diff --git a/Makefile.base.mk b/Makefile.base.mk
index 0ce426fc..5320c54f 100644
--- a/Makefile.base.mk
+++ b/Makefile.base.mk
@@ -327,6 +327,10 @@ DGL_FLAGS   += -DHAVE_VULKAN
 VULKAN_FLAGS  = $(shell $(PKG_CONFIG) --cflags vulkan)
 VULKAN_LIBS   = $(shell $(PKG_CONFIG) --libs vulkan)
 
+ifneq ($(WINDOWS),true)
+VULKAN_LIBS  += -ldl
+endif
+
 endif
 
 # ---------------------------------------------------------------------------------------------------------------------
diff --git a/dgl/ImageWidgets.hpp b/dgl/ImageWidgets.hpp
index 245daea9..8a2fe040 100644
--- a/dgl/ImageWidgets.hpp
+++ b/dgl/ImageWidgets.hpp
@@ -21,6 +21,12 @@
 #include "ImageBaseWidgets.hpp"
 #include "SubWidget.hpp"
 
+// TODO switch to use templated image type after merging widget-related PRs
+#if defined(__GNUC__) && (__GNUC__ >= 6)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
+
 START_NAMESPACE_DGL
 
 // -----------------------------------------------------------------------
@@ -241,4 +247,8 @@ private:
 
 END_NAMESPACE_DGL
 
+#if defined(__GNUC__) && (__GNUC__ >= 6)
+# pragma GCC diagnostic pop
+#endif
+
 #endif // DGL_IMAGE_WIDGETS_HPP_INCLUDED
diff --git a/dgl/OpenGL.hpp b/dgl/OpenGL.hpp
index 8c0d87d0..f7dc1e4e 100644
--- a/dgl/OpenGL.hpp
+++ b/dgl/OpenGL.hpp
@@ -198,6 +198,8 @@ public:
     // FIXME this should not be needed
     inline void loadFromMemory(const char* rawData, uint w, uint h, ImageFormat format)
     { loadFromMemory(rawData, Size<uint>(w, h), format); };
+    inline void draw(const GraphicsContext& context)
+    { drawAt(context, Point<int>(0, 0)); };
     inline void drawAt(const GraphicsContext& context, int x, int y)
     { drawAt(context, Point<int>(x, y)); };
 
diff --git a/dgl/src/ImageBaseWidgets.cpp b/dgl/src/ImageBaseWidgets.cpp
index e01e2b10..45aca12f 100644
--- a/dgl/src/ImageBaseWidgets.cpp
+++ b/dgl/src/ImageBaseWidgets.cpp
@@ -57,7 +57,7 @@ void ImageBaseAboutWindow<ImageType>::setImage(const ImageType& image)
 template <class ImageType>
 bool ImageBaseAboutWindow<ImageType>::onKeyboard(const KeyboardEvent& ev)
 {
-    if (ev.press && ev.key == kCharEscape)
+    if (ev.press && ev.key == kKeyEscape)
     {
         close();
         return true;
diff --git a/dgl/src/ImageWidgets.cpp b/dgl/src/ImageWidgets.cpp
index 371c9cca..37061969 100644
--- a/dgl/src/ImageWidgets.cpp
+++ b/dgl/src/ImageWidgets.cpp
@@ -20,9 +20,15 @@
 #include "Common.hpp"
 #include "WidgetPrivateData.hpp"
 
-// FIXME make this code more generic and move GL specific bits to OpenGL.cpp
+// TODO make this code more generic and move GL specific bits to OpenGL.cpp
 #include "../OpenGL.hpp"
 
+// TODO switch to use templated image type after merging widget-related PRs
+#if defined(__GNUC__) && (__GNUC__ >= 6)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
+
 START_NAMESPACE_DGL
 
 // -----------------------------------------------------------------------
@@ -946,3 +952,7 @@ bool ImageSwitch::onMouse(const MouseEvent& ev)
 // -----------------------------------------------------------------------
 
 END_NAMESPACE_DGL
+
+#if defined(__GNUC__) && (__GNUC__ >= 6)
+# pragma GCC diagnostic pop
+#endif
diff --git a/dgl/src/OpenGL.cpp b/dgl/src/OpenGL.cpp
index 6e733bc9..4b23758b 100644
--- a/dgl/src/OpenGL.cpp
+++ b/dgl/src/OpenGL.cpp
@@ -63,6 +63,7 @@ void Line<T>::draw(const GraphicsContext&, const T width)
     drawLine<T>(posStart, posEnd);
 }
 
+// deprecated calls
 template<typename T>
 void Line<T>::draw()
 {
@@ -122,6 +123,7 @@ void Circle<T>::drawOutline(const GraphicsContext&, const T lineWidth)
     drawCircle<T>(fPos, fNumSegments, fSize, fSin, fCos, true);
 }
 
+// deprecated calls
 template<typename T>
 void Circle<T>::draw()
 {
@@ -178,6 +180,7 @@ void Triangle<T>::drawOutline(const GraphicsContext&, const T lineWidth)
     drawTriangle<T>(pos1, pos2, pos3, true);
 }
 
