diff --git a/basis/math/bitwise/bitwise.factor b/basis/math/bitwise/bitwise.factor
index ad1907fcb0..afd83d4458 100644
--- a/basis/math/bitwise/bitwise.factor
+++ b/basis/math/bitwise/bitwise.factor
@@ -2,7 +2,7 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: arrays kernel math math.functions sequences
 sequences.private words namespaces macros hints
-combinators fry ;
+combinators fry io.binary ;
 IN: math.bitwise
 
 ! utilities
@@ -93,3 +93,11 @@ PRIVATE>
 
 : bit-count ( x -- n )
     dup 0 < [ bitnot ] when (bit-count) ; inline
+
+! Signed byte array to integer conversion
+: signed-le> ( bytes -- x )
+    [ le> ] [ length 8 * 1- on-bits ] bi
+    2dup > [ bitnot bitor ] [ drop ] if ;
+
+: signed-be> ( bytes -- x )
+    <reversed> signed-le> ;
diff --git a/basis/opengl/opengl.factor b/basis/opengl/opengl.factor
index 21fe663c44..ecb4c4a08c 100644
--- a/basis/opengl/opengl.factor
+++ b/basis/opengl/opengl.factor
@@ -64,7 +64,8 @@ MACRO: all-enabled-client-state ( seq quot -- )
     [ 2 GL_FLOAT 0 ] dip glTexCoordPointer ; inline
 
 : line-vertices ( a b -- )
-    append >c-float-array gl-vertex-pointer ;
+    [ first2 [ 0.5 + ] bi@ ] bi@ 4 narray
+    >c-float-array gl-vertex-pointer ;
 
 : gl-line ( a b -- )
     line-vertices GL_LINES 0 2 glDrawArrays ;
diff --git a/basis/ui/gadgets/buttons/buttons.factor b/basis/ui/gadgets/buttons/buttons.factor
index 11fb69fc7d..c975e64b12 100644
--- a/basis/ui/gadgets/buttons/buttons.factor
+++ b/basis/ui/gadgets/buttons/buttons.factor
@@ -111,8 +111,8 @@ TUPLE: checkmark-paint < caching-pen color last-vertices ;
 
 : checkmark-points ( dim -- points )
     {
-        [ { 0 0 } v* { 0 1 } v+ ]
-        [ { 1 1 } v* { 0 1 } v+ ]
+        [ { 0 0 } v* ]
+        [ { 1 1 } v* ]
         [ { 0 1 } v* ]
         [ { 1 0 } v* ]
     } cleave 4array ;
diff --git a/basis/ui/gadgets/editors/editors.factor b/basis/ui/gadgets/editors/editors.factor
index 74647a6afb..2cf6d24154 100644
--- a/basis/ui/gadgets/editors/editors.factor
+++ b/basis/ui/gadgets/editors/editors.factor
@@ -112,7 +112,7 @@ M: editor ungraft*
     line-height * ;
 
 : caret-loc ( editor -- loc )
-    [ editor-caret* ] keep 2dup loc>x 1+
+    [ editor-caret* ] keep 2dup loc>x
     rot first rot line>y 2array ;
 
 : caret-dim ( editor -- dim )
diff --git a/basis/ui/gadgets/grid-lines/grid-lines.factor b/basis/ui/gadgets/grid-lines/grid-lines.factor
index d7844e3fa3..adfdd16f69 100644
--- a/basis/ui/gadgets/grid-lines/grid-lines.factor
+++ b/basis/ui/gadgets/grid-lines/grid-lines.factor
@@ -27,7 +27,7 @@ M: grid-lines draw-boundary
         dup grid set
         dup rect-dim half-gap v- grid-dim set
         compute-grid
-        [ { 1 0 } draw-grid-lines ]
+        [ { -0.5 -0.5 } gl-translate { 1 0 } draw-grid-lines ]
         [
             { 0.5 -0.5 } gl-translate
             { 0 1 } draw-grid-lines
diff --git a/extra/graphics/bitmap/bitmap.factor b/extra/graphics/bitmap/bitmap.factor
index 4d83300934..4c35e3d7d0 100755
--- a/extra/graphics/bitmap/bitmap.factor
+++ b/extra/graphics/bitmap/bitmap.factor
@@ -1,11 +1,11 @@
 ! Copyright (C) 2007 Doug Coleman.
 ! See http://factorcode.org/license.txt for BSD license.
 
