module fortplot_legend_layout !! Shared legend layout calculations following DRY principle !! !! Single Responsibility: Legend box sizing and positioning calculations !! DRY: Centralized legend layout logic for consistent behavior !! KISS: Simple, clear calculation functions !! Uses text system measurements for accurate sizing use, intrinsic :: iso_fortran_env, only: wp => real64 use fortplot_text, only: calculate_text_width, calculate_text_height, init_text_system use fortplot_constants, only: STANDARD_WIDTH_PIXELS, STANDARD_HEIGHT_PIXELS, TEXT_WIDTH_RATIO use fortplot_latex_parser, only: process_latex_in_text implicit none private public :: legend_box_t, calculate_legend_box, calculate_optimal_legend_dimensions public :: get_actual_text_dimensions, get_legend_margins public :: choose_best_legend_position ! Local position constants mirror fortplot_legend_state to avoid a cyclic ! module dependency (state has no dependency on this module, and adding one ! would close a cycle through fortplot_legend_drawing). integer, parameter :: LEGEND_UPPER_LEFT = 1 integer, parameter :: LEGEND_UPPER_RIGHT = 2 integer, parameter :: LEGEND_LOWER_LEFT = 3 integer, parameter :: LEGEND_LOWER_RIGHT = 4 integer, parameter :: LEGEND_EAST = 5 type :: legend_box_t !! Single Responsibility: Legend box dimensions and position real(wp) :: x, y ! Top-left corner position real(wp) :: width, height ! Box dimensions real(wp) :: padding ! Vertical padding (Y) real(wp) :: padding_x ! Horizontal padding (X) real(wp) :: entry_height ! Height of each legend entry (text height) real(wp) :: entry_spacing ! Vertical spacing between entries real(wp) :: line_length ! Length of legend line samples real(wp) :: text_spacing ! Space between line and text end type legend_box_t contains function calculate_legend_box(labels, data_width, data_height, num_entries, position, & pixel_plot_width, pixel_plot_height) result(box) !! Calculate optimal legend box dimensions and position !! DRY: Centralized legend box calculation logic character(len=*), intent(in) :: labels(:) real(wp), intent(in) :: data_width, data_height integer, intent(in) :: num_entries, position integer, intent(in), optional :: pixel_plot_width, pixel_plot_height type(legend_box_t) :: box real(wp) :: max_text_width, total_text_width, margins(2) integer :: px_w, px_h if (num_entries == 0) then box%width = 0.0_wp box%height = 0.1_wp return end if ! Resolve pixel plot area dimensions if provided (prefer exact values) if (present(pixel_plot_width) .and. present(pixel_plot_height)) then px_w = max(1, pixel_plot_width) px_h = max(1, pixel_plot_height) else px_w = int(STANDARD_WIDTH_PIXELS) px_h = int(STANDARD_HEIGHT_PIXELS) end if ! Calculate optimal dimensions based on content with real pixel scale call calculate_optimal_legend_dimensions(labels, data_width, data_height, & max_text_width, total_text_width, box, px_w, px_h) ! Get appropriate margins for this backend margins = get_legend_margins(data_width, data_height, px_w, px_h) ! Calculate position based on legend location call calculate_legend_position(box, data_width, data_height, position, margins) end function calculate_legend_box function choose_best_legend_position(labels, data_width, data_height, & num_entries, artist_x, artist_y, & pixel_plot_width, pixel_plot_height) & result(position) !! Resolve matplotlib 'best' placement to a concrete corner. !! Computes the legend box for each candidate corner and scores it by the !! number of plotted artist sample points its bbox covers; the lowest !! overlap wins, ties broken in matplotlib's order (upper right first). character(len=*), intent(in) :: labels(:) real(wp), intent(in) :: data_width, data_height integer, intent(in) :: num_entries real(wp), intent(in) :: artist_x(:), artist_y(:) integer, intent(in), optional :: pixel_plot_width, pixel_plot_height integer :: position ! Order encodes the tie-break preference (matplotlib: upper right first). integer, parameter :: candidates(4) = & [LEGEND_UPPER_RIGHT, LEGEND_UPPER_LEFT, & LEGEND_LOWER_LEFT, LEGEND_LOWER_RIGHT] type(legend_box_t) :: box integer :: i, overlap, best_overlap position = LEGEND_UPPER_RIGHT best_overlap = huge(0) do i = 1, size(candidates) box = calculate_legend_box(labels, data_width, data_height, & num_entries, candidates(i), & pixel_plot_width, pixel_plot_height) overlap = count_points_in_box(box, artist_x, artist_y) if (overlap < best_overlap) then best_overlap = overlap position = candidates(i) end if end do end function choose_best_legend_position pure function count_points_in_box(box, artist_x, artist_y) result(n) !! Count artist sample points covered by the legend bbox. The box origin !! is its top-left corner in data-window-relative coordinates (matching !! calculate_legend_position output). type(legend_box_t), intent(in) :: box real(wp), intent(in) :: artist_x(:), artist_y(:) integer :: n real(wp) :: x0, x1, y0, y1 integer :: i x0 = box%x x1 = box%x + box%width y0 = box%y - box%height y1 = box%y n = 0 do i = 1, min(size(artist_x), size(artist_y)) if (artist_x(i) >= x0 .and. artist_x(i) <= x1 .and. & artist_y(i) >= y0 .and. artist_y(i) <= y1) n = n + 1 end do end function count_points_in_box subroutine calculate_optimal_legend_dimensions(labels, data_width, data_height, & max_text_width, total_text_width, box, & pixel_plot_width, pixel_plot_height) !! Calculate optimal legend dimensions using actual text system measurements !! KISS: Based on measured text content, not estimates character(len=*), intent(in) :: labels(:) real(wp), intent(in) :: data_width, data_height real(wp), intent(out) :: max_text_width, total_text_width type(legend_box_t), intent(inout) :: box integer, intent(in) :: pixel_plot_width, pixel_plot_height real(wp) :: data_to_pixel_ratio_x, data_to_pixel_ratio_y integer :: max_text_height_pixels logical :: text_system_available ! Initialize text system for measurements text_system_available = init_text_system() ! Calculate data-to-pixel conversion ratio using actual plot-area pixels when available data_to_pixel_ratio_x = real(pixel_plot_width, wp) / data_width data_to_pixel_ratio_y = real(pixel_plot_height, wp) / data_height ! Measure text dimensions call measure_label_dimensions(labels, text_system_available, data_to_pixel_ratio_x, & data_width, max_text_width, total_text_width, & max_text_height_pixels) ! Calculate box dimensions based on measurements call set_legend_box_dimensions(box, max_text_width, max_text_height_pixels, & data_to_pixel_ratio_x, data_to_pixel_ratio_y, & size(labels)) end subroutine calculate_optimal_legend_dimensions subroutine measure_label_dimensions(labels, text_system_available, data_to_pixel_ratio_x, & data_width, max_text_width, total_text_width, & max_text_height_pixels) !! Measure text dimensions for all labels character(len=*), intent(in) :: labels(:) logical, intent(in) :: text_system_available real(wp), intent(in) :: data_to_pixel_ratio_x, data_width real(wp), intent(out) :: max_text_width, total_text_width integer, intent(out) :: max_text_height_pixels integer :: i, text_height_pixels real(wp) :: entry_text_width, text_width_pixels character(len=:), allocatable :: trimmed_label, processed_label character(len=512) :: temp_processed_label integer :: processed_len real(wp), parameter :: FUDGE_PIXELS = 0.0_wp max_text_width = 0.0_wp total_text_width = 0.0_wp max_text_height_pixels = 16 ! Default font height do i = 1, size(labels) trimmed_label = trim(labels(i)) ! Process LaTeX to Unicode first for accurate width calculation call process_latex_in_text(trimmed_label, temp_processed_label, processed_len) processed_label = temp_processed_label(1:processed_len) if (text_system_available) then ! Calculate width of the processed text (after LaTeX conversion) text_width_pixels = real(calculate_text_width(processed_label), wp) + FUDGE_PIXELS text_height_pixels = calculate_text_height(processed_label) max_text_height_pixels = max(max_text_height_pixels, text_height_pixels) entry_text_width = text_width_pixels / data_to_pixel_ratio_x else ! For fallback, use processed text length entry_text_width = real(len_trim(processed_label), wp) * data_width * TEXT_WIDTH_RATIO end if total_text_width = total_text_width + entry_text_width max_text_width = max(max_text_width, entry_text_width) end do end subroutine measure_label_dimensions subroutine set_legend_box_dimensions(box, max_text_width, max_text_height_pixels, & data_to_pixel_ratio_x, data_to_pixel_ratio_y, num_labels) !! Set legend box dimensions based on measurements type(legend_box_t), intent(inout) :: box real(wp), intent(in) :: max_text_width integer, intent(in) :: max_text_height_pixels real(wp), intent(in) :: data_to_pixel_ratio_x, data_to_pixel_ratio_y integer, intent(in) :: num_labels real(wp) :: padding_x, label_spacing real(wp) :: aa_safety_x ! Set legend box components (matplotlib-style spacing) box%line_length = 20.0_wp / data_to_pixel_ratio_x ! 