[Feat] (ProgramState): Implement more Global-GL-State functions.

- These functions were implemented:
  - glBlendFunc
  - glBlendFuncSeparate
  - glClear
  - glClearColor
  - glClearDepth
  - glColorMask
  - glDepthFunc
  - glDepthMask
  - glDisable
  - glEnable
  - glViewport

MG/MG_GL/State/Common/CommonState.cpp

@@ -4,6 +4,11 @@
 
 #include "CommonState.h"
 
+CommonState::CommonState() {
+    pixelStoreParams[GL_PACK_ALIGNMENT] = 4;
+    pixelStoreParams[GL_UNPACK_ALIGNMENT] = 4;
+}
+
 GLenum CommonState::SetPixelStoreInt(GLenum pname, GLint param) {
     if (MG_Constants::PixelStore::VALID_PARAM_NAMES.find(pname) == MG_Constants::PixelStore::VALID_PARAM_NAMES.end()) {
         return GL_INVALID_ENUM;
@@ -54,3 +59,99 @@ GLint CommonState::QueryPixelStoreInt(GLenum pname) {
     auto defaultIt = MG_Constants::PixelStore::DEFAULT_VALUES_MAP.find(pname);
     return (defaultIt != MG_Constants::PixelStore::DEFAULT_VALUES_MAP.end()) ? defaultIt->second : 0;
 }
+
+GLenum CommonState::Enable(GLenum cap) {
+    if (MG_Constants::CommonState::VALID_CAPS.find(cap) == MG_Constants::CommonState::VALID_CAPS.end()) {
+        return GL_INVALID_ENUM;
+    }
+    capabilities[cap] = true;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::Disable(GLenum cap) {
+    if (MG_Constants::CommonState::VALID_CAPS.find(cap) == MG_Constants::CommonState::VALID_CAPS.end()) {
+        return GL_INVALID_ENUM;
+    }
+    capabilities[cap] = false;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::BlendFunc(GLenum sfactor, GLenum dfactor) {
+    if (MG_Constants::Blend::VALID_FACTORS.find(sfactor) == MG_Constants::Blend::VALID_FACTORS.end() ||
+        MG_Constants::Blend::VALID_FACTORS.find(dfactor) == MG_Constants::Blend::VALID_FACTORS.end()) {
+        return GL_INVALID_ENUM;
+    }
+
+    blendSrcRGB = blendSrcAlpha = sfactor;
+    blendDstRGB = blendDstAlpha = dfactor;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::BlendFuncSeparate(GLenum srcRGB, GLenum dstRGB,
+                                      GLenum srcAlpha, GLenum dstAlpha) {
+    if (MG_Constants::Blend::VALID_FACTORS.find(srcRGB) == MG_Constants::Blend::VALID_FACTORS.end() ||
+        MG_Constants::Blend::VALID_FACTORS.find(dstRGB) == MG_Constants::Blend::VALID_FACTORS.end() ||
+        MG_Constants::Blend::VALID_FACTORS.find(srcAlpha) == MG_Constants::Blend::VALID_FACTORS.end() ||
+        MG_Constants::Blend::VALID_FACTORS.find(dstAlpha) == MG_Constants::Blend::VALID_FACTORS.end()) {
+        return GL_INVALID_ENUM;
+    }
+    blendSrcRGB = srcRGB;
+    blendDstRGB = dstRGB;
+    blendSrcAlpha = srcAlpha;
+    blendDstAlpha = dstAlpha;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::Clear(GLbitfield mask) {
+    const GLbitfield validBits = GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT;
+    if ((mask & ~validBits) != 0) {
+        return GL_INVALID_VALUE;
+    }
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::ClearColor(GLfloat red, GLfloat green, GLfloat blue, GLfloat alpha) {
+    clearColor[0] = red;
+    clearColor[1] = green;
+    clearColor[2] = blue;
+    clearColor[3] = alpha;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::ClearDepth(GLfloat depth) {
+    clearDepth = depth;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::ColorMask(GLboolean red, GLboolean green, GLboolean blue, GLboolean alpha) {
+    colorMask[0] = red;
+    colorMask[1] = green;
+    colorMask[2] = blue;
+    colorMask[3] = alpha;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::DepthFunc(GLenum func) {
+    if (MG_Constants::Depth::VALID_FUNCS.find(func) == MG_Constants::Depth::VALID_FUNCS.end()) {
+        return GL_INVALID_ENUM;
+    }
+    depthFunc = func;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::DepthMask(GLboolean flag) {
+    depthMask = flag;
+    return GL_NO_ERROR;
+}
+
+GLenum CommonState::Viewport(GLint x, GLint y, GLsizei width, GLsizei height) {
+    if (width < 0 || height < 0) {
+        return GL_INVALID_VALUE;
+    }
+
+    viewport[0] = x;
+    viewport[1] = y;
+    viewport[2] = width;
+    viewport[3] = height;
+    return GL_NO_ERROR;
+}

MG/MG_GL/State/Common/CommonState.h

@@ -10,11 +10,51 @@
 
 class CommonState {
 private:
+    // Pixel storage parameters
     std::unordered_map<GLenum, GLint> pixelStoreParams;
+
+    // Blend state
+    GLenum blendSrcRGB = GL_ONE;
+    GLenum blendDstRGB = GL_ZERO;
+    GLenum blendSrcAlpha = GL_ONE;
+    GLenum blendDstAlpha = GL_ZERO;
+    
+    // Clear state
+    GLfloat clearColor[4] = {0.0f, 0.0f, 0.0f, 0.0f};
+    GLfloat clearDepth = 1.0f;
+    
+    // Color mask
+    GLboolean colorMask[4] = {GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE};
+    
+    // Depth state
+    GLenum depthFunc = GL_LESS;
+    GLboolean depthMask = GL_TRUE;
+    
+    // Viewport
+    GLint viewport[4] = {0, 0, 0, 0};
+    
+    // Capability enables
+    std::unordered_map<GLenum, bool> capabilities;
     
 public:
+    CommonState();
+    
     // Return: the validity of the operation, according to OpenGL 3 standard
     GLenum SetPixelStoreInt(GLenum pname, GLint param);
+
+    GLenum Enable(GLenum cap);
+    GLenum Disable(GLenum cap);
+    GLenum BlendFunc(GLenum sfactor, GLenum dfactor);
+    GLenum BlendFuncSeparate(GLenum srcRGB, GLenum dstRGB,
+                             GLenum srcAlpha, GLenum dstAlpha);
+    GLenum Clear(GLbitfield mask);
+    GLenum ClearColor(GLfloat red, GLfloat green, GLfloat blue, GLfloat alpha);
+    GLenum ClearDepth(GLfloat depth);
+    GLenum ColorMask(GLboolean red, GLboolean green,
+                     GLboolean blue, GLboolean alpha);
+    GLenum DepthFunc(GLenum func);
+    GLenum DepthMask(GLboolean flag);
+    GLenum Viewport(GLint x, GLint y, GLsizei width, GLsizei height);
     
     GLint QueryPixelStoreInt(GLenum pname);
 };