scroll_back.h

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#pragma once
 
#include "di/container/ring/prelude.h"
#include "ttx/terminal/reflow_result.h"
#include "ttx/terminal/row_group.h"
 
namespace ttx::terminal {
class ScrollBack {
    constexpr static auto target_cells_per_group = usize(di::NumericLimits<u16>::max / 2);
 
    constexpr static auto max_cells_per_group = usize(di::NumericLimits<u16>::max);
 
    // TODO: make this configurable.
    constexpr static auto max_cells = usize(target_cells_per_group * 100);
 
    constexpr static auto max_groups = di::divide_round_up(max_cells, target_cells_per_group);
 
    struct Group {
        RowGroup group;
        usize cell_count { 0 };
        di::Optional<u32> last_reflowed_to;
    };
 
public:
    auto absolute_row_start() const -> u64 { return m_absolute_row_start; }
    auto absolute_row_end() const -> u64 { return m_absolute_row_start + total_rows(); }
    auto total_rows() const -> usize { return m_total_rows; }

    void clear();

    void add_rows(RowGroup& from, usize row_index, usize row_count);

    void take_rows(RowGroup& to, u32 desired_cols, usize row_index, usize row_count);

    auto take_rows_for_reflow(RowGroup& to) -> u64;

    auto reflow_visual_rows(u64 absolute_row_start, usize row_count, u32 desired_cols) -> di::Optional<ReflowResult>;
 
    auto find_row(u64 row) const -> di::Tuple<u32, RowGroup const&>;
 
private:
    auto get_target_cells_per_group(bool last_row_overflow) const {
        // We use a larger threshold when the last row in the group has overflow set.
        // This is done to try and only break row groups on boundaries which preserve
        // logical rows.
        return last_row_overflow ? max_cells_per_group : target_cells_per_group;
    }
 
    auto find_row_group(u64 row) -> di::Tuple<u32, u64, Group&>;
    auto is_last_group_full() const -> bool;
    auto add_group() -> Group&;
 
    di::Ring<Group> m_groups;
    usize m_total_rows { 0 };
    u64 m_absolute_row_start { 0 };
};
}