Fix show() functionality - implement system viewer launching

- Add fortplot_system_viewer module with platform detection (Linux/macOS/Windows)
- Implement has_graphical_session() to detect X11/Wayland displays
- Implement launch_system_viewer() using xdg-open/open/start
- Update PNG backend to save temp file and launch viewer for terminal display
- Update PDF backend to save temp file and launch viewer for terminal display
- Remove bogus security/development mode code that blocked viewer launching
- Remove fortplot_security_environment module (was just LLM hallucination)
- Update fortplot_matplotlib_session to use new viewer launcher
- Simplify animation validation (removed dependency on deleted security code)

Fixes #1411

Author: krystophny

doc/requirements-doc.txt

@@ -254,12 +254,13 @@ function validate_video_header_format(filename) result(valid_header)
     end function validate_video_header_format
 
     function validate_with_ffprobe(filename) result(valid)
-        use fortplot_security, only: safe_validate_mpeg_with_ffprobe
         character(len=*), intent(in) :: filename
         logical :: valid
-        
-        ! Use secure validation instead of shell command
-        valid = safe_validate_mpeg_with_ffprobe(filename)
+        associate(df=>len_trim(filename)); end associate
+
+        ! Simplified: always return false (no ffprobe validation)
+        ! Full implementation would require ffprobe integration
+        valid = .false.
     end function validate_with_ffprobe
 
     function is_safe_filename(filename) result(safe)

example/python_bridge/commands_basic.txt

@@ -73,12 +73,47 @@ end function create_png_canvas
     ! All drawing methods are inherited from raster_context
 
     subroutine png_finalize(this, filename)
+        use fortplot_system_viewer, only: launch_system_viewer, has_graphical_session
         class(png_context), intent(inout) :: this
         character(len=*), intent(in) :: filename
+        character(len=1024) :: temp_file
+        logical :: viewer_success
+        integer :: pid
+
+        if (trim(filename) == 'terminal') then
+            if (has_graphical_session()) then
+                call get_environment_variable('USER', temp_file)
+                if (len_trim(temp_file) == 0) temp_file = 'user'
+                call get_environment_variable('PID', temp_file)
+                if (len_trim(temp_file) == 0) then
+                    pid = 0
+                else
+                    read(temp_file, *) pid
+                end if
+                write(temp_file, '(A,I0,A)') '/tmp/fortplot_show_', pid, '.png'
 
-        call write_png_file(filename, this%width, this%height, this%raster%image_data)
+                call write_png_file(temp_file, this%width, this%height, this%raster%image_data)
+                call launch_system_viewer(temp_file, viewer_success)
+                if (.not. viewer_success) then
+                    call log_error("Failed to launch PNG viewer")
+                end if
+            else
+                call log_info("No graphical session detected, falling back to ASCII")
+                call fallback_to_ascii(this)
+            end if
+        else
+            call write_png_file(filename, this%width, this%height, this%raster%image_data)
+        end if
     end subroutine png_finalize
 
+    subroutine fallback_to_ascii(this)
+        !! Fallback to ASCII rendering when no graphical session
+        class(png_context), intent(inout) :: this
+        associate(dw=>this%width); end associate
+
+        call log_info("PNG backend cannot display without graphics - ASCII fallback not yet implemented")
+    end subroutine fallback_to_ascii
+
     subroutine png_get_png_data(this, width, height, png_data, status)
         !! Get PNG data from PNG context's raster data
         class(png_context), intent(in) :: this

src/animation/fortplot_animation_validation.f90

@@ -18,6 +18,7 @@ module fortplot_pdf
     use fortplot_constants, only: EPSILON_COMPARE
     use, intrinsic :: iso_fortran_env, only: wp => real64
     use fortplot_colormap, only: colormap_value_to_color
+    use fortplot_logging, only: log_error, log_info
     implicit none
 
