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diff --git a/examples/shaders/rect.frag b/examples/shaders/rect.frag
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+/* The fragment shader uses the UV coordinates to calculate whether it is in
+   the T, R, B, or L border.  These are then mixed with the border color, and
+   their inverse is mixed with the fill color, to calculate the fragment color.
+   For example, if we are in the top border, then T=1, so the border mix factor
+   TRBL=1, and the fill mix factor (1-TRBL) is 0.
+
+   The use of pixel units here is handy because the border width can be
+   specified precisely in pixels to draw sharp lines.  The border width is just
+   hardcoded, but could be made a uniform or vertex attribute easily enough. */
+
+INTER(location = 0) noperspective in vec2 f_uv;
+INTER(location = 1) noperspective in vec2 f_size;
+INTER(location = 2) noperspective in vec4 f_fillColor;
+
+layout(location = 0) out vec4 FragColor;
+
+void
+main()
+{
+	const float borderWidth = 2.0;
+
+	vec4  borderColor = f_fillColor + vec4(0.0, 0.4, 0.4, 0.0);
+	float t           = step(borderWidth, f_uv[1]);
+	float r           = step(borderWidth, f_size.x - f_uv[0]);
+	float b           = step(borderWidth, f_size.y - f_uv[1]);
+	float l           = step(borderWidth, f_uv[0]);
+	float fillMix     = t * r * b * l;
+	float borderMix   = 1.0 - fillMix;
+	vec4  fill        = fillMix * f_fillColor;
+	vec4  border      = borderMix * borderColor;
+
+	FragColor = fill + border;
+}