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https://github.com/RGBCube/serenity
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LibWeb: Move FFC layout algorithm step 6 to a separate function
This commit is contained in:
Andreas Kling
parent
0fd25fcbbc
commit
0c0df78030
2 changed files with 173 additions and 166 deletions
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@ -133,172 +133,8 @@ void FlexFormattingContext::run(Box& flex_container, LayoutMode)
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// After this step no additional items are to be added to flex_lines or any of its items!
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auto flex_lines = collect_flex_items_into_flex_lines(flex_container, flex_items, main_available_size);
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// 6. Resolve the flexible lengths https://www.w3.org/TR/css-flexbox-1/#resolve-flexible-lengths
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enum FlexFactor {
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FlexGrowFactor,
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FlexShrinkFactor
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};
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FlexFactor used_flex_factor;
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// 6.1. Determine used flex factor
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for (auto& flex_line : flex_lines) {
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size_t number_of_unfrozen_items_on_line = flex_line.items.size();
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float sum_of_hypothetical_main_sizes = 0;
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for (auto& flex_item : flex_line.items) {
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sum_of_hypothetical_main_sizes += flex_item->hypothetical_main_size;
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}
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if (sum_of_hypothetical_main_sizes < main_available_size)
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used_flex_factor = FlexFactor::FlexGrowFactor;
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else
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used_flex_factor = FlexFactor::FlexShrinkFactor;
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for (auto& flex_item : flex_line.items) {
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if (used_flex_factor == FlexFactor::FlexGrowFactor)
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flex_item->flex_factor = flex_item->box.computed_values().flex_grow_factor();
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else if (used_flex_factor == FlexFactor::FlexShrinkFactor)
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flex_item->flex_factor = flex_item->box.computed_values().flex_shrink_factor();
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}
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// 6.2. Size inflexible items
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auto freeze_item_setting_target_main_size_to_hypothetical_main_size = [&number_of_unfrozen_items_on_line](FlexItem& item) {
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item.target_main_size = item.hypothetical_main_size;
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number_of_unfrozen_items_on_line--;
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item.frozen = true;
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};
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for (auto& flex_item : flex_line.items) {
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if (flex_item->flex_factor.has_value() && flex_item->flex_factor.value() == 0) {
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freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
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} else if (used_flex_factor == FlexFactor::FlexGrowFactor) {
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// FIXME: Spec doesn't include the == case, but we take a too basic approach to calculating the values used so this is appropriate
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if (flex_item->flex_base_size > flex_item->hypothetical_main_size) {
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freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
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}
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} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
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if (flex_item->flex_base_size < flex_item->hypothetical_main_size) {
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freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
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}
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}
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}
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// 6.3. Calculate initial free space
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auto calculate_free_space = [&]() {
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float sum_of_items_on_line = 0;
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for (auto& flex_item : flex_line.items) {
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if (flex_item->frozen)
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sum_of_items_on_line += flex_item->target_main_size;
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else
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sum_of_items_on_line += flex_item->flex_base_size;
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}
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return main_available_size - sum_of_items_on_line;
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};
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float initial_free_space = calculate_free_space();
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// 6.4 Loop
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auto for_each_unfrozen_item = [&flex_line](auto callback) {
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for (auto& flex_item : flex_line.items) {
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if (!flex_item->frozen)
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callback(flex_item);
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}
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};
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while (number_of_unfrozen_items_on_line > 0) {
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// b Calculate the remaining free space
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auto remaining_free_space = calculate_free_space();
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float sum_of_unfrozen_flex_items_flex_factors = 0;
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for_each_unfrozen_item([&](FlexItem* item) {
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sum_of_unfrozen_flex_items_flex_factors += item->flex_factor.value_or(1);
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});
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if (sum_of_unfrozen_flex_items_flex_factors < 1) {
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auto intermediate_free_space = initial_free_space * sum_of_unfrozen_flex_items_flex_factors;
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if (AK::abs(intermediate_free_space) < AK::abs(remaining_free_space))
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remaining_free_space = intermediate_free_space;
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}
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// c Distribute free space proportional to the flex factors
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if (remaining_free_space != 0) {
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if (used_flex_factor == FlexFactor::FlexGrowFactor) {
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float sum_of_flex_grow_factor_of_unfrozen_items = sum_of_unfrozen_flex_items_flex_factors;
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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float ratio = flex_item->flex_factor.value_or(1) / sum_of_flex_grow_factor_of_unfrozen_items;
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flex_item->target_main_size = flex_item->flex_base_size + (remaining_free_space * ratio);
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});
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} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
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float sum_of_scaled_flex_shrink_factor_of_unfrozen_items = 0;
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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flex_item->scaled_flex_shrink_factor = flex_item->flex_factor.value_or(1) * flex_item->flex_base_size;
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sum_of_scaled_flex_shrink_factor_of_unfrozen_items += flex_item->scaled_flex_shrink_factor;
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});
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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float ratio = 1.0f;
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if (sum_of_scaled_flex_shrink_factor_of_unfrozen_items != 0.0f)
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ratio = flex_item->scaled_flex_shrink_factor / sum_of_scaled_flex_shrink_factor_of_unfrozen_items;
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flex_item->target_main_size = flex_item->flex_base_size - (AK::abs(remaining_free_space) * ratio);
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});
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}
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} else {
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// This isn't spec but makes sense.
