1 files changed, 39 insertions, 0 deletions
diff --git a/src/fl_overlay.cxx b/src/fl_overlay.cxx
new file mode 100644
index 000000000..ed44ec9c6
--- /dev/null
+++ b/src/fl_overlay.cxx
@@ -0,0 +1,39 @@
+// fl_overlay.C
+
+// Extremely limited "overlay" support.  You can use this to drag out
+// a rectangle in response to mouse events.  It is your responsibility
+// to erase the overlay before drawing anything that might intersect
+// it.
+
+#include <FL/x.H>
+#include <FL/fl_draw.H>
+
+static int px,py,pw,ph;
+
+static void draw_current_rect() {
+#ifdef WIN32
+  int old = SetROP2(fl_gc, R2_NOT);
+  fl_rect(px, py, pw, ph);
+  SetROP2(fl_gc, old);
+#else
+  XSetFunction(fl_display, fl_gc, GXxor);
+  XSetForeground(fl_display, fl_gc, 0xffffffff);
+  XDrawRectangle(fl_display, fl_window, fl_gc, px, py, pw, ph);
+  XSetFunction(fl_display, fl_gc, GXcopy);
+#endif
+}
+
+void fl_overlay_clear() {
+  if (pw > 0) {draw_current_rect(); pw = 0;}
+}
+
+void fl_overlay_rect(int x, int y, int w, int h) {
+  if (w < 0) {x += w; w = -w;} else if (!w) w = 1;
+  if (h < 0) {y += h; h = -h;} else if (!h) h = 1;
+  if (pw > 0) {
+    if (x==px && y==py && w==pw && h==ph) return;
+    draw_current_rect();
+  }
+  px = x; py = y; pw = w; ph = h;
+  draw_current_rect();
+}