litehtml-sys 0.2.4

#include "flex_line.h"
#include "flex_item.h"
#include "types.h"

void litehtml::flex_line::distribute_free_space(pixel_t container_main_size)
{
	// 1 Determine the used flex factor. Sum the outer hypothetical main sizes of all items on the line.
	// If the sum is less than the flex container’s inner main size, use the flex grow factor for the
	// rest of this algorithm; otherwise, use the flex shrink factor.

	if (main_size < container_main_size)
	{
		distribute_free_space_grow(container_main_size);
	} else
	{
		distribute_free_space_shrink(container_main_size);
	}
}

void litehtml::flex_line::distribute_free_space_grow(pixel_t container_main_size)
{
	pixel_t initial_free_space = container_main_size;

	bool all_inflexible = true;

	for (auto& item : items)
	{
		// 2. Size inflexible items. Freeze, setting its target main size to its hypothetical main size
		// any item that has a flex factor of zero
		// if using the flex grow factor: any item that has a flex base size greater than its hypothetical main size

		// 3. Calculate initial free space. Sum the outer sizes of all items on the line, and subtract this
		// from the flex container’s inner main size. For frozen items, use their outer target main size; for
		// other items, use their outer flex base size.

		if (item->grow == 0 || item->base_size > item->main_size)
		{
			item->frozen = true;
			item->clamp_state = flex_clamp_state_inflexible;
			initial_free_space -= item->main_size;
		} else
		{
			initial_free_space -= item->base_size;
			all_inflexible = false;
		}
	}

	// 4. Loop:

	// 4.a Check for flexible items. If all the flex items on the line are frozen, free space has been
	// distributed; exit this loop.

	if (all_inflexible) return;

	while (true)
	{
		// 4.b Calculate the remaining free space as for initial free space, above. If the sum of the
		// unfrozen flex items’ flex factors is less than one, multiply the initial free space by this sum.
		// If the magnitude of this value is less than the magnitude of the remaining free space, use
		// this as the remaining free space. 

		int sum_flex_grow_factor = 0;
		pixel_t remaining_free_space = container_main_size;

		for (auto& item : items)
		{
			if (item->frozen)
			{
				remaining_free_space -= item->main_size;
			} else
			{
				remaining_free_space -= item->base_size;
				sum_flex_grow_factor += item->grow;
			}
		}

		if (sum_flex_grow_factor < 1000)
		{
			pixel_t adjusted_free_space = initial_free_space * (pixel_t) sum_flex_grow_factor / (pixel_t) 1000;
			if (adjusted_free_space < remaining_free_space)
			{
				remaining_free_space = adjusted_free_space;
			}
		}

		// 4.c Distribute free space proportional to the flex factors.

		// If the remaining free space is zero
		// Do nothing.

		if (remaining_free_space != 0)
		{
			for (auto& item: items)
			{
				if (!item->frozen)
				{
					// If using the flex grow factor
					// Find the ratio of the item’s flex grow factor to the sum of the flex grow factors of all
					// unfrozen items on the line. Set the item’s target main size to its flex base size plus a
					// fraction of the remaining free space proportional to the ratio.

					item->main_size = item->base_size + remaining_free_space * (pixel_t) item->grow / (pixel_t) sum_flex_grow_factor;
				}
			}
		}

		if (fix_min_max_violations()) break;
	}
}

void litehtml::flex_line::distribute_free_space_shrink(pixel_t container_main_size)
{
	pixel_t initial_free_space = container_main_size;

	bool all_inflexible = true;

	for (auto& item : items)
	{
		// 2. Size inflexible items. Freeze, setting its target main size to its hypothetical main size
		// any item that has a flex factor of zero
		// if using the flex shrink factor: any item that has a flex base size smaller than its hypothetical main size

		// 3. Calculate initial free space. Sum the outer sizes of all items on the line, and subtract this
		// from the flex container’s inner main size. For frozen items, use their outer target main size; for
		// other items, use their outer flex base size.

		if (item->shrink == 0 || item->base_size < item->main_size)
		{
			item->frozen = true;
			item->clamp_state = flex_clamp_state_inflexible;
			initial_free_space -= item->main_size;
		} else
		{
			initial_free_space -= item->base_size;
			all_inflexible = false;
		}
	}

	// 4. Loop:

	// 4.a Check for flexible items. If all the flex items on the line are frozen, free space has been
	// distributed; exit this loop.

