Fix a potential internal stack overflow in Xlib graphics driver.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12752 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

src/drivers/Xlib/Fl_Xlib_Graphics_Driver.H

@@ -46,6 +46,7 @@ struct _XRegion {
 #include <pango/pango.h>
 #endif
 
+#define FL_XLIB_GRAPHICS_TRANSLATION_STACK_SIZE (20)
 
 /**
  \brief The Xlib-specific graphics class.
@@ -56,7 +57,8 @@ class FL_EXPORT Fl_Xlib_Graphics_Driver : public Fl_Scalable_Graphics_Driver {
 private:
   int offset_x_, offset_y_; // translation between user and graphical coordinates: graphical = user + offset
   unsigned depth_; // depth of translation stack
-  int stack_x_[20], stack_y_[20]; // translation stack allowing cumulative translations
+  int stack_x_[FL_XLIB_GRAPHICS_TRANSLATION_STACK_SIZE]; // translation stack allowing cumulative translations
+  int stack_y_[FL_XLIB_GRAPHICS_TRANSLATION_STACK_SIZE];
   int line_delta_;
   virtual void set_current_();
   int clip_max_; // +/- x/y coordinate limit (16-bit coordinate space)

src/drivers/Xlib/Fl_Xlib_Graphics_Driver.cxx

@@ -263,14 +263,17 @@ Region Fl_Xlib_Graphics_Driver::scale_clip(float f) {
 
 
 void Fl_Xlib_Graphics_Driver::translate_all(int dx, int dy) { // reversibly adds dx,dy to the offset between user and graphical coordinates
-  stack_x_[depth_] = offset_x_;
-  stack_y_[depth_] = offset_y_;
-  offset_x_ = stack_x_[depth_] + dx;
-  offset_y_ = stack_y_[depth_] + dy;
+  if (depth_ < FL_XLIB_GRAPHICS_TRANSLATION_STACK_SIZE) {
+    stack_x_[depth_] = offset_x_;
+    stack_y_[depth_] = offset_y_;
+    depth_++;
+  } else {
+    Fl::warning("%s: translate stack overflow!", "Fl_Xlib_Graphics_Driver");
+  }
+  offset_x_ += dx;
+  offset_y_ += dy;
   push_matrix();
   translate(dx, dy);
-  if (depth_ < sizeof(stack_x_)/sizeof(int)) depth_++;
-  else Fl::warning("%s: translate stack overflow!", "Fl_Xlib_Graphics_Driver");
 }
 
 void Fl_Xlib_Graphics_Driver::untranslate_all() { // undoes previous translate_all()