GL: add a GL::AbstractShaderProgram::maxGeometryOutputVertices() query.

doc/changelog.dox

@@ -106,7 +106,8 @@ See also:
     more information.
 -   New @ref GL::Buffer::Buffer(Containers::ArrayView<const void>, BufferUsage)
     constructor for directly creating buffers filled with data.
--   New @ref GL::Mesh::maxVertexAttributeStride() limit query
+-   New @ref GL::Mesh::maxVertexAttributeStride() and
+    @ref GL::AbstractShaderProgram::maxGeometryOutputVertices() limit queries
 -   Added a @ref GL::Shader::Shader(NoCreateT) constructor for consistency with
     other OpenGL wrapper objects
 

doc/opengl-mapping.dox

@@ -496,7 +496,7 @@ glGet() parameter                       | Matching API
 @def_gl{MAX_FRAMEBUFFER_SAMPLES}        | |
 @def_gl{MAX_FRAMEBUFFER_WIDTH}          | |
 @def_gl{MAX_FRAGMENT_INPUT_COMPONENTS}, \n @def_gl{MAX_GEOMETRY_INPUT_COMPONENTS}, \n @def_gl{MAX_GEOMETRY_OUTPUT_COMPONENTS}, \n @def_gl{MAX_GEOMETRY_TOTAL_OUTPUT_COMPONENTS}, \n @def_gl{MAX_TESS_CONTROL_INPUT_COMPONENTS}, \n @def_gl{MAX_TESS_CONTROL_OUTPUT_COMPONENTS}, \n @def_gl{MAX_TESS_CONTROL_TOTAL_OUTPUT_COMPONENTS}, \n @def_gl{MAX_TESS_EVALUATION_INPUT_COMPONENTS}, \n @def_gl{MAX_TESS_EVALUATION_OUTPUT_COMPONENTS}, \n @def_gl{MAX_VERTEX_OUTPUT_COMPONENTS}, \n @def_gl{MAX_VARYING_VECTORS} | @ref GL::Shader::maxFragmentInputComponents(), \n @ref GL::Shader::maxGeometryInputComponents(), \n @ref GL::Shader::maxGeometryOutputComponents(), \n @ref GL::Shader::maxGeometryTotalOutputComponents(), \n @ref GL::Shader::maxTessellationControlInputComponents(), \n @ref GL::Shader::maxTessellationControlOutputComponents(), \n @ref GL::Shader::maxTessellationControlTotalOutputComponents(), \n @ref GL::Shader::maxTessellationEvaluationInputComponents(), \n @ref GL::Shader::maxTessellationEvaluationOutputComponents(), \n @ref GL::Shader::maxVertexOutputComponents()
-@def_gl{MAX_GEOMETRY_OUTPUT_VERTICES}   | |
+@def_gl{MAX_GEOMETRY_OUTPUT_VERTICES}   | @ref GL::AbstractShaderProgram::maxGeometryOutputVertices()
 @def_gl{MAX_GEOMETRY_SHADER_INVOCATIONS} | |
 @def_gl{MAX_IMAGE_SAMPLES}              | @ref GL::AbstractShaderProgram::maxImageSamples()
 @def_gl{MAX_IMAGE_UNITS}                | @ref GL::AbstractShaderProgram::maxImageUnits()

src/Magnum/GL/AbstractShaderProgram.cpp

@@ -62,6 +62,23 @@ Int AbstractShaderProgram::maxVertexAttributes() {
 }
 
 #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+Int AbstractShaderProgram::maxGeometryOutputVertices() {
+    #ifndef MAGNUM_TARGET_GLES
+    if(!Context::current().isExtensionSupported<Extensions::ARB::geometry_shader4>())
+        return 0;
+    #else
+    if(!Context::current().isExtensionSupported<Extensions::EXT::geometry_shader>())
+        return 0;
+    #endif
+
+    GLint& value = Context::current().state().shaderProgram->maxGeometryOutputVertices;
+
+    if(value == 0)
+        glGetIntegerv(GL_MAX_GEOMETRY_OUTPUT_VERTICES, &value);
+
+    return value;
+}
+
 Int AbstractShaderProgram::maxAtomicCounterBufferSize() {
     #ifndef MAGNUM_TARGET_GLES
     if(!Context::current().isExtensionSupported<Extensions::ARB::shader_atomic_counters>())

src/Magnum/GL/AbstractShaderProgram.h

@@ -462,6 +462,21 @@ class MAGNUM_GL_EXPORT AbstractShaderProgram: public AbstractObject {
         static Int maxVertexAttributes();
 
         #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+        /**
+         * @brief Max supported count of vertices emitted by a geometry shader
+         * @m_since_latest
+         *
+         * The result is cached, repeated queries don't result in repeated
+         * OpenGL calls. If neither @gl_extension{ARB,geometry_shader4} (part of
+         * OpenGL 3.2) nor @gl_extension{ANDROID,extension_pack_es31a} /
+         * @gl_extension{EXT,geometry_shader} (part of OpenGL ES 3.2) is not
+         * available, returns @cpp 0 @ce.
+         * @see @fn_gl{Get} with @def_gl_keyword{MAX_GEOMETRY_OUTPUT_VERTICES}
+         * @requires_gles30 Not defined in OpenGL ES 2.0.
+         * @requires_gles Geometry shaders are not available in WebGL.
+         */
+        static Int maxGeometryOutputVertices();
+
         /**
          * @brief Max supported atomic counter buffer size
          *

src/Magnum/GL/Implementation/ShaderProgramState.cpp

@@ -36,7 +36,7 @@ namespace Magnum { namespace GL { namespace Implementation {
 ShaderProgramState::ShaderProgramState(Context& context, std::vector<std::string>& extensions): current(0), maxVertexAttributes(0)
         #ifndef MAGNUM_TARGET_GLES2
         #ifndef MAGNUM_TARGET_WEBGL
-        , maxAtomicCounterBufferSize(0), maxComputeSharedMemorySize(0), maxComputeWorkGroupInvocations(0), maxImageUnits(0), maxCombinedShaderOutputResources(0), maxUniformLocations(0)
+        , maxGeometryOutputVertices{0}, maxAtomicCounterBufferSize(0), maxComputeSharedMemorySize(0), maxComputeWorkGroupInvocations(0), maxImageUnits(0), maxCombinedShaderOutputResources(0), maxUniformLocations(0)
         #endif
         , minTexelOffset(0), maxTexelOffset(0), maxUniformBlockSize(0)
         #ifndef MAGNUM_TARGET_WEBGL

src/Magnum/GL/Implementation/ShaderProgramState.h

@@ -97,7 +97,8 @@ struct ShaderProgramState {
     GLint maxVertexAttributes;
     #ifndef MAGNUM_TARGET_GLES2
     #ifndef MAGNUM_TARGET_WEBGL
-    GLint maxAtomicCounterBufferSize,
+    GLint maxGeometryOutputVertices,
+        maxAtomicCounterBufferSize,
         maxComputeSharedMemorySize,
         maxComputeWorkGroupInvocations,
         maxImageUnits,

src/Magnum/Platform/gl-info.cpp

@@ -687,6 +687,7 @@ MagnumInfo::MagnumInfo(const Arguments& arguments): Platform::WindowlessApplicat
         _h(EXT::geometry_shader)
         #endif
 
+        _l(GL::AbstractShaderProgram::maxGeometryOutputVertices())
         _l(GL::Shader::maxGeometryInputComponents())
         _l(GL::Shader::maxGeometryOutputComponents())
         _l(GL::Shader::maxGeometryTotalOutputComponents())