CMake: build shared libs with OPTION_CAIROEXT (issue #250)

- remove separate libfltk_cairo to avoid cyclic dependencies, but
- keep a dummy libfltk_cairo in 1.4.0 for backwards compatibility
- move cairo/Fl_Cairo.cxx to src/Fl_Cairo.cxx
- add preliminary Cairo support for Visual Studio (MSVC)

Static linking is not affected by this change, but users building
with hand-made Makefiles will have to remove libfltk_cairo starting
with FLTK 1.4.0. The dummy library can be linked for backwards
compatibility but it will be removed later (in 1.4.x or 1.5.0).

The shared FLTK library libfltk.{so|dylib|dll|..} depends on libcairo
if and only if FLTK is built with one of the Cairo options. This has
always been the case for OPTION_CAIROEXT but is now also true if only
OPTION_CAIRO is selected, i.e. FLTK programs linked with a Cairo
enabled shared FLTK library will also be linked with libcairo. The same
is true for configure options --enable-cairo and --enable-cairoext,
respectively.

Preliminary Cairo support for MSVC now detects a Cairo installation
using the CMake variable FLTK_CAIRO_DIR which must be set by the user.
Note that this feature is temporary and may be changed in the future
for a better and more comfortable version.

5 files changed, 74 insertions, 279 deletions

diff --git a/cairo/CMakeLists.txt b/cairo/CMakeLists.txt
index 1bb784362..f031d674f 100644
--- a/cairo/CMakeLists.txt
+++ b/cairo/CMakeLists.txt
@@ -1,22 +1,39 @@
+#
+# CMakeLists.txt to build a dummy Cairo library for the FLTK project using CMake
+#
+# Copyright 1998-2023 by Bill Spitzak and others.
+#
+# This library is free software. Distribution and use rights are outlined in
+# the file "COPYING" which should have been included with this file.  If this
+# file is missing or damaged, see the license at:
+#
+#     https://www.fltk.org/COPYING.php
+#
+# Please see the following page on how to report bugs and issues:
+#
+#     https://www.fltk.org/bugs.php
+#
+
+########################################################################
+# Note: since FLTK 1.4.0 Fl_Cairo_Window support [1] is included in
+# libfltk and libfltk_cairo is no longer necessary. This directory is
+# used to build an "empty" dummy library for backwards compatibility,
+# just in case users expect it to exist.
+# ----------------------------------------------------------------------
+# The entire 'cairo' folder will be removed in a later FLTK release.
+########################################################################
+
+# Build dummy fltk_cairo library
+
+set (cairo_SRCS cairo_dummy.c)
 
-include_directories (${PKG_CAIRO_INCLUDE_DIRS})
-
-# source files for cairo
-set (cairo_SRCS Fl_Cairo.cxx)
-
-#######################################################################
 FL_ADD_LIBRARY (fltk_cairo STATIC "${cairo_SRCS}")
 
-#######################################################################
-# Build shared library (optional)
-#######################################################################
+# Build shared dummy library (optional)
 
 if (OPTION_BUILD_SHARED_LIBS)
 
   FL_ADD_LIBRARY (fltk_cairo SHARED "${cairo_SRCS}")
-  target_link_libraries (fltk_cairo_SHARED fltk_SHARED ${PKG_CAIRO_LIBRARIES})
-  fl_target_link_directories (fltk_cairo_SHARED PRIVATE "${PKG_CAIRO_LIBRARY_DIRS}")
+  target_link_libraries (fltk_cairo_SHARED fltk_SHARED)
 