20 pixels for legend line box%text_spacing = 6.0_wp / data_to_pixel_ratio_x ! 6 pixels between line and text box%entry_height = real(max_text_height_pixels, wp) / data_to_pixel_ratio_y box%entry_spacing = 5.0_wp / data_to_pixel_ratio_y ! 0.5 * 10pt font = 5 pixels box%padding = 4.0_wp / data_to_pixel_ratio_y ! Vertical padding label_spacing = box%entry_spacing padding_x = 4.0_wp / data_to_pixel_ratio_x box%padding_x = padding_x ! Rendering safety: AA of slanted sqrt tick and 0.5px border can ! place coverage up to ~1px near right edge. Reserve 1px in data units. aa_safety_x = 1.0_wp / data_to_pixel_ratio_x ! Calculate total box dimensions box%width = 2.0_wp * box%padding_x + box%line_length + box%text_spacing + max_text_width + aa_safety_x box%height = 2.0_wp * box%padding + & real(num_labels, wp) * box%entry_height + & real(num_labels - 1, wp) * label_spacing end subroutine set_legend_box_dimensions function get_actual_text_dimensions(label, data_to_pixel_x, data_to_pixel_y) result(dimensions) !! Get actual text dimensions using text system measurements !! Returns [width, height] in data coordinates character(len=*), intent(in) :: label real(wp), intent(in) :: data_to_pixel_x, data_to_pixel_y real(wp) :: dimensions(2) ! [width, height] integer :: width_pixels, height_pixels, processed_len logical :: text_system_available character(len=512) :: processed_label text_system_available = init_text_system() if (text_system_available) then ! Pass original text directly - calculate_text_width handles mathtext internally width_pixels = calculate_text_width(label) height_pixels = calculate_text_height(label) dimensions(1) = real(width_pixels, wp) / data_to_pixel_x dimensions(2) = real(height_pixels, wp) / data_to_pixel_y else ! Fallback estimation - process LaTeX for accurate character count call process_latex_in_text(label, processed_label, processed_len) dimensions(1) = real(processed_len, wp) * 8.0_wp / data_to_pixel_x ! 8 pixels per char dimensions(2) = 16.0_wp / data_to_pixel_y ! 16 pixels height end if end function get_actual_text_dimensions function get_legend_margins(data_width, data_height, & pixel_plot_width, pixel_plot_height) result(margins) !! Inset between the legend box and the axes frame. !! Matches matplotlib's borderaxespad default (0.5 * 10pt font = 5pt), !! which at the standard ~100 dpi is ~7 px, independent of the data !! range. A fixed pixel inset keeps the legend flush in the corner the !! way matplotlib draws it, instead of a large data-proportional gap. real(wp), intent(in) :: data_width, data_height integer, intent(in), optional :: pixel_plot_width, pixel_plot_height real(wp) :: margins(2) ! [x_margin, y_margin] real(wp), parameter :: BORDER_AXES_PAD_PX = 7.0_wp integer :: px_w, px_h if (present(pixel_plot_width) .and. present(pixel_plot_height)) then px_w = max(1, pixel_plot_width) px_h = max(1, pixel_plot_height) margins(1) = BORDER_AXES_PAD_PX * data_width / real(px_w, wp) margins(2) = BORDER_AXES_PAD_PX * data_height / real(px_h, wp) else margins(1) = data_width * 0.02_wp margins(2) = data_height * 0.02_wp end if end function get_legend_margins subroutine calculate_legend_position(box, data_width, data_height, position, margins) !! Calculate legend position based on placement preference !! Single Responsibility: Position calculation only type(legend_box_t), intent(inout) :: box real(wp), intent(in) :: data_width, data_height, margins(2) integer, intent(in) :: position select case (position) case (LEGEND_UPPER_LEFT) box%x = margins(1) box%y = data_height - margins(2) case (LEGEND_UPPER_RIGHT) box%x = data_width - box%width - margins(1) box%y = data_height - margins(2) case (LEGEND_LOWER_LEFT) box%x = margins(1) box%y = box%height + margins(2) case (LEGEND_LOWER_RIGHT) box%x = data_width - box%width - margins(1) box%y = box%height + margins(2) case (LEGEND_EAST) box%x = data_width + margins(1) box%y = (data_height - box%height)*0.5_wp case default ! Default to upper right box%x = data_width - box%width - margins(1) box%y = data_height - margins(2) end select end subroutine calculate_legend_position end module fortplot_legend_layout