LibWeb: Allow WebGL getParameter when WEBGL_draw_buffers is enabled

When that extensions is enabled we should allow getting the parameter
value of MAX_COLOR_ATTACHMENTS_WEBGL.

Author: cqundefine

Libraries/LibWeb/WebGL/WebGL2RenderingContext.cpp

@@ -257,6 +257,11 @@ bool WebGL2RenderingContext::oes_standard_derivatives_extension_enabled() const
     return false;
 }
 
+bool WebGL2RenderingContext::webgl_draw_buffers_extension_enabled() const
+{
+    return false;
+}
+
 ReadonlySpan<WebIDL::UnsignedLong> WebGL2RenderingContext::enabled_compressed_texture_formats() const
 {
     return m_enabled_compressed_texture_formats;

Libraries/LibWeb/WebGL/WebGL2RenderingContext.h

@@ -54,6 +54,7 @@ class WebGL2RenderingContext final : public Bindings::PlatformObject
     virtual bool ext_texture_filter_anisotropic_extension_enabled() const override;
     virtual bool angle_instanced_arrays_extension_enabled() const override;
     virtual bool oes_standard_derivatives_extension_enabled() const override;
+    virtual bool webgl_draw_buffers_extension_enabled() const override;
     virtual ReadonlySpan<WebIDL::UnsignedLong> enabled_compressed_texture_formats() const override;
 
 private:

Libraries/LibWeb/WebGL/WebGLRenderingContext.cpp

@@ -295,6 +295,11 @@ bool WebGLRenderingContext::oes_standard_derivatives_extension_enabled() const
     return !!m_oes_standard_derivatives_object_extension;
 }
 
+bool WebGLRenderingContext::webgl_draw_buffers_extension_enabled() const
+{
+    return !!m_webgl_draw_buffers_extension;
+}
+
 ReadonlySpan<WebIDL::UnsignedLong> WebGLRenderingContext::enabled_compressed_texture_formats() const
 {
     return m_enabled_compressed_texture_formats;

Libraries/LibWeb/WebGL/WebGLRenderingContext.h

@@ -53,6 +53,7 @@ class WebGLRenderingContext final : public Bindings::PlatformObject
     virtual bool ext_texture_filter_anisotropic_extension_enabled() const override;
     virtual bool angle_instanced_arrays_extension_enabled() const override;
     virtual bool oes_standard_derivatives_extension_enabled() const override;
+    virtual bool webgl_draw_buffers_extension_enabled() const override;
     virtual ReadonlySpan<WebIDL::UnsignedLong> enabled_compressed_texture_formats() const override;
 
 private:

Libraries/LibWeb/WebGL/WebGLRenderingContextBase.h

@@ -47,6 +47,7 @@ class WebGLRenderingContextBase {
     virtual bool ext_texture_filter_anisotropic_extension_enabled() const = 0;
     virtual bool angle_instanced_arrays_extension_enabled() const = 0;
     virtual bool oes_standard_derivatives_extension_enabled() const = 0;
+    virtual bool webgl_draw_buffers_extension_enabled() const = 0;
     virtual ReadonlySpan<WebIDL::UnsignedLong> enabled_compressed_texture_formats() const = 0;
 
     template<typename T>

Libraries/LibWeb/WebGL/WebGLRenderingContextImpl.cpp

@@ -1246,8 +1246,8 @@ JS::Value WebGLRenderingContextImpl::get_parameter(WebIDL::UnsignedLong pname)
         set_error(GL_INVALID_ENUM);
         return JS::js_null();
     }
-    case GL_MAX_COLOR_ATTACHMENTS: {
-        if (m_context->webgl_version() == OpenGLContext::WebGLVersion::WebGL2) { // FIXME: Allow this code path for MAX_COLOR_ATTACHMENTS_WEBGL
+    case GL_MAX_COLOR_ATTACHMENTS: { // NOTE: This has the same value as MAX_COLOR_ATTACHMENTS_WEBGL
+        if (webgl_draw_buffers_extension_enabled() || m_context->webgl_version() == OpenGLContext::WebGLVersion::WebGL2) {
             GLint result { 0 };
             glGetIntegervRobustANGLE(GL_MAX_COLOR_ATTACHMENTS, 1, nullptr, &result);
             return JS::Value(result);