fix clipped drawing of non-filled rectangles

To avoid artifacts we need clip with a rectangle that is line_width()
larger than our expose area.

Noticed by: corvid <corvid@lavabit.com>

2 files changed, 14 insertions, 11 deletions

diff --git a/dw/fltkviewbase.cc b/dw/fltkviewbase.cc
index 97a78edb..437c109a 100644
--- a/dw/fltkviewbase.cc
+++ b/dw/fltkviewbase.cc
@@ -386,8 +386,11 @@ void FltkViewBase::drawRectangle (core::style::Color *color,
    int x2 = translateCanvasXToViewX (x + width);
    int y2 = translateCanvasYToViewY (y + height);
 
-   clipPoint (&x1, &y1);
-   clipPoint (&x2, &y2);
+   // We only support rectangles with line width 1px, so we clip with 
+   // a rectangle 1px wider and higher than what we actually expose.
+   // This is only really necessary for non-filled rectangles.
+   clipPoint (&x1, &y1, 1);
+   clipPoint (&x2, &y2, 1);
 
    ::fltk::Rectangle rect (x1, y1, x2 - x1, y2 - y1);
    if (filled)
diff --git a/dw/fltkviewbase.hh b/dw/fltkviewbase.hh
index fb3f2fe1..ba4cc6d2 100644
--- a/dw/fltkviewbase.hh
+++ b/dw/fltkviewbase.hh
@@ -26,16 +26,16 @@ private:
 
    void draw (const core::Rectangle *rect, DrawType type);
    void drawChildWidgets ();
-   inline void clipPoint (int *x, int *y) {
+   inline void clipPoint (int *x, int *y, int border) {
       if (exposeArea) {
-         if (*x < exposeArea->x ())
-            *x = exposeArea->x ();
-         if (*x > exposeArea->r ())
-            *x = exposeArea->r ();
-         if (*y < exposeArea->y ())
-            *y = exposeArea->y ();
-         if (*y > exposeArea->b ())
-            *y = exposeArea->b ();
+         if (*x < exposeArea->x () - border)
+            *x = exposeArea->x () - border;
+         if (*x > exposeArea->r () + border)
+            *x = exposeArea->r () + border;
+         if (*y < exposeArea->y () - border)
+            *y = exposeArea->y () - border;
+         if (*y > exposeArea->b () + border)
+            *y = exposeArea->b () + border;
       }
    }