Shaders: clean up Flat, set default color only for textured one.

Also probably fixed a few issues when compiling the shader on older GLSL
and GLSL ES (floating point literal suffixed, missing precision qualifiers).
And less crazy preprocessor.

src/Magnum/Shaders/Flat.cpp

@@ -100,7 +100,8 @@ template<UnsignedInt dimensions> Flat<dimensions>::Flat(const Flags flags): tran
 
     /* Set defaults in OpenGL ES (for desktop they are set in shader code itself) */
     #ifdef MAGNUM_TARGET_GLES
-    setColor(Color4(1.0f)); // Default to white, with full transperancy (so we can see the texture)
+    /* Default to fully opaque white so we can see the texture */
+    if(flags & Flag::Textured) setColor(Color4(1.0f));
     #endif
 }
 

src/Magnum/Shaders/Flat.frag

@@ -31,25 +31,19 @@
 
 #ifdef TEXTURED
 #ifdef EXPLICIT_TEXTURE_LAYER
-layout(binding = 0) uniform sampler2D textureData;
-#else
-uniform sampler2D textureData;
+layout(binding = 0)
 #endif
+uniform lowp sampler2D textureData;
 #endif
 
 #ifdef EXPLICIT_UNIFORM_LOCATION
-#   ifndef GL_ES
-layout(location = 1) uniform vec4 color = vec4(1.0f, 1.0f, 1.0f, 1.0f);
-#   else
-layout(location = 1) uniform vec4 color;
-#   endif
-#else
-#   ifndef GL_ES
-uniform lowp vec4 color = vec4(1.0f, 1.0f, 1.0f, 1.0f);
-#   else
-uniform lowp vec4 color;
-#   endif
+layout(location = 1)
 #endif
+uniform lowp vec4 color
+    #if !defined(GL_ES) && defined(TEXTURED)
+    = vec4(1.0)
+    #endif
+    ;
 
 #ifdef TEXTURED
 in mediump vec2 interpolatedTextureCoordinates;
@@ -60,9 +54,9 @@ out lowp vec4 fragmentColor;
 #endif
 
 void main() {
-    #ifdef TEXTURED
-    fragmentColor = color * texture(textureData, interpolatedTextureCoordinates);
-    #else
-    fragmentColor = color;
-    #endif
+    fragmentColor =
+        #ifdef TEXTURED
+        texture(textureData, interpolatedTextureCoordinates)*
+        #endif
+        color;
 }

src/Magnum/Shaders/Flat.h

@@ -50,11 +50,11 @@ Draws whole mesh with given unshaded color or texture. For colored mesh you
 need to provide @ref Position attribute in your triangle mesh and call at least
 @ref setTransformationProjectionMatrix() and @ref setColor().
 
-If you want to use texture instead of color, you need to provide also
-@ref TextureCoordinates attribute. Pass @ref Flag::Textured to constructor and
-then at render time don't forget to set also the texture via @ref setTexture().
-The texture will be multiplied with the color (which is white by default, thus
-it doesn't change texture color).
+If you want to use texture, you need to provide also @ref TextureCoordinates
+attribute. Pass @ref Flag::Textured to constructor and then at render time
+don't forget to set also the texture via @ref setTexture(). The texture is
+multipled by the color, which is by default set to fully opaque white if
+texturing is enabled.
 
 For coloring the texture based on intensity you can use the @ref Vector shader.
 
@@ -185,12 +185,14 @@ template<UnsignedInt dimensions> class MAGNUM_SHADERS_EXPORT Flat: public Abstra
          * @brief Set color
          * @return Reference to self (for method chaining)
          *
-         * If not set, default value is fully opaque white. Color will be
-         * multiplied with texture if @ref Flag::Textured is set.
+         * If @ref Flag::Textured is set, default value is `{1.0f, 1.0f, 1.0f}`
+         * and the color will be multiplied with texture.
          * @see @ref setTexture()
          */
-        /* MSVC needs inline also here to avoid linkage conflicts */
-        inline Flat<dimensions>& setColor(const Color4& color);
+        Flat<dimensions>& setColor(const Color4& color){
+            setUniform(colorUniform, color);
+            return *this;
+        }
 
         /**
          * @brief Set texture
@@ -216,11 +218,6 @@ typedef Flat<3> Flat3D;
 
 CORRADE_ENUMSET_OPERATORS(Implementation::FlatFlags)
 
-template<UnsignedInt dimensions> inline Flat<dimensions>& Flat<dimensions>::setColor(const Color4& color) {
-    setUniform(colorUniform, color);
-    return *this;
-}
-
 }}
 
 #endif