feat: implement PageStack class for multi-page navigation in LVGL apps

main/ui/page_stack.cpp

@@ -0,0 +1,115 @@
+#include "page_stack.h"
+#include "esp_log.h"
+
+static const char* TAG = "PageStack";
+
+PageStack::PageStack(lv_obj_t* parent_container)
+    : parent_container_(parent_container) {
+    if (!parent_container_) {
+        ESP_LOGE(TAG, "Parent container is null");
+    }
+}
+
+PageStack::~PageStack() {
+    clear();
+}
+
+lv_obj_t* PageStack::create_page_container() {
+    lv_obj_t* page = lv_obj_create(parent_container_);
+
+    // Fill parent container
+    lv_obj_set_size(page, LV_PCT(100), LV_PCT(100));
+    lv_obj_set_pos(page, 0, 0);
+
+    // Remove padding and scrollbars
+    lv_obj_set_style_pad_all(page, 0, 0);
+    lv_obj_set_scrollbar_mode(page, LV_SCROLLBAR_MODE_OFF);
+
+    // White background
+    lv_obj_set_style_bg_color(page, lv_color_white(), 0);
+    lv_obj_set_style_bg_opa(page, LV_OPA_COVER, 0);
+
+    // Remove border
+    lv_obj_set_style_border_width(page, 0, 0);
+
+    return page;
+}
+
+lv_obj_t* PageStack::push(PageBuilder builder, PageCleanup cleanup) {
+    if (!parent_container_) {
+        ESP_LOGE(TAG, "Cannot push page: parent container is null");
+        return nullptr;
+    }
+
+    if (!builder) {
+        ESP_LOGE(TAG, "Cannot push page: builder is null");
+        return nullptr;
+    }
+
+    // Hide current page if any
+    if (!pages_.empty()) {
+        lv_obj_add_flag(pages_.back().container, LV_OBJ_FLAG_HIDDEN);
+    }
+
+    // Create new page container
+    lv_obj_t* page = create_page_container();
+
+    // Build page content
+    builder(page);
+
+    // Add to stack
+    pages_.push_back({page, cleanup});
+
+    ESP_LOGD(TAG, "Pushed page (depth: %d)", pages_.size());
+    return page;
+}
+
+bool PageStack::pop() {
+    if (pages_.empty()) {
+        ESP_LOGW(TAG, "Cannot pop: stack is empty");
+        return false;
+    }
+
+    // Get and remove current page
+    Page current = pages_.back();
+    pages_.pop_back();
+
+    // Call cleanup callback if provided
+    if (current.cleanup) {
+        current.cleanup(current.container);
+    }
+
+    // Delete page container
+    lv_obj_del(current.container);
+
+    // Show previous page if any
+    if (!pages_.empty()) {
+        lv_obj_clear_flag(pages_.back().container, LV_OBJ_FLAG_HIDDEN);
+    }
+
+    ESP_LOGD(TAG, "Popped page (depth: %d)", pages_.size());
+    return true;
+}
+
+void PageStack::clear() {
+    ESP_LOGD(TAG, "Clearing all pages (depth: %d)", pages_.size());
+
+    // Pop all pages (calls cleanup callbacks)
+    while (!pages_.empty()) {
+        Page current = pages_.back();
+        pages_.pop_back();
+
+        if (current.cleanup) {
+            current.cleanup(current.container);
+        }
+
+        lv_obj_del(current.container);
+    }
+}
+
+lv_obj_t* PageStack::current_page() const {
+    if (pages_.empty()) {
+        return nullptr;
+    }
+    return pages_.back().container;
+}

main/ui/page_stack.h

@@ -0,0 +1,86 @@
+#pragma once
+
+#include "lvgl.h"
+#include <vector>
+#include <functional>
+
+/**
+ * @brief Reusable page stack for multi-page navigation within LVGL apps
+ *
+ * Manages a stack of LVGL containers, allowing apps to push/pop pages
+ * and implement hierarchical navigation. Thread-safe for use with LVGL.
+ */
+class PageStack {
+public:
+    /**
+     * @brief Page builder callback
+     * @param page_container The LVGL container to build the page in
+     */
+    using PageBuilder = std::function<void(lv_obj_t* page_container)>;
+
+    /**
+     * @brief Page cleanup callback
+     * @param page_container The LVGL container being destroyed
+     */
+    using PageCleanup = std::function<void(lv_obj_t* page_container)>;
+
+    /**
+     * @brief Construct page stack with parent container
+     * @param parent_container Parent LVGL container for pages
+     */
+    explicit PageStack(lv_obj_t* parent_container);
+
+    /**
+     * @brief Destructor - clears all pages
+     */
+    ~PageStack();
+
+    /**
+     * @brief Push a new page onto the stack
+     * @param builder Function to build page content
+     * @param cleanup Optional cleanup function called when page is popped
+     * @return The created page container
+     */
+    lv_obj_t* push(PageBuilder builder, PageCleanup cleanup = nullptr);
+
+    /**
+     * @brief Pop the current page and return to previous
+     * @return true if page was popped, false if stack is empty
+     */
+    bool pop();
+
+    /**
+     * @brief Clear all pages from the stack
+     */
+    void clear();
+
+    /**
+     * @brief Get the current (top) page container
+     * @return Current page or nullptr if stack is empty
+     */
+    lv_obj_t* current_page() const;
+
+    /**
+     * @brief Get the number of pages in the stack
+     */
+    size_t depth() const { return pages_.size(); }
+
+    /**
+     * @brief Check if stack is empty
+     */
+    bool empty() const { return pages_.empty(); }
+
+private:
+    struct Page {
+        lv_obj_t* container;
+        PageCleanup cleanup;
+    };
+
+    lv_obj_t* parent_container_;
+    std::vector<Page> pages_;
+
+    /**
+     * @brief Create a page container
+     */
+    lv_obj_t* create_page_container();
+};