plugins/screencast: Reset dmabufParams if SHM buffers are negotiated

m_dmabufParams is initialised after a format with modifiers is
suggested. Should the negotiation process fallback to SHM buffers, we
should reset it, so it can be used to determine if the negotiated format
is of type DmaBuf or not.

src/plugins/screencast/screencaststream.cpp

@@ -113,7 +113,7 @@ void ScreenCastStream::newStreamParams()
     qCDebug(KWIN_SCREENCAST) << "announcing stream params. with dmabuf:" << m_dmabufParams.has_value();
     uint8_t paramsBuffer[1024];
     spa_pod_builder pod_builder = SPA_POD_BUILDER_INIT(paramsBuffer, sizeof(paramsBuffer));
-    const int buffertypes = m_dmabufParams ? (1 << SPA_DATA_DmaBuf) | (1 << SPA_DATA_MemFd) : (1 << SPA_DATA_MemFd);
+    const int buffertypes = m_dmabufParams ? (1 << SPA_DATA_DmaBuf) : (1 << SPA_DATA_MemFd);
     const int bpp = m_videoFormat.format == SPA_VIDEO_FORMAT_RGB || m_videoFormat.format == SPA_VIDEO_FORMAT_BGR ? 3 : 4;
     const int stride = SPA_ROUND_UP_N(m_resolution.width() * bpp, 4);
 
@@ -171,38 +171,41 @@ void ScreenCastStream::onStreamParamChanged(uint32_t id, const struct spa_pod *f
         // Remove duplicates
         std::sort(receivedModifiers.begin(), receivedModifiers.end());
         receivedModifiers.erase(std::unique(receivedModifiers.begin(), receivedModifiers.end()), receivedModifiers.end());
-    }
-    if (modifierProperty && (!m_dmabufParams || !receivedModifiers.contains(m_dmabufParams->modifier))) {
-        if (modifierProperty->flags & SPA_POD_PROP_FLAG_DONT_FIXATE) {
-            // DRM_MOD_INVALID should be used as a last option. Do not just remove it it's the only
-            // item on the list
-            if (receivedModifiers.count() > 1) {
-                receivedModifiers.removeAll(DRM_FORMAT_MOD_INVALID);
+
+        if (!m_dmabufParams || !receivedModifiers.contains(m_dmabufParams->modifier)) {
+            if (modifierProperty->flags & SPA_POD_PROP_FLAG_DONT_FIXATE) {
+                // DRM_MOD_INVALID should be used as a last option. Do not just remove it it's the only
+                // item on the list
+                if (receivedModifiers.count() > 1) {
+                    receivedModifiers.removeAll(DRM_FORMAT_MOD_INVALID);
+                }
+                m_dmabufParams = testCreateDmaBuf(m_resolution, m_drmFormat, receivedModifiers);
+            } else {
+                m_dmabufParams = testCreateDmaBuf(m_resolution, m_drmFormat, {DRM_FORMAT_MOD_INVALID});
             }
-            m_dmabufParams = testCreateDmaBuf(m_resolution, m_drmFormat, receivedModifiers);
-        } else {
-            m_dmabufParams = testCreateDmaBuf(m_resolution, m_drmFormat, {DRM_FORMAT_MOD_INVALID});
-        }
 
-        // In case we fail to use any modifier from the list of offered ones, remove these
-        // from our all future offerings, otherwise there will be no indication that it cannot
-        // be used and clients can go for it over and over
-        if (!m_dmabufParams.has_value()) {
-            for (uint64_t modifier : receivedModifiers) {
-                m_modifiers.removeAll(modifier);
+            // In case we fail to use any modifier from the list of offered ones, remove these
+            // from our all future offerings, otherwise there will be no indication that it cannot
+            // be used and clients can go for it over and over
+            if (!m_dmabufParams.has_value()) {
+                for (uint64_t modifier : receivedModifiers) {
+                    m_modifiers.removeAll(modifier);
+                }
+            // Also in case DRM_FORMAT_MOD_INVALID was used and didn't fail, we still need to
+            // set it as our modifier, otherwise it would be set to default value (0) which is
+            // also a valid modifier, but not the one we want to actually use
+            } else if (receivedModifiers.count() == 1 && receivedModifiers.constFirst() == DRM_FORMAT_MOD_INVALID) {
+                m_dmabufParams->modifier = DRM_FORMAT_MOD_INVALID;
             }
-        // Also in case DRM_FORMAT_MOD_INVALID was used and didn't fail, we still need to
-        // set it as our modifier, otherwise it would be set to default value (0) which is
-        // also a valid modifier, but not the one we want to actually use
-        } else if (receivedModifiers.count() == 1 && receivedModifiers.constFirst() == DRM_FORMAT_MOD_INVALID) {
-            m_dmabufParams->modifier = DRM_FORMAT_MOD_INVALID;
-        }
 
-        qCDebug(KWIN_SCREENCAST) << "Stream dmabuf modifiers received, offering our best suited modifier" << m_dmabufParams.has_value();
-        char buffer[2048];
-        auto params = buildFormats(m_dmabufParams.has_value(), buffer);
-        pw_stream_update_params(m_pwStream, params.data(), params.count());
-        return;
+            qCDebug(KWIN_SCREENCAST) << "Stream dmabuf modifiers received, offering our best suited modifier" << m_dmabufParams.has_value();
+            char buffer[2048];
+            auto params = buildFormats(m_dmabufParams.has_value(), buffer);
+            pw_stream_update_params(m_pwStream, params.data(), params.count());
+            return;
+        }
+    } else {
+      m_dmabufParams.reset();
     }
 
     qCDebug(KWIN_SCREENCAST) << "Stream format found, defining buffers";