[Feat] (ShittilyDrawing): Implement DrawBuffer. Ensure read fbo is bound.

MG/MG_GL/Implementations/GL/Drawing/GL_Drawing.cpp

@@ -23,7 +23,7 @@ namespace MG_GL::GL {
                 if (outFormat)
                     *outFormat = format;
                 break;
-
+    
             case GL_DEPTH_COMPONENT24:
                 if (outInternalFormat)
                     *outInternalFormat = internalFormat;
@@ -646,7 +646,7 @@ namespace MG_GL::GL {
     }
 
     static GLuint lastBoundProgram = 0;
-    static GLuint lastBoundFBO[2] = {0};
+    static GLuint lastBoundFBO[2] = {0}; // 0: DRAW FBO, 1: READ FBO
     static std::array<GLuint, 32> lastBoundTextures;
 
     void RealizeFBOState(GLenum fbtype) {
@@ -1026,6 +1026,7 @@ namespace MG_GL::GL {
 
         // Framebuffer
         RealizeFBOState(GL_DRAW_FRAMEBUFFER);
+        RealizeFBOState(GL_READ_FRAMEBUFFER);
     }
 
     void DrawArraysSHITTILY(GLenum mode, GLint first, GLsizei count) {
@@ -1109,6 +1110,7 @@ namespace MG_GL::GL {
         SyncAllTexturesToGLES(textureState);
 
         RealizeFBOState(GL_DRAW_FRAMEBUFFER);
+        RealizeFBOState(GL_READ_FRAMEBUFFER);
 
         static GLfloat lastClearColor[4] = {-1.0f, -1.0f, -1.0f, -1.0f};
         if (memcmp(lastClearColor, commonState->clearColor, sizeof(lastClearColor)) != 0) {
@@ -1227,4 +1229,45 @@ namespace MG_GL::GL {
             }
         }
     }
+
+    void DrawBuffer(GLenum buf) {
+        SyncAllToGLES();
+        RealizeFBOState(GL_READ_FRAMEBUFFER);
+        RealizeFBOState(GL_READ_FRAMEBUFFER);
+
+        GLint currentFBO;
+        CallAndCheck(::GLES::glGetIntegerv(GL_FRAMEBUFFER_BINDING, &currentFBO);)
+
+        if (currentFBO == 0) {
+            GLenum buffers[1] = {GL_NONE};
+            switch (buf) {
+                case GL_FRONT:
+                case GL_BACK:
+                case GL_NONE:
+                    buffers[0] = buf;
+                    CallAndCheck(::GLES::glDrawBuffers(1, buffers);)
+                    break;
+                default:
+                    break;
+            }
+        } else {
+            GLint maxAttachments;
+            CallAndCheck(::GLES::glGetIntegerv(GL_MAX_COLOR_ATTACHMENTS, &maxAttachments);)
+
+            if (buf == GL_NONE) {
+                auto *buffers = (GLenum *)alloca(maxAttachments * sizeof(GLenum));
+                for (int i = 0; i < maxAttachments; i++) {
+                    buffers[i] = GL_NONE;
+                }
+                CallAndCheck(::GLES::glDrawBuffers(maxAttachments, buffers);)
+            } else if (buf >= GL_COLOR_ATTACHMENT0 &&
+                    buf < GL_COLOR_ATTACHMENT0 + maxAttachments) {
+                auto *buffers = (GLenum *)alloca(maxAttachments * sizeof(GLenum));
+                for (int i = 0; i < maxAttachments; i++) {
+                    buffers[i] = (i == (buf - GL_COLOR_ATTACHMENT0)) ? buf : GL_NONE;
+                }
+                CallAndCheck(::GLES::glDrawBuffers(maxAttachments, buffers);)
+            }
+        }
+    }
 }

MG/MG_GL/Implementations/GL/Drawing/GL_Drawing.h

@@ -11,6 +11,7 @@ namespace MG_GL::GL {
     void DrawElementsBaseVertex(GLenum mode, GLsizei count, GLenum type, const GLvoid *indices, GLint basevertex);
     void MultiDrawElements(GLenum mode, const GLsizei *count, GLenum type, const GLvoid *const *indices, GLsizei drawcount);
     void MultiDrawElementsBaseVertex(GLenum mode, const GLsizei *count, GLenum type, const GLvoid *const *indices, GLsizei drawcount, const GLint *basevertex);
+    void DrawBuffer(GLenum buf);
 }
 
 #endif //MOBILEGL_GL_DRAWING_H

MG/MG_GL/Implementations/GL/GLFuncsDefinitions/GLFuncsDefinitions.cpp

@@ -403,7 +403,7 @@ DECLARE_GL_FUNCTION_STUB_HEAD(void, EdgeFlag, GLboolean flag ) DECLARE_GL_FUNCTI
 DECLARE_GL_FUNCTION_STUB_HEAD(void, EdgeFlagv, const GLboolean *flag ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, EdgeFlagv,flag)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, ClipPlane, GLenum plane, const GLdouble *equation ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, ClipPlane,plane,equation)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, GetClipPlane, GLenum plane, GLdouble *equation ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, GetClipPlane,plane,equation)
-DECLARE_GL_FUNCTION_STUB_HEAD(void, DrawBuffer, GLenum mode ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, DrawBuffer,mode)
+DECLARE_GL_FUNCTION_HEAD(void, DrawBuffer, GLenum mode ) DECLARE_GL_FUNCTION_END_NO_RETURN(void, DrawBuffer,mode)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, EnableClientState, GLenum cap ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, EnableClientState,cap)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, DisableClientState, GLenum cap ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, DisableClientState,cap)
 DECLARE_GL_FUNCTION_STUB_HEAD(void, GetDoublev, GLenum pname, GLdouble *params ) DECLARE_GL_FUNCTION_STUB_END_NO_RETURN(void, GetDoublev,pname,params)