	if (all_inflexible) return;

	while (true)
	{
		// 4.b Calculate the remaining free space as for initial free space, above. If the sum of the
		// unfrozen flex items’ flex factors is less than one, multiply the initial free space by this sum.
		// If the magnitude of this value is less than the magnitude of the remaining free space, use
		// this as the remaining free space. 

		int sum_flex_shrink_factor = 0;
		pixel_t sum_scaled_flex_shrink_factor = 0;
		pixel_t remaining_free_space = container_main_size;

		for (auto& item : items)
		{
			if (item->frozen)
			{
				remaining_free_space -= item->main_size;
			} else
			{
				remaining_free_space -= item->base_size;
				sum_flex_shrink_factor += item->shrink;
				sum_scaled_flex_shrink_factor += item->scaled_flex_shrink_factor;
			}
		}

		if (sum_flex_shrink_factor < 1000)
		{
			pixel_t adjusted_free_space = initial_free_space * (pixel_t) sum_flex_shrink_factor / (pixel_t) 1000;
			if (adjusted_free_space > remaining_free_space)
			{
				remaining_free_space = adjusted_free_space;
			}
		}

		// 4.c Distribute free space proportional to the flex factors.

		// If the remaining free space is zero
		// Do nothing.

		if (remaining_free_space != 0)
		{
			for (auto& item: items)
			{
				if (!item->frozen)
				{
					// If using the flex shrink factor
					// For every unfrozen item on the line, multiply its flex shrink factor by its inner flex base
					// size, and note this as its scaled flex shrink factor. Find the ratio of the item’s scaled
					// flex shrink factor to the sum of the scaled flex shrink factors of all unfrozen items on
					// the line. Set the item’s target main size to its flex base size minus a fraction of the
					// absolute value of the remaining free space proportional to the ratio. 

					item->main_size = item->base_size + remaining_free_space * item->scaled_flex_shrink_factor / sum_scaled_flex_shrink_factor;
				}
			}
		}

		if (fix_min_max_violations()) break;
	}
}

bool litehtml::flex_line::fix_min_max_violations()
{
	// 4.d  Fix min/max violations. Clamp each non-frozen item’s target main size by its used min
	// and max main sizes and floor its content-box size at zero. If the item’s target main size was
	// made smaller by this, it’s a max violation. If the item’s target main size was made larger
	// by this, it’s a min violation.

	pixel_t total_violation = 0;

	for (auto& item : items)
	{
		if (!item->frozen)
		{
			if (item->main_size < item->min_size)
			{
				total_violation += item->min_size - item->main_size;
				item->main_size = item->min_size;
				item->clamp_state = flex_clamp_state_min_violation;
			} else if (!item->max_size.is_default() && item->main_size > item->max_size)
			{
				total_violation += item->max_size - item->main_size;
				item->main_size = item->max_size;
				item->clamp_state = flex_clamp_state_max_violation;
			}
		}
	}

	// 4.e Freeze over-flexed items. The total violation is the sum of the adjustments from the
	// previous step ∑(clamped size - unclamped size). If the total violation is:
	// Zero: Freeze all items.
	// Positive: Freeze all the items with min violations.
	// Negative: Freeze all the items with max violations.

	if (total_violation == 0)
	{
		return true;
	}

	bool all_frozen = true;

	flex_clamp_state state_to_freeze =
		total_violation > 0
		? flex_clamp_state_min_violation
		: flex_clamp_state_max_violation;

	for (auto& item : items)
	{
		if (!item->frozen)
		{
			if (item->clamp_state == state_to_freeze)
			{
				item->frozen = true;
			} else
			{
				all_frozen = false;
				item->clamp_state = flex_clamp_state_unclamped;
			}
		}
	}

	return all_frozen;
}

bool litehtml::flex_line::distribute_main_auto_margins(pixel_t free_main_size)
{
	if(free_main_size > 0 && (num_auto_margin_main_start || num_auto_margin_main_end))
	{
		pixel_t add =  free_main_size / (pixel_t) (items.size() * 2);
		for (auto &item: items)
		{
			if(!item->auto_margin_main_start.is_default())
			{
				item->auto_margin_main_start = add;
				item->main_size += add;
				main_size += add;
				free_main_size -= add;
			}
			if(!item->auto_margin_main_end.is_default())
			{
				item->auto_margin_main_end = add;
				item->main_size += add;
				main_size += add;
				free_main_size -= add;
			}
		}