+// deprecated calls
 template<typename T>
 void Triangle<T>::draw()
 {
@@ -244,6 +247,7 @@ void Rectangle<T>::drawOutline(const GraphicsContext&, const T lineWidth)
     drawRectangle<T>(*this, true);
 }
 
+// deprecated calls
 template<typename T>
 void Rectangle<T>::draw()
 {
@@ -312,6 +316,47 @@ static void setupOpenGLImage(const OpenGLImage& image, GLuint textureId)
     glDisable(GL_TEXTURE_2D);
 }
 
+static void drawOpenGLImage(const OpenGLImage& image, const Point<int>& pos, const GLuint textureId, bool& setupCalled)
+{
+    if (textureId == 0 || image.isInvalid())
+        return;
+
+    if (! setupCalled)
+    {
+        setupOpenGLImage(image, textureId);
+        setupCalled = true;
+    }
+
+    glEnable(GL_TEXTURE_2D);
+    glBindTexture(GL_TEXTURE_2D, textureId);
+
+    glBegin(GL_QUADS);
+
+    {
+        const int x = pos.getX();
+        const int y = pos.getY();
+        const int w = static_cast<int>(image.getWidth());
+        const int h = static_cast<int>(image.getHeight());
+
+        glTexCoord2f(0.0f, 0.0f);
+        glVertex2d(x, y);
+
+        glTexCoord2f(1.0f, 0.0f);
+        glVertex2d(x+w, y);
+
+        glTexCoord2f(1.0f, 1.0f);
+        glVertex2d(x+w, y+h);
+
+        glTexCoord2f(0.0f, 1.0f);
+        glVertex2d(x, y+h);
+    }
+
+    glEnd();
+
+    glBindTexture(GL_TEXTURE_2D, 0);
+    glDisable(GL_TEXTURE_2D);
+}
+
 OpenGLImage::OpenGLImage()
     : ImageBase(),
       textureId(0),
@@ -362,7 +407,7 @@ void OpenGLImage::loadFromMemory(const char* const rdata, const Size<uint>& s, c
 
 void OpenGLImage::drawAt(const GraphicsContext&, const Point<int>& pos)
 {
-    drawAt(pos);
+    drawOpenGLImage(*this, pos, textureId, setupCalled);
 }
 
 OpenGLImage& OpenGLImage::operator=(const OpenGLImage& image) noexcept
@@ -374,55 +419,20 @@ OpenGLImage& OpenGLImage::operator=(const OpenGLImage& image) noexcept
     return *this;
 }
 
+// deprecated calls
 void OpenGLImage::draw()
 {
-    drawAt(Point<int>(0, 0));
+    drawOpenGLImage(*this, Point<int>(0, 0), textureId, setupCalled);
 }
 
 void OpenGLImage::drawAt(const int x, const int y)
 {
-    drawAt(Point<int>(x, y));
+    drawOpenGLImage(*this, Point<int>(x, y), textureId, setupCalled);
 }
 
 void OpenGLImage::drawAt(const Point<int>& pos)
 {
-    if (textureId == 0 || isInvalid())
-        return;
-
-    if (! setupCalled)
-    {
-        setupOpenGLImage(*this, textureId);
-        setupCalled = true;
-    }
-
-    glEnable(GL_TEXTURE_2D);
-    glBindTexture(GL_TEXTURE_2D, textureId);
-
-    glBegin(GL_QUADS);
-
-    {
-        const int x = pos.getX();
-        const int y = pos.getY();
-        const int w = static_cast<int>(size.getWidth());
-        const int h = static_cast<int>(size.getHeight());
-
-        glTexCoord2f(0.0f, 0.0f);
-        glVertex2d(x, y);
-
-        glTexCoord2f(1.0f, 0.0f);
-        glVertex2d(x+w, y);
-
-        glTexCoord2f(1.0f, 1.0f);
-        glVertex2d(x+w, y+h);
-
-        glTexCoord2f(0.0f, 1.0f);
-        glVertex2d(x, y+h);
-    }
-
-    glEnd();
-
-    glBindTexture(GL_TEXTURE_2D, 0);
-    glDisable(GL_TEXTURE_2D);
+    drawOpenGLImage(*this, pos, textureId, setupCalled);
 }
 
 // -----------------------------------------------------------------------
@@ -430,7 +440,8 @@ void OpenGLImage::drawAt(const Point<int>& pos)
 template <>
 void ImageBaseAboutWindow<OpenGLImage>::onDisplay()
 {
-    img.draw();
+    const GraphicsContext& context(getGraphicsContext());
+    img.draw(context);
 }
 
 template class ImageBaseAboutWindow<OpenGLImage>;
diff --git a/tests/Makefile b/tests/Makefile
index e1d3e8c3..24c9385b 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -4,9 +4,6 @@
 # Created by falkTX
 #
 
-# debug mode by default
-DEBUG=true
-
 include ../Makefile.base.mk
 
 # ---------------------------------------------------------------------------------------------------------------------