fortplot_marker_rendering.f90 Source File

module fortplot_marker_rendering
    !! Marker rendering module
    !! 
    !! This module handles all marker-based rendering operations including
    !! scatter plot markers and single point markers.

    use, intrinsic :: iso_fortran_env, only: wp => real64
    use fortplot_context
    use fortplot_scales, only: apply_scale_transform
    use fortplot_plot_data
    implicit none
    
    private
    public :: render_markers
    public :: draw_single_point_marker
    
contains
    
    subroutine render_markers(backend, plot_data, x_min_t, x_max_t, y_min_t, y_max_t, xscale, yscale, symlog_threshold)
        !! Render markers for a plot
        class(plot_context), intent(inout) :: backend
        type(plot_data_t), intent(in) :: plot_data
        real(wp), intent(in) :: x_min_t, x_max_t, y_min_t, y_max_t
        character(len=*), intent(in) :: xscale, yscale
        real(wp), intent(in) :: symlog_threshold
        
        real(wp) :: x_scaled, y_scaled
        integer :: i
        associate(dxmin=>x_min_t, dxmax=>x_max_t, dymin=>y_min_t, dymax=>y_max_t); end associate
        
        if (.not. allocated(plot_data%marker)) return
        if (len_trim(plot_data%marker) == 0) return
        if (trim(plot_data%marker) == 'None' .or. trim(plot_data%marker) == 'none') return
        
        ! Validate input data
        if (.not. allocated(plot_data%x) .or. .not. allocated(plot_data%y)) return
        if (size(plot_data%x) == 0 .or. size(plot_data%y) == 0) return
        if (size(plot_data%x) /= size(plot_data%y)) return
        
        ! Sync marker colors with plot color (edge and face)
        call backend%set_marker_colors(plot_data%color(1), plot_data%color(2), plot_data%color(3), &
                                       plot_data%color(1), plot_data%color(2), plot_data%color(3))
        ! Keep backend current color in sync as well for backends that use it
        call backend%color(plot_data%color(1), plot_data%color(2), plot_data%color(3))
        
        do i = 1, size(plot_data%x)
            x_scaled = apply_scale_transform(plot_data%x(i), xscale, symlog_threshold)
            y_scaled = apply_scale_transform(plot_data%y(i), yscale, symlog_threshold)
            call backend%draw_marker(x_scaled, y_scaled, plot_data%marker)
        end do
    end subroutine render_markers

    subroutine draw_single_point_marker(backend, x, y)
        !! Draw a visible marker for a single point
        !! This ensures single points are visible even without explicit markers
        class(plot_context), intent(inout) :: backend
        real(wp), intent(in) :: x, y
        
        real(wp) :: marker_size
        real(wp) :: data_range_x, data_range_y
        
        ! Calculate marker size based on the current data range to ensure visibility
        ! This makes the marker a reasonable fraction of the plot area
        data_range_x = abs(backend%x_max - backend%x_min)
        data_range_y = abs(backend%y_max - backend%y_min)
        
        ! Use 1% of the smaller data range as marker size
        marker_size = 0.01_wp * min(data_range_x, data_range_y)
        
        ! Ensure minimum visibility (in case data range is very small)
        if (marker_size < epsilon(1.0_wp) * 1000) then
            marker_size = 0.1_wp * max(data_range_x, data_range_y)
        end if
        
        ! Draw a small cross or plus sign centered at the point
        ! This works across all backends (PNG, PDF, ASCII)
        
        ! Horizontal line of the cross
        call backend%line(x - marker_size, y, x + marker_size, y)
        
        ! Vertical line of the cross
        call backend%line(x, y - marker_size, x, y + marker_size)
        
    end subroutine draw_single_point_marker

end module fortplot_marker_rendering