GL: implement EXT_clip_control and WEBGL_polygon_mode on Emscripten.

Following the spirit of extension-based functionality, the entrypoints
are available always but do something (i.e., call the actual WebGL API)
only if the extension is advertised. Which it is only on Emscripten
3.1.66+ because older versions don't have the corresponding entrypoints,
so there it's marked as disabled.

Additionally, EXT_polygon_offset_clamp is now also working on 3.1.66+,
but there's no wrapper for it yet.

doc/changelog.dox

@@ -129,8 +129,9 @@ See also:
     extensions on GLES 3.1+, exposed as @ref GL::Texture::view() and similar
     APIs on other texture types
 -   Implemented the GL 4.5 @gl_extension{ARB,clip_control} extension and
-    matching @gl_extension{EXT,clip_control} extension on GLES, exposed as
+    matching @gl_extension{EXT,clip_control} and
-    @ref GL::Renderer::setClipControl(). See also [mosra/magnum#543](https://github.com/mosra/magnum/issues/543).
+    @webgl_extension{WEBGL,clip_control} extension on GLES and WebGL, exposed
+    as @ref GL::Renderer::setClipControl(). See also [mosra/magnum#543](https://github.com/mosra/magnum/issues/543).
 -   Implemented @gl_extension{EXT,texture_norm16} and
     @webgl_extension{EXT,texture_norm16} ES and WebGL extensions, making
     normalized 16-bit texture and renderbuffer formats available on all
@@ -156,18 +157,19 @@ See also:
     WebGL extensions, making @ref GL::SamplerWrapping::MirrorClampToEdge
     available on all platforms
 -   Implemented the @m_class{m-doc-external} [ANGLE_provoking_vertex](https://chromium.googlesource.com/angle/angle/+/main/extensions/ANGLE_provoking_vertex.txt)
-    and @m_class{m-doc-external} [ANGLE_polygon_mode](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_polygon_mode.txt)
+    ES extension. Recognized also on WebGL as
-    ES extensions. Recognized also on WebGL as
+    @webgl_extension{WEBGL,provoking_vertex} but with no implementation as
-    @webgl_extension{WEBGL,provoking_vertex} and
-    @webgl_extension{WEBGL,polygon_mode} but with no implementation as
     Emscripten doesn't have the required entrypoints yet.
+-   Implemented the @m_class{m-doc-external} [ANGLE_polygon_mode](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_polygon_mode.txt)
+    and @webgl_extension{WEBGL,polygon_mode} ES and WebGL extension.
 -   Implemented the @m_class{m-doc-external} [ANGLE_stencil_texturing](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_stencil_texturing.txt)
     ES and @webgl_extension{WEBGL,stencil_texturing} WebGL extensions
 -   Implemented the @gl_extension{EXT,blend_func_extended} ES and
     @webgl_extension{WEBGL,blend_func_extended} WebGL extensions
 -   Implemented the @gl_extension{INTEL,blackhole_render} desktop and ES
     extension
--   Recognizing @webgl_extension{EXT,float_blend} and
+-   Recognizing @webgl_extension{EXT,float_blend},
+    @webgl_extension{EXT,polygon_offset_clamp} and
     @webgl_extension{WEBGL,debug_shaders} WebGL extensions, no implementation
     done yet
 -   Implemented @ref GL-AbstractShaderProgram-async "Async shader compilation and linking"

doc/opengl-support.dox

@@ -576,7 +576,7 @@ Extension                                   | Status
 @webgl_extension{EXT,texture_compression_bptc} | done
 @webgl_extension{EXT,texture_norm16}        | done
 @webgl_extension{EXT,polygon_offset_clamp}  | |
-@webgl_extension{EXT,clip_control}          | |
+@webgl_extension{EXT,clip_control}          | done
 @webgl_extension{EXT,depth_clamp}           | done
 @webgl_extension{EXT,texture_mirror_clamp_to_edge} | done
 @webgl_extension{KHR,parallel_shader_compile} | done
@@ -598,7 +598,7 @@ Extension                                   | Status
 @webgl_extension{WEBGL,draw_instanced_base_vertex_base_instance} | done
 @webgl_extension{WEBGL,multi_draw_instanced_base_vertex_base_instance} | done
 @webgl_extension{WEBGL,provoking_vertex}    | missing support in Emscripten
-@webgl_extension{WEBGL,polygon_mode}        | |
+@webgl_extension{WEBGL,polygon_mode}        | done
 @webgl_extension{WEBGL,blend_func_extended} | done
 @webgl_extension{WEBGL,stencil_texturing}   | done
 

