flickable: inertial scrolling

Author: igagis

src/ruis/util/units.hpp

@@ -119,6 +119,7 @@ class units
 
 	/**
 	 * @brief Convert millimeters to pixels (dots).
+	 * The resulting value is rounded.
 	 * @param mm - value in millimeters.
 	 * @return Value in pixels.
 	 */
@@ -130,6 +131,7 @@ class units
 
 	/**
 	 * @brief Convert perception pixels to pixels.
+	 * The resulting value is rounded.
 	 * @param pp - value in perception pixels.
 	 * @return  Value in pixels.
 	 */

src/ruis/widget/base/touch/flickable.cpp

@@ -81,8 +81,8 @@ ruis::event_status flickable::on_mouse_button(const mouse_button_event& event)
 				utki::assert(event.action == button_action::release, SL);
 				this->cur_state = state::inertial_scrolling;
 
-				this->velocity = this->calculate_touch_velocity_px_per_ms();
-				std::cout << "touch release, vel = " << this->velocity << std::endl;
+				this->velocity_px_per_ms = this->calculate_touch_velocity_px_per_ms();
+				// std::cout << "touch release, vel = " << this->velocity_px_per_ms << std::endl;
 
 				this->touch_history.clear();
 
@@ -194,24 +194,30 @@ void flickable::update(uint32_t dt_ms)
 {
 	utki::assert(this->cur_state == state::inertial_scrolling, SL);
 
-	auto scrolled_by = this->flickable_scroll_by(-this->velocity * dt_ms);
+	auto scrolled_by = this->flickable_scroll_by(-this->velocity_px_per_ms * ruis::real(dt_ms));
 
 	using std::copysign;
-	auto velocity_sign = this->velocity.comp_op([](const auto& e){return copysign(real(1), e);});
+	auto velocity_sign = this->velocity_px_per_ms.comp_op([](const auto& e){return copysign(real(1), e);});
 
-	auto prev_velocity = this->velocity;
+	auto prev_velocity_px_per_ms = this->velocity_px_per_ms;
 
-	this->velocity -= velocity_sign * this->friction * dt_ms;
+	// std::cout << "velocity_sign = " << velocity_sign << ", this->friction = " << this->friction << ", dt_ms = " << dt_ms << std::endl;
+	auto dv = velocity_sign * this->friction * ruis::real(dt_ms);
+	// std::cout << "dv = " << dv << std::endl;
+	this->velocity_px_per_ms -= dv;
 
-	for(auto [prev, cur, scrolled] : utki::views::zip(prev_velocity, this->velocity, scrolled_by)){
+	// std::cout << "this->velocity_px_per_ms = " << this->velocity_px_per_ms << std::endl;
+
+	for(auto [prev, cur, scrolled_px] : utki::views::zip(prev_velocity_px_per_ms, this->velocity_px_per_ms, scrolled_by)){
 		using std::signbit;
-		if(signbit(prev) != signbit(cur) || scrolled == 0){
+		if(signbit(prev) != signbit(cur) || scrolled_px == 0){
 			cur = ruis::real(0);
 		}
 	}
 
-	if(this->velocity.is_zero()){
+	if(this->velocity_px_per_ms.is_zero()){
 		this->context.get().updater.get().stop(*this);
+		this->cur_state = state::idle;
 	}
 }
 

src/ruis/widget/base/touch/flickable.hpp

@@ -33,7 +33,7 @@ class flickable :
 {
 	constexpr static auto scroll_threshold_pp = 5;
 
-	// TODO: convert from scroll_threshold_pp in on_reload()?
+	// TODO: convert from scroll_threshold_pp if dots per pp changes
 	// NOLINTNEXTLINE(cppcoreguidelines-avoid-magic-numbers, "constant value")
 	real scroll_threshold_px = 10;
 
@@ -63,8 +63,8 @@ class flickable :
 	ruis::vec2 calculate_touch_velocity_for_at_least_3_points_using_ols_method_px_per_ms();
 
 	// inertial scrolling state
-	ruis::vec2 velocity;
-	ruis::real friction = this->context.get().units.pp_to_px(0.1);
+	ruis::real friction = this->context.get().units.dots_per_pp() * 0.005; // TODO: update if dots per pp changes
+	ruis::vec2 velocity_px_per_ms;
 
 public:
 	event_status on_mouse_button(const mouse_button_event& event) override;