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LibWeb: Move FFC layout algorithm step 6 to a separate function

This commit is contained in:
Andreas Kling 2021-10-13 22:11:50 +02:00
parent 0fd25fcbbc
commit 0c0df78030
2 changed files with 173 additions and 166 deletions

View file

@ -133,172 +133,8 @@ void FlexFormattingContext::run(Box& flex_container, LayoutMode)
// After this step no additional items are to be added to flex_lines or any of its items!
auto flex_lines = collect_flex_items_into_flex_lines(flex_container, flex_items, main_available_size);
// 6. Resolve the flexible lengths https://www.w3.org/TR/css-flexbox-1/#resolve-flexible-lengths
enum FlexFactor {
FlexGrowFactor,
FlexShrinkFactor
};
FlexFactor used_flex_factor;
// 6.1. Determine used flex factor
for (auto& flex_line : flex_lines) {
size_t number_of_unfrozen_items_on_line = flex_line.items.size();
float sum_of_hypothetical_main_sizes = 0;
for (auto& flex_item : flex_line.items) {
sum_of_hypothetical_main_sizes += flex_item->hypothetical_main_size;
}
if (sum_of_hypothetical_main_sizes < main_available_size)
used_flex_factor = FlexFactor::FlexGrowFactor;
else
used_flex_factor = FlexFactor::FlexShrinkFactor;
for (auto& flex_item : flex_line.items) {
if (used_flex_factor == FlexFactor::FlexGrowFactor)
flex_item->flex_factor = flex_item->box.computed_values().flex_grow_factor();
else if (used_flex_factor == FlexFactor::FlexShrinkFactor)
flex_item->flex_factor = flex_item->box.computed_values().flex_shrink_factor();
}
// 6.2. Size inflexible items
auto freeze_item_setting_target_main_size_to_hypothetical_main_size = [&number_of_unfrozen_items_on_line](FlexItem& item) {
item.target_main_size = item.hypothetical_main_size;
number_of_unfrozen_items_on_line--;
item.frozen = true;
};
for (auto& flex_item : flex_line.items) {
if (flex_item->flex_factor.has_value() && flex_item->flex_factor.value() == 0) {
freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
} else if (used_flex_factor == FlexFactor::FlexGrowFactor) {
// FIXME: Spec doesn't include the == case, but we take a too basic approach to calculating the values used so this is appropriate
if (flex_item->flex_base_size > flex_item->hypothetical_main_size) {
freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
}
} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
if (flex_item->flex_base_size < flex_item->hypothetical_main_size) {
freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
}
}
}
// 6.3. Calculate initial free space
auto calculate_free_space = [&]() {
float sum_of_items_on_line = 0;
for (auto& flex_item : flex_line.items) {
if (flex_item->frozen)
sum_of_items_on_line += flex_item->target_main_size;
else
sum_of_items_on_line += flex_item->flex_base_size;
}
return main_available_size - sum_of_items_on_line;
};
float initial_free_space = calculate_free_space();
// 6.4 Loop
auto for_each_unfrozen_item = [&flex_line](auto callback) {
for (auto& flex_item : flex_line.items) {
if (!flex_item->frozen)
callback(flex_item);
}
};
while (number_of_unfrozen_items_on_line > 0) {
// b Calculate the remaining free space
auto remaining_free_space = calculate_free_space();
float sum_of_unfrozen_flex_items_flex_factors = 0;
for_each_unfrozen_item([&](FlexItem* item) {
sum_of_unfrozen_flex_items_flex_factors += item->flex_factor.value_or(1);
});
if (sum_of_unfrozen_flex_items_flex_factors < 1) {
auto intermediate_free_space = initial_free_space * sum_of_unfrozen_flex_items_flex_factors;
if (AK::abs(intermediate_free_space) < AK::abs(remaining_free_space))
remaining_free_space = intermediate_free_space;
}
// c Distribute free space proportional to the flex factors
if (remaining_free_space != 0) {
if (used_flex_factor == FlexFactor::FlexGrowFactor) {
float sum_of_flex_grow_factor_of_unfrozen_items = sum_of_unfrozen_flex_items_flex_factors;
for_each_unfrozen_item([&](FlexItem* flex_item) {
float ratio = flex_item->flex_factor.value_or(1) / sum_of_flex_grow_factor_of_unfrozen_items;
flex_item->target_main_size = flex_item->flex_base_size + (remaining_free_space * ratio);
});
} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
float sum_of_scaled_flex_shrink_factor_of_unfrozen_items = 0;
for_each_unfrozen_item([&](FlexItem* flex_item) {
flex_item->scaled_flex_shrink_factor = flex_item->flex_factor.value_or(1) * flex_item->flex_base_size;
sum_of_scaled_flex_shrink_factor_of_unfrozen_items += flex_item->scaled_flex_shrink_factor;
});
for_each_unfrozen_item([&](FlexItem* flex_item) {
float ratio = 1.0f;
if (sum_of_scaled_flex_shrink_factor_of_unfrozen_items != 0.0f)
ratio = flex_item->scaled_flex_shrink_factor / sum_of_scaled_flex_shrink_factor_of_unfrozen_items;
flex_item->target_main_size = flex_item->flex_base_size - (AK::abs(remaining_free_space) * ratio);
});
}
} else {
// This isn't spec but makes sense.