src/Magnum/GL/Implementation/RendererState.cpp

@@ -31,6 +31,16 @@
 #include "Magnum/GL/Context.h"
 #include "Magnum/GL/Extensions.h"
 
+/* The __EMSCRIPTEN_major__ etc macros used to be passed implicitly, version
+   3.1.4 moved them to a version header and version 3.1.23 dropped the
+   backwards compatibility. To work consistently on all versions, including the
+   header only if the version macros aren't present.
+   https://github.com/emscripten-core/emscripten/commit/f99af02045357d3d8b12e63793cef36dfde4530a
+   https://github.com/emscripten-core/emscripten/commit/f76ddc702e4956aeedb658c49790cc352f892e4c */
+#if defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(__EMSCRIPTEN_major__)
+#include <emscripten/version.h>
+#endif
+
 namespace Magnum { namespace GL { namespace Implementation {
 
 using namespace Containers::Literals;
@@ -206,7 +216,8 @@ RendererState::RendererState(Context& context, ContextState& contextState, Conta
     #endif
     #endif
 
-    #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_WEBGL)
+    #ifdef MAGNUM_TARGET_GLES
+    #ifndef MAGNUM_TARGET_WEBGL
     if(context.isExtensionSupported<Extensions::NV::polygon_mode>()) {
         extensions[Extensions::NV::polygon_mode::Index] =
                    Extensions::NV::polygon_mode::string();
@@ -215,7 +226,15 @@ RendererState::RendererState(Context& context, ContextState& contextState, Conta
         extensions[Extensions::ANGLE::polygon_mode::Index] =
                    Extensions::ANGLE::polygon_mode::string();
         polygonModeImplementation = glPolygonModeANGLE;
-    } else {
+    } else
+    #elif __EMSCRIPTEN_major__*10000 + __EMSCRIPTEN_minor__*100 + __EMSCRIPTEN_tiny__ >= 30166
+    if(context.isExtensionSupported<Extensions::WEBGL::polygon_mode>()) {
+        extensions[Extensions::WEBGL::polygon_mode::Index] =
+                   Extensions::WEBGL::polygon_mode::string();
+        polygonModeImplementation = glPolygonModeWEBGL;
+    } else
+    #endif
+    {
         polygonModeImplementation = nullptr;
     }
     #endif

src/Magnum/GL/Implementation/RendererState.h

@@ -59,7 +59,7 @@ struct RendererState {
     void(APIENTRY *blendFuncSeparateiImplementation)(GLuint, GLenum, GLenum, GLenum, GLenum);
     void(APIENTRY *colorMaskiImplementation)(GLuint, GLboolean, GLboolean, GLboolean, GLboolean);
     #endif
-    #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_WEBGL)
+    #ifdef MAGNUM_TARGET_GLES
     void(APIENTRY *polygonModeImplementation)(GLenum, GLenum);
     #endif
     #ifndef MAGNUM_TARGET_WEBGL

