improve FltkViewBase::drawRectangle

* allow negative width / height
* clip rectangle to size of the view. This avoids issues with 16 bit X11
  coordinates overflowing and seems to improve performance.

2 files changed, 23 insertions, 0 deletions

diff --git a/dw/fltkviewbase.cc b/dw/fltkviewbase.cc
index d12050ce..1d82a661 100644
--- a/dw/fltkviewbase.cc
+++ b/dw/fltkviewbase.cc
@@ -367,10 +367,23 @@ void FltkViewBase::drawRectangle (core::style::Color *color,
                                   int x, int y, int width, int height)
 {
    setcolor(((FltkColor*)color)->colors[shading]);
+   if (width < 0) {
+      x += width;
+      width = -width;
+   }
+   if (height < 0) {
+      y += height;
+      height = -height;
+   }
+
    int x1 = translateCanvasXToViewX (x);
    int y1 = translateCanvasYToViewY (y);
    int x2 = translateCanvasXToViewX (x + width);
    int y2 = translateCanvasYToViewY (y + height);
+
+   clipPoint (&x1, &y1);
+   clipPoint (&x2, &y2);
+
    ::fltk::Rectangle rect (x1, y1, x2 - x1, y2 - y1);
    if (filled)
       fillrect (rect);
diff --git a/dw/fltkviewbase.hh b/dw/fltkviewbase.hh
index 4dc0a27f..c502d2f7 100644
--- a/dw/fltkviewbase.hh
+++ b/dw/fltkviewbase.hh
@@ -25,6 +25,16 @@ private:
 
    void draw (const core::Rectangle *rect, DrawType type);
    void drawChildWidgets ();
+   inline void clipPoint (int *x, int *y) {
+      if (*x < 0)
+         *x = 0;
+      if (*x > w ())
+         *x = w ();
+      if (*y < 0)
+         *y = 0;
+      if (*y > h ())
+         *y = h ();
+   }
 
 protected:
    core::Layout *theLayout;