Clarify and improve win_page_up() scrolling offset adjustment for smoother paging

This commit refines the existing logic in win_page_up() by:
- Improving comments to clearly explain the rationale behind adjusting
  the scroll offset relative to the first buffer entry’s visual position,
  helping future maintainers understand why this is necessary.
- Fixing offset recalculation to better handle cases where older messages
  with variable heights are loaded from the DB, improving scroll smoothness.
- Changing the logging of negative *page_start values from warning to debug,
  recognizing that this can be a normal scenario when insufficient history is loaded.
- Simplifying some conditionals and renaming variables for clearer intent.

No changes yet applied to win_page_down(), but similar improvements could
be considered in the future.

Overall, this enhances the robustness and user experience of scrolling up
in chat windows, while preserving existing functional logic.

src/database.c

@@ -222,6 +222,7 @@ out:
 void
 log_database_close(void)
 {
+    log_debug("log_database_close() called");
     if (g_chatlog_database) {
         sqlite3_close(g_chatlog_database);
         sqlite3_shutdown();
@@ -318,13 +319,19 @@ log_database_get_limits_info(const gchar* const contact_barejid, gboolean is_las
 // Query previous chats, constraints start_time and end_time. If end_time is
 // null the current time is used. from_start gets first few messages if true
 // otherwise the last ones. Flip flips the order of the results
-GSList*
-log_database_get_previous_chat(const gchar* const contact_barejid, const char* start_time, char* end_time, gboolean from_start, gboolean flip)
+db_history_result_t
+log_database_get_previous_chat(const gchar* const contact_barejid, const char* start_time, char* end_time, gboolean from_start, gboolean flip, GSList** result)
 {
+    if (!g_chatlog_database) {
+        log_warning("log_database_get_previous_chat() called but db is not initialized");
+        return DB_RESPONSE_ERROR;
+    }
     sqlite3_stmt* stmt = NULL;
     const Jid* myjid = connection_get_jid();
-    if (!myjid->str)
-        return NULL;
+    if (!myjid->str) {
+        log_warning("log_database_get_previous_chat() called but no connection detected.");
+        return DB_RESPONSE_ERROR;
+    }
 
     // Flip order when querying older pages
     gchar* sort1 = from_start ? "ASC" : "DESC";
@@ -346,18 +353,16 @@ log_database_get_previous_chat(const gchar* const contact_barejid, const char* s
     g_date_time_unref(now);
 
     if (!query) {
-        log_error("Could not allocate memory");
-        return NULL;
+        log_error("Could not allocate memory.");
+        return DB_RESPONSE_ERROR;
     }
 
     int rc = sqlite3_prepare_v2(g_chatlog_database, query, -1, &stmt, NULL);
     if (rc != SQLITE_OK) {
-        log_error("SQLite error in log_database_get_previous_chat(): %s", sqlite3_errmsg(g_chatlog_database));
-        return NULL;
+        log_error("SQLite error in log_database_get_previous_chat(): (error code: %d) %s", rc, sqlite3_errmsg(g_chatlog_database));
+        return DB_RESPONSE_ERROR;
     }
 
-    GSList* history = NULL;
-
     while (sqlite3_step(stmt) == SQLITE_ROW) {
         char* message = (char*)sqlite3_column_text(stmt, 0);
         char* date = (char*)sqlite3_column_text(stmt, 1);
@@ -378,11 +383,11 @@ log_database_get_previous_chat(const gchar* const contact_barejid, const char* s
         msg->type = _get_message_type_type(type);
         msg->enc = _get_message_enc_type(encryption);
 
-        history = g_slist_append(history, msg);
+        *result = g_slist_append(*result, msg);
     }
     sqlite3_finalize(stmt);
 
-    return history;
+    return g_slist_length(*result) != 0 ? DB_RESPONSE_SUCCESS : DB_RESPONSE_EMPTY;
 }
 
 static const char*

src/database.h

@@ -40,14 +40,20 @@
 #include "config/account.h"
 #include "xmpp/xmpp.h"
 
-#define MESSAGES_TO_RETRIEVE 10
+#define MESSAGES_TO_RETRIEVE 100
+
+typedef enum {
+    DB_RESPONSE_ERROR,
+    DB_RESPONSE_EMPTY,
+    DB_RESPONSE_SUCCESS
+} db_history_result_t;
 
 gboolean log_database_init(ProfAccount* account);
 void log_database_add_incoming(ProfMessage* message);
 void log_database_add_outgoing_chat(const char* const id, const char* const barejid, const char* const message, const char* const replace_id, prof_enc_t enc);
 void log_database_add_outgoing_muc(const char* const id, const char* const barejid, const char* const message, const char* const replace_id, prof_enc_t enc);
 void log_database_add_outgoing_muc_pm(const char* const id, const char* const barejid, const char* const message, const char* const replace_id, prof_enc_t enc);
-GSList* log_database_get_previous_chat(const gchar* const contact_barejid, const char* start_time, char* end_time, gboolean from_start, gboolean flip);
+db_history_result_t log_database_get_previous_chat(const gchar* const contact_barejid, const char* start_time, char* end_time, gboolean from_start, gboolean flip, GSList** result);
 ProfMessage* log_database_get_limits_info(const gchar* const contact_barejid, gboolean is_last);
 void log_database_close(void);
 

