Combine custom vertex with built-in fragment shader.

lib/kwinglutils.cpp

@@ -1303,6 +1303,28 @@ GLShader *ShaderManager::loadFragmentShader(ShaderType vertex, const QString &fr
     return shader;
 }
 
+GLShader *ShaderManager::loadVertexShader(ShaderType fragment, const QString &vertexFile)
+{
+    QString fragmentShader;
+    switch (fragment) {
+    // Simple and Generic Shader use same fragment Shader
+    case SimpleShader:
+    case GenericShader:
+        fragmentShader = ":/resources/scene-fragment.glsl";
+        break;
+    case ColorShader:
+        fragmentShader = ":/resources/scene-color-fragment.glsl";
+        break;
+    }
+    GLShader *shader = new GLShader(vertexFile, fragmentShader);
+    if (shader->isValid()) {
+        pushShader(shader);
+        resetShader(fragment);
+        popShader();
+    }
+    return shader;
+}
+
 GLShader *ShaderManager::loadShaderFromCode(const QString &vertexSource, const QString &fragmentSource)
 {
     GLShader *shader = new GLShader();

lib/kwinglutils.h

@@ -422,6 +422,13 @@ class KWIN_EXPORT ShaderManager
          * @return The created shader
          **/
         GLShader *loadFragmentShader(ShaderType vertex, const QString &fragmentFile);
+        /**
+         * Creates a GLShader with a built-in fragment shader and a custom vertex shader.
+         * @param fragment The generic fragment shader
+         * @param vertexFile The path to the source code of the vertex shader
+         * @return The created shader
+         **/
+        GLShader *loadVertexShader(ShaderType fragment, const QString &vertexFile);
         /**
          * Creates a GLShader with the specified sources.
          * The difference to GLShader is that it does not need to be loaded from files.