 endif (OPTION_BUILD_SHARED_LIBS)
-
-#######################################################################
diff --git a/cairo/Fl_Cairo.cxx b/cairo/Fl_Cairo.cxx
deleted file mode 100644
index 2def2698a..000000000
--- a/cairo/Fl_Cairo.cxx
+++ /dev/null
@@ -1,242 +0,0 @@
-//
-// Special Cairo support for the Fast Light Tool Kit (FLTK).
-//
-// Copyright 1998-2023 by Bill Spitzak and others.
-//
-// This library is free software. Distribution and use rights are outlined in
-// the file "COPYING" which should have been included with this file.  If this
-// file is missing or damaged, see the license at:
-//
-//     https://www.fltk.org/COPYING.php
-//
-// Please see the following page on how to report bugs and issues:
-//
-//     https://www.fltk.org/bugs.php
-//
-
-// This file implements the FLTK Cairo support (since 1.3.x):
-//
-// - ./configure --enable-cairo  and/or  --enable-cairoext
-// - cmake       -DOPTION_CAIRO  and/or  -DOPTION_CAIROEXT
-//
-// Preprocessor macro FLTK_HAVE_CAIRO is defined for both options.
-// Preprocessor macro FLTK_HAVE_CAIRO_EXT is defined only for "cairoext"
-
-#include <FL/Fl.H> // includes <FL/fl_config.h>
-
-#ifdef FLTK_HAVE_CAIRO
-
-#include <FL/platform.H>
-#include <FL/Fl_Window.H>
-
-// Cairo is currently supported for the following platforms:
-// Windows, macOS (Apple Quartz), X11, Wayland
-
-#if defined(_WIN32)               // Windows
-#  include <cairo-win32.h>
-#elif defined(FLTK_USE_WAYLAND)   // Wayland or hybrid
-#  include "../src/drivers/Wayland/Fl_Wayland_Graphics_Driver.H"
-#  include "../src/drivers/Wayland/Fl_Wayland_Window_Driver.H"
-#  if defined(FLTK_USE_X11)
-#    include <cairo-xlib.h>
-#  else
-     static void *fl_gc = NULL;
-#  endif
-#elif defined(FLTK_USE_X11)       // X11
-#  include <cairo-xlib.h>
-#elif defined(__APPLE__)          // macOS
-#  include <cairo-quartz.h>
-#else
-#  error Cairo is not supported on this platform.
-#endif
-
-// static initialization
-
-Fl_Cairo_State Fl::cairo_state_; ///< current Cairo context information
-
-// Fl_Cairo_State
-
-void Fl_Cairo_State::autolink(bool b) {
-#ifdef FLTK_HAVE_CAIROEXT
-  autolink_ = b;
-#else
-  Fl::fatal("In Fl::autolink(bool): Cairo autolink() feature is only "
-            "available with CMake OPTION_CAIROEXT "
-            "or the enable-cairoext configure option.\n"
-            "Quitting now.");
-#endif
-}
-
-/**
-  Provides a Cairo context for window \a wi.
-
-  This is needed in a draw() override if Fl::cairo_autolink_context()
-  returns false, which is the default.
-  The cairo_context() does not need to be freed as it is freed every time
-  a new Cairo context is created. When the program terminates,
-  a call to Fl::cairo_make_current(0) will destroy any residual context.
-
-  \note A new Cairo context is not always re-created when this method
-    is used. In particular, if the current graphical context and the current
-    window didn't change between two calls, the previous gc is internally kept,
-    thus optimizing the drawing performances.
-    Also, after this call, Fl::cairo_cc() is adequately updated with this
-    Cairo context.
-
-  \note Only available when configure has the --enable-cairo option
-
-  \return The valid cairo_t *cairo context associated to this window.
-  \retval NULL if \a wi is NULL or maybe with GL windows under Wayland
-*/
-cairo_t *Fl::cairo_make_current(Fl_Window *wi) {
-  if (!wi)
-    return NULL;
-  cairo_t *cairo_ctxt;
-
-#if defined(FLTK_USE_WAYLAND)
-  if (fl_wl_display()) { // true means using wayland backend
-    struct wld_window *xid = fl_wl_xid(wi);
-    if (!xid->buffer)
-      return NULL; // this may happen with GL windows
-    cairo_ctxt = xid->buffer->cairo_;
-    cairo_state_.cc(cairo_ctxt, false);
-    return cairo_ctxt;
-  }
-#endif
-
-  if (fl_gc == 0) {  // means remove current cc
-    Fl::cairo_cc(0); // destroy any previous cc
-    cairo_state_.window(0);
-    return 0;
-  }
-
-  // don't re-create a context if it's the same gc/window combination
-  if (fl_gc == Fl::cairo_state_.gc() && fl_xid(wi) == (Window)Fl::cairo_state_.window())
-    return Fl::cairo_cc();
-
-  cairo_state_.window((void *)fl_xid(wi));
-
-  // Scale the Cairo context appropriately. This is platform dependent
-
-#ifndef __APPLE__
