Shaders: assert on the wireframe flag when calling related setters.

This is to be consistent with other shaders -- failing loudly is better
than habing to spend ages wondering why it doesn't render the thing.

doc/changelog.dox

@@ -781,6 +781,10 @@ See also:
     to indicate an invalid format, better catching accidentally forgotten
     initialization. Valid code shouldn't be affected by this change, but broken
     code that seemingly worked before might start throwing assertions now.
+-   @ref Shaders::MeshVisualizer now asserts if its wireframe-related setters
+    are called when the @ref Shaders::MeshVisualizer::Flag::Wireframe flag was
+    not set, consistently with other shaders. This might cause failures in code
+    that was calling them unnecessarily before.
 
 @section changelog-2019-01 2019.01
 

src/Magnum/Shaders/CMakeLists.txt

@@ -33,7 +33,6 @@ set_target_properties(MagnumShaders_RCS-dependencies PROPERTIES FOLDER "Magnum/S
 set(MagnumShaders_SRCS
     AbstractVector.cpp
     DistanceFieldVector.cpp
-    MeshVisualizer.cpp
     Vector.cpp
     VertexColor.cpp
 
@@ -41,6 +40,7 @@ set(MagnumShaders_SRCS
 
 set(MagnumShaders_GracefulAssert_SRCS
     Flat.cpp
+    MeshVisualizer.cpp
     Phong.cpp)
 
 set(MagnumShaders_HEADERS

src/Magnum/Shaders/MeshVisualizer.cpp

@@ -164,6 +164,8 @@ MeshVisualizer& MeshVisualizer::setTransformationProjectionMatrix(const Matrix4&
 }
 
 MeshVisualizer& MeshVisualizer::setViewportSize(const Vector2& size) {
+    /* Not asserting here, since the relation to wireframe is a bit vague.
+       Also it's an ugly hack that should be removed, ideally. */
     if(_flags & Flag::Wireframe && !(_flags & Flag::NoGeometryShader))
         setUniform(_viewportSizeUniform, size);
     return *this;
@@ -175,17 +177,24 @@ MeshVisualizer& MeshVisualizer::setColor(const Color4& color) {
 }
 
 MeshVisualizer& MeshVisualizer::setWireframeColor(const Color4& color) {
-    if(_flags & Flag::Wireframe) setUniform(_wireframeColorUniform, color);
+    CORRADE_ASSERT(_flags & Flag::Wireframe,
+        "Shaders::MeshVisualizer::setWireframeColor(): the shader was not created with wireframe enabled", *this);
+    setUniform(_wireframeColorUniform, color);
     return *this;
 }
 
 MeshVisualizer& MeshVisualizer::setWireframeWidth(const Float width) {
-    if(_flags & Flag::Wireframe) setUniform(_wireframeWidthUniform, width);
+    CORRADE_ASSERT(_flags & Flag::Wireframe,
+        "Shaders::MeshVisualizer::setWireframeWidth(): the shader was not created with wireframe enabled", *this);
+    setUniform(_wireframeWidthUniform, width);
     return *this;
 }
 
 MeshVisualizer& MeshVisualizer::setSmoothness(const Float smoothness) {
-    if(_flags & Flag::Wireframe)
+    /* This is a bit vaguely related too, but less vague than setViewportSize()
+       so asserting. */
+    CORRADE_ASSERT(_flags & Flag::Wireframe,
+        "Shaders::MeshVisualizer::setSmoothness(): the shader was not created with wireframe enabled", *this);
     setUniform(_smoothnessUniform, smoothness);
     return *this;
 }

src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp

@@ -24,9 +24,11 @@
 */
 
 #include <numeric>
+#include <sstream>
 #include <Corrade/Containers/ArrayViewStl.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/PluginManager/Manager.h>
+#include <Corrade/Utility/DebugStl.h>
 #include <Corrade/Utility/Directory.h>
 
 #include "Magnum/DebugTools/CompareImage.h"
@@ -67,6 +69,8 @@ struct MeshVisualizerGLTest: GL::OpenGLTester {
 
     void constructMove();
 
+    void setWireframeNotEnabled();
+
     void renderSetup();
     void renderTeardown();
 
@@ -121,7 +125,9 @@ MeshVisualizerGLTest::MeshVisualizerGLTest() {
               #endif
               &MeshVisualizerGLTest::constructWireframeNoGeometryShader,
 
-              &MeshVisualizerGLTest::constructMove});
+              &MeshVisualizerGLTest::constructMove,
+
+              &MeshVisualizerGLTest::setWireframeNotEnabled});
 
     addTests({&MeshVisualizerGLTest::renderDefaults,
               #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
@@ -218,6 +224,21 @@ void MeshVisualizerGLTest::constructMove() {
     CORRADE_VERIFY(!b.id());
 }
 
+void MeshVisualizerGLTest::setWireframeNotEnabled() {
+    std::ostringstream out;
+    Error redirectError{&out};
+
+    MeshVisualizer shader;
+    shader.setWireframeColor({})
+        .setWireframeWidth({})
+        .setSmoothness({});
+
+    CORRADE_COMPARE(out.str(),
+        "Shaders::MeshVisualizer::setWireframeColor(): the shader was not created with wireframe enabled\n"
+        "Shaders::MeshVisualizer::setWireframeWidth(): the shader was not created with wireframe enabled\n"
+        "Shaders::MeshVisualizer::setSmoothness(): the shader was not created with wireframe enabled\n");
+}
+
 constexpr Vector2i RenderSize{80, 80};
 
 void MeshVisualizerGLTest::renderSetup() {