Navigation: ZoomIn fails when the first child says nothing (silent or invisible)

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Valutazione

Difficoltà
3/5
Tempo stimato
Mezza giornata
Idoneità per principianti
65/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
rust
Ambito
accessibility

Direzione di ricerca

Start from do_navigate_command_string and apply_navigation_rules in the Rust navigation code, especially the LOOP_LIMIT retry loop for ZoomIn/ZoomInAll. Reproduce with the silent-separator example from the issue, then try switching the retry command to MoveNext and confirm ZoomIn lands on the next spoken node. Run cargo test and check the Enhanced-mode ZoomIn cases; done means the example speaks "x plus 1" and silent-node failures drop without regressing other navigation commands.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

ZoomIn and ZoomInAll fail if they land on a node that produces no speech, such as an invisible separator with :silent:

<math><mi intent=":silent">&#x2063;</mi><mi>x</mi><mo>+</mo><mn>1</mn></math>

Reading gives "x plus 1", but ZoomIn gives "Internal error: Navigation exceeded limit of number of times no speech generated" (MathCAT Demo: "Error in Navigation"). The same happens with a plain <mi>&#x2063;</mi>, and in every language.

This matters for LaTeX: the spanish-mathml-intent package puts these silent separators in most of its output. In its 579 test formulas (tagged PDFs, mathml-SE), ZoomIn fails in 480 of them in Enhanced mode.

The cause: when a command produces no speech, do_navigate_command_string retries the same command. ZoomIn from a leaf stays on that leaf, so all three tries say nothing. A possible fix is to retry with MoveNext after ZoomIn/ZoomInAll:

             for loop_count in 0..LOOP_LIMIT {
-                let (speech, done) = apply_navigation_rules(mathml, nav_command, &rules, &mut rules_with_context, &mut nav_state, loop_count)?;
+                // If zooming in landed on a node that says nothing (e.g., a silent invisible separator), move on to the next node
+                let command = if loop_count > 0 && (nav_command == "ZoomIn" || nav_command == "ZoomInAll") {"MoveNext"} else {nav_command};
+                if command != nav_command {
+                    rules_with_context.get_context().set_variable("NavCommand", command);
+                }
+                let (speech, done) = apply_navigation_rules(mathml, command, &rules, &mut rules_with_context, &mut nav_state, loop_count)?;

With this change, the example zooms in to "x plus 1" (the next node at that level), cargo test passes, and the failures in Enhanced mode drop from 480 to 44. Forty of those are examples that are completely silenced on purpose, so there is nothing to say. Maybe you prefer to skip silent nodes in the navigation rules instead; this is only a suggestion.

Lingua principale
Rust
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131
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21h 45m
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