for_each_unfrozen_item([&](FlexItem* flex_item) {
flex_item->target_main_size = flex_item->flex_base_size;
});
}
// d Fix min/max violations.
float adjustments = 0.0f;
for_each_unfrozen_item([&](FlexItem* item) {
auto min_main = has_main_min_size(item->box)
? specified_main_min_size(item->box)
: 0;
auto max_main = has_main_max_size(item->box)
? specified_main_max_size(item->box)
: NumericLimits<float>::max();
float original_target_size = item->target_main_size;
if (item->target_main_size < min_main) {
item->target_main_size = min_main;
item->is_min_violation = true;
}
if (item->target_main_size > max_main) {
item->target_main_size = max_main;
item->is_max_violation = true;
}
float delta = item->target_main_size - original_target_size;
adjustments += delta;
});
// e Freeze over-flexed items
float total_violation = adjustments;
if (total_violation == 0) {
for_each_unfrozen_item([&](FlexItem* item) {
--number_of_unfrozen_items_on_line;
item->frozen = true;
});
} else if (total_violation > 0) {
for_each_unfrozen_item([&](FlexItem* item) {
if (item->is_min_violation) {
--number_of_unfrozen_items_on_line;
item->frozen = true;
}
});
} else if (total_violation < 0) {
for_each_unfrozen_item([&](FlexItem* item) {
if (item->is_max_violation) {
--number_of_unfrozen_items_on_line;
item->frozen = true;
}
});
}
}
// 6.5.
for (auto& flex_item : flex_line.items) {
flex_item->main_size = flex_item->target_main_size;
};
}
// 6. Resolve the flexible lengths
resolve_flexible_lengths(flex_lines, main_available_size);
// Cross Size Determination
// 7. Determine the hypothetical cross size of each item
@ -930,4 +766,173 @@ Vector<FlexLine> FlexFormattingContext::collect_flex_items_into_flex_lines(Box c
return flex_lines;
}
// https://www.w3.org/TR/css-flexbox-1/#resolve-flexible-lengths
void FlexFormattingContext::resolve_flexible_lengths(Vector<FlexLine>& flex_lines, float main_available_size)
{
enum FlexFactor {
FlexGrowFactor,
FlexShrinkFactor
};
FlexFactor used_flex_factor;
// 6.1. Determine used flex factor
for (auto& flex_line : flex_lines) {
size_t number_of_unfrozen_items_on_line = flex_line.items.size();
float sum_of_hypothetical_main_sizes = 0;
for (auto& flex_item : flex_line.items) {
sum_of_hypothetical_main_sizes += flex_item->hypothetical_main_size;
}
if (sum_of_hypothetical_main_sizes < main_available_size)
used_flex_factor = FlexFactor::FlexGrowFactor;
else
used_flex_factor = FlexFactor::FlexShrinkFactor;
for (auto& flex_item : flex_line.items) {
if (used_flex_factor == FlexFactor::FlexGrowFactor)
flex_item->flex_factor = flex_item->box.computed_values().flex_grow_factor();
else if (used_flex_factor == FlexFactor::FlexShrinkFactor)
flex_item->flex_factor = flex_item->box.computed_values().flex_shrink_factor();
}
// 6.2. Size inflexible items
auto freeze_item_setting_target_main_size_to_hypothetical_main_size = [&number_of_unfrozen_items_on_line](FlexItem& item) {
item.target_main_size = item.hypothetical_main_size;
number_of_unfrozen_items_on_line--;
item.frozen = true;
};
for (auto& flex_item : flex_line.items) {
if (flex_item->flex_factor.has_value() && flex_item->flex_factor.value() == 0) {
freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
} else if (used_flex_factor == FlexFactor::FlexGrowFactor) {
// FIXME: Spec doesn't include the == case, but we take a too basic approach to calculating the values used so this is appropriate
if (flex_item->flex_base_size > flex_item->hypothetical_main_size) {
freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
}
} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
if (flex_item->flex_base_size < flex_item->hypothetical_main_size) {
freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
}
}
}
// 6.3. Calculate initial free space