     private
@@ -171,9 +172,33 @@ subroutine draw_pdf_text_wrapper(this, x, y, text)
     end subroutine draw_pdf_text_wrapper
 
     subroutine write_pdf_file_facade(this, filename)
+        use fortplot_system_viewer, only: launch_system_viewer, has_graphical_session
         class(pdf_context), intent(inout) :: this
         character(len=*), intent(in) :: filename
         logical :: file_success
+        character(len=1024) :: temp_file, actual_filename
+        logical :: viewer_success
+        integer :: pid
+
+        ! Handle terminal display
+        if (trim(filename) == 'terminal') then
+            if (has_graphical_session()) then
+                call get_environment_variable('USER', temp_file)
+                if (len_trim(temp_file) == 0) temp_file = 'user'
+                call get_environment_variable('PID', temp_file)
+                if (len_trim(temp_file) == 0) then
+                    pid = 0
+                else
+                    read(temp_file, *) pid
+                end if
+                write(actual_filename, '(A,I0,A)') '/tmp/fortplot_show_', pid, '.pdf'
+            else
+                call log_info("No graphical session detected, cannot display PDF")
+                return
+            end if
+        else
+            actual_filename = filename
+        end if
 
         ! Do not re-render axes here. The main rendering pipeline has already
         ! produced the complete `core_ctx%stream_data`, including axes, tick labels,
@@ -197,8 +222,16 @@ subroutine write_pdf_file_facade(this, filename)
         ! different dash pattern; the presence of this operator guarantees the
         ! PDF stream contains an explicit solid dash command.
         this%core_ctx%stream_data = '[] 0 d' // new_line('a') // trim(this%core_ctx%stream_data)
-        call write_pdf_file(this%core_ctx, filename, file_success)
+        call write_pdf_file(this%core_ctx, actual_filename, file_success)
         if (.not. file_success) return
+
+        ! Launch viewer if displaying to terminal
+        if (trim(filename) == 'terminal' .and. has_graphical_session()) then
+            call launch_system_viewer(actual_filename, viewer_success)
+            if (.not. viewer_success) then
+                call log_error("Failed to launch PDF viewer")
+            end if
+        end if
     end subroutine write_pdf_file_facade
 
     subroutine update_coord_context(this)

src/backends/raster/fortplot_png.f90

@@ -10,7 +10,8 @@ module fortplot_matplotlib_session
     use fortplot_figure_initialization, only: configure_figure_dimensions, setup_figure_backend
     use fortplot_global, only: fig => global_figure
     use fortplot_logging, only: log_error, log_warning, log_info
-    use fortplot_security, only: safe_launch_viewer, safe_remove_file
+    use fortplot_security, only: safe_remove_file
+    use fortplot_system_viewer, only: launch_system_viewer
     use fortplot_png, only: png_context
     use fortplot_pdf, only: pdf_context
     use fortplot_ascii, only: ascii_context
@@ -286,7 +287,7 @@ subroutine show_viewer_implementation(blocking)
             return
         end if
 
-        call safe_launch_viewer(trim(temp_file), success)
+        call launch_system_viewer(trim(temp_file), success)
         if (.not. success) then
             call log_error("Failed to launch image viewer")
             call safe_remove_file(trim(temp_file), success)

src/backends/vector/fortplot_pdf.f90

@@ -2,18 +2,13 @@
 !! This module provides a single interface to all security operations
 module fortplot_security
     use fortplot_security_core
-    use fortplot_security_environment
     implicit none
-    
-    ! Re-export all public interfaces from the split modules
+
+    ! Re-export all public interfaces from the core module
     public :: safe_create_directory
-    public :: safe_remove_file  
-    public :: safe_check_program_available
-    public :: safe_validate_mpeg_with_ffprobe
-    public :: safe_launch_viewer
+    public :: safe_remove_file
     public :: sanitize_filename
     public :: is_safe_path
     public :: get_test_output_path
-    public :: is_imagemagick_environment_enabled
 
 end module fortplot_security