src/Magnum/GL/Implementation/driverSpecific.cpp

@@ -732,6 +732,16 @@ void Context::setupDriverWorkarounds() {
     #if __EMSCRIPTEN_major__*10000 + __EMSCRIPTEN_minor__*100 + __EMSCRIPTEN_tiny__ < 20000
     _setRequiredVersion(WEBGL::multi_draw, None);
     #endif
+    /* EXT_clip_control, EXT_polygon_offset_clamp and WEBGL_polygon_mode
+       entrypoints are only available since Emscripten 3.1.66:
+       https://github.com/emscripten-core/emscripten/pull/20841
+       However, the extension is advertised even on older versions and we have
+       no way to link to those entrypoints there. */
+    #if __EMSCRIPTEN_major__*10000 + __EMSCRIPTEN_minor__*100 + __EMSCRIPTEN_tiny__ < 30166
+    _setRequiredVersion(EXT::clip_control, None);
+    _setRequiredVersion(EXT::polygon_offset_clamp, None);
+    _setRequiredVersion(WEBGL::polygon_mode, None);
+    #endif
     #ifndef MAGNUM_TARGET_GLES2
     /* WEBGL_multi_draw_instanced_base_vertex_base_instance only since
        Emscripten 2.0.5: https://github.com/emscripten-core/emscripten/pull/12282 */

src/Magnum/GL/Renderer.cpp

@@ -33,6 +33,16 @@
 #include "Magnum/GL/Implementation/State.h"
 #include "Magnum/GL/Implementation/RendererState.h"
 
+/* The __EMSCRIPTEN_major__ etc macros used to be passed implicitly, version
+   3.1.4 moved them to a version header and version 3.1.23 dropped the
+   backwards compatibility. To work consistently on all versions, including the
+   header only if the version macros aren't present.
+   https://github.com/emscripten-core/emscripten/commit/f99af02045357d3d8b12e63793cef36dfde4530a
+   https://github.com/emscripten-core/emscripten/commit/f76ddc702e4956aeedb658c49790cc352f892e4c */
+#if defined(CORRADE_TARGET_EMSCRIPTEN) && !defined(__EMSCRIPTEN_major__)
+#include <emscripten/version.h>
+#endif
+
 namespace Magnum { namespace GL {
 
 Range1D Renderer::lineWidthRange() {
@@ -137,7 +147,6 @@ void Renderer::setProvokingVertex(const ProvokingVertex mode) {
 }
 #endif
 
-#ifndef MAGNUM_TARGET_WEBGL
 void Renderer::setPolygonMode(const PolygonMode mode) {
     #ifndef MAGNUM_TARGET_GLES
     glPolygonMode
@@ -146,7 +155,6 @@ void Renderer::setPolygonMode(const PolygonMode mode) {
     #endif
         (GL_FRONT_AND_BACK, GLenum(mode));
 }
-#endif
 
 void Renderer::setPolygonOffset(const Float factor, const Float units) {
     glPolygonOffset(factor, units);
@@ -331,15 +339,17 @@ void Renderer::depthRangefImplementationDefault(const Float near, const Float fa
 }
 #endif
 
-#ifndef MAGNUM_TARGET_WEBGL
 void Renderer::setClipControl(const ClipOrigin origin, const ClipDepth depth) {
     #ifndef MAGNUM_TARGET_GLES
     glClipControl(GLenum(origin), GLenum(depth));
-    #else
+    #elif !defined(MAGNUM_TARGET_WEBGL) || __EMSCRIPTEN_major__*10000 + __EMSCRIPTEN_minor__*100 + __EMSCRIPTEN_tiny__ >= 30166
     glClipControlEXT(GLenum(origin), GLenum(depth));
+    #else
+    static_cast<void>(origin);
+    static_cast<void>(depth);
+    CORRADE_INTERNAL_ASSERT_UNREACHABLE();
     #endif
 }
-#endif
 
 void Renderer::setColorMask(const GLboolean allowRed, const GLboolean allowGreen, const GLboolean allowBlue, const GLboolean allowAlpha) {
     glColorMask(allowRed, allowGreen, allowBlue, allowAlpha);

src/Magnum/GL/Renderer.h

@@ -417,7 +417,6 @@ class MAGNUM_GL_EXPORT Renderer {
              */
             PolygonOffsetFill = GL_POLYGON_OFFSET_FILL,
 
