Detach textures from framebuffers before deleting

GL drivers keep internal references to textures attached to
framebuffers. Deleting a texture while still attached can cause
use-after-free in driver memory, observed as crashes on NVIDIA
during rapid preset switching or window resize.

Detach all textures before deletion in both ~Framebuffer() and
SetSize(), using a three-phase detach → resize → reattach pattern
in SetSize() to avoid referencing stale texture IDs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: struktured

src/libprojectM/Renderer/Framebuffer.cpp

@@ -24,7 +24,19 @@ Framebuffer::~Framebuffer()
 {
     if (!m_framebufferIds.empty())
     {
-        // Delete attached textures first
+        // Detach all textures from each framebuffer before destroying them.
+        // The GL driver keeps internal references to attached textures, so we must
+        // detach before deleting to avoid use-after-free in driver memory.
+        for (auto& [index, attachments] : m_attachments)
+        {
+            glBindFramebuffer(GL_FRAMEBUFFER, m_framebufferIds.at(index));
+            for (auto& [type, _] : attachments)
+            {
+                glFramebufferTexture2D(GL_FRAMEBUFFER, type, GL_TEXTURE_2D, 0, 0);
+            }
+        }
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+
         m_attachments.clear();
 
         glDeleteFramebuffers(static_cast<int>(m_framebufferIds.size()), m_framebufferIds.data());
@@ -92,9 +104,21 @@ bool Framebuffer::SetSize(int width, int height)
     for (auto& attachments : m_attachments)
     {
         Bind(attachments.first);
+        // First detach all textures from framebuffer before destroying them.
+        // The GL driver keeps internal references to attached textures, so we must
+        // detach before deleting to avoid use-after-free in driver memory.
+        for (auto& texture : attachments.second)
+        {
+            glFramebufferTexture2D(GL_FRAMEBUFFER, texture.first, GL_TEXTURE_2D, 0, 0);
+        }
+        // Now safe to resize (which destroys old textures and creates new ones)
         for (auto& texture : attachments.second)
         {
             texture.second->SetSize(width, height);
+        }
+        // Reattach the new textures
+        for (auto& texture : attachments.second)
+        {
             glFramebufferTexture2D(GL_FRAMEBUFFER, texture.first, GL_TEXTURE_2D, texture.second->Texture()->TextureID(), 0);
         }
     }