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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flex_item->target_main_size = flex_item->flex_base_size;
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});
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}
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// d Fix min/max violations.
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float adjustments = 0.0f;
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for_each_unfrozen_item([&](FlexItem* item) {
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auto min_main = has_main_min_size(item->box)
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? specified_main_min_size(item->box)
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: 0;
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auto max_main = has_main_max_size(item->box)
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? specified_main_max_size(item->box)
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: NumericLimits<float>::max();
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float original_target_size = item->target_main_size;
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if (item->target_main_size < min_main) {
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item->target_main_size = min_main;
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item->is_min_violation = true;
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}
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if (item->target_main_size > max_main) {
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item->target_main_size = max_main;
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item->is_max_violation = true;
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}
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float delta = item->target_main_size - original_target_size;
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adjustments += delta;
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});
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// e Freeze over-flexed items
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float total_violation = adjustments;
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if (total_violation == 0) {
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for_each_unfrozen_item([&](FlexItem* item) {
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--number_of_unfrozen_items_on_line;
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item->frozen = true;
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});
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} else if (total_violation > 0) {
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for_each_unfrozen_item([&](FlexItem* item) {
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if (item->is_min_violation) {
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--number_of_unfrozen_items_on_line;
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item->frozen = true;
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}
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});
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} else if (total_violation < 0) {
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for_each_unfrozen_item([&](FlexItem* item) {
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if (item->is_max_violation) {
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--number_of_unfrozen_items_on_line;
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item->frozen = true;
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}
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});
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}
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}
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// 6.5.
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for (auto& flex_item : flex_line.items) {
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flex_item->main_size = flex_item->target_main_size;
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};
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}
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// 6. Resolve the flexible lengths
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resolve_flexible_lengths(flex_lines, main_available_size);
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// Cross Size Determination
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// 7. Determine the hypothetical cross size of each item
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@ -930,4 +766,173 @@ Vector<FlexLine> FlexFormattingContext::collect_flex_items_into_flex_lines(Box c
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return flex_lines;
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}
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// https://www.w3.org/TR/css-flexbox-1/#resolve-flexible-lengths
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void FlexFormattingContext::resolve_flexible_lengths(Vector<FlexLine>& flex_lines, float main_available_size)
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{
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enum FlexFactor {
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FlexGrowFactor,
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FlexShrinkFactor
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};
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FlexFactor used_flex_factor;
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// 6.1. Determine used flex factor
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for (auto& flex_line : flex_lines) {
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size_t number_of_unfrozen_items_on_line = flex_line.items.size();
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float sum_of_hypothetical_main_sizes = 0;
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for (auto& flex_item : flex_line.items) {
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sum_of_hypothetical_main_sizes += flex_item->hypothetical_main_size;
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}
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if (sum_of_hypothetical_main_sizes < main_available_size)
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used_flex_factor = FlexFactor::FlexGrowFactor;
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else
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used_flex_factor = FlexFactor::FlexShrinkFactor;
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for (auto& flex_item : flex_line.items) {
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if (used_flex_factor == FlexFactor::FlexGrowFactor)
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flex_item->flex_factor = flex_item->box.computed_values().flex_grow_factor();
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else if (used_flex_factor == FlexFactor::FlexShrinkFactor)
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flex_item->flex_factor = flex_item->box.computed_values().flex_shrink_factor();
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}
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// 6.2. Size inflexible items
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auto freeze_item_setting_target_main_size_to_hypothetical_main_size = [&number_of_unfrozen_items_on_line](FlexItem& item) {
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item.target_main_size = item.hypothetical_main_size;
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number_of_unfrozen_items_on_line--;
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item.frozen = true;
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};
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for (auto& flex_item : flex_line.items) {
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if (flex_item->flex_factor.has_value() && flex_item->flex_factor.value() == 0) {
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freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
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} else if (used_flex_factor == FlexFactor::FlexGrowFactor) {
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// FIXME: Spec doesn't include the == case, but we take a too basic approach to calculating the values used so this is appropriate
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if (flex_item->flex_base_size > flex_item->hypothetical_main_size) {
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freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
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}
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} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
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if (flex_item->flex_base_size < flex_item->hypothetical_main_size) {
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freeze_item_setting_target_main_size_to_hypothetical_main_size(*flex_item);
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}
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}
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}
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// 6.3. Calculate initial free space
