fortplot_layout.f90 Source File

module fortplot_layout
    !! Layout and margin calculations for plotting backends
    !! 
    !! This module handles plot area geometry and margin calculations,
    !! following Single Responsibility Principle by focusing solely
    !! on layout-related functionality.
    !! 
    !! Author: fortplot contributors
    
    use, intrinsic :: iso_fortran_env, only: wp => real64
    implicit none
    
    private
    public :: plot_margins_t, plot_area_t, calculate_plot_area
    
    ! Matplotlib default margins (exact values from matplotlibrc)
    type :: plot_margins_t
        real(wp) :: left = 0.125_wp    ! 12.5% left margin 
        real(wp) :: right = 0.9_wp     ! 90% right edge (not margin!)
        real(wp) :: bottom = 0.11_wp   ! 11% bottom margin
        real(wp) :: top = 0.88_wp      ! 88% top edge (not margin!)
    end type plot_margins_t
    
    ! Plot area geometry
    type :: plot_area_t
        integer :: left, bottom, width, height
    end type plot_area_t
    
contains

    subroutine calculate_plot_area(canvas_width, canvas_height, margins, plot_area)
        !! Calculate plot area based on canvas size and margins (matplotlib-compatible)
        !! Note: left/bottom are margins, right/top are edge positions
        integer, intent(in) :: canvas_width, canvas_height
        type(plot_margins_t), intent(in) :: margins
        type(plot_area_t), intent(out) :: plot_area
        
        integer :: right_edge, top_edge
        
        ! Calculate positions exactly like matplotlib
        plot_area%left = int(margins%left * real(canvas_width, wp))
        right_edge = int(margins%right * real(canvas_width, wp))
        plot_area%width = right_edge - plot_area%left
        
        ! For image coordinates (Y=0 at top), we need to flip
        ! Add 1 to bottom to match matplotlib's pixel calculation exactly
        plot_area%bottom = int((1.0_wp - margins%top) * real(canvas_height, wp)) + 1
        top_edge = int((1.0_wp - margins%bottom) * real(canvas_height, wp))
        plot_area%height = top_edge - plot_area%bottom
    end subroutine calculate_plot_area

end module fortplot_layout