3 files changed, 25 insertions, 0 deletions

diff --git a/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.H b/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.H
index 526cad688..9a3d06086 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.H
+++ b/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.H
@@ -41,6 +41,8 @@ class Fl_Cocoa_Gl_Window_Driver : public Fl_Gl_Window_Driver {
   virtual void gl_start();
   virtual char *alpha_mask_for_string(const char *str, int n, int w, int h, Fl_Fontsize fs);
   virtual Fl_RGB_Image* capture_gl_rectangle(int x, int y, int w, int h);
+  virtual bool need_scissor() { return true; }
+  void apply_scissor();
 };
 
 
diff --git a/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.cxx b/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.cxx
index d1ed8df1e..a77ff7776 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.cxx
+++ b/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.cxx
@@ -69,6 +69,9 @@ GLContext Fl_Cocoa_Gl_Window_Driver::create_gl_context(Fl_Window* window, const
   context = Fl_Cocoa_Window_Driver::create_GLcontext_for_window(((Fl_Cocoa_Gl_Choice*)g)->pixelformat, (NSOpenGLContext*)shared_ctx, window);
   if (!context) return 0;
   add_context(context);
+  Fl_Cocoa_Window_Driver::GLcontext_makecurrent((NSOpenGLContext*)context);
+  glClearColor(0., 0., 0., 1.);
+  apply_scissor();
   return (context);
 }
 
@@ -185,9 +188,28 @@ void Fl_Cocoa_Gl_Window_Driver::swap_buffers() {
 char Fl_Cocoa_Gl_Window_Driver::swap_type() {return copy;}
 
 void Fl_Cocoa_Gl_Window_Driver::resize(int is_a_resize, int w, int h) {
+  if (pWindow->shown()) apply_scissor();
   Fl_Cocoa_Window_Driver::GLcontext_update((NSOpenGLContext*)pWindow->context());
 }
 
+void Fl_Cocoa_Gl_Window_Driver::apply_scissor() {
+  CGRect *extents = Fl_Cocoa_Window_Driver::driver(pWindow)->subRect();
+  if (extents) {
+    Fl_Cocoa_Window_Driver::remove_gl_context_opacity((NSOpenGLContext*)pWindow->context());
+    glDisable(GL_SCISSOR_TEST);
+    GLdouble vals[4];
+    glGetDoublev(GL_COLOR_CLEAR_VALUE, vals);
+    glClearColor(0., 0., 0., 0.);
+    glClear(GL_COLOR_BUFFER_BIT);
+    glClearColor(vals[0], vals[1], vals[2], vals[3]);
+    float s = pWindow->pixels_per_unit();
+    glScissor(s*extents->origin.x, s*extents->origin.y, s*extents->size.width, s*extents->size.height);
+//printf("apply_scissor %dx%d %dx%d\n",extents->x, extents->y, extents->width, extents->height);
+    glEnable(GL_SCISSOR_TEST);
+  }
+}
+
+
 /* Some old Apple hardware doesn't implement the GL_EXT_texture_rectangle extension.
  For it, draw_string_legacy_glut() is used to draw text. */
 
diff --git a/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H b/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H
index ce3b15629..cbd853776 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H
+++ b/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H
@@ -154,6 +154,7 @@ public:
   static void GLcontext_makecurrent(NSOpenGLContext*); // uses Objective-c
   static void GL_cleardrawable(void); // uses Objective-c
   static void gl_start(NSOpenGLContext*); // uses Objective-c
+  static void remove_gl_context_opacity(NSOpenGLContext*); // uses Objective-c
 
   //icons
   virtual void icons(const Fl_RGB_Image *icons[], int count);