-  float scale = Fl::screen_scale(wi->screen_num()); // get the screen scaling factor
-#endif
-
-#if defined(FLTK_USE_X11)
-  cairo_ctxt = Fl::cairo_make_current(0, wi->w() * scale, wi->h() * scale);
-#else
-  // on macOS, scaling is done before by Fl_Window::make_current(), on Windows, the size is not used
-  cairo_ctxt = Fl::cairo_make_current(fl_gc, wi->w(), wi->h());
-#endif
-
-#ifndef __APPLE__
-  cairo_scale(cairo_ctxt, scale, scale);
-#endif
-  return cairo_ctxt;
-}
-
-/*
-  Creates transparently a cairo_surface_t object.
-  gc is an HDC context in Windows, a CGContext* in Quartz, and
-  a display on X11 (not used on this platform)
-*/
-
-static cairo_surface_t *cairo_create_surface(void *gc, int W, int H) {
-#if defined(FLTK_USE_X11)
-  return cairo_xlib_surface_create(fl_display, fl_window, fl_visual->visual, W, H);
-#elif defined(FLTK_USE_WAYLAND)
-  return NULL;
-#elif defined(_WIN32)
-  return cairo_win32_surface_create((HDC)gc);
-#elif defined(__APPLE__)
-  return cairo_quartz_surface_create_for_cg_context((CGContextRef)gc, W, H);
-#else
-#error Cairo is not supported on this platform.
-#endif
-}
-
-/**
-  Creates a Cairo context from a \a gc only, gets its window size or
-  offscreen size if fl_window is null.
-
-  \note Only available if CMake OPTION_CAIRO is enabled
-        or configure has the --enable-cairo option.
-*/
-cairo_t *Fl::cairo_make_current(void *gc) {
-  int W = 0, H = 0;
-#if defined(FLTK_USE_X11) || defined(FLTK_USE_WAYLAND)
-  // FIXME X11 get W,H
-  // gc will be the window handle here
-  // # warning FIXME get W,H for cairo_make_current(void*)
-#elif defined(__APPLE__)
-  if (fl_window) {
-    W = Fl_Window::current()->w();
-    H = Fl_Window::current()->h();
-  } else {
-    W = CGBitmapContextGetWidth(fl_gc);
-    H = CGBitmapContextGetHeight(fl_gc);
-  }
-#elif defined(_WIN32)
-  // we don't need any W,H for Windows
-#else
-#error Cairo is not supported on this platform.
-#endif
-
-  if (!gc) {
-    Fl::cairo_cc(0);
-    cairo_state_.gc(0); // keep track for next time
-    return 0;
-  }
-  if (gc == Fl::cairo_state_.gc() &&
-      fl_window == (Window)Fl::cairo_state_.window() &&
-      cairo_state_.cc() != 0)
-    return Fl::cairo_cc();
-  cairo_state_.gc(fl_gc); // keep track for next time
-  cairo_surface_t *s = cairo_create_surface(gc, W, H);
-  cairo_t *c = cairo_create(s);
-  cairo_surface_destroy(s);
-  cairo_state_.cc(c);
-  return c;
-}
-
-/**
-  Creates a Cairo context from a \p gc and the given size.
-
-  \note Only available if CMake OPTION_CAIRO is enabled
-        or configure has the --enable-cairo option.
-*/
-cairo_t *Fl::cairo_make_current(void *gc, int W, int H) {
-  if (gc == Fl::cairo_state_.gc() &&
-      fl_window == (Window)Fl::cairo_state_.window() &&
-      cairo_state_.cc() != 0) // no need to create a cc, just return that one
-    return cairo_state_.cc();
-
-  // we need to (re-)create a fresh cc ...
-  cairo_state_.gc(gc); // keep track for next time
-  cairo_surface_t *s = cairo_create_surface(gc, W, H);
-
-#if defined(__APPLE__) && defined(FLTK_HAVE_CAIROEXT)
-  CGAffineTransform at = CGContextGetCTM((CGContextRef)gc);
-  CGContextSaveGState((CGContextRef)gc);
-  CGContextConcatCTM((CGContextRef)gc, CGAffineTransformInvert(at));
-#endif
-
-  cairo_t *c = cairo_create(s);
-
-#if defined(__APPLE__) && defined(FLTK_HAVE_CAIROEXT)
-  CGContextRestoreGState((CGContextRef)gc);
-#endif
-
-  cairo_state_.cc(c); //  and purge any previously owned context
-  cairo_surface_destroy(s);
-  return c;
-}
-
-// Silence compiler warning if none of the Cairo options has been configured
-
-#else
-FL_EXPORT int fltk_cairo_dummy() {
-  return 1;
-}
-
-#endif // FLTK_HAVE_CAIRO
diff --git a/cairo/Makefile b/cairo/Makefile
index 3d7f79ec5..a7ca58af5 100644
--- a/cairo/Makefile
+++ b/cairo/Makefile
@@ -1,8 +1,8 @@
 #
-# CAIRO library makefile for the Fast Light Toolkit (FLTK).
+# Dummy Cairo Library Makefile for the Fast Light Toolkit (FLTK).
 #
 # Copyright 1997-2009 by Easy Software Products.
-# Copyright 2010-2021 by Bill Spitzak and others.
+# Copyright 2010-2023 by Bill Spitzak and others.
 #
 # This library is free software. Distribution and use rights are outlined in
 # the file "COPYING" which should have been included with this file.  If this
@@ -15,6 +15,15 @@
 #     https://www.fltk.org/bugs.php
 #
 
