Extend app input planning to UI state

src/app_core/app_input.h

@@ -3,6 +3,7 @@
 #include "foundation/result.h"
 
 #include <cmath>
+#include <cstddef>
 
 namespace pp::app {
 
@@ -37,6 +38,17 @@ struct AppKeyDispatchPlan {
     bool sync_vr_camera_rotation = false;
 };
 
+struct AppUiVisibilityTogglePlan {
+    bool next_ui_visible = true;
+    std::size_t first_panel_child_index = 1;
+    std::size_t panel_child_count = 0;
+};
+
+struct AppStylusAttachPlan {
+    bool set_has_stylus = true;
+    bool enable_canvas_touch_lock = false;
+};
+
 [[nodiscard]] inline pp::foundation::Status validate_input_zoom(float zoom)
 {
     if (!std::isfinite(zoom) || zoom <= 0.0F) {
@@ -163,4 +175,35 @@ struct AppKeyDispatchPlan {
     };
 }
 
+[[nodiscard]] inline pp::foundation::Result<AppUiVisibilityTogglePlan> plan_app_ui_visibility_toggle(
+    bool current_ui_visible,
+    bool has_main_layout,
+    std::size_t main_child_count,
+    std::size_t panel_child_count)
+{
+    if (!has_main_layout) {
+        return pp::foundation::Result<AppUiVisibilityTogglePlan>::failure(
+            pp::foundation::Status::invalid_argument("UI toggle requires a main layout"));
+    }
+
+    if (main_child_count <= 1U) {
+        return pp::foundation::Result<AppUiVisibilityTogglePlan>::failure(
+            pp::foundation::Status::invalid_argument("UI toggle requires a panel container child"));
+    }
+
+    return pp::foundation::Result<AppUiVisibilityTogglePlan>::success(AppUiVisibilityTogglePlan {
+        .next_ui_visible = !current_ui_visible,
+        .first_panel_child_index = 1U,
+        .panel_child_count = panel_child_count,
+    });
+}
+
+[[nodiscard]] constexpr AppStylusAttachPlan plan_app_stylus_attach(bool has_canvas) noexcept
+{
+    return AppStylusAttachPlan {
+        .set_has_stylus = true,
+        .enable_canvas_touch_lock = has_canvas,
+    };
+}
+
 } // namespace pp::app

src/app_events.cpp

@@ -661,15 +661,34 @@ bool App::key_char(char key)
 
 void App::toggle_ui()
 {
-    auto m = layout[main_id]->m_children[1];
-    ui_visible = !ui_visible;
-    for (int i = 1; i < m->m_children.size(); i++)
-        m->m_children[i]->m_display = ui_visible;
+    auto* main = layout[main_id];
+    const std::size_t main_child_count = main ? main->m_children.size() : 0U;
+    auto* panel_container = main_child_count > 1U ? main->m_children[1].get() : nullptr;
+    const auto plan = pp::app::plan_app_ui_visibility_toggle(
+        ui_visible,
+        main != nullptr,
+        main_child_count,
+        panel_container ? panel_container->m_children.size() : 0U);
+    if (!plan) {
+        LOG("UI toggle plan failed: %s", plan.status().message);
+        return;
+    }
+
+    ui_visible = plan.value().next_ui_visible;
+    if (!panel_container)
+        return;
+
+    for (std::size_t i = plan.value().first_panel_child_index;
+         i < plan.value().panel_child_count;
+         ++i) {
+        panel_container->m_children[i]->m_display = ui_visible;
+    }
 }
 
 void App::set_stylus()
 {
-    has_stylus = true;
-    if (canvas)
+    const auto plan = pp::app::plan_app_stylus_attach(canvas != nullptr);
+    has_stylus = plan.set_has_stylus;
+    if (plan.enable_canvas_touch_lock && canvas)
         canvas->m_canvas->m_touch_lock = true;
 }