glgsg: fix issue extracting texture data for multiview textures

panda/src/glstuff/glGraphicsStateGuardian_src.cxx

@@ -14270,7 +14270,17 @@ do_extract_texture_data(CLP(TextureContext) *gtc) {
     return false;
   }
 
-  tex->set_ram_image(image, compression, page_size);
+  int num_views = tex->get_num_views();
+  if (num_views == 1) {
+    // Replace the entire image, since we are modifying the only view.
+    tex->set_ram_image(image, compression, page_size);
+  } else {
+    // We're only modifying a single view, so we can't stomp all over the
+    // existing content.
+    PTA_uchar ram_image = tex->modify_ram_image();
+    nassertr(ram_image.size() == image.size() * num_views, false);
+    memcpy(ram_image.p() + image.size() * gtc->get_view(), image.p(), image.size());
+  }
 
   if (gtc->_uses_mipmaps) {
     // Also get the mipmap levels.
@@ -14286,7 +14296,12 @@ do_extract_texture_data(CLP(TextureContext) *gtc) {
                                  type, compression, n)) {
         return false;
       }
-      tex->set_ram_mipmap_image(n, image, page_size);
+      if (num_views == 1) {
+        tex->set_ram_mipmap_image(n, image, page_size);
+      } else {
+        PTA_uchar ram_mipmap_image = tex->modify_ram_mipmap_image(n);
+        memcpy(ram_mipmap_image.p() + image.size() * gtc->get_view(), image.p(), image.size());
+      }
     }
   }
 
@@ -14350,13 +14365,13 @@ extract_texture_image(PTA_uchar &image, size_t &page_size,
 #ifndef OPENGLES
   } else if (target == GL_TEXTURE_BUFFER) {
     // In the case of a buffer texture, we need to get it from the buffer.
-    image = PTA_uchar::empty_array(tex->get_expected_ram_mipmap_image_size(n));
+    image = PTA_uchar::empty_array(tex->get_expected_ram_mipmap_view_size(n));
     _glGetBufferSubData(target, 0, image.size(), image.p());
 #endif
 
   } else if (compression == Texture::CM_off) {
     // An uncompressed 1-d, 2-d, or 3-d texture.
-    image = PTA_uchar::empty_array(tex->get_expected_ram_mipmap_image_size(n));
+    image = PTA_uchar::empty_array(tex->get_expected_ram_mipmap_view_size(n));
     GLenum external_format = get_external_image_format(tex);
     GLenum pixel_type = get_component_type(type);
     glGetTexImage(target, n, external_format, pixel_type, image.p());