Texture format info: Invert R and B in RGBA4 (#2878)

* texture format info: Invert R and B in RGBA4

d3d9: Revert 06c08adc9ea586b5e1b51fd98fe403dacfef83cd to force software
      conversion because the format doesn't exist
d3d11: Force software conversion because the format doesn't exist
gl: Revert 3e3e655262c3ed39ae0115fa5509c7785c4c67eb to swizzle R and B
mtl: Swizzle channels

* metal: Remove explicit conversion of RGBA4 and RGB5A1 in osx

* metal: Set alpha bit to correct end of short

src/renderer_d3d11.cpp

@@ -4504,6 +4504,11 @@ namespace bgfx { namespace d3d11
 								bimg::imageConvert(temp, 16, bx::packBgr5a1, mip.m_data, bx::unpackRgb5a1, srd[kk].SysMemPitch*mip.m_height);
 								srd[kk].pSysMem = temp;
 								break;
+							case TextureFormat::RGBA4:
+								temp = (uint8_t*)BX_ALLOC(g_allocator, srd[kk].SysMemPitch*mip.m_height);
+								bimg::imageConvert(temp, 16, bx::packBgra4, mip.m_data, bx::unpackRgba4, srd[kk].SysMemPitch*mip.m_height);
+								srd[kk].pSysMem = temp;
+								break;
 							}
 						}
 
@@ -4845,6 +4850,11 @@ namespace bgfx { namespace d3d11
 					bimg::imageConvert(temp, 16, bx::packBgr5a1, src, bx::unpackRgb5a1, rectpitch);
 					data = temp;
 					break;
+				case TextureFormat::RGBA4:
+					temp = (uint8_t*)BX_ALLOC(g_allocator, rectpitch);
+					bimg::imageConvert(temp, 16, bx::packBgra4, src, bx::unpackRgba4, rectpitch);
+					data = temp;
+					break;
 				}
 				src += srcpitch;
 			}

src/renderer_gl.cpp

@@ -288,7 +288,7 @@ namespace bgfx { namespace gl
 		{ GL_RGBA32UI,                                 GL_ZERO,                                      RGBA_INTEGER,                                GL_RGBA_INTEGER,                             GL_UNSIGNED_INT,                 false, { $_, $_, $_, $_ } }, // RGBA32U
 		{ GL_RGBA32F,                                  GL_ZERO,                                      GL_RGBA,                                     GL_RGBA,                                     GL_FLOAT,                        false, { $_, $_, $_, $_ } }, // RGBA32F
 		{ GL_RGB565,                                   GL_ZERO,                                      GL_RGB,                                      GL_RGB,                                      GL_UNSIGNED_SHORT_5_6_5,         false, { $_, $_, $_, $_ } }, // R5G6B5
-		{ GL_RGBA4,                                    GL_ZERO,                                      GL_BGRA,                                     GL_BGRA,                                     GL_UNSIGNED_SHORT_4_4_4_4_REV,   false, { $_, $_, $_, $_ } }, // RGBA4
+		{ GL_RGBA4,                                    GL_ZERO,                                      GL_RGBA,                                     GL_RGBA,                                     GL_UNSIGNED_SHORT_4_4_4_4_REV,   false, { $_, $_, $_, $_ } }, // RGBA4
 		{ GL_RGB5_A1,                                  GL_ZERO,                                      GL_RGBA,                                     GL_RGBA,                                     GL_UNSIGNED_SHORT_1_5_5_5_REV,   false, { $_, $_, $_, $_ } }, // RGB5A1
 		{ GL_RGB10_A2,                                 GL_ZERO,                                      GL_RGBA,                                     GL_RGBA,                                     GL_UNSIGNED_INT_2_10_10_10_REV,  false, { $_, $_, $_, $_ } }, // RGB10A2
 		{ GL_R11F_G11F_B10F,                           GL_ZERO,                                      GL_RGB,                                      GL_RGB,                                      GL_UNSIGNED_INT_10F_11F_11F_REV, false, { $_, $_, $_, $_ } }, // RG11B10F

src/renderer_mtl.mm

@@ -305,8 +305,8 @@ namespace bgfx { namespace mtl
 		{ MTLPixelFormatRGBA32Uint,                     MTLPixelFormatInvalid,                       MTLReadWriteTextureTier2,    { $R, $G, $B, $A }, true  }, // RGBA32U
 		{ MTLPixelFormatRGBA32Float,                    MTLPixelFormatInvalid,                       MTLReadWriteTextureTier2,    { $R, $G, $B, $A }, true  }, // RGBA32F
 		{ MTLPixelFormat(40/*B5G6R5Unorm*/),            MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $R, $G, $B, $A }, true  }, // R5G6B5
-		{ MTLPixelFormat(42/*ABGR4Unorm*/),             MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $R, $G, $B, $A }, true  }, // RGBA4
-		{ MTLPixelFormatA1BGR5Unorm,                    MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $B, $G, $R, $A }, true  }, // RGB5A1
+		{ MTLPixelFormatABGR4Unorm,                     MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $A, $B, $G, $R }, true  }, // RGBA4
+		{ MTLPixelFormatBGR5A1Unorm,                    MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $A, $R, $G, $B }, true  }, // RGB5A1
 		{ MTLPixelFormatRGB10A2Unorm,                   MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $R, $G, $B, $A }, true  }, // RGB10A2
 		{ MTLPixelFormatRG11B10Float,                   MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $R, $G, $B, $A }, true  }, // RG11B10F
 		{ MTLPixelFormatInvalid,                        MTLPixelFormatInvalid,                       MTLReadWriteTextureTierNone, { $R, $G, $B, $A }, false }, // UnknownDepth
@@ -764,9 +764,7 @@ BX_STATIC_ASSERT(BX_COUNTOF(s_accessNames) == Access::Count, "Invalid s_accessNa
 				g_caps.formats[TextureFormat::PTC14 ] =
 				g_caps.formats[TextureFormat::PTC12A] =
 				g_caps.formats[TextureFormat::PTC14A] =
-				g_caps.formats[TextureFormat::R5G6B5] =
-				g_caps.formats[TextureFormat::RGBA4 ] =
-				g_caps.formats[TextureFormat::RGB5A1] = BGFX_CAPS_FORMAT_TEXTURE_NONE;
+				g_caps.formats[TextureFormat::R5G6B5] = BGFX_CAPS_FORMAT_TEXTURE_NONE;
 
 				g_caps.formats[TextureFormat::RGB9E5F] &= ~(BGFX_CAPS_FORMAT_TEXTURE_FRAMEBUFFER | BGFX_CAPS_FORMAT_TEXTURE_FRAMEBUFFER_MSAA);
 			}