From 80d94bd343e34c5e2be4ebc5e20a3f8efb068048 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dominic=20H=C3=B6glinger?= <dominic@hoeglinger.eu>
Date: Sat, 27 Sep 2025 21:15:10 +0200
Subject: [PATCH] LVGL Wrappers: Proposition to make oversized parents
 scrollable

---
 Tactility/Source/lvgl/wrappers/obj.cpp | 102 ++++++++++++++++++++++++-
 1 file changed, 101 insertions(+), 1 deletion(-)

diff --git a/Tactility/Source/lvgl/wrappers/obj.cpp b/Tactility/Source/lvgl/wrappers/obj.cpp
index 402a73f2..8be02ada 100644
--- a/Tactility/Source/lvgl/wrappers/obj.cpp
+++ b/Tactility/Source/lvgl/wrappers/obj.cpp
@@ -9,6 +9,101 @@ extern "C" {
 extern void __real_lv_obj_set_flex_flow(lv_obj_t* obj, lv_flex_flow_t flow);
 extern lv_obj_t* __real_lv_obj_create(lv_obj_t* parent);
 
+static bool get_children_bby(lv_obj_t * parent, lv_coord_t * out_min_y, lv_coord_t * out_max_y) {
+    lv_coord_t min_y = INT_MAX;
+    lv_coord_t max_y = INT_MIN;
+    bool has_children = false;
+    lv_area_t parent_coords;
+    lv_obj_get_coords(parent, &parent_coords);
+
+    for(size_t i = 0; i < lv_obj_get_child_count(parent); i++) {
+        lv_obj_t * child = lv_obj_get_child(parent, i);
+        // Get absolute position of child
+        lv_area_t child_coords;
+        lv_obj_get_coords(child, &child_coords);
+
+        // convert to local coordinates
+        lv_coord_t c_y1 = child_coords.y1 - parent_coords.y1;
+        lv_coord_t c_y2 = child_coords.y2 - parent_coords.y1;
+
+        // Update minimum/maximum
+        if(c_y1 < min_y) min_y = c_y1;
+        if(c_y2 > max_y) max_y = c_y2;
+
+        has_children = true;
+    }
+
+    if(has_children) {
+        *out_min_y = min_y;
+        *out_max_y = max_y;
+    }
+
+    return has_children;
+}
+
+static bool is_overflowing(lv_obj_t* obj) {
+    lv_coord_t min_y = 0;
+    lv_coord_t max_y = 0;
+
+    // Compute childrens' bounding box relative to parent
+    if(!get_children_bby(obj, &min_y, &max_y)) {
+        // Can't be overflowing when no children are present
+        return false;
+    }
+
+    lv_coord_t parent_h = lv_obj_get_height(obj);
+
+    return ((min_y < 0) || (max_y >= parent_h));
+}
+
+static void apply_scroll_styles(lv_obj_t* obj) {
+    static bool init = false;
+    static lv_style_t style_scroll_focus;
+    static lv_style_t style_scrolling;
+
+    if (!init) {
+        // Style which applies if scrollbar is focused
+        lv_style_init(&style_scroll_focus);
+        lv_style_set_bg_color(&style_scroll_focus, lv_color_make(0x40,0xA0,0xFF));
+        lv_style_set_bg_opa(&style_scroll_focus, LV_OPA_COVER);
+        lv_style_set_border_width(&style_scroll_focus, 1);
+        lv_style_set_border_color(&style_scroll_focus, lv_theme_get_color_primary(nullptr));
+
+        // Style which applies if scrollbar is clicked enough that it defocuses
+        lv_style_init(&style_scrolling);
+        lv_style_set_bg_color(&style_scrolling, lv_color_make(0x40,0xA0,0xFF));
+        lv_style_set_bg_opa(&style_scrolling, LV_OPA_COVER);
+        lv_style_set_border_width(&style_scrolling, 1);
+        // In Tactilitys' default theme, this is red, maybe there is a better color?
+        lv_style_set_border_color(&style_scrolling, lv_theme_get_color_secondary(nullptr));
+
+        init = true;
+    }
+    lv_obj_add_style(obj, &style_scroll_focus, (lv_style_selector_t)(LV_PART_SCROLLBAR | LV_STATE_FOCUSED));
+    lv_obj_add_style(obj, &style_scrolling, (lv_style_selector_t)(LV_PART_SCROLLBAR | LV_STATE_PRESSED));
+}
+
+static bool is_scrollable(lv_obj_t* obj) {
+    return lv_obj_has_flag(obj, LV_OBJ_FLAG_CLICKABLE) && lv_obj_has_flag(obj, LV_OBJ_FLAG_SCROLL_ON_FOCUS);
+}
+
+static void make_scrollable(lv_obj_t* obj) {
+    // Make the object interactive, i.e focusable
+    lv_obj_add_flag(obj, (lv_obj_flag_t)(LV_OBJ_FLAG_CLICKABLE | LV_OBJ_FLAG_SCROLL_ON_FOCUS));
+
+    // Add to default group to get it into the focus list
+    auto* group = lv_group_get_default();
+    lv_group_add_obj(group, obj);
+
+    // Apply style to scrollbar to make it visible if focused
+    apply_scroll_style(obj);
+}
+
+static void child_added_event_handler(lv_event_t* e) {
+    lv_obj_t* obj = (lv_obj_t*)lv_event_get_target(e);
+
+}
+
 void __wrap_lv_obj_set_flex_flow(lv_obj_t* obj, lv_flex_flow_t flow) {
     __real_lv_obj_set_flex_flow(obj, flow);
 
@@ -25,9 +120,14 @@ lv_obj_t* __wrap_lv_obj_create(lv_obj_t* parent) {
         lv_obj_set_style_radius(obj, 3, LV_STATE_DEFAULT);
         lv_obj_set_style_border_width(obj, 1, LV_STATE_DEFAULT);
     }
+
+    if (parent && !is_scrollable(parent) && is_overflowing(parent)) {
+        make_scrollable(parent);
+    }
+
     return obj;
 }
 
 }
 
-#endif // ESP_PLATFORM
\ No newline at end of file
+#endif // ESP_PLATFORM