-            #ifndef MAGNUM_TARGET_WEBGL
             /**
              * Offset lines. Note that this affects only filled polygons
              * rendered with @ref setPolygonMode() set to
@@ -426,15 +425,20 @@ class MAGNUM_GL_EXPORT Renderer {
              *      @ref setPolygonOffset()
              * @requires_es_extension Extension @gl_extension{NV,polygon_offset}
              *      or @m_class{m-doc-external} [ANGLE_polygon_mode](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_polygon_mode.txt)
-             * @requires_gles Only @ref Feature::PolygonOffsetFill is available
+             * @requires_webgl_extension Extension @webgl_extension{WEBGL,polygon_mode}.
-             *      in WebGL.
+             *      Note that this extension is only implemented since
+             *      Emscripten 3.1.66 and thus it's not even advertised on
+             *      older versions.
              */
             #ifndef MAGNUM_TARGET_GLES
             PolygonOffsetLine = GL_POLYGON_OFFSET_LINE,
-            #else
+            #elif !defined(MAGNUM_TARGET_WEBGL)
             PolygonOffsetLine = GL_POLYGON_OFFSET_LINE_NV,
+            #else
+            PolygonOffsetLine = GL_POLYGON_OFFSET_LINE_WEBGL,
             #endif
 
+            #ifndef MAGNUM_TARGET_WEBGL
             /**
              * Offset points. Note that this affects only filled polygons
              * rendered with @ref setPolygonMode() set to
@@ -442,8 +446,8 @@ class MAGNUM_GL_EXPORT Renderer {
              * @see @ref Feature::PolygonOffsetFill, @ref Feature::PolygonOffsetLine,
              *      @ref setPolygonOffset()
              * @requires_es_extension Extension @gl_extension{NV,polygon_offset}
-             * @requires_gles Only @ref Feature::PolygonOffsetFill is available
+             * @requires_gles Only @ref Feature::PolygonOffsetFill and
-             *      in WebGL.
+             *      @ref Feature::PolygonOffsetPoint is available in WebGL.
              */
             #ifndef MAGNUM_TARGET_GLES
             PolygonOffsetPoint = GL_POLYGON_OFFSET_POINT,
@@ -856,7 +860,6 @@ class MAGNUM_GL_EXPORT Renderer {
         static void setProvokingVertex(ProvokingVertex mode);
         #endif
 
-        #ifndef MAGNUM_TARGET_WEBGL
         /**
          * @brief Polygon mode
          *
@@ -866,7 +869,10 @@ class MAGNUM_GL_EXPORT Renderer {
          *      @m_class{m-doc-external} [ANGLE_polygon_mode](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_polygon_mode.txt).
          *      Otherwise behaves always like @ref PolygonMode::Fill. See
          *      @ref Mesh::setPrimitive() for a possible workaround.
-         * @requires_gles WebGL behaves always like @ref PolygonMode::Fill. See
+         * @requires_webgl_extension Extension @webgl_extension{WEBGL,polygon_mode}.
+         *      Note that this extension is only implemented since Emscripten
+         *      3.1.66 and thus it's not even advertised on older versions.
+         *      Otherwise behaves always like @ref PolygonMode::Fill. See
          *      @ref Mesh::setPrimitive() for a possible workaround.
          */
         enum class PolygonMode: GLenum {
@@ -875,8 +881,10 @@ class MAGNUM_GL_EXPORT Renderer {
              */
             #ifndef MAGNUM_TARGET_GLES
             Fill = GL_FILL,
-            #else
+            #elif !defined(MAGNUM_TARGET_WEBGL)
             Fill = GL_FILL_NV,
+            #else
+            Fill = GL_FILL_WEBGL,
             #endif
 
             /**
@@ -884,21 +892,26 @@ class MAGNUM_GL_EXPORT Renderer {
              */
             #ifndef MAGNUM_TARGET_GLES
             Line = GL_LINE,
-            #else
+            #elif !defined(MAGNUM_TARGET_WEBGL)
             Line = GL_LINE_NV,
+            #else
+            Line = GL_LINE_WEBGL,
             #endif
 
