Added example to demonstrate selection functions

examples/selection_ex.jl

@@ -0,0 +1,62 @@
+#!/usr/bin/env julia
+
+import Random
+srand(seed) = Random.seed!(seed)
+
+import GR
+
+function draw(selection, x_offset, y_offset)
+    GR.clearws()
+
+    srand(0)
+    xd = -2 .+ 4 * rand(100)
+    yd = -2 .+ 4 * rand(100)
+    zd = [xd[i] * exp(-xd[i]^2 - yd[i]^2) for i = 1:100]
+
+    GR.setviewport(0.1, 0.95, 0.1, 0.95)
+    GR.setwindow(-2, 2, -2, 2)
+    GR.setmarkersize(1)
+    GR.setmarkertype(GR.MARKERTYPE_SOLID_CIRCLE)
+    GR.setcharheight(0.024)
+    GR.settextalign(2, 0)
+    GR.settextfontprec(3, 0)
+
+    x, y, z = GR.gridit(xd, yd, zd, 200, 200)
+    h = -0.6:0.05:0.6
+    GR.contourf(x, y, h, z, 2)
+    GR.polymarker(xd, yd)
+    if selection > 0
+        GR.beginselection(selection, 0)
+    end
+    GR.axes(0.25, 0.25, -2, -2, 2, 2, 0.01)
+    if selection > 0
+        GR.endselection()
+        GR.moveselection(x_offset, y_offset)
+    end
+
+    GR.updatews()
+end
+
+function main()
+    mouse = Nothing
+    x_offset = y_offset = 0
+
+    draw(0, 0, 0)
+
+    while true
+        x, y, buttons = GR.samplelocator()
+        if mouse != Nothing && buttons != 0
+            x_offset += x - mouse[1]
+            y_offset += y - mouse[2]
+        end
+        mouse = [x, y]
+
+        draw(1, x_offset, y_offset)
+
+        if buttons & 0x02 != 0
+            break
+        end
+    end
+end
+
+main()