fix scroll direction: use RmlUi native touch API

Switch from mouse event emulation to RmlUi's native touch API
(ProcessTouchStart/Move/End) for natural scrolling behavior.

When dragging on scrollable content, the content now follows
the finger/cursor direction instead of scrolling in reverse.

- Designer: Use touch API when left mouse button is pressed
- Android kernel: Use touch API for all touch events

designer/main.cpp

@@ -59,6 +59,11 @@ static std::string g_test_output_path;  // Output file for record/screenshot/hie
 static mosis::testing::ActionRecorder* g_action_recorder = nullptr;
 static mosis::testing::ActionPlayer* g_action_player = nullptr;
 
+// Touch simulation state for natural scrolling behavior
+static bool g_touch_active = false;
+static int g_touch_start_x = 0;
+static int g_touch_start_y = 0;
+
 // Logging and hierarchy dump for testing
 static std::string g_log_file_path;       // Log file path (--log)
 static std::string g_hierarchy_file_path; // Continuous hierarchy dump path (--hierarchy)
@@ -211,12 +216,20 @@ static void MouseButtonCallback(GLFWwindow* window, int button, int action, int
             if (g_action_recorder && g_action_recorder->IsRecording()) {
                 g_action_recorder->RecordMouseDown(mouseX, mouseY);
             }
-            g_context->ProcessMouseButtonDown(0, key_modifier);
+            // Use touch API for natural scrolling behavior
+            g_touch_active = true;
+            g_touch_start_x = mouseX;
+            g_touch_start_y = mouseY;
+            Rml::TouchList touches = {{0, Rml::Vector2f(static_cast<float>(mouseX), static_cast<float>(mouseY))}};
+            g_context->ProcessTouchStart(touches, 0);
         } else if (action == GLFW_RELEASE) {
             if (g_action_recorder && g_action_recorder->IsRecording()) {
                 g_action_recorder->RecordMouseUp(mouseX, mouseY);
             }
-            g_context->ProcessMouseButtonUp(0, key_modifier);
+            // End touch for natural scrolling
+            g_touch_active = false;
+            Rml::TouchList touches = {{0, Rml::Vector2f(static_cast<float>(mouseX), static_cast<float>(mouseY))}};
+            g_context->ProcessTouchEnd(touches, 0);
         }
     }
 }
@@ -234,7 +247,14 @@ static void CursorPosCallback(GLFWwindow* window, double xpos, double ypos) {
     int mouseX = static_cast<int>(xpos * fbWidth / winWidth);
     int mouseY = static_cast<int>(ypos * fbHeight / winHeight);
 
+    // Always update mouse position for hover effects
     g_context->ProcessMouseMove(mouseX, mouseY, 0);
+
+    // If touch is active (left button pressed), also send touch move for natural scrolling
+    if (g_touch_active) {
+        Rml::TouchList touches = {{0, Rml::Vector2f(static_cast<float>(mouseX), static_cast<float>(mouseY))}};
+        g_context->ProcessTouchMove(touches, 0);
+    }
 }
 
 static void ScrollCallback(GLFWwindow* window, double xoffset, double yoffset) {

src/main/cpp/kernel.cpp

@@ -761,9 +761,13 @@ void Kernel::on_touch_down(float x, float y)
     m_tasks.emplace_back([x, y](Rml::Context* context){
         int px = static_cast<int>(x * 540);
         int py = static_cast<int>(y * 960);
-        bool move_handled = context->ProcessMouseMove(px, py, 0);
+
-        bool down_handled = context->ProcessMouseButtonDown(0, 0);
+        // Use native touch API for proper scroll direction (natural scrolling)
-        Logger::Log(std::format("Touch at ({}, {}): move={}, down={}", px, py, move_handled, down_handled));
+        // Touch ID 0 for primary touch point
+        Rml::TouchList touches = {{0, Rml::Vector2f(static_cast<float>(px), static_cast<float>(py))}};
+        context->ProcessTouchStart(touches, 0);
+
+        Logger::Log(std::format("Touch start at ({}, {})", px, py));
 
         // Debug: Check if there's a hover element
         auto* hover_elem = context->GetHoverElement();
@@ -782,7 +786,11 @@ void Kernel::on_touch_move(float x, float y)
     Logger::Log(std::format("on_touch_move {} - {}", x, y));
     std::lock_guard _lock(m_mutex);
     m_tasks.emplace_back([x, y](Rml::Context* context){
-        context->ProcessMouseMove(static_cast<int>(x * 540), static_cast<int>(y * 960), 0);
+        int px = static_cast<int>(x * 540);
+        int py = static_cast<int>(y * 960);
+        // Use native touch API for proper scroll direction
+        Rml::TouchList touches = {{0, Rml::Vector2f(static_cast<float>(px), static_cast<float>(py))}};
+        context->ProcessTouchMove(touches, 0);
     });
 }
 
@@ -791,8 +799,11 @@ void Kernel::on_touch_up(float x, float y)
     Logger::Log(std::format("on_touch_up {} - {}", x, y));
     std::lock_guard _lock(m_mutex);
     m_tasks.emplace_back([x, y](Rml::Context* context){
-        context->ProcessMouseMove(static_cast<int>(x * 540), static_cast<int>(y * 960), 0);
+        int px = static_cast<int>(x * 540);
-        context->ProcessMouseButtonUp(0, 0);
+        int py = static_cast<int>(y * 960);
+        // Use native touch API for proper scroll direction
+        Rml::TouchList touches = {{0, Rml::Vector2f(static_cast<float>(px), static_cast<float>(py))}};
+        context->ProcessTouchEnd(touches, 0);
     });
 }