Bug 1159117 - Enable support for legacy formats. r=jgilbert

ALPHA, LUMINANCE, and LUMINANCE_ALPHA texture formats are removed in
OpenGL core profiles. Emulate these via RED, RG and texture swizzling.

dom/canvas/WebGL2Context.cpp

@@ -128,6 +128,14 @@ WebGLContext::InitWebGL2()
             missingList.push_back(kRequiredFeatures[i]);
     }
 
+#ifdef XP_MACOSX
+    // On OSX, GL core profile is used. This requires texture swizzle
+    // support to emulate legacy texture formats: ALPHA, LUMINANCE,
+    // and LUMINANCE_ALPHA.
+    if (!gl->IsSupported(gl::GLFeature::texture_swizzle))
+        missingList.push_back(gl::GLFeature::texture_swizzle);
+#endif
+
     if (missingList.size()) {
         nsAutoCString exts;
         for (auto itr = missingList.begin(); itr != missingList.end(); ++itr) {

dom/canvas/WebGLContextGL.cpp

@@ -3198,6 +3198,9 @@ GLenum WebGLContext::CheckedTexImage2D(TexImageTarget texImageTarget,
 
     gl->fTexImage2D(texImageTarget.get(), level, driverInternalFormat, width, height, border, driverFormat, driverType, data);
 
+    if (effectiveInternalFormat != driverInternalFormat)
+        SetLegacyTextureSwizzle(gl, texImageTarget.get(), internalformat.get());
+
     GLenum error = LOCAL_GL_NO_ERROR;
     if (sizeMayChange) {
         error = GetAndFlushUnderlyingGLErrors();

dom/canvas/WebGLContextUtils.cpp

@@ -249,7 +249,7 @@ DriverFormatsFromEffectiveInternalFormat(gl::GLContext* gl,
     // in some cases we must pass a different value. On ES, they are equal by definition
     // as it is an error to pass internalformat!=format.
     GLenum driverInternalFormat = driverFormat;
-    if (!gl->IsGLES()) {
+    if (gl->IsCompatibilityProfile()) {
         // Cases where desktop OpenGL requires a tweak to 'format'
         if (driverFormat == LOCAL_GL_SRGB)
             driverFormat = LOCAL_GL_RGB;
@@ -284,11 +284,64 @@ DriverFormatsFromEffectiveInternalFormat(gl::GLContext* gl,
         }
     }
 
+    // OpenGL core profile removed texture formats ALPHA, LUMINANCE and LUMINANCE_ALPHA
+    if (gl->IsCoreProfile()) {
+        switch (driverFormat) {
+        case LOCAL_GL_ALPHA:
+        case LOCAL_GL_LUMINANCE:
+            driverInternalFormat = driverFormat = LOCAL_GL_RED;
+            break;
+
+        case LOCAL_GL_LUMINANCE_ALPHA:
+            driverInternalFormat = driverFormat = LOCAL_GL_RG;
+            break;
+        }
+    }
+
     *out_driverInternalFormat = driverInternalFormat;
     *out_driverFormat = driverFormat;
     *out_driverType = driverType;
 }
 
+// Map R to A
+static const GLenum kLegacyAlphaSwizzle[4] = {
+    LOCAL_GL_ZERO, LOCAL_GL_ZERO, LOCAL_GL_ZERO, LOCAL_GL_RED
+};
+// Map R to RGB
+static const GLenum kLegacyLuminanceSwizzle[4] = {
+    LOCAL_GL_RED, LOCAL_GL_RED, LOCAL_GL_RED, LOCAL_GL_ONE
+};
+// Map R to RGB, G to A
+static const GLenum kLegacyLuminanceAlphaSwizzle[4] = {
+    LOCAL_GL_RED, LOCAL_GL_RED, LOCAL_GL_RED, LOCAL_GL_GREEN
+};
+
+void
+SetLegacyTextureSwizzle(gl::GLContext* gl, GLenum target, GLenum internalformat)
+{
+    MOZ_RELEASE_ASSERT(gl->IsSupported(gl::GLFeature::texture_swizzle));
+    /* Only support swizzling on core profiles. */
+    if (!gl->IsCoreProfile())
+        return;
+
+    switch (internalformat) {
+    case LOCAL_GL_ALPHA:
+        gl->fTexParameteriv(target, LOCAL_GL_TEXTURE_SWIZZLE_RGBA,
+                            (GLint*) kLegacyAlphaSwizzle);
+        break;
+
+    case LOCAL_GL_LUMINANCE:
+        gl->fTexParameteriv(target, LOCAL_GL_TEXTURE_SWIZZLE_RGBA,
+                            (GLint*) kLegacyLuminanceSwizzle);
+        break;
+
+    case LOCAL_GL_LUMINANCE_ALPHA:
+        gl->fTexParameteriv(target, LOCAL_GL_TEXTURE_SWIZZLE_RGBA,
+                            (GLint*) kLegacyLuminanceAlphaSwizzle);
+        break;
+    }
+}
+
 /**
  * Return the bits per texel for format & type combination.
  * Assumes that format & type are a valid combination as checked with

dom/canvas/WebGLContextUtils.h

@@ -38,6 +38,8 @@ TexType TypeFromInternalFormat(TexInternalFormat internalformat);
 TexInternalFormat
 UnsizedInternalFormatFromInternalFormat(TexInternalFormat internalformat);
 
+void SetLegacyTextureSwizzle(gl::GLContext* gl, GLenum target, GLenum internalformat);
+
 size_t GetBitsPerTexel(TexInternalFormat effectiveinternalformat);
 
 // For use with the different texture calls, i.e.

gfx/gl/GLContext.cpp

@@ -96,6 +96,7 @@ static const char *sExtensionNames[] = {
     "GL_ARB_texture_non_power_of_two",
     "GL_ARB_texture_rectangle",
     "GL_ARB_texture_storage",
+    "GL_ARB_texture_swizzle",
     "GL_ARB_transform_feedback2",
     "GL_ARB_uniform_buffer_object",
     "GL_ARB_vertex_array_object",

gfx/gl/GLContext.h

@@ -128,6 +128,7 @@ enum class GLFeature {
     texture_half_float_linear,
     texture_non_power_of_two,
     texture_storage,
+    texture_swizzle,
     transform_feedback2,
     uniform_buffer_object,
     uniform_matrix_nonsquare,
@@ -389,6 +390,7 @@ public:
         ARB_texture_non_power_of_two,
         ARB_texture_rectangle,
         ARB_texture_storage,
+        ARB_texture_swizzle,
         ARB_transform_feedback2,
         ARB_uniform_buffer_object,
         ARB_vertex_array_object,

gfx/gl/GLContextFeatures.cpp

@@ -603,6 +603,15 @@ static const FeatureInfo sFeatureInfoArr[] = {
             GLContext::Extensions_End
         }
     },
+    {
+        "texture_swizzle",
+        GLVersion::GL3_3,
+        GLESVersion::ES3,
+        GLContext::ARB_texture_swizzle,
+        {
+            GLContext::Extensions_End
+        }
+    },
     {
         "transform_feedback2",
         GLVersion::GL4,