[(*state_bool_ptr) ? 1 : 0]);

And here’s how I add it to the ModuleWidget constructor:

StepLightWidget *step_light_widget = new StepLightWidget((module) ? &module->light_status_boolean : &dummy_boolean);
step_light_widget->box.pos = Vec(20.0, 20.0);  // Adjust this to place it where you want it

// Where dummy_boolean is defined in the module widget as bool dummy_boolean = false;

Hope this helps!

I don’t quite get it doesn’t SvgWidget do exactly what OP wanted?

I agree, and my example extends SvgWidget instead of TransparentWidget. Is my code overly verbose? I’m all ears if it can be streamlined! :ear: :+1:

I was responding to @computerscare . I didn’t look at your code, but I’m sure it’s fine.

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Very possible

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