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LibWeb: Start transitions when affected properties change

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Co-authored-by: Matthew Olsson <matthewcolsson@gmail.com>
This commit is contained in:
Sam Atkins 2024-09-19 14:13:20 +01:00 • committed by Andreas Kling
commit a1fca1a7f3
Notes: github-actions[bot] 2024-09-22 04:42:46 +00:00
8 changed files with 380 additions and 11 deletions
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201
Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
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@ -32,6 +32,7 @@
#include <LibWeb/CSS/CSSLayerBlockRule.h>
#include <LibWeb/CSS/CSSLayerStatementRule.h>
#include <LibWeb/CSS/CSSStyleRule.h>
#include <LibWeb/CSS/CSSTransition.h>
#include <LibWeb/CSS/Interpolation.h>
#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/CSS/SelectorEngine.h>
@ -1294,6 +1295,198 @@ static void compute_transitioned_properties(StyleProperties const& style, DOM::E
}
}
// https://drafts.csswg.org/css-transitions/#starting
void StyleComputer::start_needed_transitions(StyleProperties const& previous_style, StyleProperties& new_style, DOM::Element& element, Optional<Selector::PseudoElement::Type> pseudo_element) const
{
// FIXME: Implement transitions for pseudo-elements
(void)pseudo_element;
// https://drafts.csswg.org/css-transitions/#transition-combined-duration
auto combined_duration = [](Animations::Animatable::TransitionAttributes const& transition_attributes) {
// Define the combined duration of the transition as the sum of max(matching transition duration, 0s) and the matching transition delay.
return max(transition_attributes.duration, 0) + transition_attributes.delay;
};
// For each element and property, the implementation must act as follows:
auto style_change_event_time = m_document->timeline()->current_time().value();
for (auto i = to_underlying(CSS::first_longhand_property_id); i <= to_underlying(CSS::last_longhand_property_id); ++i) {
auto property_id = static_cast<CSS::PropertyID>(i);
auto matching_transition_properties = element.property_transition_attributes(property_id);
auto before_change_value = previous_style.property(property_id, StyleProperties::WithAnimationsApplied::No);
auto after_change_value = new_style.property(property_id, StyleProperties::WithAnimationsApplied::No);
auto existing_transition = element.property_transition(property_id);
bool has_running_transition = existing_transition && !existing_transition->is_finished();
bool has_completed_transition = existing_transition && existing_transition->is_finished();
auto start_a_transition = [&](auto start_time, auto end_time, auto start_value, auto end_value, auto reversing_adjusted_start_value, auto reversing_shortening_factor) {
dbgln("Starting a transition of {} from {} to {}", string_from_property_id(property_id), start_value->to_string(), end_value->to_string());
auto transition = CSSTransition::start_a_transition(element, property_id, document().transition_generation(),
start_time, end_time, start_value, end_value, reversing_adjusted_start_value, reversing_shortening_factor);
// Immediately set the property's value to the transition's current value, to prevent single-frame jumps.
new_style.set_animated_property(property_id, transition->value_at_time(style_change_event_time));
};
// 1. If all of the following are true:
if (
// - the element does not have a running transition for the property,
(!has_running_transition) &&
// - the before-change style is different from the after-change style for that property, and the values for the property are transitionable,
(!before_change_value->equals(after_change_value) && property_values_are_transitionable(property_id, before_change_value, after_change_value)) &&
// - the element does not have a completed transition for the property
// or the end value of the completed transition is different from the after-change style for the property,
(!has_completed_transition || !existing_transition->transition_end_value()->equals(after_change_value)) &&
// - there is a matching transition-property value, and
(matching_transition_properties.has_value()) &&
// - the combined duration is greater than 0s,
(combined_duration(matching_transition_properties.value()) > 0)) {
dbgln("Transition step 1.");
// then implementations must remove the completed transition (if present) from the set of completed transitions
if (has_completed_transition)
element.remove_transition(property_id);
// and start a transition whose:
// - start time is the time of the style change event plus the matching transition delay,
auto start_time = style_change_event_time + matching_transition_properties->delay;
// - end time is the start time plus the matching transition duration,
auto end_time = start_time + matching_transition_properties->duration;
// - start value is the value of the transitioning property in the before-change style,
auto start_value = before_change_value;
// - end value is the value of the transitioning property in the after-change style,
auto end_value = after_change_value;
// - reversing-adjusted start value is the same as the start value, and
auto reversing_adjusted_start_value = start_value;
// - reversing shortening factor is 1.
double reversing_shortening_factor = 1;
start_a_transition(start_time, end_time, start_value, end_value, reversing_adjusted_start_value, reversing_shortening_factor);
}
// 2. Otherwise, if the element has a completed transition for the property
// and the end value of the completed transition is different from the after-change style for the property,
// then implementations must remove the completed transition from the set of completed transitions.
else if (has_completed_transition && !existing_transition->transition_end_value()->equals(after_change_value)) {
dbgln("Transition step 2.");
element.remove_transition(property_id);
}
// 3. If the element has a running transition or completed transition for the property,
// and there is not a matching transition-property value,
if (existing_transition && !matching_transition_properties.has_value()) {
// then implementations must cancel the running transition or remove the completed transition from the set of completed transitions.
dbgln("Transition step 3.");
if (has_running_transition)
existing_transition->cancel();
else
element.remove_transition(property_id);
}
// 4. If the element has a running transition for the property,
// there is a matching transition-property value,
// and the end value of the running transition is not equal to the value of the property in the after-change style, then:
if (has_running_transition && matching_transition_properties.has_value() && !existing_transition->transition_end_value()->equals(after_change_value)) {
dbgln("Transition step 4. existing end value = {}, after change value = {}", existing_transition->transition_end_value()->to_string(), after_change_value->to_string());
// 1. If the current value of the property in the running transition is equal to the value of the property in the after-change style,
// or if these two values are not transitionable,
// then implementations must cancel the running transition.