+########################################################################
+# Note: since FLTK 1.4.0 Fl_Cairo_Window support [1] is included in
+# libfltk and libfltk_cairo is no longer necessary. This directory is
+# used to build an "empty" dummy library for backwards compatibility,
+# just in case users expect it to exist.
+# ----------------------------------------------------------------------
+# The entire 'cairo' folder will be removed in a later FLTK release.
+########################################################################
+
 # Note:	see ../configure.in and/or ../makeinclude for definition of
 #	FL_VERSION (x.y.z), FL_ABI_VERSION (x.y.0), and FL_DSO_VERSION (x.y)
 
@@ -24,8 +33,8 @@ include ../makeinclude
 #
 # Object files...
 #
-CAIROCPPFILES   = Fl_Cairo.cxx
-CAIROOBJECTS	= $(CAIROCPPFILES:.cxx=.o)
+CAIROCFILES	= cairo_dummy.c
+CAIROOBJECTS	= $(CAIROCFILES:.c=.o)
 
 #
 # Make all of the targets...
@@ -89,7 +98,7 @@ mgwfltknox_cairo-$(FL_DSO_VERSION).dll: $(CAIROLIBNAME) ../src/mgwfltknox-$(FL_D
 clean:
 	-$(RM) *.o *.dll.a core.* *~ *.bak *.bck
 	-$(RM) $(CAIROOBJECTS)  $(CAIROLIBNAME) $(CAIRODSONAME) \
-		libfltk_cairo.so src/libfltk_cairo.sl  src/libfltk_cairo.dylib
+		libfltk_cairo.so src/libfltk_cairo.sl src/libfltk_cairo.dylib
 
 #
 # Install everything...
@@ -163,8 +172,8 @@ uninstall:
 
 $(CAIROOBJECTS):	../makeinclude
 
-depend: $(CAIROCPPFILES)
-	makedepend -Y -I.. -f makedepend -w 20 $(CAIROCPPFILES)
+depend: $(CAIROCFILES)
+	makedepend -Y -I.. -f makedepend -w 20 $(CAIROCFILES)
 	echo "# DO NOT DELETE THIS LINE -- make depend depends on it." > makedepend.tmp
 	echo "" >> makedepend.tmp
 	grep '^[a-zA-Z]' makedepend | ( LC_ALL=C sort -u -f >> makedepend.tmp; )
diff --git a/cairo/cairo_dummy.c b/cairo/cairo_dummy.c
new file mode 100644
index 000000000..afa47504b
--- /dev/null
+++ b/cairo/cairo_dummy.c
@@ -0,0 +1,28 @@
+/*
+  Dummy C file to build the dummy Cairo library for the FLTK project.
+
+  Copyright 2023 by Bill Spitzak and others.
+
+  This library is free software. Distribution and use rights are outlined in
+  the file "COPYING" which should have been included with this file.  If this
+  file is missing or damaged, see the license at:
+
+      https://www.fltk.org/COPYING.php
+
+  Please see the following page on how to report bugs and issues:
+
+      https://www.fltk.org/bugs.php
+*/
+
+/*
+  Note: since FLTK 1.4.0 Fl_Cairo_Window support is included in
+  libfltk and libfltk_cairo is no longer necessary. This directory is
+  used to build an "empty" dummy library for backwards compatibility,
+  just in case users expect it to exist.
+
+  The entire 'cairo' folder will be removed in a later FLTK release.
+*/
+
+int fl_cairo_dummy() {
+  return 0;
+}
diff --git a/cairo/makedepend b/cairo/makedepend
index 8734674b2..99be05b37 100644
--- a/cairo/makedepend
+++ b/cairo/makedepend
@@ -1,19 +1,2 @@
 # DO NOT DELETE THIS LINE -- make depend depends on it.
 
-Fl_Cairo.o: ../FL/Enumerations.H
-Fl_Cairo.o: ../FL/Fl.H
-Fl_Cairo.o: ../FL/fl_attr.h
-Fl_Cairo.o: ../FL/Fl_Bitmap.H
-Fl_Cairo.o: ../FL/Fl_Cairo.H
-Fl_Cairo.o: ../FL/fl_casts.H
-Fl_Cairo.o: ../FL/fl_config.h
-Fl_Cairo.o: ../FL/Fl_Export.H
-Fl_Cairo.o: ../FL/Fl_Group.H
-Fl_Cairo.o: ../FL/Fl_Image.H
-Fl_Cairo.o: ../FL/fl_types.h
-Fl_Cairo.o: ../FL/fl_utf8.h
-Fl_Cairo.o: ../FL/Fl_Widget.H
-Fl_Cairo.o: ../FL/Fl_Window.H
-Fl_Cairo.o: ../FL/platform.H
-Fl_Cairo.o: ../FL/platform_types.h
-Fl_Cairo.o: ../FL/x11.H