-USING: alien arrays byte-arrays combinators summary
-io.backend graphics.viewer io io.binary io.files kernel libc
-math math.functions namespaces opengl opengl.gl prettyprint
-sequences strings ui ui.gadgets.panes io.encodings.binary
-accessors grouping ;
+USING: alien arrays byte-arrays combinators summary io.backend
+graphics.viewer io io.binary io.files kernel libc math
+math.functions math.bitwise namespaces opengl opengl.gl
+prettyprint sequences strings ui ui.gadgets.panes
+io.encodings.binary accessors grouping ;
 IN: graphics.bitmap
 
 ! Currently can only handle 24bit bitmaps.
@@ -56,8 +56,8 @@ M: bitmap-magic summary
 
 : parse-bitmap-header ( bitmap -- )
     4 read le> >>header-length
-    4 read le> >>width
-    4 read le> >>height
+    4 read signed-le> >>width
+    4 read signed-le> >>height
     2 read le> >>planes
     2 read le> >>bit-count
     4 read le> >>compression
diff --git a/extra/ui/render/test/reference.bmp b/extra/ui/render/test/reference.bmp
new file mode 100644
index 0000000000..0740fcc817
Binary files /dev/null and b/extra/ui/render/test/reference.bmp differ
diff --git a/extra/ui/render/test/test.factor b/extra/ui/render/test/test.factor
new file mode 100644
index 0000000000..01b5b65bcf
--- /dev/null
+++ b/extra/ui/render/test/test.factor
@@ -0,0 +1,70 @@
+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: accessors colors arrays kernel sequences math byte-arrays
+namespaces cap graphics.bitmap
+ui.gadgets ui.gadgets.packs ui.gadgets.borders ui.gadgets.grids
+ui.gadgets.grid-lines ui.gadgets.labels ui.gadgets.buttons
+ui.render ui opengl opengl.gl ;
+IN: ui.render.test
+
+SINGLETON: line-test
+
+M: line-test draw-interior
+    2drop { 0 0 } { 0 10 } gl-line ;
+
+: <line-gadget> ( -- gadget )
+    <gadget>
+        line-test >>interior
+        { 1 10 } >>dim ;
+
+TUPLE: ui-render-test < pack { first-time? initial: t } ;
+
+: message-window ( text -- )
+    <label> "Message" open-window ;
+
+: check-rendering ( gadget -- )
+    gl-screenshot
+    "resource:extra/ui/render/test/reference.bmp" load-bitmap array>>
+    = "perfect" "needs work" ? "Your UI rendering is " prepend
+    message-window ;
+
+M: ui-render-test draw-gadget*
+    [ call-next-method ] [
+        dup first-time?>> [
+            dup check-rendering
+            f >>first-time?
+        ] when
+        drop
+    ] bi ;
+
+: <ui-render-test> ( -- gadget )
+    \ ui-render-test new-gadget
+        { 1 0 } >>orientation
+        <gadget>
+            black <solid> >>interior
+            { 98 98 } >>dim
+        1 <border> add-gadget
+        <gadget>
+            gray <solid> >>boundary
+            { 94 94 } >>dim
+        3 <border>
+            red <solid> >>boundary
+        add-gadget
+            <line-gadget> <line-gadget> <line-gadget> 3array
+            <line-gadget> <line-gadget> <line-gadget> 3array
+            <line-gadget> <line-gadget> <line-gadget> 3array
+        3array <grid>
+            { 5 5 } >>gap
+            blue <grid-lines> >>boundary
+        add-gadget
+        <gadget>
+            { 14 14 } >>dim
+            black <checkmark-paint> >>interior
+            black <solid> >>boundary
+        4 <border>
+        add-gadget ;
+    
+: ui-render-test ( -- )
+    <ui-render-test> "Test" open-window ;
+
+MAIN: ui-render-test