GL: fix Framebuffer::implementationColorRead*() to follow spec.

Not sure what I thought here, but using GL_IMPLEMENTATION_COLOR_READ_*
with glGetFramebufferParameteriv() is possible only since GL 4.5
(there's no extension adding it) and there's no equivalent for it in
GLES 3.1. I assumed that since the entry point is defined in 3.1 then it
would also accept the same enum, but apparently not -- and this
inconsistency is not fixed in 3.2 either.

Funnily enough, all drivers I tried (Mesa ES, SwiftShader, ANGLE) were
accepting this. The first driver that complained was ARM Mali on Huawei
P10 and there I assumed a driver bug -- but on the contrary, this is the
only driver following the spec properly :)

Now the glGetFramebufferParameteriv() API (and the DSA equivalent) is
used only on GL 4.5 contexts and up, everywhere else it's done using
the old-style glGetInteger(). I also renamed the implementations to not
misleadingly mention ES 3.1, since it has nothing to do with this. The
code path dispatch code is a bit entangled due to all the workarounds,
hopefully not breaking any behavior that worked before.

src/Magnum/GL/AbstractFramebuffer.cpp

@@ -221,35 +221,33 @@ PixelType AbstractFramebuffer::implementationColorReadType() {
     return PixelType((this->*Context::current().state().framebuffer->implementationColorReadFormatTypeImplementation)(GL_IMPLEMENTATION_COLOR_READ_TYPE));
 }
 
-GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationDefault(const GLenum what) {
+GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationGlobal(const GLenum what) {
     bindInternal(FramebufferTarget::Read);
     GLint formatType;
     glGetIntegerv(what, &formatType);
     return formatType;
 }
 
-#if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+#ifndef MAGNUM_TARGET_GLES
-GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31(const GLenum what) {
+GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationFramebuffer(const GLenum what) {
     const FramebufferTarget target = bindInternal();
     GLint formatType;
     glGetFramebufferParameteriv(GLenum(target), what, &formatType);
     return formatType;
 }
-#endif
 
-#ifndef MAGNUM_TARGET_GLES
+GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationFramebufferDSA(const GLenum what) {
-GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31DSA(const GLenum what) {
     GLint formatType;
     glGetNamedFramebufferParameteriv(_id, what, &formatType);
     return formatType;
 }
 
-GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31DSAMesa(const GLenum what) {
+GLenum AbstractFramebuffer::implementationColorReadFormatTypeImplementationFramebufferDSAMesa(const GLenum what) {
     /* Mesa needs the framebuffer bound for read even with DSA. See the
        "mesa-implementation-color-read-format-dsa-explicit-binding" workaround
        for details. */
     bindInternal(FramebufferTarget::Read);
-    return implementationColorReadFormatTypeImplementationES31DSA(what);
+    return implementationColorReadFormatTypeImplementationFramebufferDSA(what);
 }
 #endif
 

src/Magnum/GL/AbstractFramebuffer.h

@@ -772,13 +772,11 @@ class MAGNUM_GL_EXPORT AbstractFramebuffer {
         FramebufferTarget MAGNUM_GL_LOCAL bindImplementationSingle();
         #endif
 
-        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationDefault(GLenum what);
+        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationGlobal(GLenum what);
-        #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
-        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationES31(GLenum what);
-        #endif
         #ifndef MAGNUM_TARGET_GLES
-        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationES31DSA(GLenum what);
+        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationFramebuffer(GLenum what);
-        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationES31DSAMesa(GLenum what);
+        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationFramebufferDSA(GLenum what);
+        GLenum MAGNUM_GL_LOCAL implementationColorReadFormatTypeImplementationFramebufferDSAMesa(GLenum what);
         #endif
 
         GLenum MAGNUM_GL_LOCAL checkStatusImplementationDefault(FramebufferTarget target);

src/Magnum/GL/Implementation/FramebufferState.cpp

@@ -256,50 +256,46 @@ FramebufferState::FramebufferState(Context& context, std::vector<std::string>& e
 
