From af460af119be4257d8ba515e9d05eb38418c0b73 Mon Sep 17 00:00:00 2001
From: GPF <troy_ed@yahoo.com>
Date: Tue, 4 Feb 2025 14:27:18 -0700
Subject: [PATCH] Recreated glCompressedTexSubImage2D implementation

---
 GL/texture.c             | 49 ++++++++++++++++++++++++++++++++++++++++
 include/GL/glext.h       | 10 ++++++++
 samples/nehe06_vq/main.c |  9 +++++++-
 3 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/GL/texture.c b/GL/texture.c
index 6bcfae1..e546ea8 100644
--- a/GL/texture.c
+++ b/GL/texture.c
@@ -906,6 +906,55 @@ void APIENTRY glCompressedTexImage2DARB(GLenum target,
     _glGPUStateMarkDirty();
 }
 
+void APIENTRY glCompressedTexSubImage2DARB(GLenum target,
+                                           GLint level,
+                                           GLint xoffset,
+                                           GLint yoffset,
+                                           GLsizei width,
+                                           GLsizei height,
+                                           GLenum format,
+                                           GLsizei imageSize,
+                                           const GLvoid *data) {
+    TRACE();
+
+    if (target != GL_TEXTURE_2D) {
+        _glKosThrowError(GL_INVALID_ENUM, __func__);
+        return;
+    }
+
+    if (xoffset < 0 || yoffset < 0 || width <= 0 || height <= 0) {
+        _glKosThrowError(GL_INVALID_VALUE, __func__);
+        return;
+    }
+
+    gl_assert(ACTIVE_TEXTURE < MAX_GLDC_TEXTURE_UNITS);
+    TextureObject* active = TEXTURE_UNITS[ACTIVE_TEXTURE];
+
+    if (!active) {
+        _glKosThrowError(GL_INVALID_OPERATION, __func__);
+        return;
+    }
+
+    GLuint original_id = active->index;
+
+    // Ensure that we're modifying the correct texture
+    if (active->index != original_id) {
+        _glKosThrowError(GL_INVALID_OPERATION, __func__);
+        return;
+    }
+
+    // Copy raw compressed texture data into the texture buffer.
+    GLubyte* targetData = active->data;
+    GLubyte* src = (GLubyte*)data;
+
+    // Copy the compressed data directly to the texture
+    if (data) {
+        FASTCPY(targetData + (yoffset * active->width + xoffset), src, imageSize);
+    }
+
+    _glGPUStateMarkDirty();
+}
+
 /**
  * Takes an internal format, and returns a GL format matching how we'd store
  * it internally, so it'll return one of the following:
diff --git a/include/GL/glext.h b/include/GL/glext.h
index 565ed40..ca0ad10 100644
--- a/include/GL/glext.h
+++ b/include/GL/glext.h
@@ -185,6 +185,15 @@ GLAPI void APIENTRY glCompressedTexImage2DARB(GLenum target,
         GLsizei imageSize,
         const GLvoid *data);
 
+GLAPI void APIENTRY glCompressedTexSubImage2DARB(GLenum target,
+        GLint level,
+        GLint xoffset,
+        GLint yoffset,
+        GLsizei width,
+        GLsizei height,
+        GLenum format,
+        GLsizei imageSize,
+        const GLvoid *data);
 
 /* Core aliases */
 #define GL_INVALID_FRAMEBUFFER_OPERATION GL_INVALID_FRAMEBUFFER_OPERATION_EXT
@@ -195,6 +204,7 @@ GLAPI void APIENTRY glCompressedTexImage2DARB(GLenum target,
 
 #define glGenerateMipmapEXT glGenerateMipmap
 #define glCompressedTexImage2D glCompressedTexImage2DARB
+#define glCompressedTexSubImage2D glCompressedTexSubImage2DARB
 
 #ifndef GL_VERSION_1_4
 #define GL_VERSION_1_4 1
diff --git a/samples/nehe06_vq/main.c b/samples/nehe06_vq/main.c
index 754f458..bd0df56 100644
--- a/samples/nehe06_vq/main.c
+++ b/samples/nehe06_vq/main.c
@@ -165,9 +165,16 @@ void LoadGLTextures() {
 
     // 2d texture, level of detail 0 (normal), 3 components (red, green, blue), x size from image, y size from image,
     // border 0 (normal), rgb color data, unsigned byte data, and finally the data itself.
+    // Allocate texture memory (but don't upload compressed data yet)
     glCompressedTexImage2DARB(
         GL_TEXTURE_2D, 0, image1->internalFormat, image1->sizeX, image1->sizeY, 0,
-        image1->dataSize, image1->data
+        image1->dataSize, NULL  // NULL here means we are not uploading data yet
+    );
+
+    // Now use glCompressedTexSubImage2DARB to upload the compressed data to the texture
+    glCompressedTexSubImage2DARB(
+        GL_TEXTURE_2D, 0, 0, 0, image1->sizeX, image1->sizeY, 
+        image1->internalFormat, image1->dataSize, image1->data
     );
 
     free(image1);