Add jngl::UpdateModelview effect

src/jngl/Widget.cpp

@@ -46,7 +46,11 @@ void Widget::draw() const {
 	for (const auto& effect : effects) {
 		effect->beginDraw();
 	}
-	drawSelf(jngl::modelview());
+	auto mv = jngl::modelview();
+	for (const auto& effect : effects) {
+		effect->updateModelview(mv);
+	}
+	drawSelf(mv);
 	for (const auto& effect : effects) {
 		effect->endDraw();
 	}

src/jngl/effects.cpp

@@ -13,6 +13,28 @@ namespace jngl {
 
 Effect::~Effect() = default;
 
+void Effect::updateModelview(Mat3& modelview) const {
+}
+
+UpdateModelview::UpdateModelview(std::function<void(float t, Mat3&)> function)
+: function(std::move(function)) {
+}
+
+auto UpdateModelview::step() -> Action {
+	time += 1.f / static_cast<float>(getStepsPerSecond());
+	return Action::NONE;
+}
+
+void UpdateModelview::beginDraw() const {
+}
+
+void UpdateModelview::endDraw() const {
+}
+
+void UpdateModelview::updateModelview(Mat3& modelview) const {
+	function(time, modelview);
+}
+
 Zoom::Zoom(std::function<float(float)> function) : function(std::move(function)) {
 }
 

src/jngl/effects.hpp

@@ -10,6 +10,8 @@
 
 namespace jngl {
 
+class Mat3;
+
 /// Base class for effects that can be applied to jngl::Widget
 class Effect {
 public:
@@ -23,6 +25,33 @@ class Effect {
 	[[nodiscard]] virtual Action step() = 0;
 	virtual void beginDraw() const = 0;
 	virtual void endDraw() const = 0;
+
+	/// Called before drawing the widget
+	virtual void updateModelview(Mat3& modelview) const;
+};
+
+class UpdateModelview : public Effect {
+public:
+	/// Pass a function that gets the time the effect is in use and a reference to the Modelview so
+	/// that it can update it
+	///
+	/// Wiggle effect example:
+	/// \code
+	/// widget->addEffect<jngl::UpdateModelview>([](float t, jngl::Mat3& modelview) {
+	/// 	float effectIntensity = std::max(std::sin(t * 3), 0.f);
+	/// 	modelview.rotate(std::sin(t * 50) * 0.08 * effectIntensity)
+	/// 	         .scale(1 + effectIntensity * 0.1);
+	/// });
+	/// \endcode
+	explicit UpdateModelview(std::function<void(float t, Mat3&)>);
+	Action step() override;
+	void beginDraw() const override;
+	void endDraw() const override;
+	void updateModelview(Mat3& modelview) const override;
+
+private:
+	std::function<void(float t, Mat3&)> function;
+	float time = 0;
 };
 
 /// Scales the ModelView matrix