		pixel_t ditribute_step = 1;
		while (free_main_size > 0)
		{
			for (auto &item: items)
			{
				if(!item->auto_margin_main_start.is_default())
				{
					item->auto_margin_main_start = item->auto_margin_main_start + ditribute_step;
					free_main_size -= ditribute_step;
					if(free_main_size < ditribute_step) break;
				}
				if(!item->auto_margin_main_end.is_default())
				{
					item->auto_margin_main_end = item->auto_margin_main_end + ditribute_step;
					free_main_size -= ditribute_step;
					if(free_main_size < ditribute_step) break;
				}
			}
		}
		return true;
	}
	return false;
}

void litehtml::flex_line::init(pixel_t container_main_size, bool fit_container, bool is_row_direction,
							   const litehtml::containing_block_context &self_size,
							   litehtml::formatting_context *fmt_ctx)
{
	if(!fit_container)
	{
		distribute_free_space(container_main_size);
	}

	cross_size = 0;
	main_size = 0;
	first_baseline.set(0, baseline::baseline_type_none);
	last_baseline.set(0, baseline::baseline_type_none);
	
	if(is_row_direction)
	{
		def_value<pixel_t> first_baseline_top = 0;
		def_value<pixel_t> first_baseline_bottom = 0;
		def_value<pixel_t> last_baseline_top = 0;
		def_value<pixel_t> last_baseline_bottom = 0;
		pixel_t non_baseline_height = 0;

		// Calculate maximum cross size
		def_value<pixel_t> max_cross_size(0);
		if(self_size.height.type != containing_block_context::cbc_value_type_auto)
		{
			max_cross_size = self_size.height;
		}
		if(self_size.max_height.type != containing_block_context::cbc_value_type_none)
		{
			if(max_cross_size.is_default())
			{
				max_cross_size = self_size.max_height;
			} else
			{
				max_cross_size = std::max((pixel_t) max_cross_size, (pixel_t) self_size.max_height);
			}
		}

		/// Render items into new size
		/// Find line cross_size
		/// Find line first/last baseline
		for (auto &item: items)
		{
			item->el->render(0,
							 0,
							 self_size.new_width(item->main_size - item->el->render_offset_width(), containing_block_context::size_mode_exact_width), fmt_ctx, false);

			if((item->align & 0xFF) == flex_align_items_baseline)
			{
				if(item->align & flex_align_items_last)
				{
					last_baseline.type(reverse_cross ? baseline::baseline_type_top : baseline::baseline_type_bottom);

					pixel_t top = -item->el->get_last_baseline();
					pixel_t bottom = top + item->el->height();

					if(last_baseline_top.is_default()) last_baseline_top = top;
					else last_baseline_top = std::min((pixel_t) last_baseline_top, top);

					if(last_baseline_bottom.is_default()) last_baseline_bottom = bottom;
					else last_baseline_bottom = std::max((pixel_t) last_baseline_bottom, bottom);
				} else
				{
					first_baseline.type(reverse_cross ? baseline::baseline_type_bottom : baseline::baseline_type_top);
					pixel_t top = -item->el->get_first_baseline();
					pixel_t bottom = top + item->el->height();

					if(first_baseline_top.is_default()) first_baseline_top = top;
					else first_baseline_top = std::min((pixel_t) first_baseline_top, top);

					if(first_baseline_bottom.is_default()) first_baseline_bottom = bottom;
					else first_baseline_bottom = std::max((pixel_t) first_baseline_bottom, bottom);
				}
			} else
			{
				non_baseline_height = std::max(non_baseline_height, item->el->height());
			}
			main_size += item->el->width();
		}

		cross_size = std::max(first_baseline_bottom - first_baseline_top,last_baseline_bottom - last_baseline_top);
		cross_size = std::max(cross_size, non_baseline_height);
		if(!max_cross_size.is_default() && cross_size > max_cross_size)
		{
			cross_size = max_cross_size;
		}

		first_baseline.calc(first_baseline_top, first_baseline_bottom);
		last_baseline.calc(last_baseline_top, last_baseline_bottom);
	} else
	{
		// Calculate maximum cross size
		def_value<pixel_t> max_cross_size(0);
		if(self_size.width.type != containing_block_context::cbc_value_type_auto)
		{
			max_cross_size = self_size.width;
		}
		if(self_size.max_width.type != containing_block_context::cbc_value_type_none)
		{
			if(max_cross_size.is_default())
			{
				max_cross_size = self_size.max_width;
			} else
			{
				max_cross_size = std::max((pixel_t) max_cross_size, (pixel_t) self_size.max_width);
			}
		}

