drm: drop buffers from KMS on .destroy

include/aquamarine/backend/DRM.hpp

@@ -86,12 +86,19 @@ namespace Aquamarine {
         Hyprutils::Memory::CWeakPointer<CDRMBackend> backend;
         std::array<uint32_t, 4>                      boHandles = {0, 0, 0, 0};
 
+        // true if the original buffer is gone and this has been released.
+        bool dead = false;
+
       private:
         CDRMFB(Hyprutils::Memory::CSharedPointer<IBuffer> buffer_, Hyprutils::Memory::CWeakPointer<CDRMBackend> backend_);
         uint32_t submitBuffer();
         void     import();
 
         bool     dropped = false, handlesClosed = false;
+
+        struct {
+            Hyprutils::Signal::CHyprSignalListener destroyBuffer;
+        } listeners;
     };
 
     struct SDRMLayer {

src/allocator/GBM.cpp

@@ -53,8 +53,7 @@ static SDRMFormat guessFormatFrom(std::vector<SDRMFormat> formats, bool cursor)
 }
 
 Aquamarine::CGBMBuffer::CGBMBuffer(const SAllocatorBufferParams& params, Hyprutils::Memory::CWeakPointer<CGBMAllocator> allocator_,
-                                   Hyprutils::Memory::CSharedPointer<CSwapchain> swapchain) :
-    allocator(allocator_) {
+                                   Hyprutils::Memory::CSharedPointer<CSwapchain> swapchain) : allocator(allocator_) {
     if (!allocator)
         return;
 

src/backend/drm/DRM.cpp

@@ -1308,6 +1308,11 @@ bool Aquamarine::CDRMOutput::commitState(bool onlyTest) {
             return false;
         }
 
+        if (drmFB->dead) {
+            backend->backend->log(AQ_LOG_ERROR, "drm: KMS buffer is dead?!");
+            return false;
+        }
+
         if (!isNew && backend->primary) {
             // this is not a new buffer, and we are not on a primary GPU, which means
             // this buffer lives on the primary. We need to re-import it to update
@@ -1507,6 +1512,13 @@ void Aquamarine::CDRMFB::import() {
 
     // FIXME: why does this implode when it doesnt on wlroots or kwin?
     // closeHandles();
+
+    listeners.destroyBuffer = buffer->events.destroy.registerListener([this](std::any d) {
+        drop();
+        dead      = true;
+        id        = 0;
+        boHandles = {0, 0, 0, 0};
+    });
 }
 
 void Aquamarine::CDRMFB::reimport() {