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

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Avaliação

Dificuldade
3/5
Tempo estimado
Meio dia
Facilidade para iniciantes
65/100
Tipo de issue
Bug
Clareza
Claramente especificada
Status de atividade
Ativa
Stack de tecnologia
rust
Domínio
accessibility

Direção de pesquisa

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.

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Descrição

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.

Linguagem predominante
Rust
Estrelas
131
Forks
97
Merge médio
21h 45min
PRs com merge (30d)
95

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