     /* Implementation-specific color read format/type implementation */
     #ifndef MAGNUM_TARGET_GLES
-    if(context.isExtensionSupported<Extensions::ARB::direct_state_access>() && context.isExtensionSupported<Extensions::ARB::ES3_1_compatibility>()) {
+    /* Get(Named)FramebufferParameteriv() supports querying
+       GL_IMPLEMENTATION_COLOR_READ_{FORMAT,TYPE} since GL 4.5. No
+       corresponding extension enabling this, only a mention of Bug 12360
+       that's supposed to have more information about this. But the Khronos
+       bugzilla is lost to internet history now and everything gets redirected
+       to the mostly-empty GitHub issue tracker (and it doesn't even have the
+       old bugs imported), so this is all I got. The whole thing is a
+       clusterfuck:
+        -   ES3.1 adds GetFramebufferParameteriv() but it *doesn't* allow
+            GL_IMPLEMENTATION_COLOR_READ_FORMAT to be used with it. ES3.2
+            doesn't fix that omission either. Funnily enough, most drivers
+            (including NV, Mesa and SwiftShader) support such a query, the only
+            driver which doesn't (and thus matches the spec) is on my Huawei
+            P10. What.
+        -   Intel implementation on Windows, even though supporting 4.5 and
+            DSA, returns absolute garbage on everything except the most basic
+            GetInteger query
+        -   NVidia returns broken values when calling the DSA code path
+        -   Mesa needs the framebuffer to be bound even for DSA queries */
+    if(context.isVersionSupported(Version::GL450)
         #ifdef CORRADE_TARGET_WINDOWS
-        if((context.detectedDriver() & Context::DetectedDriver::IntelWindows) &&
+        && !((context.detectedDriver() & Context::DetectedDriver::IntelWindows) &&
-            !context.isDriverWorkaroundDisabled("intel-windows-implementation-color-read-format-completely-broken")) {
+        !context.isDriverWorkaroundDisabled("intel-windows-implementation-color-read-format-completely-broken"))
-            implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationDefault;
-
-        } else
         #endif
-        {
+    ) {
+        if(context.isExtensionSupported<Extensions::ARB::direct_state_access>()
+            && !((context.detectedDriver() & Context::DetectedDriver::NVidia) && !context.isDriverWorkaroundDisabled("nv-implementation-color-read-format-dsa-broken"))
+        ) {
             /* DSA extension added above */
-            extensions.push_back(Extensions::ARB::ES3_1_compatibility::string());
-
-            if((context.detectedDriver() & Context::DetectedDriver::NVidia) &&
-                !context.isDriverWorkaroundDisabled("nv-implementation-color-read-format-dsa-broken")) {
-                implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31;
-            } else if((context.detectedDriver() & Context::DetectedDriver::Mesa) &&
-                !context.isDriverWorkaroundDisabled("mesa-implementation-color-read-format-dsa-explicit-binding")) {
-                implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31DSAMesa;
-            } else {
-                implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31DSA;
-            }
-        }
-    } else
-    #endif
-    #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
-    /* Checks for 3.1 on ES and for ARB_ES3_1_compatibility on desktop */
-    if(context.isVersionSupported(Version::GLES310)) {
-        #ifdef CORRADE_TARGET_WINDOWS
-        if((context.detectedDriver() & Context::DetectedDriver::IntelWindows) &&
-            !context.isDriverWorkaroundDisabled("intel-windows-implementation-color-read-format-completely-broken")) {
-            implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationDefault;
-        } else
-        #endif
-        {
-            #ifndef MAGNUM_TARGET_GLES
-            extensions.push_back(Extensions::ARB::ES3_1_compatibility::string());
-            #endif
 
-            implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationES31;
+            if((context.detectedDriver() & Context::DetectedDriver::Mesa) && !context.isDriverWorkaroundDisabled("mesa-implementation-color-read-format-dsa-explicit-binding"))
+                implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationFramebufferDSAMesa;
+            else implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationFramebufferDSA;
+        } else {
+            implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationFramebuffer;
         }
     } else
     #endif
     {
-        implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationDefault;
+        implementationColorReadFormatTypeImplementation = &AbstractFramebuffer::implementationColorReadFormatTypeImplementationGlobal;
     }
 
     /* Framebuffer reading implementation in desktop/ES */