+            #ifndef MAGNUM_TARGET_WEBGL
             /**
              * Starts of boundary edges are drawn as points. See also
              * @ref setPointSize().
              * @requires_es_extension Extension @gl_extension{NV,polygon_mode},
              *      not available with @m_class{m-doc-external} [ANGLE_polygon_mode](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_polygon_mode.txt)
+             * @requires_gles Not available in @webgl_extension{WEBGL,polygon_mode}
              */
             #ifndef MAGNUM_TARGET_GLES
             Point = GL_POINT
             #else
             Point = GL_POINT_NV
             #endif
+            #endif
         };
 
         /**
@@ -910,11 +923,13 @@ class MAGNUM_GL_EXPORT Renderer {
          *      @m_class{m-doc-external} [ANGLE_polygon_mode](https://chromium.googlesource.com/angle/angle/+/HEAD/extensions/ANGLE_polygon_mode.txt).
          *      Otherwise behaves always like the default. See
          *      @ref Mesh::setPrimitive() for possible workaround.
-         * @requires_gles WebGL behaves always like the default. See
+         * @requires_webgl_extension Extension @webgl_extension{WEBGL,polygon_mode}.
+         *      Note that this extension is only implemented since Emscripten
+         *      3.1.66 and thus it's not even advertised on older versions.
+         *      Otherwise behaves always like the default. See
          *      @ref Mesh::setPrimitive() for possible workaround.
          */
         static void setPolygonMode(PolygonMode mode);
-        #endif
 
         /**
          * @brief Set polygon offset
@@ -1234,7 +1249,6 @@ class MAGNUM_GL_EXPORT Renderer {
 
         /** @{ @name Depth testing and clip control */
 
-        #ifndef MAGNUM_TARGET_WEBGL
         /**
          * @brief Clip origin
          * @m_since_latest
@@ -1243,7 +1257,9 @@ class MAGNUM_GL_EXPORT Renderer {
          * @m_enum_values_as_keywords
          * @requires_gl45 Extension @gl_extension{ARB,clip_control}
          * @requires_es_extension Extension @gl_extension{EXT,clip_control}
-         * @requires_gles Clip control is not available in WebGL.
+         * @requires_webgl_extension Extension @webgl_extension{EXT,clip_control}.
+         *      Note that this extension is only implemented since Emscripten
+         *      3.1.66 and thus it's not even advertised on older versions.
          */
         enum class ClipOrigin: GLenum {
             /** Lower left */
@@ -1269,7 +1285,9 @@ class MAGNUM_GL_EXPORT Renderer {
          * @m_enum_values_as_keywords
          * @requires_gl45 Extension @gl_extension{ARB,clip_control}
          * @requires_es_extension Extension @gl_extension{EXT,clip_control}
-         * @requires_gles Clip control is not available in WebGL.
+         * @requires_webgl_extension Extension @webgl_extension{EXT,clip_control}.
+         *      Note that this extension is only implemented since Emscripten
+         *      3.1.66 and thus it's not even advertised on older versions.
          */
         enum class ClipDepth: GLenum {
             /** -1 to 1 */
@@ -1286,7 +1304,6 @@ class MAGNUM_GL_EXPORT Renderer {
             ZeroToOne = GL_ZERO_TO_ONE_EXT,
             #endif
         };
-        #endif
 
         /**
          * @brief Depth function
@@ -1335,7 +1352,6 @@ class MAGNUM_GL_EXPORT Renderer {
          */
         static void setDepthRange(Float near, Float far);
 
-        #ifndef MAGNUM_TARGET_WEBGL
         /**
          * @brief Set clipping behavior
          * @m_since_latest
@@ -1345,10 +1361,11 @@ class MAGNUM_GL_EXPORT Renderer {
          * @see @fn_gl_keyword{ClipControl}
          * @requires_gl45 Extension @gl_extension{ARB,clip_control}
          * @requires_es_extension Extension @gl_extension{EXT,clip_control}
-         * @requires_gles Clip control is not available in WebGL.
+         * @requires_webgl_extension Extension @webgl_extension{EXT,clip_control}.
+         *      Note that this extension is only implemented since Emscripten
+         *      3.1.66 and thus it's not even advertised on older versions.
          */
         static void setClipControl(ClipOrigin origin, ClipDepth depth);
-        #endif
 
