outputconfigurationstore: add a fallback for when edid parsing fails

When edid parsing fails, KWin will base output settings on the connector, which
isn't great on its own, but at least works in many cases. When the edid can be
parsed later though, the display settings will reset because now the edid identifier
is used to exclude the old config (in which the latter is missing).
To work around that, this commit adds output identification based on the edid hash,
which is also not ideal, but can be safely matched with in case no output config
with a matching edid identifier exists.

src/outputconfigurationstore.cpp

@@ -133,10 +133,13 @@ std::optional<size_t> OutputConfigurationStore::findOutput(Output *output, const
     const bool uniqueEdid = !output->edid().identifier().isEmpty() && std::none_of(allOutputs.begin(), allOutputs.end(), [output](Output *otherOutput) {
         return otherOutput != output && otherOutput->edid().identifier() == output->edid().identifier();
     });
+    const bool uniqueEdidHash = !output->edid().hash().isEmpty() && std::none_of(allOutputs.begin(), allOutputs.end(), [output](Output *otherOutput) {
+        return otherOutput != output && otherOutput->edid().hash() == output->edid().hash();
+    });
     const bool uniqueMst = !output->mstPath().isEmpty() && std::none_of(allOutputs.begin(), allOutputs.end(), [output](Output *otherOutput) {
         return otherOutput != output && otherOutput->edid().identifier() == output->edid().identifier() && otherOutput->mstPath() == output->mstPath();
     });
-    const auto it = std::find_if(m_outputs.begin(), m_outputs.end(), [uniqueEdid, uniqueMst, output](const auto &outputState) {
+    auto it = std::find_if(m_outputs.begin(), m_outputs.end(), [&](const auto &outputState) {
         if (output->edid().isValid()) {
             if (outputState.edidIdentifier != output->edid().identifier()) {
                 return false;
@@ -144,6 +147,13 @@ std::optional<size_t> OutputConfigurationStore::findOutput(Output *output, const
                 return true;
             }
         }
+        if (!output->edid().hash().isEmpty()) {
+            if (outputState.edidHash != output->edid().hash()) {
+                return false;
+            } else if (uniqueEdidHash) {
+                return true;
+            }
+        }
         if (outputState.mstPath != output->mstPath()) {
             return false;
         } else if (uniqueMst) {
@@ -151,6 +161,12 @@ std::optional<size_t> OutputConfigurationStore::findOutput(Output *output, const
         }
         return outputState.connectorName == output->name();
     });
+    if (it == m_outputs.end() && uniqueEdidHash) {
+        // handle the edge case of EDID parsing failing in the past but not failing anymore
+        it = std::find_if(m_outputs.begin(), m_outputs.end(), [&](const auto &outputState) {
+            return outputState.edidHash == output->edid().hash();
+        });
+    }
     if (it != m_outputs.end()) {
         return std::distance(m_outputs.begin(), it);
     } else {
@@ -197,6 +213,7 @@ void OutputConfigurationStore::storeConfig(const QList<Output *> &allOutputs, bo
             m_outputs[*outputIndex] = OutputState{
                 .edidIdentifier = output->edid().identifier(),
                 .connectorName = output->name(),
+                .edidHash = output->edid().isValid() ? output->edid().hash() : QString{},
                 .mstPath = output->mstPath(),
                 .mode = ModeData{
                     .size = mode->size(),
@@ -229,6 +246,7 @@ void OutputConfigurationStore::storeConfig(const QList<Output *> &allOutputs, bo
             m_outputs[*outputIndex] = OutputState{
                 .edidIdentifier = output->edid().identifier(),
                 .connectorName = output->name(),
+                .edidHash = output->edid().isValid() ? output->edid().hash() : QString{},
                 .mstPath = output->mstPath(),
                 .mode = ModeData{
                     .size = mode->size(),
@@ -554,6 +572,12 @@ void OutputConfigurationStore::load()
                 hasIdentifier = true;
             }
         }
+        if (const auto it = data.find("edidHash"); it != data.end()) {
+            if (const auto str = it->toString(); !str.isEmpty()) {
+                state.edidHash = str;
+                hasIdentifier = true;
+            }
+        }
         if (const auto it = data.find("connectorName"); it != data.end()) {
             if (const auto str = it->toString(); !str.isEmpty()) {
                 state.connectorName = str;
@@ -576,6 +600,7 @@ void OutputConfigurationStore::load()
         const bool hasDuplicate = std::any_of(outputDatas.begin(), outputDatas.end(), [&state](const auto &data) {
             return data
                 && data->edidIdentifier == state.edidIdentifier
+                && data->edidHash == state.edidHash
                 && data->mstPath == state.mstPath
                 && data->connectorName == state.connectorName;
         });
@@ -808,6 +833,9 @@ void OutputConfigurationStore::save()
         if (output.edidIdentifier) {
             o["edidIdentifier"] = *output.edidIdentifier;
         }
+        if (!output.edidHash.isEmpty()) {
+            o["edidHash"] = output.edidHash;
+        }
         if (output.connectorName) {
             o["connectorName"] = *output.connectorName;
         }

src/outputconfigurationstore.h

@@ -62,6 +62,7 @@ private:
         std::optional<QString> edidIdentifier;
         std::optional<QString> connectorName;
         // empty if invalid
+        QString edidHash;
         QString mstPath;
         // actual state
         std::optional<ModeData> mode;