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