gl_rasterizer: Fix buffers without size

On NVN buffers can be enabled but have no size. According to deko3d and
the behavior we see in Animal Crossing: New Horizons these buffers get
the special address of 0x1000 and limit themselves to 0xfff.

Implement buffers without a size by binding a null buffer to OpenGL
without a side.

https://github.com/devkitPro/deko3d/blob/1d1930beea093b5a663419e93b0649719a3ca5da/source/maxwell/gpu_3d_vbo.cpp#L62-L63

1 files changed, 8 insertions, 4 deletions

diff --git a/src/video_core/renderer_opengl/gl_rasterizer.cpp b/src/video_core/renderer_opengl/gl_rasterizer.cpp
index 175374f0d..1c3b3b644 100644
--- a/src/video_core/renderer_opengl/gl_rasterizer.cpp
+++ b/src/video_core/renderer_opengl/gl_rasterizer.cpp
@@ -185,8 +185,12 @@ void RasterizerOpenGL::SetupVertexBuffer() {
         const GPUVAddr start = vertex_array.StartAddress();
         const GPUVAddr end = regs.vertex_array_limit[index].LimitAddress();
 
-        ASSERT(end > start);
-        const u64 size = end - start + 1;
+        ASSERT(end >= start);
+        const u64 size = end - start;
+        if (size == 0) {
+            glBindVertexBuffer(static_cast<GLuint>(index), 0, 0, vertex_array.stride);
+            continue;
+        }
         const auto [vertex_buffer, vertex_buffer_offset] = buffer_cache.UploadMemory(start, size);
         glBindVertexBuffer(static_cast<GLuint>(index), vertex_buffer, vertex_buffer_offset,
                            vertex_array.stride);
@@ -310,8 +314,8 @@ std::size_t RasterizerOpenGL::CalculateVertexArraysSize() const {
         const GPUVAddr start = regs.vertex_array[index].StartAddress();
         const GPUVAddr end = regs.vertex_array_limit[index].LimitAddress();
 
-        ASSERT(end > start);
-        size += end - start + 1;
+        size += end - start;
+        ASSERT(end >= start);
     }
 
     return size;