the start of a new adventure

.gitignore

@@ -0,0 +1,10 @@
+*.mod
+*.o
+*.scratch
+*.tga
+
+*.png
+!picz/*.png
+
+spirale
+

Makefile

@@ -0,0 +1,19 @@
+
+all:		spirale.png
+
+# -----------------------------------------------
+
+genplotting.o:	genplotting.f90 Makefile
+	gfortran -Wall -c $< 
+
+# -----------------------------------------------
+
+spirale:	spirale.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
+spirale.png:	spirale Makefile
+	./spirale > s.scratch
+	genplot2 -s 512x512 s.scratch a.tga
+	convert a.tga $@
+
+# -----------------------------------------------

README.md

@@ -1,3 +1,11 @@
 # GenPlotting90
 
-Diverses tentatives de dessins inutiles avec du Fortran moderne. Croisimot #UselessGraphic dans le grabd Ternet sauvage.
+Voici quelques tentatives de dessins inutiles réalisés avec du
+[Fortran moderne](https://fortran-lang.org/fr/learn/), et quelques
+morceaux de C parce que *why not ?*
+
+Un peu de lecture : [utilisation](usage.md) et [exemples](exemples.md).
+
+Vous pouvez suivre le croisimot [#UselessGraphic](https://mastodon.tetaneutral.net/tags/uselessgraphic)
+dans le grand Ternet sauvage. Pour me contacter, il faut utiliser les
+[méthodes](

exemples.md

@@ -0,0 +1,10 @@
+# Genplotting exemples
+
+## Spiral
+
+Code source : [spirale.f90](spirale.f90) / if you change the parameter
+in the call to `do_spirale`, you can see some nice variations on the
+spiraling thing.
+
+![#UselessGraphic : la spirale](picz/spirale.png)
+

genplotting.f90

@@ -0,0 +1,76 @@
+!                    SPIRALING...
+! new Thu Apr 23 01:13.37 PM UTC 2026
+!
+module genplotting
+  implicit none
+
+  real      ::    xmin, xmax, ymin, ymax
+  private   ::    xmin, xmax, ymin, ymax
+
+  real      ::    xoffset, yoffset, xscale, yscale
+  private   ::    xoffset, yoffset, xscale, yscale
+
+  integer   ::    outunit
+  private   ::    outunit
+
+contains
+! ---------------------------------------------------------
+subroutine genp_init (foo, fname)
+  integer, intent(in)             :: foo
+  character (len=*), intent(in)   :: fname
+
+  outunit = 6          ! stdout
+  if (len(fname) .gt. 0) then
+    write (0, '("genplot init opening : ", A)') fname
+    open(newunit=outunit,file=fname)
+  endif
+
+  xmin = 9e9       ;       xmax = -9e9
+  ymin = 9e9       ;       ymax = -9e9
+  xoffset = 0.0    ;       yoffset = 0.0
+  xscale  = 0.0    ;       yscale  = 0.0
+end subroutine
+! ---------------------------------------------------------
+subroutine genp_move (px, py)
+  real, intent(in)        :: px, py
+  write (outunit, '(2F12.5, I5)') px, py, -1
+  if (px .lt. xmin)      xmin = px
+  if (px .gt. xmax)      xmax = px
+  if (py .lt. ymin)      ymin = py
+  if (py .gt. ymax)      ymax = py
+end subroutine
+! ---------------------------------------------------------
+subroutine genp_draw (px, py, color)
+  real, intent(in)        :: px, py
+  integer, intent(in)     :: color
+  write (outunit, '(2F12.5, I5)') px, py, color
+  if (px .lt. xmin)      xmin = px
+  if (px .gt. xmax)      xmax = px
+  if (py .lt. ymin)      ymin = py
+  if (py .gt. ymax)      ymax = py
+end subroutine
+! ---------------------------------------------------------
+! ---------------------------------------------------------
+subroutine genp_end (foo)
+  integer, intent(in)    :: foo
+
+  write (0, '("--- genp_end ---")')
+  write (0, '("minmax X", 2F16.5)') xmin, xmax
+  write (0, '("minmax Y", 2F16.5)') ymin, ymax
+
+  write (outunit, '(2F16.5, I6)') xmin*1.05, ymin*1.05, -1
+  write (outunit, '(2F16.5, I6)') xmin*1.05, ymax*1.05,  0
+  write (outunit, '(2F16.5, I6)') xmax*1.05, ymax*1.05,  0
+  write (outunit, '(2F16.5, I6)') xmax*1.05, ymin*1.05,  0
+  write (outunit, '(2F16.5, I6)') xmin*1.05, ymin*1.05,  0
+  close (outunit)
+
+  if (6 .ne. outunit) then
+    write (0, '("genp_end on ", I6, " is ", I6)') outunit, foo
+  endif
+
+end subroutine
+! ---------------------------------------------------------
+! ---------------------------------------------------------
+
+end module genplotting

spirale.f90

@@ -0,0 +1,34 @@
+!                    SPIRALING...
+! new Thu Apr 23 04:27:03 PM UTC 2026
+!
+
+program spirale
+  use genplotting
+  implicit none
+
+  write (0, '(A)') "----[ genplotting spirale ]----"
+
+  call genp_init (0, 's.scratch')
+  call do_spirale (1337)
+  call genp_end (0)
+
+contains
+! ---------------------------------------------------------
+subroutine do_spirale (nbpass)
+  integer, intent(in)     :: nbpass
+  integer         idx, col
+  real            rad, px, py, dist
+
+  px = 0.0 ; py = 0.0
+  call genp_move (px, py)
+  do idx=1, nbpass
+    dist = real(idx) * 0.51
+    rad = real(idx) * 0.0666
+    px = dist * sin(rad)
+    py = dist * cos(rad)
+    col = 3
+    call genp_draw (px, py, col)
+  enddo
+end subroutine
+! ---------------------------------------------------------
+end program

usage.md

@@ -0,0 +1,22 @@
+# Usage
+
+Three steps : initialize, use and terminating.
+
+## Initialize
+
+Call the subroutine `genp_init` with two parameters.
+The first is an integer and must be 0. 
+The second is the filename for recording the plottings instructions,
+if this filename is an empty string, *stdout* will be used.
+
+## Use it
+
+- call genp_move(x, y)
+- call genp_draw(x, y, c)
+
+## Terminator
+
+- call genp_end(0)
+
+
+