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auto calculate_free_space = [&]() {
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float sum_of_items_on_line = 0;
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for (auto& flex_item : flex_line.items) {
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if (flex_item->frozen)
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sum_of_items_on_line += flex_item->target_main_size;
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else
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sum_of_items_on_line += flex_item->flex_base_size;
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}
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return main_available_size - sum_of_items_on_line;
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};
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float initial_free_space = calculate_free_space();
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// 6.4 Loop
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auto for_each_unfrozen_item = [&flex_line](auto callback) {
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for (auto& flex_item : flex_line.items) {
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if (!flex_item->frozen)
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callback(flex_item);
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}
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};
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while (number_of_unfrozen_items_on_line > 0) {
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// b Calculate the remaining free space
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auto remaining_free_space = calculate_free_space();
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float sum_of_unfrozen_flex_items_flex_factors = 0;
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for_each_unfrozen_item([&](FlexItem* item) {
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sum_of_unfrozen_flex_items_flex_factors += item->flex_factor.value_or(1);
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});
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if (sum_of_unfrozen_flex_items_flex_factors < 1) {
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auto intermediate_free_space = initial_free_space * sum_of_unfrozen_flex_items_flex_factors;
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if (AK::abs(intermediate_free_space) < AK::abs(remaining_free_space))
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remaining_free_space = intermediate_free_space;
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}
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// c Distribute free space proportional to the flex factors
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if (remaining_free_space != 0) {
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if (used_flex_factor == FlexFactor::FlexGrowFactor) {
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float sum_of_flex_grow_factor_of_unfrozen_items = sum_of_unfrozen_flex_items_flex_factors;
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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float ratio = flex_item->flex_factor.value_or(1) / sum_of_flex_grow_factor_of_unfrozen_items;
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flex_item->target_main_size = flex_item->flex_base_size + (remaining_free_space * ratio);
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});
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} else if (used_flex_factor == FlexFactor::FlexShrinkFactor) {
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float sum_of_scaled_flex_shrink_factor_of_unfrozen_items = 0;
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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flex_item->scaled_flex_shrink_factor = flex_item->flex_factor.value_or(1) * flex_item->flex_base_size;
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sum_of_scaled_flex_shrink_factor_of_unfrozen_items += flex_item->scaled_flex_shrink_factor;
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});
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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float ratio = 1.0f;
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if (sum_of_scaled_flex_shrink_factor_of_unfrozen_items != 0.0f)
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ratio = flex_item->scaled_flex_shrink_factor / sum_of_scaled_flex_shrink_factor_of_unfrozen_items;
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flex_item->target_main_size = flex_item->flex_base_size - (AK::abs(remaining_free_space) * ratio);
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});
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}
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} else {
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// This isn't spec but makes sense.
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for_each_unfrozen_item([&](FlexItem* flex_item) {
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flex_item->target_main_size = flex_item->flex_base_size;
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});
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}
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// d Fix min/max violations.
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float adjustments = 0.0f;
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for_each_unfrozen_item([&](FlexItem* item) {
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auto min_main = has_main_min_size(item->box)
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? specified_main_min_size(item->box)
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: 0;
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auto max_main = has_main_max_size(item->box)
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? specified_main_max_size(item->box)
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: NumericLimits<float>::max();
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float original_target_size = item->target_main_size;
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if (item->target_main_size < min_main) {
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item->target_main_size = min_main;
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item->is_min_violation = true;
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}
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if (item->target_main_size > max_main) {
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item->target_main_size = max_main;
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item->is_max_violation = true;
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}
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float delta = item->target_main_size - original_target_size;
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adjustments += delta;
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});
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// e Freeze over-flexed items
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float total_violation = adjustments;
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if (total_violation == 0) {
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for_each_unfrozen_item([&](FlexItem* item) {
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--number_of_unfrozen_items_on_line;
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item->frozen = true;
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});
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} else if (total_violation > 0) {
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for_each_unfrozen_item([&](FlexItem* item) {
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if (item->is_min_violation) {
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--number_of_unfrozen_items_on_line;
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item->frozen = true;
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}
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});
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} else if (total_violation < 0) {
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for_each_unfrozen_item([&](FlexItem* item) {
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if (item->is_max_violation) {
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--number_of_unfrozen_items_on_line;
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item->frozen = true;
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}
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});
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}
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}
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// 6.5.
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for (auto& flex_item : flex_line.items) {
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flex_item->main_size = flex_item->target_main_size;
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}
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}
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}
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}
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