Cairo support under macOS 10.14 Mojave: slightly simpler implementation

This post http://www.fltk.org/newsgroups.php?s36927+gfltk.general+v36944
reports a full-size Cairo-using FLTK app to be OK under Mojave with the
equivalent of this fix for the 1.4 branch.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@13114 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/Fl.H

@@ -166,9 +166,6 @@ public: // should be private!
   static int compose_state; // used for dead keys (WIN32) or marked text (MacOS)
   static void call_screen_init(); // recompute screen number and dimensions
 #ifdef __APPLE__
-#  ifdef FLTK_HAVE_CAIRO
-      static bool using_cairo_context;
-#  endif
   static void reset_marked_text(); // resets marked text
   static void insertion_point_location(int x, int y, int height); // sets window coordinates & height of insertion point
 #endif

cairo/Fl_Cairo.cxx

@@ -34,7 +34,6 @@
 # elif defined(WIN32)
 #  include <cairo-win32.h>
 # elif defined(__APPLE_QUARTZ__)
-bool Fl::using_cairo_context = false;
 #  include <cairo-quartz.h>
 # else
 #  error Cairo is not supported on this platform.
@@ -79,15 +78,9 @@ cairo_t * Fl::cairo_make_current(Fl_Window* wi) {
     if (fl_gc==0) { // means remove current cc
 	Fl::cairo_cc(0); // destroy any previous cc
 	cairo_state_.window(0);
-#if defined(__APPLE_QUARTZ__)
-      Fl::using_cairo_context = false;
-#endif
 	return 0;
     }
 
-#if defined(__APPLE_QUARTZ__)
-  Fl::using_cairo_context = true;
-#endif
     // don't re-create a context if it's the same gc/window couple
     if (fl_gc==Fl::cairo_state_.gc() && fl_xid(wi) == (Window) Fl::cairo_state_.window())
 	return Fl::cairo_cc();

src/Fl_cocoa.mm

@@ -2420,20 +2420,8 @@ static CGContextRef prepare_bitmap_for_layer(int w, int h ) {
   }
   if (window->damage()) {
     through_drawRect = YES;
-#ifdef FLTK_HAVE_CAIRO
-    CGFloat before_flush = CGContextGetCTM(layer_gc).d;
-    Fl::using_cairo_context = false;
-#endif
     i->flush();
     Fl_X::q_release_context();
-#ifdef FLTK_HAVE_CAIRO
-    if (Fl::using_cairo_context && CGContextGetCTM(layer_gc).d != before_flush ) {
-      // necessary for Cairo and layer-backed views
-      CGContextRestoreGState(layer_gc);
-      CGContextSaveGState(layer_gc);
-    }
-    Fl::using_cairo_context = false;
-#endif
     through_drawRect = NO;
     window->clear_damage();
     if (layer_gc) {
@@ -3549,6 +3537,13 @@ void Fl_Window::make_current()
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_8
   if (views_use_CA) {
     i->gc = ((FLView*)[fl_window contentView])->layer_gc;
+#  ifdef FLTK_HAVE_CAIRO
+    // make sure the GC starts with an identity transformation matrix as do native Cocoa GC's
+    CGAffineTransform mat = CGContextGetCTM(i->gc);
+    if (!CGAffineTransformIsIdentity(mat)) { // 10.4
+      CGContextConcatCTM(i->gc, CGAffineTransformInvert(mat));
+    }
+#  endif
   } else
 #endif
   {
@@ -4480,7 +4475,7 @@ static NSBitmapImageRep* rect_to_NSBitmapImageRep_layer(Fl_Window *win, int x, i
   int resolution = i->mapped_to_retina() ? 2 : 1;
   if (x || y || w != win->w() || h != win->h()) {
     CGRect rect = CGRectMake(x * resolution, y * resolution, w * resolution, h * resolution);
-    CGImageRef cgimg2 = CGImageCreateWithImageInRect(cgimg, rect);
+    CGImageRef cgimg2 = CGImageCreateWithImageInRect(cgimg, rect); //10.4
     CGImageRelease(cgimg);
     cgimg = cgimg2;
   }