Tracker: expand use of mime sniffer

* Add Model::SniffMimeIfNeeded as a faster alternative to
  Model::Mimeset, useful for ensuring that Model::fMimeType is
  initialized regardless of whether the filesystem supports MIME.
* Use SniffMimeIfNeeded when the user interacts with a file.
* Change the return value of Model::Mimeset to match the comment in
  Model.h, although currently no client functions pay attention to the
  return value.
* Fixes #19284.

The SniffMimeIfNeeded calls provide the following behavior:
* AddOneRefSignatures - Populate Open With
* SearchForSignatureEntryList::Relation - Populate Open With
* SearchForSignatureEntryList::RelationDescription - Populate Open
  With descriptions (e.g. "Preferred for Text file").
* TTracker::OpenInfoWindows - Set up Get Info window

Change-Id: Icd0aa98781e191d3f804235b0ab8acfdbe47582d
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9683
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: Adrien Destugues <[email protected]>

src/kits/tracker/Model.cpp

@@ -1281,7 +1281,24 @@ Model::Mimeset(bool force)
 	opener.OpenNode();
 	AttrChanged(NULL);
 
-	return !oldType.ICompare(MimeType());
+	return oldType.ICompare(MimeType()) != 0;
+}
+
+
+void
+Model::SniffMimeIfNeeded()
+{
+	if (fMimeType != B_FILE_MIMETYPE)
+		return;
+
+	BVolume volume(fStatBuf.st_dev);
+	if (volume.InitCheck() == B_OK && !volume.KnowsMime()) {
+		BMimeType mimeType;
+		if (BMimeType::GuessMimeType(&fEntryRef, &mimeType) == B_OK)
+			fMimeType = mimeType.Type();
+	}
+
+	return;
 }
 
 

src/kits/tracker/Model.h

@@ -208,6 +208,9 @@ public:
 
 	bool Mimeset(bool force);
 		// returns true if mime type changed
+	void SniffMimeIfNeeded();
+		// if the filesystem does not support MIME, sets fMimeType using the MIME sniffer;
+		// makes no attempt to write the file's MIME attribute
 
 	bool HasLocalizedName() const;
 

src/kits/tracker/OpenWithWindow.cpp

@@ -617,6 +617,7 @@ AddOneRefSignatures(const entry_ref* ref, void* castToIterator)
 	Model model(ref, true, true);
 	if (model.InitCheck() != B_OK)
 		return NULL;
+	model.SniffMimeIfNeeded();
 
 	BString mimeType(model.MimeType());
 
@@ -1586,6 +1587,7 @@ SearchForSignatureEntryList::Relation(const BMessage* entriesToOpen,
 		Model model(&ref, true, true);
 		if (model.InitCheck())
 			continue;
+		model.SniffMimeIfNeeded();
 
 		int32 result = Relation(&model, applicationModel);
 		if (result != kNoRelation) {
@@ -1626,6 +1628,7 @@ SearchForSignatureEntryList::RelationDescription(const BMessage* entriesToOpen,
 		Model model(&ref, true, true);
 		if (model.InitCheck())
 			continue;
+		model.SniffMimeIfNeeded();
 
 		BMimeType mimeType;
 		int32 result = Relation(&model, applicationModel);

src/kits/tracker/Tracker.cpp

@@ -1171,6 +1171,7 @@ TTracker::OpenInfoWindows(BMessage* message)
 				wind->Activate();
 				delete model;
 			} else {
+				model->SniffMimeIfNeeded();
 				wind = new BInfoWindow(model, index, &fWindowList);
 				wind->PostMessage(kRestoreState);
 			}