auto current_value = existing_transition->value_at_time(style_change_event_time);
if (current_value->equals(after_change_value) || !property_values_are_transitionable(property_id, current_value, after_change_value)) {
dbgln("Transition step 4.1");
existing_transition->cancel();
}
// 2. Otherwise, if the combined duration is less than or equal to 0s,
// or if the current value of the property in the running transition is not transitionable with the value of the property in the after-change style,
// then implementations must cancel the running transition.
else if ((combined_duration(matching_transition_properties.value()) <= 0)
|| !property_values_are_transitionable(property_id, current_value, after_change_value)) {
dbgln("Transition step 4.2");
existing_transition->cancel();
}
// 3. Otherwise, if the reversing-adjusted start value of the running transition is the same as the value of the property in the after-change style
// (see the section on reversing of transitions for why these case exists),
else if (existing_transition->reversing_adjusted_start_value()->equals(after_change_value)) {
dbgln("Transition step 4.3");
// implementations must cancel the running transition and start a new transition whose:
existing_transition->cancel();
// AD-HOC: Remove the cancelled transition, otherwise it breaks the invariant that there is only one
// running or completed transition for a property at once.
element.remove_transition(property_id);
// - reversing-adjusted start value is the end value of the running transition,
auto reversing_adjusted_start_value = existing_transition->transition_end_value();
// - reversing shortening factor is the absolute value, clamped to the range [0, 1], of the sum of:
// 1. the output of the timing function of the old transition at the time of the style change event,
// times the reversing shortening factor of the old transition
auto term_1 = existing_transition->timing_function_output_at_time(style_change_event_time) * existing_transition->reversing_shortening_factor();
// 2. 1 minus the reversing shortening factor of the old transition.
auto term_2 = 1 - existing_transition->reversing_shortening_factor();
double reversing_shortening_factor = clamp(abs(term_1 + term_2), 0.0, 1.0);
// - start time is the time of the style change event plus:
// 1. if the matching transition delay is nonnegative, the matching transition delay, or
// 2. if the matching transition delay is negative, the product of the new transition’s reversing shortening factor and the matching transition delay,
auto start_time = style_change_event_time
+ (matching_transition_properties->delay >= 0
? (matching_transition_properties->delay)
: (reversing_shortening_factor * matching_transition_properties->delay));
// - end time is the start time plus the product of the matching transition duration and the new transition’s reversing shortening factor,
auto end_time = start_time + (matching_transition_properties->duration * reversing_shortening_factor);
// - start value is the current value of the property in the running transition,
auto start_value = current_value;
// - end value is the value of the property in the after-change style,
auto end_value = after_change_value;
start_a_transition(start_time, end_time, start_value, end_value, reversing_adjusted_start_value, reversing_shortening_factor);
}
// 4. Otherwise,
else {
dbgln("Transition step 4.4");
// implementations must cancel the running transition and start a new transition whose:
existing_transition->cancel();
// AD-HOC: Remove the cancelled transition, otherwise it breaks the invariant that there is only one
// running or completed transition for a property at once.
element.remove_transition(property_id);
// - start time is the time of the style change event plus the matching transition delay,
auto start_time = style_change_event_time + matching_transition_properties->delay;
// - end time is the start time plus the matching transition duration,
auto end_time = start_time + matching_transition_properties->duration;
// - start value is the current value of the property in the running transition,
auto start_value = current_value;
// - end value is the value of the property in the after-change style,
auto end_value = after_change_value;
// - reversing-adjusted start value is the same as the start value, and
auto reversing_adjusted_start_value = start_value;
// - reversing shortening factor is 1.
double reversing_shortening_factor = 1;
start_a_transition(start_time, end_time, start_value, end_value, reversing_adjusted_start_value, reversing_shortening_factor);
}
}
}
}
// https://www.w3.org/TR/css-cascade/#cascading
// https://drafts.csswg.org/css-cascade-5/#layering
void StyleComputer::compute_cascaded_values(StyleProperties& style, DOM::Element& element, Optional<CSS::Selector::PseudoElement::Type> pseudo_element, bool& did_match_any_pseudo_element_rules, ComputeStyleMode mode) const
@ -1440,7 +1633,9 @@ void StyleComputer::compute_cascaded_values(StyleProperties& style, DOM::Element
// Important user agent declarations
cascade_declarations(style, element, pseudo_element, matching_rule_set.user_agent_rules, CascadeOrigin::UserAgent, Important::Yes);
// FIXME: Transition declarations [css-transitions-1]
// Transition declarations [css-transitions-1]
// Note that we have to do these after finishing computing the style,
// so they're not done here, but as the final step in compute_style_impl()
}
DOM::Element const* element_to_inherit_style_from(DOM::Element const* element, Optional<CSS::Selector::PseudoElement::Type> pseudo_element)
@ -2197,6 +2392,10 @@ RefPtr<StyleProperties> StyleComputer::compute_style_impl(DOM::Element& element,
// 9. Transition declarations [css-transitions-1]
// Theoretically this should be part of the cascade, but it works with computed values, which we don't have until now.
compute_transitioned_properties(style, element, pseudo_element);
if (auto const* previous_style = element.computed_css_values()) {
start_needed_transitions(*previous_style, style, element, pseudo_element);
}
return style;
}