		for (auto &item: items)
		{
			pixel_t el_ret_width = item->el->render(0,
												0,
												self_size, fmt_ctx, false);
			item->el->render(0,
							 0,
							 self_size.new_width_height(el_ret_width - item->el->content_offset_width(),
														item->main_size - item->el->content_offset_height(),
														containing_block_context::size_mode_exact_width |
														containing_block_context::size_mode_exact_height),
							 fmt_ctx, false);
			main_size += item->el->height();
			cross_size = std::max(cross_size, item->el->width());
		}
		if(!max_cross_size.is_default() && cross_size > max_cross_size)
		{
			cross_size = max_cross_size;
		}
	}
}

litehtml::pixel_t litehtml::flex_line::calculate_items_position(pixel_t container_main_size,
												  flex_justify_content justify_content,
												  bool is_row_direction,
												  const containing_block_context &self_size,
												  formatting_context *fmt_ctx)
{
	/// Distribute main axis free space for auto-margins
	pixel_t free_main_size = container_main_size - main_size;
	distribute_main_auto_margins(free_main_size);
	free_main_size = container_main_size - main_size;

	/// Fix justify-content property
	switch (justify_content)
	{
		case flex_justify_content_left:
		case flex_justify_content_right:
			if(!is_row_direction)
			{
				justify_content = flex_justify_content_start;
			}
			break;
		case flex_justify_content_space_between:
			// If the leftover free-space is negative or there is only a single flex item on the line, this
			// value is identical to flex-start.
			if(items.size() == 1 || free_main_size < 0)  justify_content = flex_justify_content_flex_start;
			break;
		case flex_justify_content_space_around:
		case flex_justify_content_space_evenly:
			// If the leftover free-space is negative or there is only a single flex item on the line, this
			// value is identical to center
			if(items.size() == 1 || free_main_size < 0)  justify_content = flex_justify_content_center;
			break;
		default:
			break;
	}

	/// Distribute free main size using justify-content property
	pixel_t main_pos = 0;
	pixel_t add_before_item = 0;
	pixel_t add_after_item = 0;
	pixel_t item_remainder = 0;

	/// find initial main position and spaces between items
	switch (justify_content)
	{

		case flex_justify_content_right:
			main_pos = free_main_size;
			break;
		case flex_justify_content_left:
		case flex_justify_content_start:
			main_pos = 0;
			break;
		case flex_justify_content_end:
			main_pos = free_main_size;
			break;
		case flex_justify_content_flex_end:
			if(!reverse_main)
			{
				main_pos = free_main_size;
			}
			break;
		case flex_justify_content_center:
			main_pos = free_main_size / 2;
			break;
		case flex_justify_content_space_between:
			add_after_item = free_main_size / (pixel_t) (items.size() - 1);
			item_remainder = free_main_size - (add_after_item * (pixel_t) (items.size() - 1));
			break;
		case flex_justify_content_space_around:
			add_after_item = add_before_item = free_main_size / (pixel_t) (items.size() * 2);
			item_remainder = free_main_size - (add_after_item * (pixel_t) items.size() * 2);
			break;
		case flex_justify_content_space_evenly:
			add_before_item = free_main_size / (pixel_t) (items.size() + 1);
			item_remainder = free_main_size - add_before_item * (pixel_t) (items.size() + 1);
			break;
		default:
			if(reverse_main)
			{
				main_pos = free_main_size;
			}
			break;
	}

	/// Place all items in main and cross positions
	pixel_t height =  0;

	pixel_t distribute_step = 1;
	for(auto &item : items)
	{
		main_pos += add_before_item;
		if(add_before_item > 0 && item_remainder > 0)
		{
			main_pos += distribute_step;
			item_remainder -= distribute_step;
		}
		item->place(*this, main_pos, self_size, fmt_ctx);
		main_pos += item->get_el_main_size() + add_after_item;
		if(add_after_item > 0 && item_remainder > 0)
		{
			main_pos += distribute_step;
			item_remainder -= distribute_step;
		}
		height = std::max(height, item->el->bottom());
	}
	return height;
}