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LibWeb: Calculate sizes of FlexibleLength grid tracks

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martinfalisse 2022-09-07 15:47:58 +02:00 • committed by Andreas Kling
parent fbe703e2bd
commit f558fd93b7
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Userland/Libraries/LibWeb/Layout/GridFormattingContext.cpp
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@ -799,6 +799,130 @@ void GridFormattingContext::run(Box const& box, LayoutMode)
// max-width/height, then redo this step, treating the available grid space as equal to the grid
// container’s inner size when it’s sized to its max-width/height.
// FIXME: Do later as at the moment all growth limits are equal to base sizes.
// https://drafts.csswg.org/css-grid/#algo-flex-tracks
// 12.7. Expand Flexible Tracks
// This step sizes flexible tracks using the largest value it can assign to an fr without exceeding
// the available space.
// First, find the grid’s used flex fraction:
auto column_flex_factor_sum = 0;
for (auto& grid_column : grid_columns) {
if (grid_column.min_track_sizing_function.is_flexible_length())
column_flex_factor_sum++;
}
// See 12.7.1.
// Let flex factor sum be the sum of the flex factors of the flexible tracks. If this value is less
// than 1, set it to 1 instead.
if (column_flex_factor_sum < 1)
column_flex_factor_sum = 1;
// See 12.7.1.
float sized_column_widths = 0;
for (auto& grid_column : grid_columns) {
if (!grid_column.min_track_sizing_function.is_flexible_length())
sized_column_widths += grid_column.base_size;
}
// Let leftover space be the space to fill minus the base sizes of the non-flexible grid tracks.
double free_horizontal_space = box_state.content_width() - sized_column_widths;
// If the free space is zero or if sizing the grid container under a min-content constraint:
// The used flex fraction is zero.
// FIXME: Add min-content constraint check.
// Otherwise, if the free space is a definite length:
// The used flex fraction is the result of finding the size of an fr using all of the grid tracks
// and a space to fill of the available grid space.
if (free_horizontal_space > 0) {
for (auto& grid_column : grid_columns) {
if (grid_column.min_track_sizing_function.is_flexible_length()) {
// See 12.7.1.
// Let the hypothetical fr size be the leftover space divided by the flex factor sum.
auto hypothetical_fr_size = static_cast<double>(1.0 / column_flex_factor_sum) * free_horizontal_space;
// For each flexible track, if the product of the used flex fraction and the track’s flex factor is
// greater than the track’s base size, set its base size to that product.
grid_column.base_size = max(grid_column.base_size, hypothetical_fr_size);
}
}
}
// First, find the grid’s used flex fraction:
auto row_flex_factor_sum = 0;
for (auto& grid_row : grid_rows) {
if (grid_row.min_track_sizing_function.is_flexible_length())
row_flex_factor_sum++;
}
// See 12.7.1.
// Let flex factor sum be the sum of the flex factors of the flexible tracks. If this value is less
// than 1, set it to 1 instead.
if (row_flex_factor_sum < 1)
row_flex_factor_sum = 1;
// See 12.7.1.
float sized_row_heights = 0;
for (auto& grid_row : grid_rows) {
if (!grid_row.min_track_sizing_function.is_flexible_length())
sized_row_heights += grid_row.base_size;
}
// Let leftover space be the space to fill minus the base sizes of the non-flexible grid tracks.
double free_vertical_space = box_state.content_height() - sized_row_heights;
// If the free space is zero or if sizing the grid container under a min-content constraint:
// The used flex fraction is zero.
// FIXME: Add min-content constraint check.
// Otherwise, if the free space is a definite length:
// The used flex fraction is the result of finding the size of an fr using all of the grid tracks
// and a space to fill of the available grid space.
if (free_vertical_space > 0) {
for (auto& grid_row : grid_rows) {
if (grid_row.min_track_sizing_function.is_flexible_length()) {
// See 12.7.1.
// Let the hypothetical fr size be the leftover space divided by the flex factor sum.
auto hypothetical_fr_size = static_cast<double>(1.0 / row_flex_factor_sum) * free_vertical_space;
// For each flexible track, if the product of the used flex fraction and the track’s flex factor is
// greater than the track’s base size, set its base size to that product.
grid_row.base_size = max(grid_row.base_size, hypothetical_fr_size);
}
}
}
// Otherwise, if the free space is an indefinite length:
// FIXME: No tracks will have indefinite length as per current implementation.
// The used flex fraction is the maximum of:
// For each flexible track, if the flexible track’s flex factor is greater than one, the result of
// dividing the track’s base size by its flex factor; otherwise, the track’s base size.
// For each grid item that crosses a flexible track, the result of finding the size of an fr using
// all the grid tracks that the item crosses and a space to fill of the item’s max-content
// contribution.
// If using this flex fraction would cause the grid to be smaller than the grid container’s
// min-width/height (or larger than the grid container’s max-width/height), then redo this step,
// treating the free space as definite and the available grid space as equal to the grid container’s
// inner size when it’s sized to its min-width/height (max-width/height).
// For each flexible track, if the product of the used flex fraction and the track’s flex factor is
// greater than the track’s base size, set its base size to that product.
// https://drafts.csswg.org/css-grid/#algo-find-fr-size
// 12.7.1. Find the Size of an fr
// This algorithm finds the largest size that an fr unit can be without exceeding the target size.
// It must be called with a set of grid tracks and some quantity of space to fill.
// 1. Let leftover space be the space to fill minus the base sizes of the non-flexible grid tracks.
// 2. Let flex factor sum be the sum of the flex factors of the flexible tracks. If this value is less
// than 1, set it to 1 instead.
// 3. Let the hypothetical fr size be the leftover space divided by the flex factor sum.
// FIXME: 4. If the product of the hypothetical fr size and a flexible track’s flex factor is less than the
// track’s base size, restart this algorithm treating all such tracks as inflexible.
// 5. Return the hypothetical fr size.
}
}