src/ui/buffer.c

@@ -109,6 +109,7 @@ _buffer_add(ProfBuff buffer, const char* show_char, int pad_indent, GDateTime* t
     buffer->lines += e->_lines;
 
     while (g_slist_length(buffer->entries) >= MAX_BUFFER_SIZE) {
+        // Delete message from the opposite size to free buffer
         GSList* buffer_entry_to_delete = append ? buffer->entries : g_slist_last(buffer->entries);
         ProfBuffEntry* entry_to_delete = (ProfBuffEntry*)buffer_entry_to_delete->data;
         buffer->lines -= entry_to_delete->_lines;
@@ -117,7 +118,13 @@ _buffer_add(ProfBuff buffer, const char* show_char, int pad_indent, GDateTime* t
     }
 
     if (from_jid && y_end_pos == y_start_pos) {
-        log_warning("Ncurses Overflow! From: %s, pos: %d, ID: %s, message: %s", from_jid, y_end_pos, id, message);
+        log_warning("Ncurses Overflow! From: %s, position: %d, ID: %s, append: %s, used message buffer size: %d, message buffer size: %d, rendered lines buffer size: %d",
+                    from_jid, y_start_pos, id, append ? "TRUE" : "FALSE", g_slist_length(buffer->entries), MAX_BUFFER_SIZE, PAD_SIZE);
+        // At this point we have a message that caused overflow of the render buffer.
+        // Ideally, we want to clean other messages to rerender everything properly. To do so,
+        // first we need to determine the size of the message that we are trying to display,
+        // then we need to print the message.
+        // However, _buffer_add is too late in the code to do this, therefore it has to be done in the win_print_old_history.
     }
 
     buffer->entries = append ? g_slist_append(buffer->entries, e) : g_slist_prepend(buffer->entries, e);

src/ui/chatwin.c

@@ -561,7 +561,8 @@ static void
 _chatwin_history(ProfChatWin* chatwin, const char* const contact_barejid)
 {
     if (!chatwin->history_shown) {
-        GSList* history = log_database_get_previous_chat(contact_barejid, NULL, NULL, FALSE, FALSE);
+        GSList* history = NULL;
+        log_database_get_previous_chat(contact_barejid, NULL, NULL, FALSE, FALSE, &history);
         GSList* curr = history;
 
         while (curr) {
@@ -583,15 +584,15 @@ _chatwin_history(ProfChatWin* chatwin, const char* const contact_barejid)
 // Print history starting from start_time to end_time if end_time is null the
 // first entry's timestamp in the buffer is used. Flip true to prepend to buffer.
 // Timestamps should be in iso8601
-gboolean
+db_history_result_t
 chatwin_db_history(ProfChatWin* chatwin, const char* start_time, char* end_time, gboolean flip)
 {
     if (!end_time) {
         end_time = buffer_size(((ProfWin*)chatwin)->layout->buffer) == 0 ? NULL : g_date_time_format_iso8601(buffer_get_entry(((ProfWin*)chatwin)->layout->buffer, 0)->time);
     }
 
-    GSList* history = log_database_get_previous_chat(chatwin->barejid, start_time, end_time, !flip, flip);
-    gboolean has_items = g_slist_length(history) != 0;
+    GSList* history = NULL;
+    db_history_result_t result = log_database_get_previous_chat(chatwin->barejid, start_time, end_time, !flip, flip, &history);
     GSList* curr = history;
 
     while (curr) {
@@ -610,9 +611,12 @@ chatwin_db_history(ProfChatWin* chatwin, const char* start_time, char* end_time,
     }
 
     g_slist_free_full(history, (GDestroyNotify)message_free);
+    // TODO: Potential optimization
+    // if (flip)
+    // since adding messages to history without overflowing buffer does not require a win_redraw
     win_redraw((ProfWin*)chatwin);
 
-    return has_items;
+    return result;
 }
 
 static void

src/ui/ui.h

@@ -43,6 +43,7 @@
 #include "config/account.h"
 #include "config/preferences.h"
 #include "command/cmd_funcs.h"
+#include "database.h"
 #include "ui/win_types.h"
 #include "xmpp/message.h"
 #include "xmpp/muc.h"
@@ -145,7 +146,7 @@ void chatwin_set_incoming_char(ProfChatWin* chatwin, const char* const ch);
 void chatwin_unset_incoming_char(ProfChatWin* chatwin);
 void chatwin_set_outgoing_char(ProfChatWin* chatwin, const char* const ch);
 void chatwin_unset_outgoing_char(ProfChatWin* chatwin);
-gboolean chatwin_db_history(ProfChatWin* chatwin, const char* start_time, char* end_time, gboolean flip);
+db_history_result_t chatwin_db_history(ProfChatWin* chatwin, const char* start_time, char* end_time, gboolean flip);
 