         /* Since 1.8.17, the original short-hand group closing doesn't work
            anymore. FFS. */

src/Magnum/GL/Test/RendererGLTest.cpp

@@ -61,9 +61,7 @@ struct RendererGLTest: OpenGLTester {
 
     void maxLineWidth();
     void pointCoord();
-    #ifndef MAGNUM_TARGET_WEBGL
     void polygonMode();
-    #endif
     #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
     void patchParameters();
     #endif
@@ -72,9 +70,7 @@ struct RendererGLTest: OpenGLTester {
     void drawBuffersBlend();
     #endif
     template<class T> void clearDepthDepthRange();
-    #ifndef MAGNUM_TARGET_WEBGL
     void clipControl();
-    #endif
 
     private:
         PluginManager::Manager<Trade::AbstractImporter> _manager{"nonexistent"};
@@ -89,9 +85,7 @@ using namespace Math::Literals;
 RendererGLTest::RendererGLTest() {
     addTests({&RendererGLTest::maxLineWidth,
               &RendererGLTest::pointCoord,
-              #ifndef MAGNUM_TARGET_WEBGL
               &RendererGLTest::polygonMode,
-              #endif
               #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
               &RendererGLTest::patchParameters,
               #endif
@@ -103,10 +97,7 @@ RendererGLTest::RendererGLTest() {
               &RendererGLTest::clearDepthDepthRange<Double>,
               #endif
               &RendererGLTest::clearDepthDepthRange<Float>,
-              #ifndef MAGNUM_TARGET_WEBGL
+              &RendererGLTest::clipControl});
-              &RendererGLTest::clipControl
-              #endif
-              });
 
     /* Load the plugins directly from the build tree. Otherwise they're either
        static and already loaded or not present in the build tree */
@@ -259,9 +250,11 @@ void RendererGLTest::pointCoord() {
         (DebugTools::CompareImageToFile{_manager, maxThreshold, meanThreshold}));
 }
 
-#ifndef MAGNUM_TARGET_WEBGL
 void RendererGLTest::polygonMode() {
-    #ifdef MAGNUM_TARGET_GLES
+    #ifdef MAGNUM_TARGET_WEBGL
+    if(!Context::current().isExtensionSupported<Extensions::WEBGL::polygon_mode>())
+        CORRADE_SKIP(Extensions::WEBGL::polygon_mode::string() << "is not supported.");
+    #elif defined(MAGNUM_TARGET_GLES)
     if(!Context::current().isExtensionSupported<Extensions::NV::polygon_mode>() &&
        !Context::current().isExtensionSupported<Extensions::ANGLE::polygon_mode>())
         CORRADE_SKIP("Neither" << Extensions::NV::polygon_mode::string() << "nor" << Extensions::ANGLE::polygon_mode::string() << "is supported.");
@@ -273,7 +266,6 @@ void RendererGLTest::polygonMode() {
     Renderer::setPolygonMode(Renderer::PolygonMode::Fill);
     MAGNUM_VERIFY_NO_GL_ERROR();
 }
-#endif
 
 #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
 void RendererGLTest::patchParameters() {
@@ -343,7 +335,6 @@ template<class T> void RendererGLTest::clearDepthDepthRange() {
     MAGNUM_VERIFY_NO_GL_ERROR();
 }
 
-#ifndef MAGNUM_TARGET_WEBGL
 void RendererGLTest::clipControl() {
     #ifndef MAGNUM_TARGET_GLES
     if(!Context::current().isExtensionSupported<Extensions::ARB::clip_control>())
@@ -359,7 +350,6 @@ void RendererGLTest::clipControl() {
 
     MAGNUM_VERIFY_NO_GL_ERROR();
 }
-#endif
 
 }}}}