commit 0d594319c1f423679c7e7cd712003921da103c70
Author:     ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
AuthorDate: Tue Nov 3 18:05:10 2020 +0100
Commit:     ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
CommitDate: Tue Nov 3 18:05:18 2020 +0100

    Add extra argument to Fl_SVG_File_Surface constructor.
    
    This makes processing of the underlying FILE object consistant by classes
    Fl_SVG_File_Surface, Fl_EPS_File_Surface and Fl_PostScript_File_Surface.

 FL/Fl_SVG_File_Surface.H                | 17 +++++++++++------
 src/drivers/SVG/Fl_SVG_File_Surface.cxx | 12 ++++--------
 test/device.cxx                         |  2 +-
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git FL/Fl_SVG_File_Surface.H FL/Fl_SVG_File_Surface.H
index 7443732..67d0aa4 100644
--- FL/Fl_SVG_File_Surface.H
+++ FL/Fl_SVG_File_Surface.H
@@ -46,17 +46,21 @@
 */
 class FL_EXPORT Fl_SVG_File_Surface : public Fl_Widget_Surface {
   int width_, height_;
+  int (*closef_)(FILE*);
 public:
   /**
   Constructor of the SVG drawing surface.
   \param width,height Width and height of the graphics area in FLTK drawing units
   \param svg A writable FILE pointer where the SVG data are to be sent. The resulting SVG data are not complete until after destruction of the Fl_SVG_File_Surface object or after calling close().
-  */
-  Fl_SVG_File_Surface(int width, int height, FILE *svg);
+  \param closef If not NULL,  the destructor and close() will call \p closef(svg) after all
+    SVG data has been sent. If NULL, \p fclose(svg) is called instead. This allows to close the FILE
+    pointer by, e.g., \p pclose, or, using a function such as \p "int keep_open(FILE*){return 0;}", to keep it open after
+    completion of all output to \p svg. Function \p closef should return non zero to indicate an error.
+   */
+  Fl_SVG_File_Surface(int width, int height, FILE *svg, int (*closef)(FILE*) = NULL);
   /**
    Destructor.
-   The underlying FILE pointer remains open after destruction of the Fl_SVG_File_Surface object
-   unless close() was called.
+   The underlying FILE pointer is processed as by close().
    */
   ~Fl_SVG_File_Surface();
   /** Returns the underlying FILE pointer */
@@ -65,9 +69,10 @@ public:
   virtual void translate(int x, int y);
   virtual void untranslate();
   virtual int printable_rect(int *w, int *h);
-  /** Closes with function fclose() the FILE pointer where SVG data is output.
+  /** Closes the FILE pointer where SVG data is output.
+  The underlying FILE is closed by function fclose() unless another function was set at object's construction time.
   The only operation possible after this on the Fl_SVG_File_Surface object is its destruction.
-  \return The value returned by fclose(). */
+  \return The value returned by the closing function call. */
   int close();
 };
 
diff --git src/drivers/SVG/Fl_SVG_File_Surface.cxx src/drivers/SVG/Fl_SVG_File_Surface.cxx
index ae0172f..2a48ac8 100644
--- src/drivers/SVG/Fl_SVG_File_Surface.cxx
+++ src/drivers/SVG/Fl_SVG_File_Surface.cxx
@@ -305,7 +305,8 @@ int Fl_SVG_Graphics_Driver::descent() {
   return Fl_Display_Device::display_device()->driver()->descent();
 }
 
-Fl_SVG_File_Surface::Fl_SVG_File_Surface(int w, int h, FILE *f) : Fl_Widget_Surface(new Fl_SVG_Graphics_Driver(f)) {
+Fl_SVG_File_Surface::Fl_SVG_File_Surface(int w, int h, FILE *f, int (*closef)(FILE*)) : Fl_Widget_Surface(new Fl_SVG_Graphics_Driver(f)) {
+  closef_ = closef;
   Fl_Window *win = Fl::first_window();
   float s = (win ? Fl::screen_scale(win->screen_num()) : 1);
   int sw = w * s, sh = h * s;
@@ -321,12 +322,7 @@ Fl_SVG_File_Surface::Fl_SVG_File_Surface(int w, int h, FILE *f) : Fl_Widget_Surf
 }
 
 Fl_SVG_File_Surface::~Fl_SVG_File_Surface() {
-  Fl_SVG_Graphics_Driver *driver = (Fl_SVG_Graphics_Driver*)this->driver();
-  if (driver) {
-    fputs("</g></g></svg>\n", driver->file());
-    fflush(driver->file());
-    delete driver;
-  }
+  if (driver()) close();
 }
 
 FILE *Fl_SVG_File_Surface::file() {
@@ -337,7 +333,7 @@ FILE *Fl_SVG_File_Surface::file() {
 int Fl_SVG_File_Surface::close() {
   Fl_SVG_Graphics_Driver *driver = (Fl_SVG_Graphics_Driver*)this->driver();
   fputs("</g></g></svg>\n", driver->file());
-  int retval = fclose(driver->file());
+  int retval = (closef_ ? closef_(driver->file()) : fclose(driver->file()));
   delete driver;
   this->driver(NULL);
   return retval;
diff --git test/device.cxx test/device.cxx
index 8b04e53..518612c 100644
--- test/device.cxx
+++ test/device.cxx
@@ -677,7 +677,7 @@ void copy(Fl_Widget *, void *data) {
         if (surface.file()) {
           if (target->as_window()) surface.draw_decorated_window(target->as_window());
           else surface.draw(target);
-          surface.close();
+          if (surface.close()) fl_message("Error while writing to SVG file %s", fnfc.filename());
         }
       }
     }