 // MUC window
 ProfMucWin* mucwin_new(const char* const barejid);

src/ui/window.c

@@ -35,6 +35,7 @@
  */
 
 #include "config.h"
+#include "database.h"
 #include "ui/window_list.h"
 
 #include <stdlib.h>
@@ -628,54 +629,68 @@ win_free(ProfWin* window)
 void
 win_page_up(ProfWin* window, int scroll_size)
 {
+    // Page offset from the start of the NCurses PAD (invisible window)
     int* page_start = &(window->layout->y_pos);
     int page_start_initial = *page_start;
-    int total_rows = getcury(window->layout->win);
+    // Size of the visible chat page
     int page_space = getmaxy(stdscr) - 4;
     if (scroll_size == 0)
         scroll_size = page_space;
     win_scroll_state_t* scroll_state = &window->scroll_state;
     *scroll_state = (*scroll_state == WIN_SCROLL_REACHED_BOTTOM) ? WIN_SCROLL_INNER : *scroll_state;
     *page_start -= scroll_size;
+    gboolean has_scroll_past_buffer = *page_start < 0;
 
-    if (*page_start == -scroll_size && window->type == WIN_CHAT) {
+    if (has_scroll_past_buffer && window->type == WIN_CHAT) {
         ProfChatWin* chatwin = (ProfChatWin*)window;
         ProfBuffEntry* first_entry = buffer_size(window->layout->buffer) != 0 ? buffer_get_entry(window->layout->buffer, 0) : NULL;
 
-        // Don't do anything if still fetching mam messages
-        if (first_entry && !(first_entry->theme_item == THEME_ROOMINFO && g_strcmp0(first_entry->message, LOADING_MESSAGE) == 0)) {
+        gboolean is_still_fetching_mam = first_entry && (first_entry->theme_item == THEME_ROOMINFO && g_strcmp0(first_entry->message, LOADING_MESSAGE) == 0);
+        if (!is_still_fetching_mam) {
+            // WIN_SCROLL_REACHED_TOP means that we reached top of DB and there is no need to refetch data from it
+            gboolean is_db_offset_jump_needed = false;
             if (*scroll_state != WIN_SCROLL_REACHED_TOP) {
-                *scroll_state = !chatwin_db_history(chatwin, NULL, NULL, TRUE) ? WIN_SCROLL_REACHED_TOP : WIN_SCROLL_INNER;
+                db_history_result_t db_response = chatwin_db_history(chatwin, NULL, NULL, TRUE);
+                is_db_offset_jump_needed = db_response == DB_RESPONSE_SUCCESS;
+                *scroll_state = db_response == DB_RESPONSE_EMPTY ? WIN_SCROLL_REACHED_TOP : WIN_SCROLL_INNER;
+                log_debug("Scroll state after DB history fetch: %s", *scroll_state ? "WIN_SCROLL_REACHED_TOP" : "WIN_SCROLL_INNER");
             }
 
-            if (*scroll_state == WIN_SCROLL_REACHED_TOP && prefs_get_boolean(PREF_MAM)) {
-                win_print_loading_history(window);
-                iq_mam_request_older(chatwin);
+            if (*scroll_state == WIN_SCROLL_REACHED_TOP) {
+                *page_start = 0;
+                if (prefs_get_boolean(PREF_MAM)) {
+                    win_print_loading_history(window);
+                    iq_mam_request_older(chatwin);
+                }
             }
 
-            int buff_size = buffer_size(window->layout->buffer);
-            int offset_entry_id = buff_size > 10 ? 10 : buff_size - 1;
-            int offset = buffer_get_entry(window->layout->buffer, offset_entry_id)->y_end_pos;
-            *page_start = offset - page_space;
+            // Recalculate scroll offset after loading older messages from the DB.
+            // *page_start may become negative due to paging up beyond the current buffer.
+            // To maintain smooth scroll positioning, we adjust it relative to the visual offset
+            // (y_start_pos) of the first buffer entry *before* DB fetch.
+            // This ensures a seamless transition as older messages are prepended, regardless
+            // of how many visual lines they occupy (since messages can vary in height).
+            // For example, if *page_start == -5 and first_entry->y_start_pos == 40,
+            // we shift the scroll to 35, preserving the visual context for the user.
+            if (is_db_offset_jump_needed) {
+                *page_start = first_entry ? first_entry->y_start_pos + *page_start : 0;
+            }
         }
     }
 
-    // went past beginning, show first page
     if (*page_start < 0) {
+        log_debug("win_page_up(): *page_start adjusted to 0 due to negative value (expected if insufficient history messages). Previous value: %d", *page_start);
         *page_start = 0;
     }
 
-    window->layout->paged = 1;
-
-    // update only if position has changed
+    // Update window location only if position has changed
     if (page_start_initial != *page_start) {
         win_update_virtual(window);
     }
 
-    // switch off page if last line and space line visible
-    if ((total_rows) - *page_start == page_space) {
-        window->layout->paged = 0;
-    }
+    // Update scrolling state
+    int total_rows = getcury(window->layout->win);
+    window->layout->paged = (total_rows) - *page_start > page_space;
 }
 
 void