diff --git a/lib/kwinglutils.cpp b/lib/kwinglutils.cpp
index 21fa7aa319..a494822009 100644
--- a/lib/kwinglutils.cpp
+++ b/lib/kwinglutils.cpp
@@ -545,10 +545,7 @@ void GLTexture::render( QRegion region, const QRect& rect, bool useShader )
         m_vbo->setData( 4, 2, verts, texcoords );
         }
     if (useShader) {
-        GLint currentProgram;
-        glGetIntegerv( GL_CURRENT_PROGRAM, &currentProgram );
-        GLint location = glGetUniformLocation(currentProgram, "geometry");
-        glUniform4f(location, rect.x(), rect.y(), 0.0f, 0.0f);
+        ShaderManager::instance()->getBoundShader()->setUniform("offset", QVector2D(rect.x(), rect.y()));
     } else {
 #ifndef KWIN_HAVE_OPENGLES
         glTranslatef( rect.x(), rect.y(), 0.0f );
@@ -1260,10 +1257,11 @@ void ShaderManager::resetShader(ShaderType type)
     // resetShader is either called from init or from push, we know that a built-in shader is bound
     GLShader *shader = getBoundShader();
     switch (type) {
-    case SimpleShader:
-        shader->setUniform("displaySize", QVector2D(displayWidth(), displayHeight()));
-        // TODO: has to become offset
-        shader->setUniform("geometry", QVector4D(0, 0, 0, 0));
+    case SimpleShader: {
+        QMatrix4x4 projection;
+        projection.ortho(0, displayWidth(), displayHeight(), 0, 0, 65535);
+        shader->setUniform("projection", projection);
+        shader->setUniform("offset", QVector2D(0, 0));
         shader->setUniform("debug", 0);
         shader->setUniform("sample", 0);
         // TODO: has to become textureSize
@@ -1274,6 +1272,7 @@ void ShaderManager::resetShader(ShaderType type)
         shader->setUniform("brightness", 1.0f);
         shader->setUniform("saturation", 1.0f);
         break;
+    }
     case GenericShader: {
         shader->setUniform("debug", 0);
         shader->setUniform("sample", 0);
@@ -1305,13 +1304,15 @@ void ShaderManager::resetShader(ShaderType type)
         shader->setUniform("saturation", 1.0f);
         break;
     }
-    case ColorShader:
-        shader->setUniform("displaySize", QVector2D(displayWidth(), displayHeight()));
-        // TODO: has to become offset
-        shader->setUniform("geometry", QVector4D(0, 0, 0, 0));
+    case ColorShader: {
+        QMatrix4x4 projection;
+        projection.ortho(0, displayWidth(), displayHeight(), 0, 0, 65535);
+        shader->setUniform("projection", projection);
+        shader->setUniform("offset", QVector2D(0, 0));
         shader->setUniform("geometryColor", QVector4D(0, 0, 0, 1));
         break;
     }
+    }
 }
 
 /***  GLRenderTarget  ***/
diff --git a/scene-color-vertex.glsl b/scene-color-vertex.glsl
index 09759c5395..651e22ab3a 100644
--- a/scene-color-vertex.glsl
+++ b/scene-color-vertex.glsl
@@ -1,11 +1,10 @@
-// size of the complete display in pixels, x==width, y==height
-uniform vec2 displaySize;
-// geometry of the window/texture to be rendered: x, y, width, height in display geometry
-uniform vec4 geometry;
+uniform mat4 projection;
+// offset of the window/texture to be rendered
+uniform vec2 offset;
 
 // passed in vertex - only x and y are used
 attribute vec4 vertex;
 
 void main() {
-    gl_Position.xy = 2.0*vec2(geometry.x + vertex.x, displaySize.y - vertex.y - geometry.y)/displaySize - vertex.ww;
+    gl_Position = vec4(vertex.xy + offset, vertex.zw) * projection;
 }
diff --git a/scene-vertex.glsl b/scene-vertex.glsl
index 766609f286..d3b1c223cd 100644
--- a/scene-vertex.glsl
+++ b/scene-vertex.glsl
@@ -1,7 +1,6 @@
-// size of the complete display in pixels, x==width, y==height
-uniform vec2 displaySize;
-// geometry of the window/texture to be rendered: x, y, width, height in display geometry
-uniform vec4 geometry;
+uniform mat4 projection;
+// offset of the window/texture to be rendered
+uniform vec2 offset;
 
 // passed in vertex - only x and y are used
 attribute vec4 vertex;
@@ -13,5 +12,5 @@ varying vec2 varyingTexCoords;
 
 void main() {
     varyingTexCoords = texCoord;
-    gl_Position.xy = 2.0*vec2(geometry.x + vertex.x, displaySize.y - vertex.y - geometry.y)/displaySize - vertex.ww;
+    gl_Position = vec4(vertex.xy + offset, vertex.zw) * projection;
 }
diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index adb706eb63..2366bfc1f1 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -457,7 +457,7 @@ void SceneOpenGL::Window::performPaint( int mask, QRegion region, WindowPaintDat
             data.shader = ShaderManager::instance()->pushShader(ShaderManager::GenericShader);
         } else {
             data.shader = ShaderManager::instance()->pushShader(ShaderManager::SimpleShader);
-            data.shader->setUniform("geometry", QVector4D(x, y, toplevel->width(), toplevel->height()));
+            data.shader->setUniform("offset", QVector2D(x, y));
         }
         sceneShader = true;
     }
@@ -1141,7 +1141,7 @@ void SceneOpenGL::EffectFrame::render( QRegion region, double opacity, double fr
             ShaderManager::instance()->pushShader(shader);
         }
         if( sceneShader )
-            shader->setUniform("geometry", QVector4D(0, 0, 0, 0));
+            shader->setUniform("offset", QVector2D(0, 0));
         shader->setUniform("saturation", 1.0f);
         shader->setUniform("brightness", 1.0f);
 
@@ -1282,7 +1282,7 @@ void SceneOpenGL::EffectFrame::render( QRegion region, double opacity, double fr
         m_unstyledTexture->bind();
         const QPoint pt = m_effectFrame->geometry().topLeft();
         if (sceneShader) {
-            shader->setUniform("geometry", QVector4D(pt.x(), pt.y(), 0.0f, 0.0f));
+            shader->setUniform("geometry", QVector2D(pt.x(), pt.y()));
         } else {
 #ifndef KWIN_HAVE_OPENGLES
             glTranslatef( pt.x(), pt.y(), 0.0f );
diff --git a/scene_opengl_egl.cpp b/scene_opengl_egl.cpp
index 58a0f3f0d8..4d3a668d45 100644
--- a/scene_opengl_egl.cpp
+++ b/scene_opengl_egl.cpp
@@ -280,7 +280,8 @@ void SceneOpenGL::paintBackground(QRegion region)
     vbo->setUseColor(true);
     vbo->setUseShader(true);
     vbo->setData(verts.count() / 2, 2, verts.data(), NULL);
-    ShaderManager::instance()->pushShader(ShaderManager::ColorShader);
+    GLShader *shader = ShaderManager::instance()->pushShader(ShaderManager::ColorShader);
+    shader->setUniform("offset", QVector2D(0, 0));
     vbo->render(GL_TRIANGLES);
     ShaderManager::instance()->popShader();
 }