auto calculate_free_space = [&]() {
float sum_of_items_on_line = 0;
for (auto& flex_item : flex_line.items) {
if (flex_item->frozen)
sum_of_items_on_line += flex_item->target_main_size;
else
sum_of_items_on_line += flex_item->flex_base_size;
}
return main_available_size - sum_of_items_on_line;
};
float initial_free_space = calculate_free_space();
// 6.4 Loop
auto for_each_unfrozen_item = [&flex_line](auto callback) {
for (auto& flex_item : flex_line.items) {
if (!flex_item->frozen)
callback(flex_item);
}
};
while (number_of_unfrozen_items_on_line > 0) {
// b Calculate the remaining free space
auto remaining_free_space = calculate_free_space();
float sum_of_unfrozen_flex_items_flex_factors = 0;
for_each_unfrozen_item([&](FlexItem* item) {
sum_of_unfrozen_flex_items_flex_factors += item->flex_factor.value_or(1);
});
if (sum_of_unfrozen_flex_items_flex_factors < 1) {
auto intermediate_free_space = initial_free_space * sum_of_unfrozen_flex_items_flex_factors;
if (AK::abs(intermediate_free_space) < AK::abs(remaining_free_space))
remaining_free_space = intermediate_free_space;
}
// c Distribute free space proportional to the flex factors
if (remaining_free_space != 0) {
if (used_flex_factor == FlexFactor::FlexGrowFactor) {
float sum_of_flex_grow_factor_of_unfrozen_items = sum_of_unfrozen_flex_items_flex_factors;
for_each_unfrozen_item([&](FlexItem* flex_item) {
float ratio = flex_item->flex_factor.value_or(1) / sum_of_flex_grow_factor_of_unfrozen_items;
flex_item->target_main_size = flex_item->flex_base_size + (remaining_free_space * ratio);
});
} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
float sum_of_scaled_flex_shrink_factor_of_unfrozen_items = 0;
for_each_unfrozen_item([&](FlexItem* flex_item) {
flex_item->scaled_flex_shrink_factor = flex_item->flex_factor.value_or(1) * flex_item->flex_base_size;
sum_of_scaled_flex_shrink_factor_of_unfrozen_items += flex_item->scaled_flex_shrink_factor;
});
for_each_unfrozen_item([&](FlexItem* flex_item) {
float ratio = 1.0f;
if (sum_of_scaled_flex_shrink_factor_of_unfrozen_items != 0.0f)
ratio = flex_item->scaled_flex_shrink_factor / sum_of_scaled_flex_shrink_factor_of_unfrozen_items;
flex_item->target_main_size = flex_item->flex_base_size - (AK::abs(remaining_free_space) * ratio);
});
}
} else {
// This isn't spec but makes sense.
for_each_unfrozen_item([&](FlexItem* flex_item) {
flex_item->target_main_size = flex_item->flex_base_size;
});
}
// d Fix min/max violations.
float adjustments = 0.0f;
for_each_unfrozen_item([&](FlexItem* item) {
auto min_main = has_main_min_size(item->box)
? specified_main_min_size(item->box)
: 0;
auto max_main = has_main_max_size(item->box)
? specified_main_max_size(item->box)
: NumericLimits<float>::max();
float original_target_size = item->target_main_size;
if (item->target_main_size < min_main) {
item->target_main_size = min_main;
item->is_min_violation = true;
}
if (item->target_main_size > max_main) {
item->target_main_size = max_main;
item->is_max_violation = true;
}
float delta = item->target_main_size - original_target_size;
adjustments += delta;
});
// e Freeze over-flexed items
float total_violation = adjustments;
if (total_violation == 0) {
for_each_unfrozen_item([&](FlexItem* item) {
--number_of_unfrozen_items_on_line;
item->frozen = true;
});
} else if (total_violation > 0) {
for_each_unfrozen_item([&](FlexItem* item) {
if (item->is_min_violation) {
--number_of_unfrozen_items_on_line;
item->frozen = true;
}
});
} else if (total_violation < 0) {
for_each_unfrozen_item([&](FlexItem* item) {
if (item->is_max_violation) {
--number_of_unfrozen_items_on_line;
item->frozen = true;
}
});
}
}
// 6.5.
for (auto& flex_item : flex_line.items) {
flex_item->main_size = flex_item->target_main_size;
}
}
}
}