Sanity check the shader limitations to protect against implementations

returning bogus values.

FIXED-IN: 4.5
BUG: 241449

svn path=/trunk/KDE/kdebase/workspace/; revision=1137677

effects/blur/blur.cpp

@@ -116,8 +116,7 @@ void BlurEffect::propertyNotify(EffectWindow *w, long atom)
 bool BlurEffect::supported()
 {
     return GLRenderTarget::supported() && GLTexture::NPOTTextureSupported() &&
-           ((GLShader::vertexShaderSupported() && GLShader::fragmentShaderSupported()) ||
-            hasGLExtension("GL_ARB_fragment_program"));
+           (GLSLBlurShader::supported() || ARBBlurShader::supported());
 }
 
 QRect BlurEffect::expand(const QRect &rect) const

effects/blur/blurshader.cpp

@@ -39,7 +39,7 @@ BlurShader::~BlurShader()
 
 BlurShader *BlurShader::create()
 {
-    if (GLShader::vertexShaderSupported() && GLShader::fragmentShaderSupported())
+    if (GLSLBlurShader::supported())
         return new GLSLBlurShader();
 
     return new ARBBlurShader();
@@ -122,6 +122,34 @@ void GLSLBlurShader::reset()
     setIsValid(false);
 }
 
+bool GLSLBlurShader::supported()
+{
+    if (!GLShader::fragmentShaderSupported() || !GLShader::vertexShaderSupported())
+        return false;
+
+    (void) glGetError(); // Clear the error state
+
+    // These are the minimum values the implementation is required to support
+    int value = 0;
+
+    glGetIntegerv(GL_MAX_VARYING_FLOATS, &value);
+    if (value < 32)
+        return false;
+
+    glGetIntegerv(GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &value);
+    if (value < 64)
+        return false;
+
+    glGetIntegerv(GL_MAX_VERTEX_UNIFORM_COMPONENTS, &value);
+    if (value < 512)
+        return false;
+
+    if (glGetError() != GL_NO_ERROR)
+        return false;
+
+    return true;
+}
+
 void GLSLBlurShader::setPixelDistance(float val)
 {
     if (!isValid())
@@ -312,6 +340,42 @@ void ARBBlurShader::reset()
     setIsValid(false);
 }
 
+bool ARBBlurShader::supported()
+{
+    if (!hasGLExtension("GL_ARB_fragment_program"))
+        return false;
+
+    (void) glGetError(); // Clear the error state
+
+    // These are the minimum values the implementation is required to support
+    int value = 0;
+
+    glGetProgramivARB(GL_FRAGMENT_PROGRAM_ARB, GL_MAX_PROGRAM_PARAMETERS_ARB, &value);
+    if (value < 24)
+        return false;
+
+    glGetProgramivARB(GL_FRAGMENT_PROGRAM_ARB, GL_MAX_PROGRAM_TEMPORARIES_ARB, &value);
+    if (value < 16)
+        return false;
+
+    glGetProgramivARB(GL_FRAGMENT_PROGRAM_ARB, GL_MAX_PROGRAM_INSTRUCTIONS_ARB, &value);
+    if (value < 72)
+        return false;
+
+    glGetProgramivARB(GL_FRAGMENT_PROGRAM_ARB, GL_MAX_PROGRAM_TEX_INSTRUCTIONS_ARB, &value);
+    if (value < 24)
+        return false;
+
+    glGetProgramivARB(GL_FRAGMENT_PROGRAM_ARB, GL_MAX_PROGRAM_TEX_INDIRECTIONS_ARB, &value);
+    if (value < 4)
+        return false;
+
+    if (glGetError() != GL_NO_ERROR)
+        return false;
+
+    return true;
+}
+
 void ARBBlurShader::setPixelDistance(float val)
 {
     float firstStep = val * 1.5;

effects/blur/blurshader.h

@@ -78,6 +78,8 @@ public:
     void bind();
     void unbind();
 
+    static bool supported();
+
 protected:
     void init();
     void reset();
@@ -108,6 +110,8 @@ public:
     void bind();
     void unbind();
 
+    static bool supported();
+
 protected:
     void init();
     void reset();